April–June 2015

Perspective 1

MG Steve Jones

The Role of Strength and Power During Performance of High Intensity 3

Military Tasks Under Heavy Load Carriage

Jesse Mala, MS; Tunde K. Szivak, MA; Shawn D. Flanagan, MA; Brett A. Comstock, PhD; et al

Performance Differences Between Male and Female Marines on Standardized 12

Physical Fitness Tests and Combat Proxy Tasks: Identifying the Gap

James Jameson, PhD; Leon Pappa; Brian McGuire; Karen R. Kelly, PhD

Musculoskeletal, Biomechanical, and Physiological Gender 22

Differences in the US Military

Katelyn F. Allison, PhD; Karen A Keenan, PhD, ATC; Timothy C. Sell, PhD, PT; et al

The Effects of Cross-Training on Fitness and Injury in Women 33

Tyson Grier, MS; Michelle Canham-Chervak, PhD; Morgan K. Anderson, MPH, CPH; et al

Physical Training, Smoking, and Injury During Deployment: 42

A Comparison of Men and Women in the US Army

Morgan K. Anderson, MPH, CPH; Tyson Grier, MS; Michelle Canham-Chervak, PhD; et al

Physical Fitness and Injury Reporting Among Active Duty and National Guard/ 49

Reserve Women: Associations with Risk and Lifestyle Factors

Josh B. Kazman, MS; Sarah de la Motte, PhD, MPH, ATC; Elizabeth M. S. Bramhall, MPH; et al

Women and Exertional Heat Illness: Identification of Gender-Specific Risk Factors 58

Josh B. Kazman, MS; Diana L. Purvis, PhD; Yuval Heled, PhD; Peter Lisman, PhD; et al

Effects of Basic Combat Training on Iron Status in Male and Female Soldiers: 67

A Comparative Study

MAJ Ran Yanovich, ISDF; J. Philip Karl, PhD, RD; Einat Yanovich, PhD; et al

Female Combat Amputees Have Higher Rates of Posttraumatic 74

Stress Disorder Disability

MAJ Jessica C. Rivera; CPT (P) Chad A. Krueger; LTC (P) Anthony E. Johnson

Comparison of Female and Male Casualty Cohorts from Conflicts 80

in Iraq and Afghanistan

CPT Christina Hylden; LTC (P) Anthony E. Johnson; MAJ Jessica C. Rivera

Creating and Sustaining a Military Women’s Health Research Interest Group 86

Lt Col Candy Wilson, USAF; COL Lori Trego; CAPT Jacqueline Rychnovsky, USN; et al

Also in this Issue

Complex d-TGA Status Post Rastelli Repair Presenting with Palpitations: 91

Cardiac CTA Imaging Findings and Discussion of Long Term Outcomes

Capt Ross Pinson, USAF; MAJ Dustin Thomas; Maj S. Jared Bentley, USAF

US Army Psychiatry in the Vietnam War

A New Offering from the Borden Institute History Series 97

Reviewed by LTC Daniel E. Banks and COL (Ret) Hershell L. Moody

JOURNAL

THE UNITED STATES ARMY

MEDICAL DEPARTMENT

Physiological Factors of Expanded Roles for Military Women

Article Retracted

By Authors

May 6, 2015
JOURNAL

A Professional Publication

of the AMEDD Community THE UNITED STATES ARMY

MEDICAL DEPARTMENT

Online issues of the AMEDD Journal are available at http://www.cs.amedd.army.mil/amedd_journal.aspx

April–June 2015 US Army Medical Department Center & School PB 8-15-4/5/6

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MG Steve Jones

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Health Sciences, Bethesda, MD 
April – June 2015 1

Perspective

Commander’s Introduction

MG Steve Jones

Women have been part of the Army since 1775, serving 

with skill, determination, and valor. In Army Medicine 

they have played a critical role maintaining the health 

readiness of the force and caring for the injured and 

ill. The Army began expanding the role of women 40 

years ago, allowing them to train and fight alongside 

men as members of the profession of arms. During the 

campaigns in Afghanistan and Iraq they have done their 

share of fighting and dying. On June 23, 2005, three 

women Marines were killed when their convoy was attacked by a suicide bomber outside Fallujah. Of the 13 

Marines wounded in that attack, 11 were women.2 This 

incident represented the largest loss of women in uniform since World War II. On June 16, 2005, SGT Leigh 

Ann Hester of Nashville, Tennessee was awarded the 

Silver Star in a ceremony at Camp Liberty, Iraq. An 

MP in the 617th MP Company of the Kentucky National 

Guard, she fought back fiercely when her convoy was 

ambushed. During the fight, Hester’s squad moved to 

the side of the road, flanking the insurgents and cutting 

off their escape. She led her team through the kill zone 

and into their position where she assaulted a trench line 

with grenades and an M203 grenade-launcher. She and 

her squad leader cleared 2 trenches and when the fight 

was over, 27 insurgents were dead, 6 were wounded, 

and one was captured.3 PFC Monica Brown, a combat 

medic from the 82nd Airborne Division’s 782nd Brigade 

Support Battalion, 4th Brigade Combat Team, was on a 

routine security patrol along in Afghanistan’s Paktika 

province when insurgents attacked her convoy in April 

2007. Brown and her platoon sergeant exited their vehicle and ran several hundred meters under heavy fire 

to a burning Humvee. She provided aid to her fellow 

Soldiers under heavy fire, protecting them with her body 

while rounds were missing her by inches. Brown was the 

second woman awarded the Silver Star since World War 

II.4 CPT Jennifer Moreno, an Army nurse, volunteered 

to serve on the Cultural Support Team of a Joint Special 

Operations Task Force in Afghanistan. During combat 

operations in Kandahar Province on October 5, 2013, 

she joined a team from the 3rd Battalion, 75th Ranger 

Regiment as they assaulted a remote compound occupied by enemy insurgents. During the assault, the enemy 

triggered multiple suicide and improvised explosive devices, wounding several Rangers. Fully understanding 

the risk, CPT Moreno ran through an area seeded with 

explosive devices to render aid to the casualties and assist with evacuation. While moving toward a wounded 

soldier, she triggered a device and was killed in action. 

CPT Moreno was awarded the Bronze Star Medal posthumously for her valor.5

Throughout our history, women have proven there are 

few limits to the contributions they are capable of making on the battlefield. It is time to allow them to serve 

in any unit or position for which they qualified, and the 

Army is working to remove as many barriers as possible. In 2012, the Army initiated Soldier 2020, a deliberate, service-wide effort to staff its units with the 

best qualified soldiers. The initiative is based on 3 principals: maintain the dominance of our nation’s warfighting forces by preserving unit readiness, cohesion, and 

morale; validate both physical and mental occupational 

performance standards for all military occupational 

specialties; and set the conditions so all Soldiers, men 

or women, have an opportunity to succeed as their talents allow. The US Army Training and Doctrine Command began the process by studying attitudes of women 

in combat units. They found that most men who had 

worked and fought beside women expected them to 

perform well in combat roles; it is those with little or 

no experience serving beside women who require more 

convincing that women will perform well. There was 

agreement across the force that we not lower the standards for service in combat roles, and that women, based 

on their wartime performance, have earned the opportunity to stand in any of our formations for which they 

qualify, if they wish to do so. In just over 2 years, Soldier 

2020 has opened 6 previously closed military occupational specialties and over 55,000 positions across all 

Women in Combat

The contributions and sacrifices made by women have challenged many long-standing assumptions about their 

roles in battle as well as the efficacy of the rules meant to keep them from serving in combat units.

GEN Robert W. Cone1
2 http://www.cs.amedd.army.mil/amedd_journal.aspx

Army components. Among the newly opened positions 

are 1,562 in the US Army Special Operations Command, including the 160th Special Operations Aviation 

Regiment. The Army is proceeding in an incremental, 

scientifically based approach, validating gender neutral 

physical standards and conducting a gender integration study to inform decisions on opening the remaining 14 military occupational specialties currently closed 

to women. The AMEDD is playing a major role in the 

process. Upon completion of the study, the Army will 

recommend to the Secretary of Defense the opening of 

as many as 166,000 positions in the Active and Reserve 

Components to women while preserving readiness, unit 

cohesion, discipline, and morale.1,6

Having served shoulder to shoulder with women during operations in Afghanistan and Iraq, I have seen firsthand their ability to perform on the battlefield. Soldier 

2020 is setting the conditions for them to succeed in 

their new roles while strengthening the force.

REFERENCES

1. GEN Robert W. Cone. Soldier 2020. Army Magazine. 2013;63(11):29-32. Available at: http://

www.ausa.org/publications/armymagazine/ar

chive/2013/11/documents/cone_nov2013.pdf. Accessed April 20, 2015.

2. Moss M. A mission that ended in inferno for 3 

women. New York Times. December 20, 2005. 

Available at: http://www.nytimes.com/2005/12/20/

international/middleeast/20marines.html. Accessed April 20, 2015.

3. Wood S. Woman Soldier receives Silver Star for 

valor in Iraq. American Forces Press Service [serial online]. June 16, 2005. Available at: http://www.

defense.gov/news/newsarticle.aspx?id=16391. Accessed April 20, 2015.

4. Clare M. Face of defense: Woman Soldier receives 

Silver Star. American Forces Press Service [serial 

online]. March 24, 2008. Available at: http://www.

defense.gov/news/newsarticle.aspx?id=49348. Accessed April 20, 2015.

5. Ashton A. The last moments of Jennifer Moreno, an Army nurse killed in Afghanistan. Army 

Times [internet]. April 29, 2014. Available at: 

http://archive.armytimes.com/article/20140429/

NEWS/304290068/. Accessed April 20, 2015.

6. US Department of the Army. Statement by the Honorable John M. McHugh, Secretary of the Army, 

and General Raymond T. Odierno, Chief of Staff, 

United States Army, before the Senate Committee 

on Appropriations, Subcommittee on Defense. First 

Session, 114th Congress on the Posture of the United States Army [record version]. Washington, DC: 

US Dept of the Army; March 11, 2015:19-20. Available at: http://usarmy.vo.llnwd.net/e2/rv5_down

loads/aps/aps_2015.pdf. Accessed April 20, 2015.

PERSPECTIVE
April – June 2015 3

Throughout history, load carriage has been shown to be 

an essential aspect of soldiering during military operations. During training and on the battlefield, Warfighters 

are required to carry various loads on their person or in 

a pack while engaging in demanding activities, ranging 

from long distance marching to short explosive sprints. 

The speed with which the soldier is able to maneuver 

on an objective carrying these loads, while performing 

strenuous activities, is critical to the completion of missions and survivability of personnel.

Knapik et al1 characterized the various loads that were 

carried by different Soldiers throughout history, from 

the Greek Hoplites to the US infantryman in Afghanistan during Operation Enduring Freedom, showing an 

increase in loads carried into battle. Load carriage has 

been shown to increase physiological strain, leading to 

excessive fatigue and attenuating combat effectiveness.2-4

Much of the increase in load can be attributed to technological advances in weaponry and armor, which aim 

to improve the combat effectiveness and survivability 

of the Soldier, but have negative implications on mobility and endurance due to the increase in weight.3,4 With 

the increase in weight resulting in a greater performance 

decrement, several studies have investigated approaches 

to optimal training programs designed to improve the 

load carriage capabilities of the Warfighter.5-7

The majority of the current research on military load 

carriage has examined the physiological determinants, 

the effects of various loads, and the training required 

to improve the speed of load carriage over medium to 

long distances, ranging from 2.5 km to 25 km.8-10 While 

medium to long distance marching with various loads 

may be required on the battlefield and during training, it 

is merely a single component of the multifaceted occupational demands Warfighters face today. The emphasis 

on medium to long distance load carriage reflects the 

tactics of past wars where Soldiers would march long 

distances, over several days, carrying their supplies into 

battle. However, combat operations have evolved from 

marching into battle to primarily conducting direct 

The Role of Strength and Power During

 Performance of High Intensity Military Tasks

 Under Heavy Load Carriage

Jesse Mala, MS Justin Z. Laferrier, PhD

Tunde K. Szivak, MA Carl M. Maresh, PhD

Shawn D. Flanagan, MA William J. Kraemer, PhD

Brett A. Comstock, PhD

Abstract

Objective: Previous research has investigated the physiological determinants of heavy load carriage while performing medium to long distance road marching, yet research examining the physiological underpinnings of 

high-intensity battlefield tasks is limited. This study sought to examine the role of strength and power during 

high-intensity combat tasks under heavy load carriage.

Methods: Eighteen recreationally trained men (mean±SD: age, 21±2 years; height, 172±6 cm; weight, 80±13 

kg) participated in this study and performed an anaerobic combat course under 2 randomized experimental 

conditions; unloaded and loaded. Subjects performed 3 trials under each condition on separate days, with a 

5-minute rest between each trial. In the unloaded trial, subjects wore a uniform with boots weighing approximately 3.2 kg. During the loaded trial, in addition to the uniform and boots, subjects wore Interceptor body 

armor (6.94 kg-9.10 kg) and a MOLLE rucksack weighing 30 kg. The course consisted of 3 consecutive tasks, 

which began from the prone position, led into a 30 m sprint, followed by a 27 m zigzag run, and ended with a 

10 m casualty drag weighing approximately 79.4 kg.

Results: Pearson correlations showed significant (P≤.05) strong correlations between lower body strength

(r=-0.63, -0.62), lower body power (r=-0.67, -0.67) and upper body strength (r=-0.60, -0.62) and overall performance times in the unloaded and loaded condition, respectively.

Conclusion: Strength and power are strongly related to high-intensity military tasks with and without heavy 

load carriage.
4 http://www.cs.amedd.army.mil/amedd_journal.aspx

action raids. During raids, troops 

are transported near or directly 

onto an objective and must quickly 

traverse the objective, performing anaerobic tasks such as sprinting, lifting, pulling, crawling, and 

climbing, while still carrying significant loads.

With the landscape of the modern 

battlefield becoming primarily anaerobic, more studies examining 

the demands of this “anaerobic 

battlefield”11 are necessary, so that 

Soldiers can train optimally to meet 

these demands. There is limited research investigating the physiological underpinnings and effects of 

heavy load carriage during the performance of short duration, highintensity anaerobic tasks, which 

more closely reflect the demands of 

the current battlefield. Treloar et al4

examined the overall effect of a combat load (21.8 kg) 

during five 30 m rushes, and identified lower body power 

as having a strong relationship with unloaded and loaded 

sprint time (r =-0.80, P ≤.01), however no strength measures were examined in this investigation. Pandorf et al12

examined the correlates of load carriage during the performance of a military obstacle course, yet no upper or 

lower body strength and power variables were assessed. 

Therefore the purpose of this investigation was to clarify 

the relationship between upper and lower body strength 

and lower body power and short duration, high-intensity 

military relevant tasks, while carrying heavy loads.

Methods

Experimental Approach to the Problem

To examine the role of strength and power in high-intensity military tasks under heavy load carriage, lower 

body and upper body strength were measured using a 

one repetition maximum (1RM) squat and bench press 

protocol, and lower body power was assessed using 

countermovement jumps as measured by a force plate, 

using previously described methods.13 Three military 

relevant tasks (30 m sprint, 27 m zigzag run, 10 m casualty drag) were used to simulate explosive offensive 

and defensive maneuvers routinely encountered on the 

battlefield.4,12 During the performance of the tasks, subjects wore an Army combat uniform, boots, Interceptor 

body armor (IBA), and a Modular Lightweight Loadcarrying Equipment (MOLLE) rucksack, resulting in a 

total weight of approximately 42 kg (body size dependent), which is representative of the typical load carried 

by US Army Soldiers during recent 

combat operations.14

Subjects

Eighteen recreationally active 

men (age: 21.8±2.4 years, height: 

172.9±6.4 cm, weight: 80.7±13 kg) 

participated in this study. The physical characteristics of the subjects 

are presented in Table 1. To reduce 

variance caused by differences in 

age, and to be able to generalize 

our findings to an average military 

population, subjects recruited for 

this study were men between the 

ages of 18 and 35. Also, since most 

active combat units physically train 

at least 3 times a week to maintain 

a level of fitness and combat readiness,15 subjects in this study were 

recreationally trained men who 

exercised at least 3 times a week 

for 60 minutes each day. Twelve 

subjects were from the Army Reserve Officer Training 

Corps (ROTC) unit from the university population, and 

6 subjects were civilian students from the university 

population. Subjects were required to complete a medical questionnaire and were screened by a physician for 

any orthopedic, cardiovascular, or other medical problems that may have prevented a subject from safely completing the study or may have confounded the results of 

this investigation. Participants were briefed on the risks 

and benefits of the investigation and afterwards completed a written informed consent form to participate 

in the study. This investigation was approved by the 

local university Institutional Review Board for use of 

human subjects.

Procedures

To minimize learning effects related to the unfamiliarity 

of the different protocols in the study, participants underwent a familiarization session prior to any data collection, which exposed the subjects to the experimental conditions of the performance testing protocol, the 

Army Physical Fitness Test (APFT) protocol, and the 

military course protocol. In addition, anthropometric 

measurements were collected, and subjects were familiarized with a standardized dynamic warmup protocol 

that would be used before all experimental visits. The 

standardized warmup consisted of 5 minutes on a cycle 

ergometer at a resistance level of 5, with a speed maintained under 60 rpm, followed by dynamic stretches, 

including forward and lateral lunges, knee hugs, quadriceps stretches, straight leg marches, and body weight 

THE ROLE OF STRENGTH AND POWER DURING PERFORMANCE OF

HIGH INTENSITY MILITARY TASKS UNDER HEAVY LOAD CARRIAGE

Table 1. Overall Subject Characteristics.

Subject

Number

Height

(cm)

Weight

(kg) 

Age

(yr)

1 178 86.1 22

2 168 81.1 21

3 173.5 58.9 21

4 162 61.4 22

5 173 78 19

6 165 66.6 21

7 179.5 80 22

8 169.5 98.8 21

9 176.2 104.9 30

10 173.5 84.7 24

11 162 69.7 20

12 187 103.6 23

13 173.5 88.6 22

14 177 72.1 21

15 177 74.9 20

16 175 78.3 20

17 167 77.9 21

18 176 86.4 22

Mean±SD 172.9±6.4 80.7±13 21.8±2.4
April – June 2015 5

THE ARMY MEDICAL DEPARTMENT JOURNAL

squats.16 Furthermore, to reduce any discomfort related 

to the military load, subjects were fitted for the IBA and 

MOLLE rucksack and also were instructed on proper 

wear technique.

Performance Testing Protocol

Following the familiarization session, participants completed a countermovement jump protocol, a 1 repetition maximum (1RM) squat protocol and a 1RM bench 

press protocol in the same visit. After performing the 

standardized warmup, countermovement vertical jump 

power was assessed using a force plate (Fitness Technology, Skye, South Australia) and Ballistic Measurement 

System software (http://ballistic-measurement-system.

software.informer.com/2.0/). Lower body power and 

1RM strength were assessed using previously described 

methods.13 For the countermovement jump, subjects 

were asked to perform 3 consecutive maximal jumps 

with their hands on their hips. Participants performed 

2 sets of the countermovement jumps, with at least 2 

minutes of rest between sets. Peak power for each set 

was recorded. Subsequently, after the countermovement 

jump testing and a 5 minute rest, lower body strength 

was assessed by a 1RM squat protocol using a Smith 

machine, and upper body strength was assessed with 

the use of a 1RM free-weight (barbell) bench press protocol. For each 1RM test, subjects performed 8-10 repetitions at approximately 50% of estimated 1RM, followed by another set of 3-5 repetitions at 85% of 1RM. 

Up to 4 maximal trials separated by 2-3 minutes of rest 

were used to determine individual 1RMs for the squat 

and bench press exercise.13

Army Physical Fitness Testing

Following the performance testing protocol, civilian 

subjects were given at least 24 hours of rest before performing the APFT. After completing the standardized 

warmup, subjects performed the APFT, which consists 

of 2 minutes of maximal push-ups, 2 minutes of maximal sit-ups, and a timed 2-mile run, following guidelines outlined in Army Field Manual 7-22.

15 A rest of 

5-10 minutes was allotted between each test. The ROTC 

cadets in this study performed the APFT with the ROTC 

cadre one week prior to participation in this study, following the same testing guidelines. The APFT scores 

were used from this testing session and were deemed reliable, since the test was administered by qualified and 

experienced Army personnel familiar with the testing 

procedures outlined in Field Manual 7-22.

15

Military Course Protocol

To control for any extraneous variables in the participant’s diet and activity, subjects were asked to record 

their diet and activity for 48 hours prior to their first performance of the military course. Participants were encouraged to continue their normal exercise routines, but 

were asked to refrain from strenuous exercise during the 

48 hours prior to the first visit. Following a minimum of 

48 hours of rest, subjects completed their first visit in random order, which was performed in either the unloaded 

(combat uniform and boots [approximately 3.2 kg]) or 

loaded condition (combat uniform, boots, IBA [6.9 kg, 

8.1 kg, or 9.1 kg depending on body size], and MOLLE 

rucksack [30 kg]; total weight of approximately 42 kg). 

The final visit was completed after another 48 hours of 

rest, with subjects replicating their diet and activity logs 

during the 48 hours prior to their final performance of 

the military course, ensuring that subjects would be in a 

similar physiological state during both visits.

For each visit, after performing a standardized warmup, 

subjects were reminded of the test protocols for the 

military course. The military course, illustrated in Figure 1, consisted of 3 consecutive military relevant tasks 

and began from the prone position, leading into a 30 m 

sprint, followed by a 27 m zigzag run, and concluding 

Figure 1. Military course design. Time check points are represented by T1, T2, T3, and T4.

Start

5 m

Finish

Task 3:

10 m

Casualty Drag

T1 T3 T4 T2

Task 2: 27 m Zigzag Run

Task 1: Sprint 30 m from prone position
6 http://www.cs.amedd.army.mil/amedd_journal.aspx

with a 10 m, 79.5 kg casualty drag, which is the approximate weight of a US infantryman with a combat load.14

Timing for the course began with the first upward movement from the prone position, and finished when the end 

of the casualty drag apparatus passed the 10 m mark. 

Times were hand-recorded by the same timer using a 

stopwatch (Thermo Fisher Scientific, Waltham, MA). 

Three trials were performed to increase the reliability 

of recorded performance times,12 and a 5-minute rest 

between each trial ensured adequate recovery. Subjects 

also performed both of the military course visits during 

the same time of day, reducing the influence of diurnal 

hormone variations. All of the military task visits were 

conducted in the evening, since the majority of direct 

action raids and combat operations take place during 

this time. Lastly, to reduce tester induced variability, the 

same tester recorded the timing of the military course 

for each subject for both visits.

Statistical Analysis

It was determined that a sample size of 18 would be sufficient to defend the 0.05 alpha level of significance with 

a Cohen probability of 0.80 or more for each dependent 

variable (nQuery Advisor software, Statistical Solutions, 

Saugus, MA). Subjects were separated into 2 different 

groups, shown in Table 2, based on their primary modality of training for the past year (resistance-trained 

[RT] and traditional Army-trained [AT]). A 2 (traditional Army-trained vs strength-trained) by 2 (loaded trial 

vs unloaded trial) by 5 (total time, 5m time, 30 m time, 

agility time, casualty drag time) mixed methods analysis of variance (ANOVA) was used to detect significant 

mean differences (SPSS Version 21, IBM Corp, Armonk, 

NY). When significant differences were observed, a 

Fisher’s least significant difference post-hoc analysis 

was used to make pairwise comparisons. A Pearson 

product moment correlation was used to determine the 

relationship between potential anthropometric and performance predictors and military task performance. We 

also used independent t-tests to compare mean values 

for these potential predictors in the 2 groups. All values 

are presented as means and standard deviations, and significance was set at P≤.05.

Results

Differences Between Unloaded and Loaded Times

The means and standard deviations of the unloaded military course time and the loaded military course time for 

the RT and AT groups are depicted in Figure 2.

In the AT group, significant differences were found between the unloaded (28.7±2.5 sec) and loaded (38.7±4.8 

sec) conditions, with the loaded condition eliciting a 

significant 35% increase in overall course time when 

compared to the unloaded time (10.0±3.4 sec, P≤.05). 

Significant differences were also found within the RT 

group between the unloaded (25.4±1.8 sec) and loaded 

(32.7±3.6 sec) conditions, with the loaded condition 

eliciting a significant 29% increase in overall course 

time when compared to the unloaded time (7.3±2.1 sec, 

P≤.05). The AT group took significantly longer to complete the military course under load when compared to 

the RT group (RT: 7.3±2.1 sec, 29% increase vs AT: 

10.0±3.4 sec, 35% increase, P≤.05).

Overall Loaded Course Time and Times for Each 

Course Component

Average time to complete the total course and each component within the course in the loaded condition are depicted in Figure 3.

THE ROLE OF STRENGTH AND POWER DURING PERFORMANCE OF

HIGH INTENSITY MILITARY TASKS UNDER HEAVY LOAD CARRIAGE

Table 2. Subject Characteristics for RT and AT Groups.

RT AT 

Age

(yr)

Height

(cm)

Weight

(kg)

Age

(yr)

Height

(cm)

Weight

(kg)

22 178 86.1 21 168 81.1

22 179.5 80 21 173.5 58.9

21 169.5 98.8 22 162 61.4

30 176.25 104.9 21 165 66.6

24 173.5 84.7 20 162 69.7

23 187 103.6 20 177 74.9

22 173.5 88.6 20 175 78.3

21 167 77.9 21 177 72.1

22 176 86.4

19 173 78

22.6±2.9 175.3±5.6 *88.9±10.1 20.8±0.7 169.9±6.5 *70.4±7.8

NOTE: Bottom row presents mean±SD(*Indicates significant difference).

RT indicates resistance-trained.

AT indicates Army-trained.

45

40

35

30

25

20

UNLD LD

*

*

RT AT

Time (sec)

Figure 2. Means and standard deviations of unloaded 

(UNLD) and loaded (LD) total course time for RT (resistancetrained) and AT (Army-trained) groups.

RT: UNLD 25.4±1.8 sec; LD 32.7±3.6 sec.

AT: UNLD 28.75±2.5 sec; LD 38.7±4.8 sec.

*indicates significant difference.
April – June 2015 7

THE ARMY MEDICAL DEPARTMENT JOURNAL

In the loaded condition, the RT group performed the entire military course significantly 

faster (P≤.05) than the AT group. Within the 

course, the RT group performed significantly 

faster when rising from the prone position to 

the first 5 meters, and performing the casualty 

drag (P≤.05).

Group-specific Differences in Strength and 

Power Variables

The means and standard deviations of peak power for the RT and AT groups are shown in Figure 4. The 2 groups differed significantly, with 

the RT group averaging 44% greater peak power (watts) than the AT group (RT=4806.7±936.3 

W; AT=3333.6±449.5 W). Squat 1RM means 

and standard deviations for the RT and AT 

groups are shown in Figure 5. Significant differences were found between the RT (155.5±54 

kg) and AT groups (84.7±16.9 kg), with the RT group 

averaging 83% greater lower body strength.

The means and standard deviations of bench press 1RM 

are listed in Figure 6 for the RT and AT groups. Significant differences (P≤.05) were found between the RT 

(121.6±29.9 kg) and AT groups (75.6±10.9 kg), with the 

RT group averaging 61% greater bench press 1RM than 

the AT group.

No significant differences were found for any of the 

APFT components between the RT and AT groups. The 

means and standard deviations of performance outcomes for each APFT component for the two groups are 

provided in Table 3.

Relating Performance Test Variables to Loaded 

Military Course Performance

The correlation of all the performance testing variables 

with the loaded military course time and its 3 components is shown in Table 4. There was a strong negative 

correlation between total loaded time and peak power 

(watts) (r=-0.67, P≤.05), total loaded time and squat 

1RM (kg) (r=-0.62, P≤.05), and total loaded time and 

bench press 1RM (kg) (r=-0.62, P≤.05). Strong correlations were also observed between the strength and power measures and the majority of the components within 

the overall course. There was only one significant correlation between a component of the APFT (number 

of push-ups) and performance on the loaded military 

course (total time).

Comment

The purpose of this study was to determine the role of 

strength and power in short duration, high-intensity 

military tasks incorporating heavy load carriage. Most 

studies that have examined strength and power in military tasks have not employed significant loads, nor have 

assessed strength and power in conjunction with performance outcomes on high-intensity tasks with significant 

loads. This investigation used only 3 military relevant 

tasks (prone position into 30 m sprint, 27 m zigzag run, 

10 m casualty drag) vs the multistation (8-19) obstacle 

courses frequently used in other investigations, since 

direct action raids mostly involve short distance sprinting around obstacles and to points of cover. The first 

5 meters of the 30 m sprint began from the prone position, because it was here that Treloar et al4

 observed 

the greatest decrement in 30 m loaded sprint times. This 

is also the starting position for basic offensive and defensive maneuvers. A short distance casualty drag was 

Figure 3. Mean times for each component of the military course for RT 

(resistance-trained) and AT (Army-trained) groups.

*indicates significant difference.

3.54

3.1*

8.5 12.9 11.4* *

9.2 13.5 15.4

0 10 20 30 40 50

RT

AT

5 m 30 m Zigzag Casualty Drag

Time (sec)

*

Power (watts)

RT AT

7000

6000

5000

4000

3000

2000

1000

Figure 4. Mean differences between RT (resistance-trained) 

and AT (Army-trained) groups in peak power.

RT: 4806.7±963.3 W

AT: 3333.6±449.5 W

*indicates significant difference.
8 http://www.cs.amedd.army.mil/amedd_journal.aspx

included to simulate a battlefield scenario where the Soldier would quickly transfer the casualty behind a point 

of cover to administer first aid. Also, the overall load 

used in this investigation (approximately 42 kg) is typical of loads carried by US infantrymen during modern 

combat operations.14

There were strong negative correlations between upper 

body strength, lower body strength, lower body power, 

and overall loaded military course time, highlighting 

the role of strength and power during high-intensity, 

combat-relevant tasks. It is important to mention that 

the negative correlations indicate that greater strength 

and power were associated with shorter course completion times. These findings coincide with those of Jette et 

al,17 Bishop et al,18 and Treloar et al,4 who found significant correlations between strength and power and military obstacle course performance. Strength and power 

being highly correlated to high-intensity military tasks 

is also congruent with the findings of Harman et al19

who found that lower body power could predict simulated battlefield performance on a course that included 

a 30 m run and a 27 m zigzag run with an 18 kg combat 

load. In the present study, lower body strength was the 

only variable that had a consistently strong correlation 

with overall loaded course time, as well as with every 

individual component of the course (prone position to 

5 m, 30 m sprint, 27 m zigzag run, 10 m casualty drag).

Another important observation is the lack of a significant 

relationship between push-ups, sit-ups, and 2-mile run 

time with respect to overall time on the loaded military 

course. This coincides with previous findings by Pandorf et al20 who observed that APFT scores did not correlate with performance on a loaded military obstacle 

course. The only significant correlation between any 

APFT component and military course time was the association between the number of push-ups performed and 

time to rise from the prone position and begin the first 

5 m sprint of the course. This coincides with previous 

findings, which suggested that push up ability is related 

to the performance of fire and movement techniques.4,19

The lack of correlation between push-ups, sit-ups, and 

2-mile run time with respect to high-intensity combat 

tasks is highly relevant; as the majority of the military 

continues to use calisthenics and aerobic training as the 

primary methods of preparation for combat deployment. 

Yet, the physical demands of deployment more closely 

mirror the conditions of the loaded military course used 

in the present investigation. Given the observed strength 

of correlations between strength/power and performance on the high-intensity combat task, it is likely that 

a strength and conditioning program that focuses on the 

development of strength and power will better prepare 

Warfighters to meet the modern-day demands of the 

battlefield.5,7,11

To further illustrate differences between resistance 

training and traditional Army training in terms of the 

performance on high-intensity combat tasks, groups 

were dichotomized based on training history over the 

previous year, resulting in placement into a RT or traditional AT group. Significant differences between the 

groups were found for lower body power, squat 1RM, 

bench press 1RM, and most importantly, performance 

on the loaded military course. It is important to note 

that while the RT group outperformed the AT group on 

the overall loaded military course by on average 5.99 

THE ROLE OF STRENGTH AND POWER DURING PERFORMANCE OF

HIGH INTENSITY MILITARY TASKS UNDER HEAVY LOAD CARRIAGE

180

160

140

120

100

80

60

40

20

*

RT AT

Kilograms

Figure 6. Mean differences between RT (resistance trained) 

and AT (Army trained) groups in bench press.

RT: 121.6±29.9 kg

AT: 75.6±10.9 kg

*indicates significant difference.

*

RT AT

240

190

140

90

40

Kilograms

Figure 5. Mean differences between RT (resistance-trained) 

and AT (Army-trained) groups in 1 repetition maximum squat 

test.

RT: 155.5±54 kg

AT: 84.7±16.9 kg

*indicates significant difference.
April – June 2015 9

THE ARMY MEDICAL DEPARTMENT JOURNAL

seconds (P≤.05), 4.95 seconds 

(82%) of that time difference was 

attributed to performance of the 

casualty drag component. This 

is not surprising, as the casualty 

drag was the most heavily loaded 

component of the course, and was 

therefore likely to be most sensitive to differences in upper and 

lower body strength. As measured 

by the squat 1RM, the RT group 

had substantially greater lower body strength when compared to the AT group (RT: 155.5±54 kg. AT: 84.6±16.9 

kg, P≤.05). Significant differences were also found for 

bench press 1RM (RT: 121.6±29.9 kg. AT: 75.5±10.9 kg, 

P≤.05). In view of these differences, it is no surprise 

that the RT group performed significantly better in the 

casualty drag, since this task involves the same muscle 

groups in the upper and lower body as the squat and 

bench press exercises.

The 2 groups also differed on the time to complete the 

first 5 m of the course, where subjects rose from the 

prone position to sprint 30 m. On average, this segment 

accounted for 10% of the difference in total course time 

(0.5 seconds), with RT outperforming AT. The action of 

rising from the prone position with a load into a sprint 

requires significant upper and lower body strength, 

which is also reinforced by the strong correlations of the 

bench press 1RM and the squat 1RM with the prone to 

5 m task (r=-0.65, r=-0.70, respectively, P≤.05). There 

were no significant differences between the RT group 

and the AT group for the loaded 30 m sprint time, and 

the loaded 27 m zigzag run time, which coincides with 

Harman et al,21 who observed no significant differences 

between 8 weeks of Army training and weight training 

in terms of timed 30 m rushes with fighting loads.

The observed effect of loading on military course performance was expected and corresponds with previous 

research. Overall, performance on the military course 

decreased 31% when loaded (26.8±2.7 seconds vs 

35.3±5.0 seconds, P≤.05). This is similar to the findings of Treloar et al4

 who observed a 29% increase in 

time when a 21.6 kg load was added to 30 m sprints. 

The larger performance decrements observed in this 

study may be explained by the use of a heavier loading 

scheme. The increase of the weight of body armor has 

also been shown to significantly impair repeated highintensity military tasks, with time to completion being 

10% slower during armored trials.3 An examination of 

overall performance decrements during loaded trials in 

the RT and AT groups showed that the AT group had a 

35% increase in course time versus the RT group, for 

which a 29% increase in course 

time was observed. The significant difference in performance 

between the RT and AT groups 

can be attributed to the significant 

difference (P≤.05) in group average body mass (RT 88.9±10.1 kg; 

AT 70.4±7.8 kg). This finding is in 

line with previous investigations, 

which have shown that larger, 

more muscular individuals perform better and are less affected by heavier loads than 

smaller, less muscular individuals.20,22

The lack of a significant difference between the RT and 

the AT group in the loaded 30 m sprint time and the 

27 m zigzag run time may be due to the familiarity of 

the AT group with military loads and equipment. Even 

though each subject was familiarized with the course 

and the load, the AT group may have had an advantage 

due to prior training exposure. The AT group consisted 

of ROTC cadets, while the RT group was mainly comprised of civilians who had no prior experience carrying 

military loads. Thus even larger differences might have 

been evident if both groups had similar overall exposure 

to military load carriage.

Furthermore, a significant difference in body mass was 

observed between the RT and the AT groups (88.9±10 

kg vs 70.4±7.8 kg, P≤.05), which may help explain 

the lack of difference in the 30 m and 27 m zigzag run 

time. Individuals with more body weight carry their 

own weight, in addition to the external load, with the 

heavier subjects carrying a greater overall load, which 

may place the heavier subject at a disadvantage in the 

30 m sprint and 27 m zigzag run. Despite the significant differences in weight, 30 m sprint time (RT 8.5±0.9 

seconds vs AT 9.3±1.1 sec) and 27 m zigzag run times 

(RT 12.8±1.1 seconds vs AT 13.7±0.9 seconds) were not 

statistically different between the RT and AT groups. 

This may be explained by the RT group possessing a 

Table 4. Correlation of Performance Testing Variables with the 

Military Course and Individual Components.

Total

Loaded 

Loaded

5 m

Loaded

30 m

Loaded

Zigzag

Loaded

Casualty

Drag

Peak power -0.67* -0.66* -0.60* -0.39 -0.64*

Squat 1RM -0.62* -0.70* -0.58† -0.48† -0.57†

Bench press 1RM -0.62* -0.65* -0.54† -0.44 -0.59*

Push-ups -0.38† -0.507 -0.428 -0.254 -0.34

Sit-ups 0.113 0.104 -0.069 0.095 0.138

2 Mile run time -0.374 -0.112 -0.285 0.043 0.036

*Indicates significant difference (P≤ .01).

†Indicates significant difference (P≤ .05).

1 RM indicates one repition maximum.

Table 3. Raw scores for each component (max 

push-ups in 2 minutes, max sit-ups in 2 minutes, and 2 mile run) of the Army Physical Fitness Test (APFT) for the RT and AT groups.

APFT

Components

RT

(mean±SD)

AT

(mean±SD)

Push-ups (repetitions) 72±17 66±10

Sit-ups (repetitions) 64±17 71±5

2 Mile run (seconds) 954±133 891±51

RT indicates resistance-trained.

AT indicates Army-trained.
10 http://www.cs.amedd.army.mil/amedd_journal.aspx

significantly greater amount of lower body power, offsetting the detrimental effects of extra weight, reinforcing the importance of lower body power.

Subjects were also placed in the RT and AT groups on 

the basis of their training history (exercise at least 3 

times per week for the past year in one modality) with 

no information on the specific variables of their training 

programs (power, hypertrophy, strength, intensity, etc). 

Greater differences may be observed if strictly poweror strength-trained subjects are compared with traditional Army-trained subjects. There is a need for further 

investigation concerning the effects of different training 

programs (strength, power, hypertrophy, calisthenics, 

etc) on the performance of short duration, high-intensity 

military load carriage tasks.

Relevance to the Performance Triad

This investigation examined the role of upper and lower 

body strength and power in the performance of short 

duration, high-intensity, combat relevant tasks, under 

conditions of heavy load carriage. While the combat 

task length examined in the current investigation was 

distinctly different from previous work (3 tasks vs 8-19 

tasks in other studies), the current findings support the 

observations of previous studies. The physiological underpinnings of the modern battlefield remain to be fully 

clarified; nevertheless, this investigation has underscored the overriding importance of strength and power 

in today’s “anaerobic battlefield.”11 The findings from 

this investigation can be used by military leadership 

and strength coaches working with the military population in providing a basis to develop optimal training 

regimens that include strength, power, and hypertrophy training. For modern combat occupations, training 

approaches which emphasize strength, power, and hypertrophy would likely improve combat effectiveness 

by helping Warfighters train for specific anaerobic demands of the battlefield, and thus enable them complete 

the mission with decreased injury risk, contributing to 

the overall resilience of the Soldier.

Acknowledgements

The authors thank LTC James Zopelis, MSG Matthew 

Ladd, MSG William Terry, CPT Corey Holmes and all 

of the cadets of the Army ROTC unit at the University of 

Connecticut for their participation in and support of this 

study. The authors also thank Dr Bradley Nindl and the 

US Army Public Health Command for their support of 

this study. Also, many thanks to the graduate assistants 

and undergraduate students for their hard work and dedication during data collection and manuscript preparation. 

This study was funded by internal laboratory funds and 

was not formally endorsed by the Department of Defense.

References

1. Knapik JJ, Reynolds KL, Harman E. Soldier load 

carriage: historical, physiological, biomechanical, 

and medical aspects. Mil Med. 2004;169(1):45-56.

2. Dubik JM, Fullerton TD. Soldier overloading in 

Grenada. Mil Rev. 1987;67:38-47.

3. Martin PE, Nelson RC. The effect of carried loads 

on the combative movement performance of men 

and women. Mil Med. 1985;150(7):357-362.

4. Treloar AK, Billing DC. Effect of load carriage on 

performance of an explosive, anaerobic military 

task. Mil Med. 2011;176(9):1027-1031.

5. Hendrickson NR, Sharp MA, Alemany JA, et 

al. Combined resistance and endurance training 

improves physical capacity and performance on 

tactical occupational tasks. Eur J Appl Physiol. 

2010;109(6):1197-1208.

6. Kraemer WJ, Mazzetti SA, Nindl BC, et al. Effect 

of resistance training on women’s strength/power 

and occupational performances. Med Sci Sports 

Exerc. 2001;33(6):1011-1025.

7. Kraemer WJ, Vescovi JD, Volek JS, et al. Effects of 

concurrent resistance and aerobic training on loadbearing performance and the Army physical fitness 

test. Mil Med. 2004;169(12):994-999.

8. Dziados JE, Damokosh AI, Mello RP, Vogel JA, 

Farmer KL. Physiological Determinants of Load 

Bearing Capacity. Natick, MA: US Army Research Institute of Environmental Medicine; June 

1987. Report No. T19-87. Available at: http://oai.

dtic.mil/oai/oai?verb=getRecord&metadataPrefix

=html&identifier=ADA184977. Accessed February 

20, 2015.

9. Knapik J, Staab J, Bahrke M, et al. Relationship 

of Soldier Load Carriage to Physiological Factors, 

Military Experience and Mood States. Natick, MA: 

US Army Research Institute of Environmental 

Medicine; May 1990. Report No. T17-90. Available 

at: http://oai.dtic.mil/oai/oai?verb=getRecord&m

etadataPrefix=html&identifier=ADA227007. Accessed February 20, 2015.

10. Mello RP, Damokosh AI, Reynolds KL, Witt CE, 

Vogel JA. The Physiological Determinants of Load 

Bearing Performance at Different March Distances. Natick, MA: US Army Research Institute of 

Environmental Medicine; April 1988. Report No. 

T15-88. Available at: http://oai.dtic.mil/oai/oai?ve

rb=getRecord&metadataPrefix=html&identifier=

ADA197733. Accessed February 20, 2015.

11. Kraemer WJ, Szivak TK. Strength training for the 

warfighter. J Strength Cond Res. 2012;26(suppl 

2):S107-S118.

12. Pandorf CE, Nindl BC, Montain SJ, et al. Reliability assessment of two militarily relevant occupational physical performance tests. Can J Appl 

Physiol. 2003;28(1):27-37.

THE ROLE OF STRENGTH AND POWER DURING PERFORMANCE OF

HIGH INTENSITY MILITARY TASKS UNDER HEAVY LOAD CARRIAGE
April – June 2015 11

THE ARMY MEDICAL DEPARTMENT JOURNAL

13. Kraemer WJ, Hatfield DL, Volek JS, et al. Effects 

of amino acids supplement on physiological adaptations to resistance training. Med Sci Sports Exerc. 

2009;41(5):1111-1121.

14. Dean CE. The Modern Warrior’s Combat Load. 

Dismounted Operations in Afghanistan, April-May 

2003. Fort Leavenworth, KS: US Army Center for 

Lessons Learned; 2004. Available at: http://thedon

ovan.com/archives/modernwarriorload/Modern

WarriorsCombatLoadReport.pdf. Accessed February 20, 2015.

15. Field Manual 7-22: Army Physical Readiness Training. Washington DC: US Dept of the Army; 2012.

16. Hooper DR, Szivak TK, Distefano LJ, et al. Effects 

of resistance training fatigue on joint biomechanics. 

J Strength Cond Res. 2013;27(1):146-153.

17. Jette M, Kimick A, Sidney K. Evaluation of an 

indoor standardized obstacle course for Canadian 

infantry personnel. Can J Sport Sci. 1990;15:59-64.

18. Bishop PA, Fielitz LR, Crowder TA, Anderson CL, 

Smith JH, Derrick KR. Physiological determinants 

of performance on an indoor military obstacle 

course test. Mil Med 1999;164(12):891-896.

19. Harman E, Gutekunst DJ, Frykman PN, et al. 

Prediction of simulated battlefield physical performance from field-expedient tests. Mil Med. 

2008;173(1):36-41.

20. Pandorf CE, Harman EA, Frykman PN, Patton JF, 

Mello RP, Nindl BC. Correlates of load carriage 

and obstacle course performance among women. 

Work. 2002;18(2):179-189.

21. Harman EA, Gutekunst DJ, Frykman PN, et al. Effects of two different eight-week training programs 

on military physical performance. J Strength Cond 

Res. 2008;22(2):524-534.

22. Koerhuis CL, Veenstra BJ, van Dijk JJ, Delleman NJ. Predicting marching capacity while 

carrying extremely heavy loads. Mil Med. 

2009;174(12):1300-1307.

Authors

Mr Mala is A Doctoral Fellow in the Department of 

Educational Leadership at the University of Connecticut. He deployed to Afghanistan in 2002 and 2004, and 

Iraq in 2003 with the 3rd Ranger Battalion, 75th Ranger 

Regiment.

Ms Szivak is a Doctoral Fellow in the Department of Human Sciences at The Ohio State University. A former US 

Army officer, she deployed to Iraq in 2004 and 2007 as a 

member of the 101st Airborne Division.

Mr Flanagan is a Doctoral Fellow in the Department of 

Human Sciences at The Ohio State University.

Dr Comstock is an Assistant Professor in the Department 

of Kinesiology and Sport Science at the University of 

South Dakota.

Dr Laferrier is an Assistant Professor in the Department 

of Physical Therapy at the University of Connecticut. 

A former US Army officer, he served as the officer-incharge of physical therapy for the Department of Defense 

Extremity Trauma and Amputation Center for Excellence.

Dr Maresh is a Professor and Department Chair for 

the Department of Human Sciences at The Ohio State 

University.

Dr Kraemer is a Professor in the Department of Human 

Sciences at The Ohio State University. While a former 

US Army officer, he was a Research Physiologist at the 

US Army Research Institute of Environmental Medicine 

from 1984 to 1987.
12 http://www.cs.amedd.army.mil/amedd_journal.aspx

For decades women have been restricted from direct 

assignment to certain military occupational specialties 

(MOSs), such as infantry. These restrictions can limit 

the advancement of women through the ranks of military 

leadership, and could also potentially deprive the military of a rich pool of talented applicants. Since World 

War II, there has been a gradual push to open closed occupations (primarily combat roles) to women. Eventually 

this trend became policy when Section 535 of the National Defense Authorization Act for Fiscal Year 2011 (Pub 

L No. 111-383, 124 Stat 4137) specifically directed that:

The Secretary of Defense, in coordination with the Secretaries of the military departments, shall conduct a 

review of laws, policies, and regulations, including the 

collocation policy, that may restrict the service of female 

members of the Armed Forces to determine whether 

changes in such laws, policies, and regulations are needed to ensure that female members have an equitable opportunity to compete and excel in the Armed Forces.

To ensure that this integration satisfies the goal of fairness without sacrificing military readiness, 2 important questions must be answered, each pointing to a 

potential barrier women might face: (1) What are the 

physical requirements of combat that could potentially 

prevent women from assignment to closed positions? 

(2) Can readiness for combat be assessed in a fair way, 

one that captures the actual physical requirements of 

those combat situations, and would not unfairly exclude 

women? This initial effort, as part of a larger physical 

Performance Differences Between Male and

 Female Marines on Standardized Physical

 Fitness Tests and Combat Proxy Tasks:

 Identifying the Gap

Jason Jameson, PhD

Leon Pappa

Brian McGuire

Karen R. Kelly, PhD

Abstract

Objectives: For decades women have been restricted from direct assignment to certain military occupational 

specialties such as infantry. These restrictions can limit the advancement of women through the ranks of military 

leadership. Thus, the purpose of this effort was to identify those physical requirements most likely to serve as 

barriers for women wanting to enter closed combat arms positions, and to evaluate the quality of existing 

physical fitness tests as potential measures of assessment of combat readiness.

Methods: Data were collected from 3 different sites within the US Marine Corps Training and Education 

Command. All participants (409 male, 379 female) were active-duty Marines who recently completed the 

Physical Fitness Test (PFT) and Combat Fitness Test (CFT). Participants completed 6 physical tasks: 120-mm 

tank loading drill, 155-mm artillery round carry, negotiating an obstacle course wall while wearing a fighting 

load (≈30 lb), pull-ups, deadlift, and clean and press.

Results: Overall, there was a high rate of successful completion on the combat proxy tasks (men, ≈80% to 100%; 

women, ≈70% to 100%), with the notable exception being the clean and press (men, 80%; women, 9%) and 

pull-ups (men, 16±4; women, 4±2). The PFT and CFT components tasks were also related, strongly in some 

cases, with performance on combat-related proxy tasks (Spearman’s ρ typically ranged from 0.60 to 0.80). 

Estimates of fat-free mass and VO2max were also strongly related to an overall measure of combat readiness 

(Spearman’s ρ=0.77 and ρ=0.56, respectively).

Conclusions: The primary physical obstacle for women is upper body strength. However, some women could 

successfully complete all of the proxy tasks and thus are physically capable of meeting the demands of closed 

combat occupations. The fact that some female Marines could complete the most challenging upper body 

strength tasks suggests that these barriers are not inherent but might be due to a lack of training specificity.

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April – June 2015 13

standards validation effort, was aimed at answering 

these questions.

The general approaches in addressing the 2 questions 

have been:

Question 1

(a) Identify or develop tasks that could reasonably 

serve as proxies for important combat-related 

tasks.

(b) Identify and describe the physical capabilities 

required to meet the corresponding occupational 

demand.

(c) Compare the performance of women to the performance of men. The performance of active 

duty male Marines can serve as standard against 

which to evaluate the readiness of women for 

combat assignment.

Question 2

(a) Identify existing physical fitness tests currently 

in use to assess physical fitness, and analyze the 

extent to which those tests can accurately identify combat-ready Marines.

(b) Evaluate candidate static measures (like estimated fat-free mass and VO2max) as predictors 

of physical fitness and combat readiness.

Currently, all Marines, irrespective of sex, are required 

to pass 2 standard physical fitness tests semiannually: 

the Physical Fitness Test (PFT) and the Combat Fitness Test (CFT). The PFT assesses the “collective level 

of physical fitness Marine Corps wide and is a measurement of general fitness vice combat readiness and 

unit/MOS capability.”1 The CFT extends the PFT by 

incorporating physical activities that directly mirror 

(ie, exhibit greater fidelity to) actual combat tasks. The 

Commandant of the Marine Corps initiated the development of the CFT as a training and assessment tool 

in response to increased casualties that were related to 

common combat maneuvers. The CFT was developed in 

2008, guided by the goal of incorporating high fidelity, 

functional movements that a Marine may face on a daily 

basis during training and/or combat.2

Thus the purpose of this effort was two-fold: (1) determine whether the existing physical fitness tests are good 

predictors of performance on ground combat element 

tasks; (2) identify physical obstacles that women may 

face during integration into previously closed combat 

arms positions. Second to these primary aims, the relationship between estimated aerobic capacity, body composition, and performance was also investigated.

Methods

Subjects

Active-duty male and female Marines were recruited 

from 3 different sites within the US Marine Corps: Marine Corps Recruit Depot, Parris Island, South Carolina; School of Infantry East, Marine Corps Base Camp 

Lejeune, North Carolina; and The Basic School, Quantico, Virginia. A briefing on the events was conducted for 

all participants, and informed consent was provided by 

those who volunteered. The combat-related tasks were 

designated as the physical training for the day, which is 

a mandatory requirement for active duty Marines. The 

volunteer rate for study participation was high at 98%. 

The testing protocol was reviewed and approved by the 

Marine Corps Combat Development Command Institutional Review Board.

Data Collection

All participants in the study were required to have completed a PFT and CFT within the last 6 months. The official PFT and CFT composite scores, as well as individual component scores, were acquired for each participant 

from their respective command so as not to rely on individual recall. All combat proxy tasks were performed 

on the same day to reduce between-day variability, and 

participants were asked to refrain from physical training 

on the day of participation.

Combat Fitness Test

Following observations of increased casualties related 

to common combat maneuvers, the Commandant of the 

Marine Corps initiated the development of a training 

and assessment tool that goes beyond those factors measured by the existing PFT. The CFT consists of basic 

aerobic (880 yd run), strength testing (ammunition can 

lift of 97 repetitions or to exhaustion in 2 minutes), and 

the maneuver under fire (MANUF), which incorporates 

multiple combat-related tasks and emphasizes both fitness and technical skill in carrying out the maneuvers 

effectively.

The events within the MANUF are representative of 

the types of movements that Marines routinely make 

in training and in combat. A sprint-to-J-hook turn is a 

proxy for a quick momentum and directional change as 

may occur under sniper fire, while a low crawl to high 

crawl maneuver is reflective of a Marine covertly covering a distance and then transitioning to a faster high 

crawl to maneuver between 2 points for safety. A casualty evacuation is a lifesaving technique that requires 

dragging (and/or fireman carry) a fellow Marine out of 

danger to a safer location as quickly as possible. The 

MANUF also incorporates an ammunition can carry 

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14 http://www.cs.amedd.army.mil/amedd_journal.aspx

and run, as well as a grenade toss, all of which are common combat skills. These individual MANUF tasks 

are combined into a single timed event, which enables 

assessment of a Marine’s combat capability and physical fitness, effectively measuring the simultaneous operation of multiple energy systems: strength, anaerobic, 

and aerobic.

The CFT score is a composite of scores from the 3 components. The maximum achievable score is 300 points.

Combat Proxy Tasks

All participants completed a dynamic warm-up prior to 

testing on the combat proxy tasks. The warm-up consisted of a 50-m jog, 50-m backward run, 25-m walking 

toe touch, 25 butt kickers, 25-m lateral shuffle, 10 body 

weight squats, 10 push-ups, and 10 burpees. Following 

the warm-up period, participants completed 6 combat 

proxy tasks in sequential order: maximum set of pullups, dead-lift, clean and press, 120-mm tank round lift 

and load, 155-mm artillery round lift and carry, and negotiating a 7-ft wall with a box lift. Specifically, participants were asked to execute as many full pull-ups (no 

kipping) as possible. The dead-lift drill required participants to complete one repetition of a set of progressively 

increasing weights: 60 lb, 70 lb, 80 lb, 95 lb, 115 lb, and 

135 lb. Similarly, the clean and press was performed in 

progression from 6 lifts of 65 lb to single lifts of 70 lb, 

80 lb, 95 lb, and 115 lb. If a participant could not lift a 

weight with proper technique and/or lock out the weight 

above their head, the lower weight was considered their 

maximal lift. The 120-mm (replica) tank round lift and 

load involved lifting and loading five 120-mm projectiles (replica rounds weighing 55 lb) in 35 seconds. The 

155-mm (replica) artillery round lift and carry consisted 

of picking up and carrying a 155-mm projectile (replica 

round weighing 95 lb) a distance of 50 m in 2 minutes. 

The final task required Marines to navigate a 7-ft obstacle course wall using a lower level entry (a 20-in assist 

box to standardize the 1-person or 2-person lift in a field 

environment), while wearing a fighting load (flak jacket 

with Small Arms Protective Insert plates).

One important note is in order regarding the use of pullups as a combat proxy task, despite its prominent use 

in the PFT for testing with male Marines: while pullups have been included as part of the combat proxy test 

set, the task has been treated in this article as akin to a 

component of the PFT, to facilitate direct comparison 

between men and women.

Anthropometrics and Aerobic Capacity

Height and weight were measured and body mass index (BMI) calculated as a function of height and weight. 

From this information, percent body fat was calculated 

using the Gallagher equation.3 Fat-free mass was then 

calculated for each individual. From these data, estimates of volume of oxygen consumption (VO2

max) were 

made for both men and women (AR, for “activity code” 

was set to 7, which is the code for estimated physical 

activity. On a coarse ordinal scale, “7” indicates “Run 

over 10 miles per week or spend over 3 hours per week 

in comparable physical activity”) 3-5:

For women, VO2max (ml/kg/min)=

45.628-(0.265×age)-(0.309×%fat)+(2.175×AR)-(0.044×%fat×AR)

For men, VO2max (ml/kg/min)=

47.820-(0.259×age)-(0.216×%fat)+(3.275×AR)-(0.082×%fat×AR)

Statistical Analysis

Descriptive statistics and results are presented as means 

and standard deviations. Performance scores (on the 

PFT and CFT) between Marines who passed the combat proxy tasks and those who failed were compared 

using t tests. In addition, the results in this study were 

also corroborated by the nonparametric equivalents of 

these tests (eg, Mann-Whitney U ), when concerns were 

raised about satisfaction of required parametric assumptions (eg, normality). The conclusions of the study are 

the same, regardless of the test type used.

As an index of overall combat readiness, the proportion 

of all combat proxy tasks that were successfully completed was computed (note: only the pass/fail combat 

proxy tasks were included in this overall measure, not 

the pull-ups task, which was treated as a predictor, not 

outcome variable). Bivariate correlation analyses (nonparametric rank correlation coefficient, Spearman’s ρ) 

were used to measure statistical dependence between 

variables. Spearman’s ρ is useful for describing monotonic trends between 2 variables when it is not appropriate to assume that the relationship is linear, which was 

the case with the measured variables in this study (eg, 

cut-off scores producing restricted ranges; non-normal 

distributions; a key outcome measure being a proportion 

of tasks successfully completed). Interpretation of magnitudes is similar to that of the Pearson product-moment 

correlation.

To facilitate comparison between sexes, overlapping 

density plots (ie, estimates of the underlying probability density function, using a Gaussian kernel) were 

constructed separately for men and women.6 Density 

plots represent the distribution of a variable and can 

be interpreted in way similar to histograms, however, 

the smoothed patterns of density plots better reveal 

the differences in performance between males and 

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females. All analyses were performed with SPSS 19.0 

(IBM Corp, Armonk, NY) and R (http://www.r-proj

ect.org/). The packages dplyr (http://cran.r-project.org/

web/packages/dplyr/index.html), ggplot2,7

 and scales (http://CRAN.R-project.org/package=scales) were employed 

for data preprocessing, visualization, 

and variable rescaling, respectively. 

The code used to generate the results is 

available upon request. Statistical significance was accepted when P<.05.

Results

Subjects

The sample comprised 788 Marines (409 

male, 379 female). Summaries of key 

demographic variables (eg, age, height, 

weight) as well as body composition 

estimates (eg, BMI, percentage fat, and 

VO2max) are presented in Table 1. Note 

that overall means for the body composition variables were not included, as 

the calculation of percentage fat and 

VO2max values were sex-dependent.

Fitness Tests

Descriptive statistics for the breakdown of the PFT and CFT, by overall 

score and by component task, are provided in Tables 

2A and 2B. Overall, men outperformed women on all 

component tasks; densities comparing performance are 

represented in Figures 1 and 2. Note that the pull-ups 

from the combat proxy testing were used as the basis 

of comparison, since both males and females completed 

the task. The component tasks of the PFT that do not 

admit direct comparison between males and females (ie, 

flexed-arm hang) have been excluded from the analysis.

Collectively, these data illustrate 2 key patterns: female scores tend to vary more than 

male scores, and men generally outperform 

women on the physical tasks. To illustrate this 

pattern more clearly, the measures associated 

with each physical fitness test (crunches, run, 

pull-ups, and the component CFT tasks) were 

rescaled into a range from 0 to 100; the mean of 

the rescaled test scores was then adopted as the 

measure of “overall performance” (scores for 

the timed events were reversed, before range 

rescaling, so that shorter duration times were 

translated into higher performance scores). The 

derived scale represents relative performance, 

anchored by the worst performer in the sample 

as a whole (a score of 0) and the best performer 

(a score of 100), with greater magnitudes reflecting better performance. The resulting density is provided in 

Figure 3.

Combat Proxy Tasks

Performance differences between men 

and women across all combat proxy 

tasks are shown in Figure 4A. Overall, there was a high rate of successful 

completion on the combat proxy tasks 

(men, ≈80% to 100%; women, ≈70% to 

100%), with the notable exception being 

the clean and press (men, 80%, women, 

9%). Given the low rate of completion, 

a breakdown of the clean and press task 

was conducted separately (Figure 4B).

Correlations

As expected, there were strong relationships between components of the PFT 

and CFT and the overall measure of 

combat readiness (Table 3A). The CFT 

tasks, in general, exhibited stronger 

relationships to combat readiness, as 

expected. Relationships between physical characteristics (eg, BMI, VO2max, 

fat-free mass) and the other physical 

tests, including the composite measure 

of overall mission readiness, were also relatively high, 

with fat-free mass performing particularly well as a predictor (Table 3B). All correlations were statistically significant at P<.01.

Comment

In general, men outperformed women on physical ability 

tasks and combat proxy tasks. However, this difference 

was most pronounced for those tasks requiring a significant upper body strength component (ie, clean and press, 

Table 1. Demographic Characteristics of Study Participants.*

Mean SD Min Max

Age (years)

Men 22 4.3 17 42

Women 22 4.6 17 39

All 22 4.4 17 42

Height (cm)

Men 175 6.8 147 196

Women 163 6.9 152 183

All 170 9.4 147 196

Weight (kg)

Men 76 12 51 108

Women 60 7.0 43 81

All 68 12 43 108

BMI (kg/cm2)

Men 24 3.0 17 33

Women 23 1.9 17 32

Body Fat (%)

Men 16 4.5 5.6 30

Women 25 2.8 17 40

VO2max (ml/kg/min)

Men 52 4.1 39 61

Women 39 2.3 30 45

*N=788 (men, n=409; women, n=379)

Table 2A. Physical Fitness Test Component Tasks.*

Mean SD Min Max

Crunches (repetitions)

Men 99 5 45 100

Women 94 11 48 100

All 96 8.85 45 100

3-Mile Run (seconds)

Men 1,282 115 994 1,729

Women 1,470 131 1,088 1,857

All 1,372 155 994 1,857

Pull-Ups (repetitions)

Men 16 6 2 33

Women 4 4 0 23

All 10 8 0 33

*N=788 (men, n=409; women, n=379)

Table 2B. Combat Fitness Test 

Component Tasks.*

Mean SD Min Max

Movement to Contact (seconds)

Men 173 15 132 233

Women 211 22 126 292

All 192 27 126 292

Maneuver Under Fire (seconds)

Men 145 18 108 235

Women 200 26 138 308

All 172 36 108 308

Ammo Can Lift (repetitions)

Men 97 10 55 125

Women 57 15 16 117

All 78 23 16 125

*N=788 (men, n=409; women, n=379)

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Figure 1. Comparison between men and women on the Physical Fitness Test (PFT) events: Crunches (A), 3-Mile Run (B), and 

Pull-ups (C). Data are presented as density plots, which are 

normalized representations of each distribution that facilitate 

comparison between samples differing in size. The dashed line 

in each plot represents the median performance of that group. 

Note that the Pull-ups event was tested along with the other 

combat proxy tasks and was not taken from the PFT proper, as 

it is the only version of pull-ups that enables direct comparison 

of men and women. Density

PFT Pull-ups (repetitions)

0

–– 10 – 20 30

–

0.05 –

0.10 –

0.15 –

0.00 –

Men

Women

C

Density

1000

–

–

1250 –

1500 1750–

0.001 –

0.002 –

0.003 –

0.000 –

Men

Women

B

Time (seconds)

PFT 3-Mile Run

Density

PFT Crunches (repetitions)

25

–

0

–– 50 – 75 100–

0.1 –

0.2 –

0.0 –

Men

Women

A

pull-ups). Thus, the most compelling finding is that upper body strength is a potential barrier to full integration 

of women into previously closed combat arms positions. 

How significant is this barrier? Can it be overcome? If 

it were an insurmountable barrier, we would expect few 

if any women to be capable of surpassing men in upper 

body strength. On the contrary, some women were able 

to perform well, or at least better, than many men. For 

example, 66 women outperformed the worst performing, lowest decile of male performers (subsample of 44 

men). The best performing female Marine completed 23 

pull-ups, a performance that exceeded 87% of all men 

tested.

In addition, as expected, there were strong relationships 

between performance on upper body tasks as well as 

between estimated body fat percentage and estimated 

VO2max, and various performance metrics. Indeed, the 

relative strength of the relationships between the derived measures of fat-free mass, VO2max, and the physical tasks is striking and in line with previous research 

in the military which suggests that aerobic performance 

is related to body fat.8,9

Additionally, increased body fat has been associated with 

poor performance in female Army Soldiers. Therefore, 

based on this current and past efforts, it can be suggested 

that body composition standards should be established 

in parallel with physical standards for individuals seeking a direct combat MOS. The fact that this study used 

previously established regression equations and gleaned 

such valuable information with so little effort suggests 

that they may serve as useful replacements when laboratory measures such as DEXA scan or VO2max testing are 

not available or practical.

These findings suggest that women who might be considered trained for overall fitness, as determined by existing, standardized fitness tests, are limited by upper 

body strength when it comes to lifting heavy objects. 

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Figure 2. Comparison between men and women on the Combat 

Fitness Test (CFT) events: Movement to Contact (A), Maneuver 

Under Fire (B), and Ammo Can Lift (C). Data are presented as 

density plots, which are normalized representations of each 

distribution that facilitate comparison between samples differing in size. The dashed line in each plot represents the median 

performance of that group. Density

Time (seconds)

CFT Movement to Contact

Men

Women

150

––

200 –

250 300–

0.01 –

0.02 –

0.00 –

A

Time (seconds)

CFT Maneuver Under Fire

Density

100

––

200 –

150 250 –300–

0.005 –

0.010 –

0.015 –

0.020 –

0.025 –

0.000 –

Women

Men

B

Density

Ammo Can Lift (repetitions)

25

–– 50 – 75 100–

125–

0.05 –

0.10 –

0.00 –

C

Men

Women

0

–

– 25 – 50 75–

100–

Density

Performance

Men

Women

0.00 –

0.02 –

0.04 –

Figure 3. Comparison between men and women on a derived measure of overall performance. The raw scores for 

crunches, run, pull-ups, and the component CFT tasks, 

were rescaled into a range from 0 to 100; the mean of the 

rescaled test scores was then adopted as the measure of 

“overall performance” (scores for the timed events were 

reversed, before range rescaling, so that shorter duration 

times were translated into higher performance scores). The 

derived scale represents relative performance, anchored by 

the worst performer in the sample as a whole (a score of 0) 

and the best performer (a score of 100), with greater magnitudes reflecting better performance. The dashed line in 

each plot represents the median performance of that group.

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It is important to note, however, that female Marines 

were not trained for these specific movements, and were 

likely not properly conditioned to perform these types 

of physical tasks. Thus, while the majority of women 

could be considered successful on most of the combat 

proxy tasks, the discrepancy in upper body strength 

may point to lack of conditioning, which could potentially be overcome with training.10,11 Previous studies 

have shown that women who are strength trained and/

or endurance trained can increase their performance on 

combat-related tasks.10-12 Specifically, pull-ups training 

has been shown to be effective at increasing the number 

of pull-ups completed by women, as well as improving 

overall upper body muscle endurance. This may translate to other upper body exercises, such as push-ups. 

In a separate Marine Corps study, a 12-week training 

program increased the number of women who could 

perform more than 3 pull-ups by 30%.15 In addition, the 

authors of the study concluded that pull-ups were a good 

indicator of upper body strength and that pull-up training may be the best way to increase upper body strength 

for female Marines. While women in this study were 

less successful than men in upper body strength tasks, 

existing literature suggests that, with proper training, 

women could increase their upper body strength and reduce the size of this gap.

In addition, an important question to address is whether 

PFT and CFT performances translate to performance on 

combat-related tasks. Specifically, Marines are currently 

required to complete both the PFT and CFT semiannually, and the results from those tests serve as markers 

of mission readiness. The question then becomes: Are 

these tests useful for achieving these aims? That is, do 

the PFT and CFT successfully distinguish those who 

are likely to perform well (physically) during combat? 

This consideration touches on the validity of the PFT 

and CFT—the extent to which the interpretations drawn 

from those tests are valid16 (ie, does successful PFT and 

CFT performance predict better combat performance?). 

A thorough investigation of test validity is a challenging 

and (potentially) indefinite endeavor, which is beyond 

the scope of the present study and is currently being addressed in a separate physical standards validation effort. Performance on the physical tasks in this study was 

limited to plausible occupational constraints (eg, particular weights, limited repetitions) and did not account for 

measuring maximum physical capacity. Thus, the resulting restricted range may underestimate the true validity 

of the PFT and CFT for predicting performance during 

combat. With this caveat in mind, one of the aims of this 

effort was to determine whether the PFT and CFT could 

be used as predictors of performance on combat proxy 

tasks. To what extent does the performance on one test 

indicate more successful performance on the other? In 

relation to the existing dataset, does better performance 

on the PFT and CFT translate to a more successful performance on the combat proxy tasks? Statistically, this 

question was addressed by separating women who were 

successful on the combat proxy tasks from those who 

were unsuccessful, and then examining their respective 

PFT and CFT scores as shown in Table 4. As expected, 

women who performed well on their semiannual physical fitness tests were more successful on combat proxy 

tasks. Also, a difference of 2 pull-ups separated successful from unsuccessful performers, with the exception of 

Figure 4. Comparison between men and women on Combat 

Proxy Tasks (A) and Clean and Press (B).

Combat Proxy Tasks

Proportion Successful Completion

Men

Women

0.25 –

0.50 –

0.75 –

1.00 –

0.00 – Clean & Press

115 lb

O-Course WallDead

Lift 155-mm

Round

120-mm

Round

A

Clean and Press

65 lb, 6 reps 70 lb, 1 rep 80 lb, 1 rep 95 lb, 1 rep 115 lb, 1 rep

Proportion Successful Completion 0.25 –

0.50 –

0.75 –

1.00 –

0.00 –

B

Men

Women

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the clean and press in which 5 pull-ups separated successful from unsuccessful performers. Further, a 20-second difference on the MANUF, which is a short burst 

aerobic activity, separated successful from unsuccessful performers. Not surprisingly, 3-mile run time was 

strongly related to performance on the MANUF. Additionally, those women were more aerobically fit (as indicated by a nearly 30 second difference in MANUF times) 

and were more successful on the most challenging clean 

and press weight. This finding is consistent with other 

studies demonstrating a strong relationship between fatfree mass, aerobic capacity, and overhead lifting.14,15 The 

results also provide evidence for a strong relationship 

between the PFT and CFT components tasks and overall 

mission readiness (Table 3A). In all, these results suggest 

that the PFT and CFT could serve as reliable indicators 

of performance on ground combat elements.

While the results provided in the study support reasonably strong conclusions, there are limitations that must 

be addressed. The primary limitation derived from 

necessary restrictions on allowable performance, constraints that were required due to the large population 

being sampled in a field environment. The resulting 

range restriction on performance scores likely underestimated the true population correlation coefficients. 

However, the goal of the study was simply to establish 

that the physical tests were good predictors of performance on combat-related tasks, which was amply demonstrated by the uncorrected correlations.

Another limitation concerned the high success rates of performance on most of the 

combat proxy tasks. Once a participant 

successfully completed a task, the test was 

terminated rather than allowing someone 

to reach their true maximum, as in the 

deadlift. In that task, there were no weights 

available above 135 lb, nor were the participants asked to complete as many repetitions 

as possible. Those weights were chosen 

to be reflective of actual occupational demands, and not to be unnecessarily taxing. 

If a more accurate picture of the 

maximum capabilities of Marines 

is required, additional, nonrestricted testing would be required. 

Similarly, at the time of this study, 

women did not perform pull-ups 

in the PFT (except for infrequent 

exceptions), and thus the pull-ups 

task tested during the combat 

proxy task was used as a replacement test to enable comparison between men and women. However, this decision 

means that the correlations computed in the study were 

measuring something closer to concurrent validity than 

predictive validity. In our opinion, these nuances are unlikely to matter as far as the practical decision to include 

pull-ups as an assessment instrument is concerned.

In conclusion, the key limiting factor for females is 

upper body strength and greater emphasis should be 

placed on developing this capability in female Marines 

if they intend to serve in closed combat arms positions. 

The results also suggest that the PFT and CFT serve as 

useful indicators of combat readiness. However, further 

study on unrestricted performance will likely shed light 

on the validity of the PFT and CFT as predictors of performance on combat-relevant tasks.

Acknowledgement

This study was supported by the US Marine Corps Training and Education Command, under work unit N1235. 

The research was conducted in compliance with all applicable federal regulations governing the protection of 

human subjects in research

References

1. Marine Corps Order 6100.13: Marine Corps Physical Fitness Test and Body Composition Program 

Manual [w/chng 2]. Washington, DC: Dept of the 

Navy; January 30, 2015. Available at: http://www.

marines.mil/Portals/59/Publications/MCO%20

6100.13%20CH%202.pdf. Accessed May 8, 2015.

Table 3A. Spearman Correlations Among the PFT and CFT Tasks, and Overall 

Mission Readiness.

Spearman's ρ Crunches 3-Mile

Run

MTC AL MANUF Overall Mission 

Readiness

Pull-ups 0.46 -0.66 -0.76 0.74 -0.76 0.75

Crunches -0.37 -0.43 0.43 -0.41 0.38

3-mile run 0.80 -0.63 0.74 -0.61

CFT MTC -0.75 0.83 -0.71

CFT AL -0.78 0.76

CFT MANUF -0.77

PFT indicates physical fitness test. CFT indicates combat fitness test. MTC indicates 

movement to contact. AL indicates ammunition can lift. MANUF indicates maneuver under 

fire.

Table 3B. Spearman Correlations Among Physical Characteristics and Physical Tasks.

Spearman’s ρ Pull-ups Crunches 3-Mile

Run

MTC AL MANUF Overall Mission 

Readiness

Height 0.53 0.29 -0.53 -0.62 0.68 -0.67 0.67

Weight 0.46 0.26 -0.44 -0.53 0.64 -0.61 0.68

BMI 0.20 0.10 -0.16 -0.20 0.34 -0.29 0.39

Body Fat % -0.63 -0.28 0.52 0.61 -0.59 0.61 -0.50

FFM 0.62 0.32 -0.57 -0.67 0.78 -0.75 0.77

VO2max 0.64 0.27 -0.55 -0.62 0.64 -0.64 0.56

MTC indicates movement to contact. AL indicates ammunition can lift. MANUF indicates maneuver under 

fire. FFM indicates fat-free mass.

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2. United States Marine Corps. A Concept for Functional Fitness. Quantico, VA: Marine Corps Combat Development Command; November 9, 2006. 

Available at: http://www.crossfit.com/journal/

library/USMCFunctionalFitnessConcept.pdf. Accessed October 20, 2014.

3. Gallagher D, Visser M, Sepulveda D, Pierson 

RN, Harris T, Heymsfield SB. How useful is body 

mass index for comparison of body fatness across 

age, sex and ethnic groups?. Am J Epidemiol. 

1996;143(3):228-239.

Combat Proxy Task PFT/CFT

Event Results

Outcome n Mean SD sig (P)

Clean & Press, 

115 lb

PFT Crunches

Pass 33 96 9 .19 Fail 346 93 11

PFT 3-mile Run (sec)

Pass 33 1,400 137 <.01 Fail 346 1,477 128

PFT Pull-ups

Pass 33 8 6 <.01 Fail 346 3 4

CFT Movement to Contact 

(sec)

Pass 33 194 19 <.01 Fail 345 213 21

CFT Ammunition Can Lift

Pass 33 68 16 <.01 Fail 345 56 14

CFT Maneuver Under Fire 

(sec)

Pass 33 174 23 <.01 Fail 345 203 25

120-mm Tank 

Round

Lift and Carry

PFT Crunches

Pass 309 94 11 .25 Fail 70 92 13

PFT 3-mile Run (sec)

Pass 309 1,457 130 <.01 Fail 70 1,526 119

PFT Pull-ups

Pass 309 4 4

<.01 Fail 70 2 3

CFT Movement to Contact 

(sec)

Pass 308 209 22 <.01 Fail 70 222 18

CFT Ammunition Can Lift

Pass 308 58 15 <.01 Fail 70 51 14

CFT Maneuver Under Fire 

(sec)

Pass 308 197 25 <.01 Fail 70 215 25

Combat Proxy Task PFT/CFT

Event Results

Outcome n Mean SD sig (P)

155-mm

Artillery Round

Lift and Carry

PFT Crunches

Pass 271 95 9 <.01 Fail 108 89 13

PFT 3-mile Run (sec)

Pass 271 1,446 133 <.01 Fail 108 1,531 102

PFT Pull-ups

Pass 271 4 5 <.01 Fail 108 2 2

CFT Movement to Contact 

(sec)

Pass 270 206 21 <.01 Fail 108 224 18

CFT Ammunition Can Lift

Pass 270 60 14 <.01 Fail 108 48 13

CFT Maneuver Under Fire 

(sec)

Pass 270 194 26 <.01 Fail 108 216 22

Obstacle

Course Wall

PFT Crunches

Pass 298 94 10 <.05 Fail 81 91 13

PFT 3-mile Run (sec)

Pass 298 1,455 129 <.01 Fail 81 1,525 120

PFT Pull-ups

Pass 298 4 4

<.01 Fail 81 2 2

CFT Movement to Contact 

(sec)

Pass 297 209 21 <.01 Fail 81 221 20

CFT Ammunition Can Lift

Pass 297 58 15 <.01 Fail 81 53 14

CFT Maneuver Under Fire 

(sec)

Pass 297 197 26 <.01 Fail 81 214 24

Table 4. Successes and Failures of Female Marines on Combat Proxy Tasks in Relation to Physical Fitness Test 

(PFT) and Combat Fitness Test (CFT) Scores (continued on next page).

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4. Jackson AS, Blair SN, Mahar MT, Wier LT, Ross 

RM, Stuteville JE. Prediction of functional aerobic 

capacity without exercise testing. Med Sci Sports 

Exerc. 1990;22(6):863-870.

5. Jackson AS, Beard EF, Wier LT, Ross RM, Stuteville JE, Blair SN. Changes in aerobic power 

in men, ages 25-70 yr. Med Sci Sports Exerc. 

1995;27(1):113-120.

6. Jackson AS, Wier LT, Ayers GW, Beard EF, Stuteville JE, Blair SN. Changes in aerobic power in 

women, ages 20-64 yr. Med Sci Sports Exerc. 

1996;28(7):884-891.

7. Wickham H. ggplot2: Elegant Graphics for 

Data Analysis (Use R!). New York, NY: Springer 

Science+Business Media, LLC; 2009.

8. Mikkola I, Keinänen-Kiukaanniemi S, Jokelainen 

J, Peitso A, Härkönen P, Timonen M, Ikäheimo T. 

Aerobic performance and body composition changes during military service. Scand J Prim Health 

Care: 2012;30(2):95-100.

9. Anderson MK, Grier T, Canham-Chervak M, 

Bushman TT, Jones BH. Risk factors associated 

with higher body fat in US Army female soldiers. 

US Army Med Dep J. April-June 2014:75-82.

10. Hendrickson NR, Sharp MA, Alemany JA, et 

al. Combined resistance and endurance training 

improves physical capacity and performance on 

tactical occupational tasks. Eur J Appl Physiol.

2010;109(6):1197-1208.

11. Kraemer WJ, Mazzetti SA, Nindl BC, et al. Effect 

of resistance training on women’s strength/power 

and occupational performances. Med Sci Sports 

Exerc. 2001;33(6):1011-1025.

12. Szivak TK, Kraemer WJ, Nindl BC, et al. Relationships of physical performance tests to military-relevant tasks in women. US Army Med Dep J. AprilJune 2014:20-26.

13. McGuire B, Vickers RR, Reynolds JH, Curry A, 

Bockelman T, Massimo R. Examination of Pullups and Push-ups as Possible Alternatives to the 

Flexed Arm Hang on the Marine Corps Physical Fitness Test. San Diego, CA: Naval Health 

Research Center; 2011. Technical Report No. 11-

21. Available at: http://oai.dtic.mil/oai/oai?verb=

getRecord&metadataPrefix=html&identifier=A

DA554498. Accessed March 2, 2015.

14. Jackson AS, Borg G, Zhang JJ, Laughery KR, 

Chen J. Role of physical work capacity and load 

weight on psychophysical lift ratings. Int J Ind Ergon. 1997;20(3):181-190.

15. Friedl KE. Body composition and military performance–many things to many people. J Strength 

Cond Res. 2012;26(suppl 2):S87-S100.

16. Kane MT. Validating the interpretations and uses 

of test scores. J Educ Meas. 2013;50(1):1-73.

Authors

Dr Jameson and Dr Kelly are with the Warfighter Performance Department of Operational Readiness, Naval 

Health Research Center, San Diego, California.

Mr Pappa and Mr McGuire are with the US Marine 

Corps Training and Education Command, Marine 

Corps Base, Quantico, Virginia.

Table 4 (continued). Successes and Failures of Female 

Marines on Combat Proxy Tasks in Relation to Physical Fitness Test (PFT) and Combat Fitness Test (CFT) 

Scores (continuation from previous page).

Combat Proxy Task PFT/CFT

Event Results

Outcome n Mean SD sig (P)

Deadlift

135 lb

PFT Crunches

Pass 368 94 11 .95 Fail 11 93 13

PFT 3-mile Run (sec)

Pass 368 1,467 130 <.01 Fail 11 1,586 103

PFT Pull-ups

Pass 368 4 4 <.01 Fail 11 2 2

CFT Movement to Contact 

(sec)

Pass 367 211 21 <.01 Fail 11 233 20

CFT Ammunition Can Lift

Pass 367 57 15 .20 Fail 11 52 12

CFT Maneuver Under Fire 

(sec)

Pass 367 200 26

<.01 Fail 11 221 21

THIS ARTICLE

RETRACTED BY AUTHORS

MAY 6, 2015
12 http://www.cs.amedd.army.mil/amedd_journal.aspx

Women have historically played an important role in the 

US military despite facing restrictions on unit assignment.1

 Since the repeal of the Direct Ground Combat 

and Assignment Rule, the US armed forces renewed focus on evaluation of women performing in previouslyrestricted military occupational specialties (MOSs) by 

assessing sex-neutral performance standards and training capabilities. Previous research demonstrated male 

and female athletes and military personnel possess different musculoskeletal, biomechanical, and physiological profiles 2-4 and suffer musculoskeletal injuries at differing rates and severity.5

 Physical, physiological, and 

musculoskeletal profiles of male and female military 

personnel are important to determine the potential for 

women to safely and successfully occupy newly-opened 

MOSs, and if modifiable risk factors for performance 

and injury can be addressed in sex-specific physical 

training programs.

Epidemiological research has explored injury rates, 

types, and causes in military personnel.5-9 Studies investigating nonbattle injuries sustained during deployment 

revealed female Soldiers had a significantly higher incidence of injury than male Soldiers.10,11 Other research 

indicated female Soldiers sustain a greater proportion 

of lower extremity and overuse injuries.6-8 Researchers 

Musculoskeletal, Biomechanical, and

 Physiological Gender Differences

 in the US Military

Katelyn F. Allison, PhD Takashi Nagai, PhD, ATC

Karen A. Keenan, PhD, ATC Jennifer Deluzio, MS

Timothy C. Sell, PhD, PT COL Mark McGrail, MC, USA

John P. Abt, PhD, ATC Scott M. Lephart, PhD

Abstract

The repeal of the Direct Ground Combat Assignment Rule has renewed focus on examining performance 

capabilities of female military personnel and their ability to occupy previously restricted military occupational 

specialties. Previous research has revealed female Soldiers suffer a greater proportion of musculoskeletal injuries 

compared to males, including a significantly higher proportion of lower extremity, knee, and overuse injuries. 

Potential differences may also exist in musculoskeletal, biomechanical, and physiological characteristics 

between male and female Soldiers requiring implementation of gender-specific training in order to mitigate 

injury risk and enhance performance.

Purpose: To examine differences in musculoskeletal, biomechanical, and physiological characteristics in male 

and female Soldiers.

Methods: A total of 406 101st Airborne Division (Air Assault) Soldiers (348 male; 58 female) participated. 

Subjects underwent testing for flexibility, isokinetic and isometric strength (percent body weight), single-leg 

balance, lower body biomechanics during a stop jump and drop landing, body composition, anaerobic power/

capacity, and aerobic capacity. Independent t tests assessed between-group comparisons.

Results: Women demonstrated significantly greater flexibility (P<.01-P<.001) and better balance (P≤.001) 

than men. Men demonstrated significantly greater strength (P≤.001), aerobic capacity (47.5±7.6 vs 40.3±5.4 

ml/kg/min, P<.001), anaerobic power (13.3±2.1 vs 9.5±1.7 W/kg, P<.001), and anaerobic capacity (7.8±1.0 

vs 6.1±0.8 W/kg, P<.001) and lower body fat (20.1±7.5 vs 26.7±5.7 (%BF), P<.001). Women demonstrated 

significantly greater hip flexion and knee valgus at initial contact during both the stop jump and drop landing 

tasks and greater knee flexion at initial contact during the drop landing task (P<.05-P<.001).

Conclusions: Gender differences exist in biomechanical, musculoskeletal, and physiological characteristics. 

Sex-specific interventions may aid in improving such characteristics to optimize physical readiness and 

decrease the injury risk during gender-neutral training, and decreasing between-sex variability in performance 

characteristics may result in enhanced overall unit readiness. Identification of sex-specific differences in injury 

patterns and characteristics should facilitate adjustments in training in order for both sexes to meet the genderneutral occupational demands for physically demanding military occupational specialties.
April – June 2015 13

reporting 50% of female Soldiers will sustain one or 

more injury, including stress fractures, by the end of 

Basic Combat Training, postulated the increased rate of 

injury in female Soldiers may be because female and 

male Soldiers of differing fitness levels participate in 

the same training.12 Although the reason(s) for sex differences in injury rates, types, and causes are unclear, 

they may result from sex differences in physical, physiological, and musculoskeletal characteristics and differences in training intensity during basic combat training, 

daily physical training, and deployment.

Previous research evaluating requirements for physically-demanding jobs, like lifting, carrying, pushing/

pulling loads, and basic soldiering tasks, identified 

components of fitness necessary for safe and successful completion of these tasks, including strength, power, 

endurance, mobility, and flexibility.13,14 It is well known 

that female Soldiers, on average, possess less absolute 

strength and force generating capacity, less endurance 

and higher fatigability during repetitive tasks, and less 

aerobic capacity than male Soldiers.14 Studies investigating movement patterns of military personnel also 

demonstrated significant sex differences in parachute 

landing techniques that may contribute to ACL injury 

risk,15,16 which is important in airborne units. Sex disparities in physical, physiological, and musculoskeletal 

characteristics should be examined further in contemporary military populations to determine the capability 

of women to safely and successfully perform strenuous 

occupational tasks and to reduce performance gaps between sexes.

The purpose of this study was to investigate potential 

sex differences across a comprehensive set of physical, physiological, musculoskeletal, and biomechanical 

characteristics within a modern military population. It 

was hypothesized that male and female Soldiers would 

display significantly different physical, physiological, 

musculoskeletal, and biomechanical profiles. If differences in characteristics are identified, targeted, genderspecific physical training may increase overall force 

readiness and resiliency, especially as women are integrated into previously restricted MOSs.

Materials and Methods

Subjects

A total of 406 Soldiers (348 male, 58 female) of the 

101st Airborne Division (Air Assault) at Fort Campbell, Kentucky, participated in this study. Demographic information is presented in Table 1. Subjects 

are a subset of subjects enrolled in the Human Performance and Injury Prevention Initiative (Eagle Tactical Athlete Program) 6-step model derived from the 

public health model of injury prevention and control.9,17

All subjects met the following criteria: 18 to 45 years of 

age and no current medical or musculoskeletal conditions that prevented full active duty. Human protection 

for the current study was approved by the appropriate 

civilian and military institutional review boards. Written informed consent was obtained from each subject 

prior to participation in this study.

Procedures

Testing occurred over 2 days (approximately one week 

apart) at the University of Pittsburgh Human Performance Research Center (Fort Campbell). Each session 

lasted 2 hours. Testing was performed bilaterally where 

applicable; only right-sided data is presented, as no between side differences were noted.

A standard goniometer or digital inclinometer was 

used to measure passive range of motion of the shoulder, hip, and knee (flexion) and active range of motion 

of the knee (extension) and ankle.18 Reliability of these 

measurements has been previously established.19,20 Hip 

flexion was assessed in the supine position with the 

knee flexed while hip extension and knee flexion were 

assessed in the prone position. Shoulder flexion, abduction, and internal and external rotation were assessed in 

the supine position. Shoulder extension was assessed in 

the prone position. Posterior shoulder tightness was also 

assessed passively in the supine position. Active range 

of motion was used to assess hamstring flexibility at the 

knee with the active knee extension test and to assess 

gastrocnemius-soleus flexibility at the ankle with active 

dorsiflexion with the knee straight. The Biodex MultiJoint System 3 Pro (Biodex Medical Systems, Inc, Shirley, NY) measured active torso range of motion, with 

the subject seated and actively rotating in the right and 

left directions.

The Biodex Multi-Joint System 3 Pro measured shoulder 

internal/external rotation, shoulder abduction/adduction, 

hip abduction/adduction, knee flexion/extension, ankle 

plantarflexion/dorsiflexion, and torso rotation strength. 

The reliability of isokinetic strength testing has been 

previously established for peak torque/body weight 

(intraclass correlation coefficient [ICC]=0.73-0.97).21

For shoulder, knee, and torso strength testing, subjects 

Table 1. Subject Demographics

Men Women P

Value n Mean ±SD n Mean ±SD

Age (years) 348 28.06 6.63 58 26.72 5.48 .147

Height (m)a 348 1.77 0.07 58 1.65 0.06 <.001

Weight (kg)a 348 83.48 12.57 58 64.93 9.90 <.001

aStatistically significant difference between men and women (P<.05).
14 http://www.cs.amedd.army.mil/amedd_journal.aspx

performed 3 practice trials at 50% maximum effort followed by 3 more at 100% effort. Following a rest period 

of 60 seconds, 5 repetitions of reciprocal concentric isokinetic testing were performed at 60° per second. Hip 

abduction/adduction was assessed isometrically in a 

sidelying, neutral hip position. Subjects performed 3 sets 

of 5-second isometric contractions, alternating between 

hip abduction and adduction. Ankle plantarflexion/dorsiflexion was assessed isometrically in a seated position 

with the knee and hip at 90°. Subjects performed 3 sets 

of 5-second isometric contractions, alternating between 

plantarflexion and dorsiflexion.

A hand held dynamometer (Lafayette Instrument Company, Lafayette, IN) assessed ankle inversion and eversion strength. Strength measured via hand held dynamometry has been demonstrated to be reliable for ankle 

inversion and eversion (ICC=0.84-0.86 and ICC=0.74-

0.85, respectively) 22,23 and is a valid measurement of ankle strength.22-24 Ankle inversion and eversion strength 

was tested with the subject long-sitting with the foot and 

ankle off the end of the table.

A single force plate (Kistler 9286A, Amherst, NY), with 

a sampling frequency of 100 Hz, measured balance. 

Three, 10 second trials of single-leg standing balance 

were performed with subjects barefooted with their 

hands on their hips, with eyes opened and eyes closed 

conditions based on Goldie et al.25,26 This protocol was 

previously demonstrated valid and reliable.20,25-27 Trials were discarded and recollected if the subject’s nonstance leg hit the stance limb or the ground outside of 

the force plate. Subjects were permitted to briefly touch 

down on the force plate with their non-stance leg and 

immediately lift the leg back into test position.

A portable metabolic system (OxyCon Mobile, Viasys, 

Yorba Linda, CA) and lactate analyzer (Arkray, Inc, 

Kyoto, Japan) captured maximal oxygen consumption 

(VO2max) and lactate threshold during an incremental 

ramp protocol. The OxyCon Mobile has been demonstrated as a valid metabolic system with less than 3% 

difference compared to simulated VO2 during a maximal cardiopulmonary exercise test.28 Following a 5-minute warm-up, the test was performed in 3-minute stages, 

with the initial at 0% grade and each subsequent stage 

increased by 2.5% grade until exhaustion (cardiovascular or peripheral inhibition). Speed was set at 70% of 

each subject’s 2-mile run time during the Army Physical Fitness Test and remained constant throughout the 

test. Blood samples were obtained via a finger prick during the last minute of each stage prior to an increase in 

incline in order to assess blood lactate levels. Heart rate 

(Polar USA, Lake Success, NY) and VO2 were collected 

and monitored continuously throughout the test. Relative VO2max, maximum heart rate, VO2 at lactate threshold, percent of VO2max at lactate threshold, heart rate at 

lactate threshold, and percentage of maximum heart rate 

at lactate threshold were reported.

An electromagnetic cycle ergometer (RacerMate, Inc, 

Seattle, WA) measured anaerobic power and capacity during a Wingate protocol,29 which has been previously demonstrated as a highly valid and reliable test of 

these variables.30 Following a warm-up at a self-selected 

cadence at 125 watts, the 50-second protocol was performed: 15 seconds maintaining 100 RPM at 125 W 

with minimal resistance; 5 seconds sprinting to generate 

maximum speed prior to initiation of normalized resistance; and 30 seconds attempting to sprint and maintain maximal speed against the normalized resistance. 

Braking torque was standardized to 9% and 7.5% body 

weight for men and women, respectively.

The Bod Pod Body Composition System (Life Measurement Instruments, Concord, CA) assessed body composition, which has previously demonstrated reliability 

(ICC=0.98, SEM=0.47% BF) 21 and validity.31 Men wore 

spandex shorts and a swim cap while women wore spandex shorts, a sports bra, and swim cap. Once 2 consistent body volume measurements were obtained, percent 

body fat was calculated using predicted lung volume 

and the appropriate body densitometry equation; body 

mass index (BMI) was also calculated.

Six high-speed cameras (Vicon, Centennial, CO) with 

200 Hz sampling frequency captured biomechanical 

data during an athletic task (stop jump task) and functional landing task (drop landing task). Following Vicon’s Plug-in-Gait model, 16 retro-reflective markers 

were affixed to the anterior superior iliac spine, posterior superior iliac spines lateral thigh, lateral femoral 

condyle, lateral lower leg, lateral malleous, posterior 

calcaneus, and head of the second metatarsal. Appropriate anthropometrics were measured with an anthropometer (Lafayette Instrument, Lafayette, IN). A static trial 

in an anatomical neutral position captured a baseline 

for joint angle calculations. The accuracy and validity 

of the Plug-in Gait model have been previously established.32-34 The stop jump task was a standing broad 

jump, initiated from a normalized distance of 40% of 

the subject’s height, followed immediately (after landing 

on the force plates) by a maximal effort vertical jump. 

The drop landing was initiated by subjects leaning forward while standing on a standardized, 0.51 meter high 

platform, allowing gravity to drive the drop movement, 

followed by landing with one foot on each of the force 

plates (1200 Hz).

MUSCULOSKELETAL, BIOMECHANICAL, AND PHYSIOLOGICAL

GENDER DIFFERENCES IN THE US MILITARY
April – June 2015 15

THE ARMY MEDICAL DEPARTMENT JOURNAL

Data Processing and Reduction

Flexibility/range of motion and handheld dynamometer strength measures were averaged across 3 trials. 

Strength obtained with The Biodex dynamometer was 

reported as the peak average torque across 5 trials normalized to each subject’s individual body mass.

For VO2max data, a 15-second moving window was used 

to filter metabolic data in order to reduce the overall 

breath-by-breath data points. Maximal oxygen uptake 

was calculated as the highest consecutive oxygen uptake levels over one minute of data collection relative 

to body mass. Lactate threshold was identified by the 

inflection point when blood lactate levels increased by 

one mmol/L or more between stages. Anaerobic power output was identified as the peak power within the 

first 5 seconds of the test following resistance initiation, 

while anaerobic capacity was calculated as 

the mean power output over the 30 seconds 

of the test following resistance initiation normalized to body mass.

For both balance and biomechanical data, 

force plate data were passed through an amplifier and analog to a digital board (DT3010, 

Digital Translation, Marlboro, MA) and 

stored on a personal computer. A custom 

MATLAB Version 7.0.4 (MathWorks, Inc, 

Natick, MA) script processed ground reaction force data. For eyes opened and eyes 

closed balance conditions, the standard deviation for the ground reaction forces for each 

direction (anterior-posterior, medial-lateral, 

vertical) was calculated and then averaged 

across all 3 trials. Prior to calculation of joint kinematics, 

the Vicon Nexus software reconstructed 3-dimensional 

trajectories of the reflective markers, and smoothed with 

a general cross-validation Woltring filter. Trajectories of 

hip, knee, and ankle joint centers were estimated based 

on marker locations and anthropometric parameters according to Vicon’s Plug-in Gait model. Joint kinematics including the following variables were calculated for 

the stop jump and drop landing tasks: hip flexion and 

abduction angles at initial contact, knee flexion and valgus/varus angles at initial contact, and maximum knee 

flexion angle. The maximum vertical ground reaction 

force was identified for each trial. Data were averaged 

across the 3 trials prior to analysis.

Statistical Analysis

All variables were assessed for normality and frequency 

distribution. The mean and standard deviation were calculated for each of the variables included in the study. 

All variables were analyzed with independent t tests to 

examine potential sex differences. An alpha level of 0.05 

was chosen a priori to denote statistical significance for 

comparisons. Statistical analyses were performed with 

IBM SPSS Statistics Version 19.0 (IBM Corp, Armonk, 

NY).

Results

Range of motion and flexibility data are presented in 

Table 2. Female Soldiers demonstrated significantly 

greater shoulder extension, abduction, and external rotation range of motion and hip extension and knee flexion. Female Soldiers had significantly lower values for 

active knee extension, indicating significantly better 

hamstring flexibility than male Soldiers. Female Soldiers also had significantly more range of motion for the 

posterior shoulder tightness test, indicating less posterior shoulder tightness than male Soldiers.

Strength data are presented in Table 3. Female Soldiers 

demonstrated significantly weaker shoulder internal and 

external rotation and shoulder abduction and adduction. 

Shoulder internal/external rotation strength ratio was 

significantly higher in female Soldiers. Knee flexion 

and extension, ankle inversion, eversion, and dorsiflexion and torso rotation were significantly lower in female 

Soldiers.

Balance data are presented in Table 4. Male Soldiers 

demonstrated significantly higher anterior/posterior, 

medial/lateral, and vertical scores bilaterally, under both 

eyes open and eyes closed conditions. Higher scores 

represent poor balance.

Physiology data are presented in Table 5. Female Soldiers demonstrated significantly higher BMI and body 

fat percentage. Male Soldiers had significantly higher 

anaerobic power, anaerobic capacity, VO2max, and VO2

at lactate threshold.

Table 2. Range of Motion and Flexibility (in degrees)

Men Women P

Value n Mean ±SD n Mean ±SD

Shoulder Flexion 160 187.2 7.3 35 188.0 14.7 .636

Shoulder Extensiona 338 70.8 13.3 56 83.6 9.8 <.001

Shoulder Abductiona 159 206.1 9.5 34 211.8 8.8 .002

Shoulder External Rotationa 340 109.9 13.2 57 120.3 16.8 <.001

Shoulder Internal Rotation 340 58.5 10.6 57 59.9 11.6 .399

Posterior Shoulder Tightnessa 299 102.4 9.7 52 108.7 7.5 <.001

Knee Flexiona 156 143.1 6.6 33 148.5 5.9 <.001

Active Knee Extensiona 340 18.8 9.4 57 11.4 7.9 <.001

Hip Flexion 170 133.1 7.1 35 135.8 16.9 .126

Hip Extensiona 340 29.3 8.0 56 33.9 7.3 <.001

Calf Flexibility 340 15.9 6.8 57 15.1 5.4 .399

Torso Rotation 341 70.4 11.0 57 72.7 11.5 .147

aStatistically significant difference between men and women (P<.05).
16 http://www.cs.amedd.army.mil/amedd_journal.aspx

Biomechanical data are presented in Table 6 for the stopjump task and vertical drop 

landing. Female Soldiers demonstrated significantly greater 

hip flexion at initial contact 

and greater knee valgus at 

initial contact during both the 

stop jump and drop landing 

tasks. Female Soldiers demonstrated significantly greater 

knee flexion at initial contact 

during the drop landing task.

Comment

The elimination of the Direct 

Ground Combat and Assignment Rule and the potential 

for an increased number of 

female service members in 

combat arms warrants examination of potential sex 

differences that may result 

in decreased performance 

and increased injury risk depending on occupational task 

requirements. The purpose 

of this study was to assess 

musculoskeletal, biomechanical, and physiological differences between sexes in 

a modern military population. Significant betweensex differences were found in Soldiers of the 101st 

Airborne Division (Air Assault) in range of motion 

and flexibility, strength, static balance, physiology, 

and biomechanics. However, within-sex variability 

of characteristics and specific occupational task requirements should be considered when determining 

individual job-specific performance capabilities and 

injury risk.

Male Soldiers demonstrated significantly less range 

of motion and flexibility in both lower and upper extremities compared to female Soldiers. Previous research demonstrated deficits in range of motion or flexibility increase risk of acute and overuse musculoskeletal injuries,35-39 while high or excessive flexibility has 

also been demonstrated to increase the risk of musculoskeletal injury.7

 A previous study identified Australian 

footballers with greater than 27° of knee flexion during 

active knee extension were almost 3 times more likely 

to sustain a hamstring strain (RR=2.8; 95% CI, 0.9-8.5). 

However, both men and women in the current study 

were, on average, well below this threshold.40 Men with 

first and third tertiles for hamstring flexibility assessed 

with the sit-and-reach test were at more than 2 times the 

risk to sustain a time-loss injury during basic combat 

training than those in the middle tertile.7 No such relationship was seen in women in basic combat training. 

Other researchers demonstrated decreased knee flexion 

and quadriceps flexibility increase the risk of quadriceps muscle injury, patellofemoral pain syndrome, and 

patellar tendinitis.37-39 Similarly, subjects with shoulder 

instability and impingement demonstrated deficits in 

shoulder range of motion.41 However, due to methodological differences in testing positions and the use of 

Table 4. Single-leg Balance: Variability (SD) in Ground Reaction 

Forces (N)

Men Women P

Value n Mean ±SD n Mean ±SD

Eyes Open

 Anterior/Posteriora 267 2.78 0.86 51 2.02 0.55 <.001

 Medial/Laterala 266 3.44 1.16 51 2.43 0.96 <.001

 Verticala 267 4.65 2.19 51 3.18 1.34 <.001

Eyes Closed

 Anterior/Posteriora 267 6.44 2.66 51 4.43 1.77 <.001

 Medial/Laterala 266 10.11 4.57 51 6.15 2.39 <.001

 Verticala 267 14.53 12.22 51 8.61 5.52 .001

aStatistically significant difference between men and women (P<.05).

Table 3. Strength

Men Women P

Value n Mean ±SD n Mean ±SD

Shoulder Strength

 Internal Rotation (%BW)a 334 59.6 15.5 57 36.3 8.5 <.001

 External Rotation (%BW)a 334 42.1 8.8 57 29.9 5.1 <.001

Internal/External Strength Ratioa 334 0.73 0.14 57 0.85 0.20 <.001

 Abduction (%BW)a 169 78.1 15.2 24 55.3 6.7 <.001

 Adduction (%BW)a 169 83.1 25.5 24 55.7 16.2 <.001

Abduction/Addubction Strength Ratio 169 1.00 0.30 24 1.16 0.87 .077

Knee Strength

 Flexion (%BW)a 334 114.8 27.1 57 93.0 21.1 <.001

 Extension (%BW)a 334 236.1 48.0 57 191.3 37.2 <.001

Flexion/Extension Strength Ratio 334 0.49 0.09 57 0.49 0.06 1.000

Hip Strength

 Abduction (%BW) 169 167.3 34.2 24 158.8 32.9 .254

 Adduction (%BW) 169 148.1 35.8 24 139.5 30.4 .264

Abduction/Adduction Strength Ratio 169 0.89 0.18 24 0.89 0.19 1.000

Ankle Strength

 Plantar Flexion (%BW) 150 133.6 45.9 22 120.9 44.9 .226

 Dorsiflexion (%BW)a 150 45.4 10.2 22 37.40 8.1 .001

Plantar Flexion/Dorsiflexion Strength Ratio 150 3.06 1.20 22 3.44 1.59 .186

 Inversion Strength (kg) a 335 34.4 7.2 57 24.9 6.7 <.001

 Eversion Strength (kg) a 335 30.5 6.7 57 22.2 5.9 <.001

Inversion/Eversion Strength Ratio 335 1.15 0.19 57 1.13 0.21 .470

Torso Strength

 Rotation (%BW)a 340 145.1 33.1 57 110.5 32.9 <.001

aStatistically significant difference between men and women (P<.05).

BW indicates body weight.

MUSCULOSKELETAL, BIOMECHANICAL, AND PHYSIOLOGICAL

GENDER DIFFERENCES IN THE US MILITARY
April – June 2015 17

THE ARMY MEDICAL DEPARTMENT JOURNAL

pathological populations in these studies, comparisons 

cannot be made between the results from these studies 

and those in the current study. Further, no threshold for 

increased injury risk was reported in any of these studies. Based on this previous research and current findings, 

it may be beneficial for Soldiers, regardless of sex, with 

less flexibility/range of motion to incorporate flexibility 

exercises into training to decrease injury risk. Future 

research should investigate if such thresholds exist (and 

if they are gender-specific) using the methods in the current study, which are representative of typical goniometric measures obtained in clinical settings.

Female Soldiers demonstrated strength deficits compared to men even after normalization to body mass. Yet, 

in the US Army, male and female Soldiers may be called 

upon to perform the same occupational tasks. Strength 

differences may put female Soldiers at increased risk of 

unintentional musculoskeletal injury while performing 

the duties required of their positions. 

Additionally, since women generally use a greater percentage of their 

absolute strength than males during 

high intensity repetitive tasks, they 

are more likely to fatigue earlier,14

and may be at higher injury risk due 

to compensated technique. Previous 

research revealed targeted resistance 

training programs result in increased 

performance on military specific 

tasks and reduce gender disparity in 

strength and occupational lifting/carrying tasks,42,43 indicating these programs and subsequent adaptations are 

beneficial in increasing the proportion of women able to 

successfully perform physically demanding jobs.

Lower extremity strength deficits may contribute to increased injury risk. Weak hamstrings have been demonstrated to increase the risk of hamstring strain.44 Lower 

hamstring to quadriceps ratios, falling below the optimal range of 0.60 to 0.90, increases the risk of hamstring 

strain and injury to the lower leg.44,45 Although there was 

no significant difference between men and women in 

hamstring to quadriceps ratio, both demonstrated ratios 

(0.49 to 0.50) well below the ratios recommended for decreased injury risk. This may indicate training for both 

men and women should be adjusted to increase hamstring strength while maintaining quadriceps strength in 

order to achieve more favorable ratios. Female Soldiers 

possess less ankle dorsiflexion, inversion, and eversion 

strength than male Soldiers. Individuals with less ankle strength may be at increased risk for ankle sprains, 

chronic ankle instability, and 

other lower leg injuries,46-49

so targeted programs may be 

beneficial for any Soldier with 

less ankle strength in order to 

reduce injury risk.

Female Soldiers demonstrated 

significantly weaker shoulder 

and torso musculature than 

male Soldiers. Tasks identified 

in Soldiers with physicallydemanding MOSs (lifting/lowering, carrying/load bearing, 

pulling) each rely heavily on 

upper body and core strength. 

Individuals with shoulder instability and shoulder impingement have demonstrated deficits 

in shoulder strength.41 Studies 

Table 6. Biomechanical Analysis

Men Women P

Value n Mean ±SD n Mean ±SD

Stop-Jump Task

 Hip Flexion at Initial Contact (°)a 259 42.37 11.26 49 45.87 11.74 .048

 Hip Abduction at Initial Contact (°) 259 -3.70 4.07 49 -2.58 3.48 .072

 Knee Flexion at Initial Contact (°) 259 25.79 8.02 49 26.82 7.73 .408

 Knee Varus/Valgus at Initial Contact (°)a,b 259 4.58 6.25 49 -1.36 5.58 <.001

 Maximum Knee Flexion (°) 259 91.98 13.97 49 89.41 13.40 .236

 Maximal Vertical GRF (%BW) 258 205.28 56.32 49 201.64 63.88 .685

Vertical Drop Landing

 Hip Flexion at Initial Contact (°)a 237 19.4 7.3 50 23.6 6.7 <.001

 Hip Abduction at Initial Contact (°) 237 -3.7 3.4 50 -2.7 4.0 .068

 Knee Flexion at Initial Contact (°)a 237 17.9 6.1 50 20.1 6.4 .022

 Knee Varus/Valgus at Initial Contact (°)a,b 237 2.8 5.0 50 -0.5 4.4 <.001

 Maximum Knee Flexion (°) 237 86.7 18.9 50 90.5 14.0 .264

 Maximal Vertical GRF (%BW) 236 365.3 98.4 50 359.2 92.3 .688

aStatistically significant difference between men and women (P<.05).

bNegative value indicates valgus.

Table 5. Physiology

Men Women P

Value n Mean ±SD n Mean ±SD

Body Mass Index (kg/m2)a 347 23.0 2.9 58 24.0 3.1 .017

Body Fat (%)a 338 20.1 7.5 57 26.7 5.7 <.001

Anaerobic Power (watts/kg)a 326 13.3 2.1 56 9.5 1.7 <.001

Anaerobic Capacity (watts/kg)a 326 7.8 1.0 55 6.1 0.8 <.001

VO2 Max (mL/kg/min)a 322 47.5 7.6 54 40.3 5.4 <.001

VO2 at Lactate Threshold (mL/kg/min)a 320 39.0 7.0 54 33.5 5.5 <.001

VO2% at Lactate Threshold 320 81.8 10.3 54 82.2 14.0 .803

HR Max (bpm) 322 188.6 14.2 53 188.9 9.6 .882

HR at Lactate Threshold (bpm) 319 169.4 15.3 53 171.4 12.1 .366

HR% at Lactate Threshold 319 89.6 7.2 53 91.0 5.2 .176

aStatistically significant difference between men and women (P<.05).
18 http://www.cs.amedd.army.mil/amedd_journal.aspx

in civilians and in the workplace have associated low 

torso rotation strength with low back pain.50,51 Soldiers 

with lower levels of strength may benefit from increasing 

upper body and torso strength in an attempt to decrease 

injury risk and increase performance capabilities.

Previous research demonstrated female Soldiers possess less absolute strength than males. However, data 

revealed some women are stronger than some men, and 

strength overlap is increased when strength is normalized for body mass and fat-free body mass.14 This evidence suggests the ability to produce a muscle force is 

similar between sexes, but differences in quantity of 

muscle mass between males and females limits the absolute amount of force able to be generated.14 In the current 

study, while female Soldiers, on average, possess less 

strength than male Soldiers, examination of individual 

variability among strength characteristics revealed the 

top performing women possess similar or better strength 

characteristics than the bottom performing men, indicating a potential strength capability overlap. Specifically, when assessed by percentiles, the top 25th percentile of women demonstrated greater shoulder strength 

than the bottom 10th percentile of men and better knee 

and torso strength than the bottom 25th percentile of 

men. The top 25th percentile of women demonstrated 

greater ankle plantar- and dorsiflexion than the bottom 

50% of men, and the top 10th percentile of women demonstrated greater ankle inversion and eversion strength 

than the bottom 50% of men. Therefore, individual variability should be considered when assessing capabilities 

of male and female Soldiers to safely and successfully 

perform tactical activities. Strength overlaps should be 

interpreted with caution, as strength in the current study 

is normalized to body weight, and absolute strength sex 

overlaps are likely more conservative.

Male Soldiers demonstrated worse static balance than 

female Soldiers. Balance plays an important role in 

athletic and tactical tasks by providing a stable base 

of support and enhancing overall joint stability, especially with unstable surfaces or unexpected perturbations. Prospective studies demonstrated athletes with 

increased postural sway in the anterior/posterior and 

medial/lateral directions have increased risk of sustaining an ankle injury.52-54 Female Soldiers may possess 

better balance, because, on average, the center of gravity/center of mass is lower than in male Soldiers. However, previous research revealed men tend to have better 

balance as the difficulty of the balance task increases, 

like during tasks involving dynamic postural stability.55

Further research is warranted to investigate sex differences in postural control during more challenging tactical tasks and maneuvers.

Male Soldiers demonstrated significantly higher anaerobic power and capacity. These characteristics are reflective of the ability to perform quick burst activity and to 

sustain that performance for a period of time. By participating in training targeting anaerobic components of 

fitness, female Soldiers will be able to sprint faster and 

maintain a higher intensity longer. A limitation of the 

current study is the braking torque applied during the 

Wingate test differed for male and female Soldiers, so 

results must be interpreted with caution, and may differ 

compared to what would have been demonstrated with 

uniform braking torque.

Male Soldiers also had higher VO2max and VO2 at lactate threshold in the current study. Previous research 

postulated women may have reduced aerobic capacity 

because they carry less fat-free mass and a greater percentage of nonmetabolic (fat) tissue, have a lower oxygen carrying capacity, and possess a decreased cardiac 

output compared to males.14,56 While VO2max is largely 

based these factors, in addition to genetics and age, it 

can be positively affected by training. Perhaps more importantly, the point at which lactate threshold occurs is 

more readily influenced by training. If lactate threshold 

occurs at a higher percentage of maximal oxygen consumption, then an individual will be able to train at a 

higher intensity for a longer period of time. Individuals who train to enhance lactate threshold may be able 

to perform physical activity longer and at a higher intensity, thereby potentially improving performance and 

maximizing operational readiness. Overall, increasing 

cardiovascular fitness and anaerobic threshold may play 

a role in mitigating onset of fatigue and reducing risk of 

unintentional, musculoskeletal injuries.

When anaerobic and aerobic data was assessed by percentiles to investigate variance within sex, an overlap of 

capabilities was revealed. While considering the limitation of different braking torques, the top 25th percentile 

of women demonstrated better anaerobic power and capacity than the bottom 10th percentile of men. The top 

25th percentile of women demonstrated better aerobic 

capacity than the bottom 25th percentile of men. The 

top 50% of women demonstrated a higher lactate threshold (%VO2max) than the bottom 25th percentile of men. 

Therefore, physiological capabilities must be assessed 

on an individual level when determining job-specific 

injury risk and performance capabilities.

Female Soldiers demonstrated significantly higher BMI 

and body fat percentage than male Soldiers, similar 

to previous findings that female Soldiers possess 20% 

less overall body mass, 10% greater body fat, and 30% 

less muscle mass than their male counterparts.57 Since 

MUSCULOSKELETAL, BIOMECHANICAL, AND PHYSIOLOGICAL

GENDER DIFFERENCES IN THE US MILITARY
April – June 2015 19

THE ARMY MEDICAL DEPARTMENT JOURNAL

fat-free mass is positively correlated with maximum 

muscular strength, and body fat is negatively correlated 

with aerobic capacity,57,58 body composition plays an 

important role in force generating capacity and performance capability. Previous retrospective research found 

higher BMI is associated with increased injury risk, 

including plantar fasciitis and ankle sprain.59,60 Higher 

body mass and BMI are prospectively demonstrated risk 

factors of injury to the low back and lower extremity in 

a military population.61 Soldiers with lower (BMI<18 

kg/m2) and higher BMI (BMI>33 kg/m2) had higher 

rates of medical and all-cause discharges compared to 

those classified into the median category (BMI=24.0-

24.9 kg/m2) during the first year of enlistment, suggesting Soldiers with a normal/average body composition 

are least likely to sustain an injury.62 Soldiers with body 

fat percentages considered to be too high or too low may 

benefit from nutritional and physical training programs 

designed to optimize body composition to reduce injury 

risk, enhance performance, and augment health/longevity, but an appropriate range of body fat for male and 

female Soldiers should be assessed separately.

Biomechanical differences were found between male 

and female Soldiers during both the stop-jump and 

the vertical drop landing. Women tended to land with 

greater hip flexion and knee valgus at initial contact during both tasks. During the drop landing, women landed 

with increased knee flexion at initial contact, similar to 

previous research in the athletic population revealing 

sex differences in cutting, stopping, and jumping maneuvers.2,27,63-65 Prospective research found individuals 

who land with greater knee valgus are at increased risk 

of anterior cruciate ligament injury.66 Subjects with injury to the anterior cruciate ligament land with increased 

hip flexion compared to controls; similar increases have 

been noted in fatigued subjects.67-69 Insufficient muscular strength and endurance may play a role in the increased hip flexion and knee valgus demonstrated by 

female Soldiers. Poor landing mechanics may be a function of these deficits coupled with a lack of training in 

proper landing mechanics. Previous research demonstrated training programs that address both strength and 

landing mechanics are able to improve landing biomechanics and reduce the injury risk.70

A limitation of the current study is the uneven distribution of male and female Soldiers available for analysis. 

However, the percentage of female Soldiers in the current study (≈14.3%) mirrors the approximate distribution 

of female Soldiers in the US Army (≈13.6%).13 Another 

limitation is that job-specific tasks were not assessed 

in the current study. Future research should assess the 

performance of specific occupational tasks, especially 

those unique to ground combat units.

Conclusion

The current study demonstrated female Soldiers are significantly different from male Soldiers across a majority 

of physical, physiological, and musculoskeletal characteristics. Targeted training may be beneficial in order to 

address the sex-specific differences and to induce adaptions specific to job task requirements. While both male 

and female Soldiers possess the capability to perform 

physically-demanding job requirements, on average, female Soldiers possessed lower strength, power, endurance, and worse body composition and biomechanics 

than male Soldiers. Therefore, progressive, periodized 

programs designed to enhance these characteristics in 

female Soldiers may increase the proportion of women 

capable of safely and successfully performing job tasks 

and reduce the sex disparity evidenced in the current 

study. At the same time, within-sex variability of characteristics demonstrating the highest performing women possess comparable or better strength, anaerobic, and 

aerobic characteristics than the lowest performing men 

suggests military personnel should be evaluated on an 

individual (gender neutral) basis to determine performance capabilities, injury risk, and targeted program 

implementation. Overall, targeted, sex-specific training 

adaptations may be critical to improving overall forcewide safety, efficiency, and tactical preparedness, especially as female Soldiers are integrated into ground 

combat positions.

Acknowledgement

This work was supported by the US Army Medical Research and Materiel Command under Award No. W81XWH-06-2-0070/W81XWH-09-2-0095, W81XWH-11-2-

0097.

References

1. Sharp MA. Physical fitness and occupational 

performance of women in the US Army. Work. 

1994;4(2):80-92.

2. Lephart SM, Ferris CM, Riemann BL, Myers JB, 

Fu FH. Gender differences in strength and lower 

extremity kinematics during landing. Clin Orthop 

Relat Res. 2002(401):162-169.

3. Ford KR, Myer GD, Hewett TE. Valgus knee motion during landing in high school female and 

male basketball players. Med Sci Sports Exerc. 

2003;35(10):1745-1750.

4. Lephart SM, Smoliga JM, Myers JB, Sell TC, Tsai 

YS. An eight-week golf-specific exercise program 

improves physical characteristics, swing mechanics, and golf performance in recreational golfers. J 

Strength Cond Res. 2007;21(3):860-869.
20 http://www.cs.amedd.army.mil/amedd_journal.aspx

5. Tiesman H, Peek-Asa C, Zwerling C, Sprince N, 

Amoroso P. Occupational and non-occupational injuries in the United States Army: focus on gender. 

Am J Prev Med. 2007;33(6):464-470.

6. Knapik JJ, Jones SB, Darakjy S, et al. Injury rates 

and injury risk factors among US Army wheel vehicle mechanics. Mil Med. 2007;172(9):988-996.

7. Knapik JJ, Sharp MA, Canham-Chervak M, 

Hauret K, Patton JF, Jones BH. Risk factors for 

training-related injuries among men and women 

in basic combat training. Med Sci Sports Exerc. 

2001;33(6):946-954.

8. Lovalekar M, Sell TC, Nagai T, House A, Pederson J, Lephart SM. Comparison of self-reported 

musculoskeletal injury history between female 

and male US Army Soldiers. Paper presented at: 

American Public Health Association 139th Annual 

Meeting and Exposition; October 29-November 2, 

2011; Washington, DC.

9. Sell T, Abt J, Crawford K, et al. Warrior model for 

human performance and injury prevention: Eagle 

Tactical Athlete Program (ETAP) Part I. J Spec 

Oper Med. 2010;10(4):2-21.

10. Roy TC, Knapik JJ, Ritland BM, Murphy N, Sharp 

MA. Risk factors for musculoskeletal injuries for 

soldiers deployed to Afghanistan. Aviat Space Environ Med. 2012;83(11):1060-1066.

11. Skeehan CD, Tribble DR, Sanders JW, Putnam 

SD, Armstrong AW, Riddle MS. Nonbattle injury 

among deployed troops: an epidemiologic study. 

Mil Med. 2009;174(12):1256-1262.

12. Friedl K, Evans R, Moran D. Stress fracture and 

military medical readiness: bridging basic and applied research. Med Sci Sports Exerc. 2008;40(suppl 

11):S609-S622.

13. Sauers SE, Scofield DE. Strength and conditioning strategies for females in the military. Strength 

Cond J. 2014;36(3):1-7.

14. Sharp MA. Physical Fitness, Physical Training and 

Occupational Performance of Men and Women in 

the US Army: A Review of Literature. Natick, MA: 

US Army Research Institute of Environmental 

Medicine; July 1993. Report No. TN93-7. Available 

at: http://www.dtic.mil/dtic/tr/fulltext/u2/a266297.

pdf. Accessed March 10, 2015.

15. Beutler A, Sarah J, Marshall S, Padua D, Boden B. 

Muscle strength and qualitative jump-landing differences in male and female military cadets: The 

jump-ACL study. J Sports Sci Med. 2009;8:663-671.

16. Niu W, Wang Y, He Y, Fan Y, Zhao Q. Biomechanical gender differences of the ankle joint during simulated half-squat parachute landing. Aviat 

Space Environ Med. 2010;81(8):761-767.

17. Abt J, Sell T, Crawford K, et al. Warior model for 

human performance and injury prevention: Eagle 

Tactical Athlete Program (ETAP) Part II. J Spec 

Oper Med. 2010;10(4):22-33.

18. Norkin CC, White DJ. Measurement of Joint Motion: A Guide to Goniometry. 3rd ed. Philadelphia, 

PA: FA Davis; 2003.

19. Myers JB, Oyama S, Wassinger CA, et al. Reliability, precision, accuracy, and validity of posterior 

shoulder tightness assessment in overhead athletes. 

Am J Sports Med. 2007;35(11):1922-1930.

20. Sell TC, Tsai Y-S, Smoliga JM, Myers JB, Lephart 

SM. Strength, flexibility, and balance characteristics of highly proficient golfers. J Strength Cond Res. 

2007;21(4):1166-1171.

21. Crawford K, Fleishman K, Abt JP, et al. Less body 

fat improves physical and physiological performance in army soldiers. Mil Med. 2011;176(1):35-43.

22. Kelln BM, McKeon PO, Gontkof LM, Hertel J. 

Hand-held dynamometry: reliability of lower extremity muscle testing in healthy, physically active, 

young adults. J Sport Rehabil. 2008;17(2):160-170.

23. Spink M, Fotoohabadi M, Menz H. Foot and ankle 

strength assessment using hand-held dynamometry: reliability and age-related differences. Gerontology. 2009.

24. Wang CY, Olson SL, Protas EJ. Test-retest strength 

reliability: hand-held dynamometry in community-dwelling elderly fallers. Arch Phys Med Rehab. 

2002;83(6):811-815.

25. Goldie PA, Bach TM, Evans OM. Force platform measures for evaluating postural control: 

reliability and validity. Arch Phys Med Rehab. 

1989;70(7):510-517.

26. Goldie PA, Evans OM, Bach TM. Steadiness in 

one-legged stance: development of a reliable forceplatform testing procedure. Arch Phys Med Rehabil. 

1992;73(4):348-354.

27. Sell TC, Ferris CM, Abt JP, et al. Predictors of 

proximal tibia anterior shear force during a vertical stop‐jump. J Orthop Res. 2007;25(12):1589-1597.

28. Attinger A, Tuller C, Souren T, Tamm M, Schindler 

C, Brutsche MH. Feasibility of mobile cardiopulmonary exercise testing. Swiss Med Wkly. 

2006;136(1-2):13-18.

29. Smith J, Hill D. Contribution of energy systems 

during a Wingate power test. Br J Sports Med. 

1991;25(4):196-199.

30. Bar-Or O. The Wingate anaerobic test an update on 

methodology, reliability and validity. Sports Med. 

1987;4(6):381-394.

MUSCULOSKELETAL, BIOMECHANICAL, AND PHYSIOLOGICAL

GENDER DIFFERENCES IN THE US MILITARY
April – June 2015 21

THE ARMY MEDICAL DEPARTMENT JOURNAL

31. Vescovi JD, Zimmerman SL, Miller WC, Hildebrandt L, Hammer RL, Fernhall B. Evaluation of the 

BOD POD for estimating percentage body fat in a 

heterogeneous group of adult humans. Eur J Appl 

Physiol. 2001;85(3-4):326-332.

32. Bell AL, Pedersen DR, Brand RA. A comparison 

of the accuracy of several hip center location prediction methods. J Biomech. 1990;23(6):617-621.

33. Davis III RB, Ounpuu S, Tyburski D, Gage JR. A 

gait analysis data collection and reduction technique. Hum Mov Sci. 1991;10(5):575-587.

34. Kadaba MP, Ramakrishnan H, Wootten M. Measurement of lower extremity kinematics during 

level walking. J Orthop Res. 1990;8(3):383-392.

35. Kaufman KR, Brodine SK, Shaffer RA, Johnson 

CW, Cullison TR. The effect of foot structure and 

range of motion on musculoskeletal overuse injuries. Am J Sports Med. 1999;27(5):585-593.

36. Pope R, Herbert R, Kirwan J. Effects of ankle 

dorsiflexion range and pre-exercise calf muscle 

stretching on injury risk in Army recruits. Aust J 

Physiother. 1998;44(3):165-172.

37. Witvrouw E, Bellemans J, Lysens R, Danneels L, 

Cambier D. Intrinsic risk factors for the development of patellar tendinitis in an athletic population. 

A two-year prospective study. Am J Sports Med. 

2001;29(2):190-195.

38. Witvrouw E, Danneels L, Asselman P, D’Have T, 

Cambier D. Muscle flexibility as a risk factor for 

developing muscle injuries in male professional 

soccer players. A prospective study. Am J Sports 

Med. 2003;31(1):41-46.

39. Witvrouw E, Lysens R, Bellemans J, Cambier D, 

Vanderstraeten G. Intrinsic risk factors for the development of anterior knee pain in an athletic population. A two-year prospective study. Am J Sports 

Med. 2000;28(4):480-489.

40. Gabbe BJ, Bennell KL, Finch CF, Wajswelner H, 

Orchard JW. Predictors of hamstring injury at the 

elite level of Australian football. Scand J Med Sci 

Sports. 2006;16(1):7-13.

41. Warner JJ, Micheli LJ, Arslanian LE, Kennedy 

J, Kennedy R. Patterns of flexibility, laxity, and 

strength in normal shoulders and shoulders with 

instability and impingement. Am J Sports Med. 

1990;18(4):366-375.

42. Kraemer WJ, Mazzetti SA, Nindl BC, et al. Effect 

of resistance training on women’s strength/power 

and occupational performances. Med Sci Sports 

Exerc. 2001;33(6):1011-1025.

43. Harman E, Frykman P, Palmer C, Lammi E, Reynolds K. Effects of a Specifically Designed Physical 

Conditioning Program on the Load Carriage and 

Lifting Performance of Female Soldiers. Natick, 

MA: US Army Research Institute of Environmental Medicine; November 1997. Report No. 

T98-1. Available at: http://oai.dtic.mil/oai/oai?ver

b=getRecord&metadataPrefix=html&identifier=A

DA333437. Accessed March 10, 2015.

44. Yeung SS, Suen AM, Yeung EW. A prospective 

cohort study of hamstring injuries in competitive 

sprinters: preseason muscle imbalance as a possible 

risk factor. Br J Sports Med. 2009;43(8):589-594.

45. Knapik JJ, Bauman CL, Jones BH, Harris JM, 

Vaughan L. Preseason strength and flexibility imbalances associated with athletic injuries in 

female collegiate athletes. Am J Sports Med. 

1991;19(1):76-81.

46. Arnold B, Linens S, Sarah J, Ross S. Concentric evertor strength differences and functional 

ankle instability: a meta-analysis. J Athl Train. 

2009;44(6):653-662.

47. Baumhauer J, Alosa D, Renstrom P, Trevino S, 

Beynnon B. A prospective study of ankle injury 

risk factors. Am J Sports Med. 1995;23(5):564-570.

48. Pontaga I. Ankle joint evertor-invertor muscle 

torque ratio decrease due to recurrent lateral 

ligament sprains. Clin Biomech (Bristol, Avon).

2004;19(7):760-762.

49. Willems T, Witvrouw E, Verstuyft J, Vaes P, De 

Clercq D. Proprioception and muscle strength in 

subjects with a history of ankle sprains and chronic 

instability. J Athl Train. 2002;37(4):487-493.

50. Lee JH, Ooi Y, Nakamura K. Measurement of 

muscle strength of the trunk and the lower extremities in subjects with history of low back pain. Spine 

(Phila Pa 1976). 1995;20(18):1994-1996.

51. Mandell PJ, Weitz E, Bernstein JI, et al. Isokinetic 

trunk strength and lifting strength measures. Differences and similarities between low-back-injured 

and noninjured workers. Spine (Phila Pa 1976). 

1993;18(16):2491-2501.

52. McGuine TA, Greene JJ, Best T, Leverson G. 

Balance as a predictor of ankle injuries in high 

school basketball players. Clin J Sport Med. 

2000;10(4):239-244.

53. Trojian TH, McKeag DB. Single leg balance test 

to identify risk of ankle sprains. Br J Sports Med. 

2006;40(7):610-613.

54. Wang HK, Chen CH, Shiang TY, Jan MH, Lin 

KH. Risk-factor analysis of high school basketballplayer ankle injuries: A prospective controlled 

cohort study evaluating postural sway, ankle 

strength, and flexibility. Arch Phys Med Rehabil. 

2006;87(6):821-825.
22 http://www.cs.amedd.army.mil/amedd_journal.aspx

55. Wikstrom EA, Tillman MD, Kline KJ, Borsa PA. 

Gender and limb differences in dynamic postural stability during landing. Clin J Sport Med. 

2006;16(4):311-315.

56. Wells CL. Women, Sport, & Performance: A Physiological Perspective. 2nd ed. Champaign, IL: Human Kinetics Books; 1991.

57. Fitzgerald PI, Vogel JA, Daniels WL, et al. The 

Body Composition Project: A Summary Report and 

Descriptive Data. Natick, MA: US Army Research 

Institute of Environmental Medicine; December 

1986. Report No. T 5/87. Available at: http://www.

dtic.mil/dtic/tr/fulltext/u2/a177679.pdf. Accessed 

March 10, 2015.

58. Teves MA, Vogel JA, Carlson DE, Schnakenberg 

DD. Body Composition and Muscle Performance 

Aspects of the 1985 CFFS Test. Natick, MA: US 

Army Research Institute of Environmental Medicine; April 1986. Report No. T12/86. Available at: 

http://oai.dtic.mil/oai/oai?verb=getRecord&metad

ataPrefix=html&identifier=ADA172752. Accessed 

March 10, 2015.

59. Riddle DL, Pulisic M, Pidcoe P, Johnson RE. Risk 

factors for Plantar fasciitis: A matched case-control 

study. J Bone Joint Surg Am. 2003;85-A(5):872-877.

60. McHugh MP, Tyler TF, Tetro DT, Mullaney MJ, 

Nicholas SJ. Risk factors for noncontact ankle 

sprains in high school athletes: the role of hip 

strength and balance ability. Am J Sports Med. 

2006;34(3):464-470.

61. Reynolds K, Cosio-Lima L, Bovill M, Tharion W, 

Williams J, Hodges T. A comparison of injuries, 

limited-duty days, and injury risk factors in infantry, artillery, construction engineers, and special 

forces soldiers. Mil Med. 2009;174(7):702-708.

62. Packnett ER, Niebuhr DW, Bedno SA, Cowan DN. 

Body mass index, medical qualification status, and 

discharge during the first year of US Army service. 

Am J Clin Nutr. 2011;93(3):608-614.

63. Benjaminse A, Habu A, Sell TC, et al. Fatigue alters lower extremity kinematics during a single-leg 

stop-jump task. Knee Surg Sports Traumatol Arthrosc. 2008;16(4):400-407.

64. Rozzi SL, Lephart SM, Gear WS, Fu FH. Knee 

joint laxity and neuromuscular characteristics of 

male and female soccer and basketball players. Am 

J Sports Med. 1999;27(3):312-319.

65. Sell TC, Ferris CM, Abt JP, et al. The effect of 

direction and reaction on the neuromuscular and 

biomechanical characteristics of the knee during 

tasks that simulate the noncontact anterior cruciate ligament injury mechanism. Am J Sports Med. 

2006;34(1):43-54.

66. Hewett TE, Myer GD, Ford KR, et al. Biomechanical measures of neuromuscular control and valgus 

loading of the knee predict anterior cruciate ligament injury risk in female athletes: a prospective 

study. Am J Sports Med. 2005;33(4):492-501.

67. Boden BP, Torg JS, Knowles SB, Hewett TE. Video analysis of anterior cruciate ligament injury: 

abnormalities in hip and ankle kinematics. Am J 

Sports Med. 2009;37(2):252-259.

68. Jacobs CA, Uhl TL, Mattacola CG, Shapiro R, 

Rayens WS. Hip abductor function and lower extremity landing kinematics: sex differences. J Athl 

Train. 2007;42(1):76-83.

69. Kernozek TW, Torry MR, Iwasaki M. Gender differences in lower extremity landing mechanics 

caused by neuromuscular fatigue. Am J Sports Med. 

2008;36(3):554-565.

70. Lephart SM, Abt JP, Ferris CM, et al. Neuromuscular and biomechanical characteristic 

changes in high school athletes: a plyometric versus basic resistance program. Br J Sports Med. 

2005;39(12):932-938.

Authors

Dr Allison, Dr Keenan, Dr Sell, Dr Abt, Dr Nagai, and 

Ms Deluzio are with the Neuromuscular Research Laboratory of the Department of Sports Medicine and Nutrition, University of Pittsburgh, Pittsburgh, Pennsylvania.

COL McGrail is with the Blanchfield Army Community 

Hospital, Fort Campbell, Kentucky.

Dr Lephart is with the College of Health Sciences, University of Kentucky, Lexington, Kentucky.

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GENDER DIFFERENCES IN THE US MILITARY
April – June 2015 23

As combat arms occupations become available to women, 

adequate muscular strength and aerobic endurance will 

be essential for the completion of physically demanding, 

job-related tasks. The Army Physical Readiness Training Manual (Field Manual 7-22)1

 provides guidance on 

developing strength, endurance, and mobility among 

Soldiers. However, the Physical Readiness Training system is performed in groups and may not always meet the 

needs of an individual Soldier’s personal fitness goals 

or objectives. Therefore, in addition to Army Physical 

Readiness Training, Soldiers will often engage in their 

own personal physical fitness training programs.

The ultimate goal of physical training is to improve occupational or physical performance. In an attempt to optimize training goals, the frequency, intensity, and duration of workouts can be manipulated over time. However, 

performing too much of one activity, exercising too long, 

and improper technique can result in both overuse and 

traumatic injury. Therefore in an attempt to minimize 

The Effects of Cross-Training on

 Fitness and Injury in Women

Tyson Grier, MS

Michelle Canham-Chervak, PhD

Morgan K. Anderson, MPH, CPH

Timothy T. Bushman, MS

Bruce H. Jones, MD, MPH

Abstract

Background: As combat arms occupations become available to women, adequate muscular strength and aerobic 

endurance will be essential for the completion of physically demanding job-related tasks. Therefore, in addition to 

US Army Physical Readiness Training, Soldiers will often engage in their own personal physical fitness training 

programs.

Purpose: To evaluate fitness and injury outcomes for women participating in personal cross-training programs 

compared to women performing one mode of training or having no personal fitness program.

Methods: Demographics, physical training activities, physical fitness, and injuries were obtained from surveys administered to female Soldiers in an infantry division. Women were categorized into the following 4 groups based on 

their personal physical fitness program: cross-training (CT), running only (R), weight training only (WT), and no 

personal fitness program (NPF). An ANOVA was used to compare physical training, health behaviors, and physical 

fitness across groups. A χ2 test was used to compare injury rates between fitness programs. Risk (%), risk ratios (RR) 

and 95% confidence intervals (95% CI) were used to determine injury risk.

Results: A total of 620 women completed the survey and indicated whether or not they had a personal fitness program (cross-training, n=260; running only, n=93; weight training only, n=86; no personal fitness program, n=181). 

Average age and body mass index was 26.2±5.8 years and 24.5±3.3 kg/m2 respectively with no differences between 

the 4 fitness groups. The cross-training group had higher physical performance on the muscular endurance (pushups and sit-ups) portion of the Army physical fitness test (APFT) when compared to the 3 other groups (CT 42 pushups vs (R 38, WT 35, NPF 36)); (CT 68 sit-ups vs (R 63, WT 62, NPF 62)). For the aerobic endurance (2-mile run) 

portion of the APFT, the cross-training group had higher performance when compared to those with no personal 

fitness program (CT 17.4 minutes vs NPF 18.5 minutes). Overall, 53% of female Soldiers sustained an injury over 

a 12-month period. All injury rates and lower extremity injury rates among women with a cross-training personal 

fitness program were not different from the other personal fitness programs. Those performing cross-training were 

2.6 and 2.1 times more likely to experience a running related injury when compared to those in the weight training 

and no personal fitness group, respectively. On the other hand, women performing cross-training were 65% less 

likely to experience a lifting/moving heavy objects related injury when compared to the weight training only group.

Conclusions: Women who participated in a cross-training program for personal physical fitness training had higher 

muscular endurance compared to the other fitness groups and higher aerobic endurance when compared to the no 

personal fitness group. There were no differences for all injuries and lower body injuries between cross-training and 

other fitness programs. Cross-training may be the best option for improving physical fitness when compared to just 

one mode of fitness training.
24 http://www.cs.amedd.army.mil/amedd_journal.aspx

injuries and improve or maintain performance, some 

athletes have tried cross-training.2-6 Cross-training is 

defined as training for more than one sport simultaneously, or training for several different components of fitness such as endurance, strength, and flexibility.7

Previous studies investigating cross-training type programs have found that performance remains similar or 

improves with the addition of a different training component.2-5 As part of a study investigating female distance 

runners, 50% of running training volume was substituted with cycling. They found no change in VO2max

and concluded that aerobic performance was adequately 

maintained in the running/cycling group when compared to the running only group.3

 In an investigation of 

competitive swimmers, the intervention group (performing both strength and endurance training) improved their 

land strength, tethered swimming force and 400 meter 

freestyle performance when compared to the control 

group (endurance training only).2 It has also been shown 

that 60 minutes of cross-training (combined aerobic and 

resistance training) results in improved state anxiety or 

mental health 10 minutes after exercising,8 whereas acute 

bouts of resistance training have resulted in no reductions9

 or delayed reductions occurring at 180 minutes.10

Single mode training such as aerobic or resistance training has also been shown to improve occupational and fitness performance.11-16 The purpose of this investigation 

was to evaluate fitness and injury outcomes for women 

participating in personal cross-training programs (more 

than one mode of training) compared to women performing one mode of training or having no personal fitness program.

Methods

Population

The population consisted of 620 female Soldiers within 

3 light infantry brigades. Each brigade consisted of 6 

battalions/regiments including a special troops battalion, 

a cavalry regiment, an armor regiment, an infantry regiment (1 brigade had 2 infantry regiments and no 

armor regiment), a field artillery regiment and a 

brigade support battalion. Rosters of unit members were requested and obtained through the 

S-1 offices. Roster information included name, 

sex, rank and battalion.

Survey

Surveys were administered between 2010 and 

2011. The surveys were used to collect information from the Soldiers about personal characteristics, physical training, performance on their 

most recent Army physical fitness test (APFT), 

and injuries occurring within the last 12 months. Women who indicated that they performed strength training, 

distance running or sprinting/interval training once or 

more a week as part of their personal physical fitness 

program were considered as having participated in these 

personal fitness programs. Women who indicated that 

they performed personal strength training, distance running or sprinting/interval training less than once a week 

or not at all were considered as not participating in these 

fitness programs. Based on their personal fitness programs, the women were then categorized into a crosstraining group, running only group, weight training only 

group, and no personal fitness program group (Table 1).

Army Physical Fitness Test

Performance on the APFT was used as a measure of 

physical fitness. Soldiers’ most recent APFT scores were 

obtained from the survey. High correlations have been 

shown between unit records and self-reported APFT 

scores.17 The APFT consisted of 3 events: a 2 minute 

maximal effort push-up event, a 2 minute maximal effort sit-up event, and a 2-mile run for time. Events were 

performed in accordance with instructions contained in 

Field Manual 7-22.

1

 Predicted VO2max was estimated 

from 2-mile run times using the following equation: predicted VO2max = 72.9-(1.77×(2-mile run time)).18

Data Analysis

The application SPSS 19.0 (IBM Corp, Armonk, New 

York) was used for statistical analysis. Frequencies and 

percent distribution were calculated for categorical variables such as age groups, military occupational specialty, body mass index (BMI) level, etc, as shown in Table 

2. Means and SD were calculated for continuous variables such as age in years, weight, height, miles run per 

week, 2-mile run times in minutes, number of push-ups, 

etc, shown in Table 3. The BMI (weight in kilograms 

divided by height in meters squared (kg/m2)) was categorized according to the Centers for Disease Control 

and Prevention classifications for underweight, normal, 

overweight, and obese.19

THE EFFECTS OF CROSS-TRAINING ON FITNESS AND INJURY IN WOMEN

Table 1. Fitness Group Categories Defined by Physical Training Activities.

Personal Fitness

Training Program 

WT, RUN, 

ST

WT,

RUN

WT,

ST

RUN,

ST

RUN WT NPF

Cross-Training   

Running Only  

Weight Training Only 

No Personal Fitness Program 

WT: Performed weight training as part of a personal physical training program one or 

more times a week.

RUN: Performed distance running (1 mile or more) as part of a personal physical 

training program one or more times a week.

ST: Performed sprinting/interval training as part of a personal physical training 

program one or more times a week.

NPF: Reported no personal fitness program.
April – June 2015 25

THE ARMY MEDICAL DEPARTMENT JOURNAL

A χ2 test was used to compare injury rates between fitness 

programs. Injury rates were calculated for all (overall) 

injuries, lower extremity injuries, and upper extremity 

injuries. An ANOVA was used to compare descriptive 

statistics, physical training, and physical fitness. A post 

hoc Tukey test was used to look for specific interactions. 

An independent t test was used to determine any differences in miles run per week. For injury cause, risks (%) 

of injury and risk ratios with 95% confidence intervals 

(95% CI) were calculated for different risk factors.

Results

The average age of the female Soldiers was 26.2±5.8 

years with an average BMI of 24.5±3.3 kg/m2. A majority of the Soldiers were of ranks E4 and E5, in a combat 

services support role, and had a normal BMI. A majority of the Soldiers reported participating in personal 

and unit distance running, personal strength training, 

and unit sprint/interval training one or more times per 

week. Less than half of the Soldiers reported participating in unit resistance training, agility training, and 

personal sprint/interval training one or more times 

per week. As shown in Table 2, 42% of the women 

were classified as performing cross-training for personal fitness, with 15% having a running only program, 14% having a weight training only program, 

and 29% with no personal fitness program.

Age, height, weight, and BMI were similar among participants of the various personal fitness programs. The 

cross-training group was different from the running 

group in that they ran more miles per week during personal fitness training. The cross-training group also 

performed more push-ups and sit-ups on their APFT 

compared to the other 3 groups. The cross-training 

group had better performance and higher estimated 

VO2max times for the APFT 2-mile run compared to 

the no personal fitness program group (Table 3).

Overall, 53% of female Soldiers sustained an injury 

over a 12-month period. Table 4 displays injury rates 

by personal fitness training program. All injury rates 

and lower extremity injury rates among women with a 

cross-training personal fitness program were not different from the other personal fitness programs. Women with a cross-training personal fitness program had 

a lower risk of upper extremity injury when compared 

to the weight training only program. The running only 

and no personal fitness program groups also had lower 

injury rates than the weight training only group for 

both all injuries and upper extremity injuries.

Table 5 displays the activities associated with injuries 

for women participating in the cross-training and running only programs. There were no statistically significant differences in injury risk by activity between the 2 

groups.

Table 6 displays the activities associated with injuries 

for women participating in a cross-training and weight 

training only programs. The comparison of injury incidence by fitness program showed women performing 

cross-training were more likely to experience a running related injury when compared to women performing weight training only. However, women performing 

weight training only were more likely to experience a 

lifting/moving heavy objects related injury in comparison to women performing cross-training.

Table 2. Personal Characteristics, Physical Fitness Activities, 

and Fitness Training Group Categories Among Women in 3 Light 

Infantry Brigades (N=620).

Variable Subcategory of Variable n % N

Age (years)

18-22 178 29%

23-27 255 41%

≥28 184 30%

Body Mass Index

<18.5 kg/m2 (underweight) 15 3%

18.5-24.9 kg/m2 (normal) 332 54%

25-29 kg/m2 (overweight) 237 39%

30+ kg/m2 (obese) 28 5%

Rank

E1-E3 138 23%

E4-E5 357 58%

E6-E9 55 9%

Officer/Warrant Officer 64 10%

Military Occupational 

Specialty

Combat Support 176 30%

Combat Services Support 429 70%

Brigade

Infantry brigade A 196 32%

Infantry brigade B 253 41%

Infantry brigade C 171 28%

Unit Distance Running

None 178 30%

≥1 time per week 423 70%

Unit Strength Training None/<1 time per week 417 69%

≥1 time per week 186 31%

Unit Sprinting/Interval 

Training

None/<1 time per week 198 33%

≥1 time per week 407 67%

Unit Agility Training None/<1 time per week 392 65%

≥1 time per week 208 35%

Personal Distance Running None/<1 time per week 298 48%

≥1 time per week 322 52%

Personal Strength Training None/<1 time per week 274 44%

≥1 time per week 346 56%

Personal Sprinting/Interval 

Training

None/<1 time per week 390 63%

≥1 time per week 174 37%

Fitness Training Group

Cross-Training 260 42%

Running Only 93 15%

Weight Training Only 86 14%

No Personal Fitness Training 181 29%
26 http://www.cs.amedd.army.mil/amedd_journal.aspx

Table 7 displays the activities associated with injuries 

for women participating in a cross-training program 

and women with no personal fitness training program. 

The comparison of injury incidence by fitness program 

showed women performing cross-training were more 

likely to experience a running related injury when compared to women with no fitness training program. However, women with no fitness program were more likely 

to experience a walking, hiking, or marching with no 

load injury in comparison to the cross-training group.

Comment

This analysis assessed fitness and injury outcomes for 

women with personal cross-training programs compared to women performing only one mode of personal 

fitness training (running only or weight training only) 

or having no personal fitness program. Women with 

a cross-training program had greater 

muscular endurance as measured by 

performance on APFT push-up and situp tests compared to women with other types of personal fitness programs. 

Women who participated in cross-training also had a higher estimated VO2max

as measured by APFT run time performance compared to women with no 

personal fitness program. There were 

no differences for all injuries and lower 

body injuries between cross-training 

and the other programs. However, the 

cross-training group had a lower risk of upper body injury when compared to the weight training only group.

An examination of activities associated with injury 

showed women with a cross-training program were 

more than twice as likely to experience a running related 

injury when compared to women with a personal fitness 

program focused on weight training only and women 

with no personal fitness program. However, women with 

no fitness program or just a weight training program 

were twice as likely to experience a walking, hiking, or 

marching with no load injury, and were almost 3 times 

as likely to experience a lifting/moving heavy objects related injury when compared to the cross-training group.

Higher muscular and aerobic endurance have been demonstrated in other studies of cross-training programs. 

THE EFFECTS OF CROSS-TRAINING ON FITNESS AND INJURY IN WOMEN

Table 3. Personal Characteristics, Physical Training, and Physical Fitness Performance Averages by Personal Fitness Training 

Program.

Variables Cross-Training Running Only Weight

Training Only

No Personal

Fitness Program

ANOVA ANOVA With Tukey 

(Specific Interactions)

Age (years) 25.8±5.5

(n=259)

26.6±6.4

(n=93)

27.3±6.1

(n=85)

26.2±5.9

(n=180)

0.20 –

Height (cm) 164.3±8.1

(n=256)

163.0±7.6

(n=92)

165.0±7.1

(n=86)

163.6±7.0

(n=181)

0.24 –

Weight (kg) 65.7±9.6

(n=255)

66.2±9.2 

(n=90)

68.3±9.2

(n=86)

65.7±10.2

(n=181)

0.09 –

BMI (kg/m2) 24.3±3.3

(n=234)

24.9±3.3

(n=90)

25.0±3.1

(n=86)

24.3±3.2

(n=181)

0.10 –

Miles Run

Per Week

7.7±6.5

(n=234)

6.1±5.2

(n=78) – – 0.03* –

APFT

Push-Up

41.8±12.2

(n=243)

37.7±13.8

(n=85)

35.4±10.9

(n=80)

36.3±11.3

(n=160)

<0.01 Cross-Training – Running Program P=.04

Cross-Training – Weight Training P<.01

Cross-Training – No Program P<.01

APFT

Sit-up

67.8±13.5

(n=244)

63.4±15.1

(n=86)

61.7±10.9

(n=76)

61.8±11.3

(n=156)

<0.01 Cross-Training – Running Program P=.04

Cross-Training – Weight Training P<.01

Cross-Training – No Program P<.01

APFT 2-mile 

Run

17.4±2.1

(n=230)

18.0±2.1

(n=76)

17.8±1.6

(n=49)

18.5±2.3

(n=136)

<0.01 Cross-Training – No Program P<.01

Estimated 

VO2max

(ml/kg/min)

42.1±3.7 41.0±3.8 41.5±2.9 40.2±4.1 <0.01 Cross-Training – No Program P<.01

*Independent t test

Table 4. Comparison of Injury Incidence by Personal Fitness Training Program.

Injury

Type*

Cross-Training Running 

Only

Weight 

Training Only

No Personal

Fitness Program

P

Value

All Injuries 55%

(n=260)

40%†

(n=93)

65%

(n=86)

49%†

(n=181) <.01

Lower

Extremity

Injuries

24%

(n=235)

20%

(n=91)

23%

(n=78)

24%

(n=174)

.47

Upper

Extremity

Injuries

23%†

(n=235)

19%†

(n=91)

39%

(n=78)

24%†

(n=174)

.02

*Approximately 7% (n=42) of the injuries could not be classified as either upper or lower 

extremity injuries due to incomplete survey data or injuries containing both upper and lower 

body areas.

†Significantly different from Weight Training Only.
April – June 2015 27

THE ARMY MEDICAL DEPARTMENT JOURNAL

Studies examining the addition of 

a resistance training program to 

an already established endurance 

training program found improvement in both strength and aerobic 

performance.20-24 These findings 

are also supported by a recent meta-analysis of concurrent resistance 

and endurance training, where investigators found larger effects on 

strength (1.76 (95% CI, 1.34-2.18)) 

and endurance (1.44 (95% CI, 1.03-

1.84)), when compared to endurance 

training alone (0.78 (95% CI, 0.36-

1.19)).25 Previous studies investigating resistance training and running 

performance found increased running economy24,26,27 and improved 

running performance when resistance training was incorporated 

into their training program.27,28 In 

another study investigating moderately trained runners participating in a running, sprinting, and weight 

training program (RSW) compared to 

a running only program (RO), the RSW 

program showed improvements in running performance and dynamic strength 

over the RO program.29 As suggested by 

this analysis, these studies indicate that 

a fitness program with 2 or more fitness 

components is more effective than a fitness program with one mode of training.

Overall (all) injury rates among women 

with a cross-training personal fitness 

program were not different from injury 

rates among women with other training 

programs. In previous military studies 

investigating the implementation of new 

exercise programs (incorporating additional cross-training components), injury rates neither increased nor decreased 

with implementation of a cross-traininglike program.6,30,31

Women who performed weight training only were more 

likely to experience an upper body injury compared to 

the cross-training group as well as the other programs. 

Women performing weight training only as part of their 

personal fitness program also had a higher risk of overall 

injury when compared to women with a program based 

on running only or those with no personal fitness program. In a study comparing women who participated 

in a resistance training program to a control group, the 

resistance training group had higher injury rates (23% 

per year) compared to the control group (7% per year).32

The investigators went on to say that strength training 

provided favorable changes in lean mass and strength, 

while injury rates were lower than previously reported 

population-based survey rates. Even though injury rates 

were higher for the weight only group when compared to 

the running only and no personal fitness program group, 

Table 6. Activity Associated with Injury for Women Performing Cross-Training Compared to Women with a Weight Training Personal Fitness Training Program.

Cause of Injury Cross-training Weight

Training Only

Risk Ratio

(Cross-Training/No Program)

P

Value

Running 33% (44) 13% (7) 2.55 (1.23-5.31) <.01

Other Exercise 15% (20) 13% (7) 1.16 (0.52-2.58) .71

Walking, Hiking, 

or Marching 

with no load

11% (15) 11% (6) 1.02 (0.42-2.48) .97

Lifting/Moving

Heavy 

Objects

10% (13) 28% (15) 0.35 (0.18-0.69) <.01

Sports 9% (12) 4% (2) 2.44 (0.56-10.52) .35*

Stepping, 

Climbing

5% (6) 0% (0) – –

Marching with 

a load

4% (5) 4% (2) 1.02 (0.20-5.07) .99*

Riding/Driving 

in a Motorized Vehicle

3% (4) 4% (2) 0.81 (0.15-4.30) .99*

Repairing / 

Maintaining 

Equipment

0 (0%) 4% (2)

– –

Other 11% (14) 20% (11) 0.52 (0.25-1.07) .07

*Fisher exact test used due to at least one cell count <5.

Table 5. Activity Associated with Injury for Women Performing Cross-Training Compared 

to Women with a Running Only Personal Fitness Training Program.

Cause of Injury Cross-Training

% (n)

Running Only

% (n)

Risk Ratio

(Cross-Training/No Program)

Chi square

P Value

Running 33% (44) 19% (7) 1.75 (0.86-3.56) .10

Other Exercise 15% (20) 19% (7) 0.79 (0.36-1.73) .57

Walking, Hiking, 

or Marching 

with no load

11% (15) 8% (3) 1.39 (0.43-4.55) .84*

Lifting/Moving

Heavy 

Objects

10% (13) 14% (5) 0.72 (0.28-1.90) .51

Sports 9% (12) 5% (2) 1.67 (0.39-7.13) .75*

Stepping, 

Climbing 5% (6) 11% (4) 0.42 (0.12-1.40) .30*

Marching with 

a load

4% (5) 8% (3) 0.46 (0.12-1.85) .48*

Riding/Driving 

in a Motorized Vehicle

3% (4) 8% (3) 0.37 (0.09-1.58) .35*

Repairing/

Maintaining 

Equipment

0% (0) 0% (0)

---- ----

Other 11% (14) 8% (3) 1.30 (0.39-4.28) .94*

*Fisher exact test used due to at least one cell count <5.
28 http://www.cs.amedd.army.mil/amedd_journal.aspx

previous studies have shown that resistance training improves physical and occupational task performance.12-16

However, it is more effective to use 2 modes of training 

rather than one, as shown by improved muscular endurance in the cross-training group when compared to the 

weight training only group

For men, resistance training has been shown to be protective against injury.33 When looking at sex differences in resistance training, women were found to have 

a 69% greater risk of being accidentally injured when 

compared to men.34 It may be that women have less experience with weight training, poor exercise technique, 

or lack of coaching education when compared to men, 

placing them at a greater risk of injury and possibly an 

even higher risk of upper body injury. It is likely that 

muscular strength would also have improved had it been 

measured. Other studies have shown an increase in muscular strength after the addition of a resistance training 

program.15,35 In a 6-week study of untrained (regarding 

resistance training) college women, absolute one repetition maximum (1RM) leg press strength was improved 

by 62%, absolute 1RM squat strength by 46%, and absolute 1RM knee extension strength by 54% using a traditional strength training program. In another resistance 

and aerobic training study, women who participated in 

a 12 week aerobic and resistance training program improved their 1RM squat and shoulder press by 26% and 

17% respectively, compared to a control group where no 

changes were found.35 Strength training programs would 

likely show similar outcomes in Army populations.

In this investigation, women performing cross-training were more than 

twice as likely to experience a running related injury when compared to 

the weight training and no personnel 

fitness program groups, who reported 

very minimal (less that once a week) 

or no additional running per week 

beyond unit PT. The greater exposure to running in the cross-training 

group placed them at a higher risk 

of injury. Prior studies have shown 

increased risk of injury with miles 

run per week.36-38 In another crosstraining study consisting of running, 

sprinting, weight training, backpacking, and lift and carry drills, weight 

lifting accounted for about one third 

of the injuries and clinic visits, while 

running injuries accounted for about 

one fifth of the injuries and clinic 

visits.5 These results are different from the current study 

in that those participating in cross-training were more 

likely to experience a running related injury. It may be 

that the participants in the current investigation ran more 

miles per week, whereas the other study had a more diverse training program with quite a few more strength 

training activities.

Women who performed weight training only were at almost 3 times the risk of injury for moving/lifting heavy 

objects when compared to the cross-training group. It 

may be that women in the weight training group spent 

more time per week weight training or had advanced to 

lifting heavier weights, possibly increasing their risk for 

strains and sprains when compared to the cross-training 

group. However additional data about the specifics of 

their weight training program would be required to determine why their risk of injury was higher.

Those with no personal fitness program were at a higher 

risk of injury for walking, hiking, and marching without a load when compared to the cross-training group. 

The women in the no personal fitness group also had 

lower estimated aerobic capacities when compared to 

the cross-training group. Soldiers with lower aerobic 

capacities will likely experience greater amounts of 

physiological stress and/or fatigue during tasks such 

as running, marching and hiking due to exercising at 

a higher percentage of their maximum aerobic capacity in comparison with Soldiers with greater fitness 

levels. The greater physiological stress and/or fatigue 

THE EFFECTS OF CROSS-TRAINING ON FITNESS AND INJURY IN WOMEN

Table 7. Activity Associated with Injury for Women Performing Cross-Training Compared to Women with a No Personal Fitness Training Program.

Cause of Injury Cross-training No Personal

Fitness Program

Risk Ratio

(Cross-Training/No Program)

P

Value

Running 33% (44) 16% (13) 2.14 (1.23-3.72) <.01

Other Exercise 15% (20) 13% (11) 1.15 (0.58-2.27) .69

Walking, Hiking, 

or Marching 

With No Load

11% (15) 23% (19) 0.50 (0.27-0.93) .03

Lifting/Moving

Heavy 

Objects

10% (13) 14% (12) 0.68 (0.33-1.43) .31

Sports 9% (12) 6% (5) 1.52 (0.55-4.15) .41

Stepping, 

Climbing

5% (6) 6% (5) 0.76 (0.24-2.41) .64

Marching with 

a Load

4% (5) 5% (4) 0.79 (0.22-2.86) .97*

Riding/Driving 

in a Motorized Vehicle

3% (4) 1% (1) 2.53 (0.29-22.22) .71*

Repairing/

Maintaining 

Equipment

0 (0%) 0 (0%)

– –

Other 11% (14) 17% (14) 0.63 (0.32-1.26) .19

*Fisher exact test used due to at least one cell count <5.
April – June 2015 29

THE ARMY MEDICAL DEPARTMENT JOURNAL

experienced may lead to a higher risk of injury. Studies 

on fatigue have demonstrated decrements in proprioceptive ability,39 a decrease in joint stability,40 alterations 

in muscle activity,39 changes in gait,41-45 balance,46,47 low 

frequency fatigue,48 neuromuscular function,49 and ligament laxity.50

Conclusion

Women with a cross-training personal fitness program 

had higher muscular endurance compared to women 

with a personal fitness program based on single mode 

training or no personal fitness program. Women with a 

cross-training personal fitness program also had higher 

estimated VO2max when compared to the no personal 

fitness group. There were no differences for all injuries 

and lower body injuries between cross-training and other fitness programs. Those performing cross-training 

were more than twice as likely to experience a running 

related injury when compared to weight training and no 

personal fitness group. Cross-training may be the best 

option for improving physical fitness when compared to 

just one mode of fitness training.

References

1. Field Manual 7-22: Army Physical Readiness Training. Washington DC: US Dept of the Army; 2012.

2. Aspenes S, Kjendlie P, Hoff J, Helgerud J. Combined 

strength and endurance training in competitive 

swimmers. J Strength Cond Res. 2009;8:357-365.

3. White L, Dressendorfer R, Muller S, Ferguson 

M. Effectiveness of cycle cross-training between 

competitive seasons in female distance runners. J 

Strength Cond Res. 2003;17:319-323.

4. Mutton D, Loy S, Roger D, Holland G, Vincent W, 

Heng M. Effect of run vs combined cycle/run training on VO2max and running performance. Med Sci 

Sports Exerc. 1993;25:1393-1397.

5. Reynolds K, Harman E, Worsham R, Sykes M, 

Frykman P, Backus V. Injuries in women associated with a periodized strength training and running 

program J Strength Cond Res. 2001;15:136-143.

6. Walker T, Lennemann L, Zupan M, Anderson V, 

Lyons W. Adaptations to a New Physical Training 

Program in the Combat Controller Training Pipeline. Brooks City-Base, TX: Air Force Research 

Laboratory; September 2010. Technical Report No. 

AFRL-RH-BR-TR-2010-0067.

7. Wilmore JH, Costill DL. Physiology of Sports and 

Exercise. Champaign, Illinois: Human Kinetics; 

1994.

8. Hale B, Koch K, Raglin J. State anxiety responses 

to 60 minutes of cross training. Br J Sports Med. 

2002;36:105-107.

9. Raglin JS. Anxiety and sports performance. In: Holloszy JO, ed. Exercise and Sports Science Reviews. 

Baltimore: Williams and Wilkins; 1992:243-274.

10. Focht B, Koltyn K. Influence of resistance exercise 

of different intensities on state anxiety and blood 

pressure. Med Sci Sports Exerc. 1999;31:456-463.

11. Eldridge JA, DiClemente C, Frankeiwicz RG, 

Zhang JJ, Jackson AS. The function of maximal 

oxygen consumption, job intensity, smoking, and 

gender on work-related injuries 199. Med Sci Sports 

Exerc. 1997;29(suppl):35.

12. Kraemer W, Mazzetti S, Nindl B, et al. Effect of 

resistance training on women’s strength/power and 

occupational peformances. Med Sci Sports Exerc. 

2000;33:1011-1025.

13. Rosenblum K, Shankar A. A study of the effects 

of isokinetic pre-employment physical capability 

screening in the reduction of musculoskeletal disorders in a labor intensive work environment. Work. 

2006;26:215-228.

14. Knapik JJ, Gerber J. Influence of Physical Fitness 

Training on the Manual Material Handling Capability and Road Marching Performance of Female 

Soldiers. Aberdeen Proving Ground, MD: Human 

Research and Engineering Directorate, US Army 

Research Laboratory; March 1996. Report No. 

ARL-TR-1064. Available at: http://www.dtic.mil/

dtic/tr/fulltext/u2/a307175.pdf. Accessed March 5, 

2015.

15. Rana SR, Chleboun GS, Gilders RM, et al. Comparison of early phase adaptations for traditional 

strength and endurance, and low velocity resistance training programs in college-aged women. J 

Strength Cond Res. 2008;22(1):119-127.

16. Hendrickson N, Sharp M, Alemany J, et al. Combined resistance and endurance training improves physical capactiy and performance on 

tactical occupational tasks. Eur J Appl Physiol. 

2010;109:1197-1208.

17. Jones SB, Knapik JJ, Sharp M, Darakjy S, Jones 

BH. Validity of self-reported physical fitness test 

scores. Mil Med. 2007;172:115-120.

18. Mello R, Murphy M, Vogel J. Relationship Between a Two Mile Run for Time and Maximal Oxygen Uptake. Natick, MA: Army Research Institute 

of Environmental Medicine; 1987. Report No. ADA179 343.

19. Centers for Disease Control and Prevention. About 

BMI for Adults [internet]. February 23, 2015. 

Available at: http://www.cdc.gov/healthyweight/

assessing/bmi/adult_bmi/index.html. Accessed 

March 5, 2015.
30 http://www.cs.amedd.army.mil/amedd_journal.aspx

20. Aagaard P, Andersen J. Effects of strength training 

on endurance capacity in top-level endurance athletes. Scand J Med Sci Sports. 2010;20:39-47.

21. Storen O, Helgerud J, Stoa E, Hoff J. Maximal strength training improves running economy in distance runners. Med Sci Sports Exerc. 

2008;40:1087-1092.

22. Hickson R, Dvorak B, Gorostiaga E, Kurowski 

T, Foster C. Potential for strength and endurance 

training to amplify endurance performance. J Appl 

Physiol. 1988;65:2285-2290.

23. Sedano S, Marin P, Cuadrado G, Redondo J. Concurrent training in elite male runners: the influence 

of strength versus muscular endurance training 

on performance outcomes. J Strength Cond Res. 

2013;27:2433-2443.

24. Barnes K, Hopkins W, McGuigan M, Northuis M. 

Effects of resistance training on running economy 

and cross-country performance. Med Sci Sports 

Exerc. 2013;45:2322-2331.

25. Wilson J, Marin P, Rhea M, Wilson S, Loenneke J, 

Anderson J. Concurrent training: a meta-analysis 

examining interference of aerobic and resistance 

exercises. J Strength Cond Res 2012;26:2293-2307.

26. Johnston R, Quinn T, Kerter R, Vroman N. 

Strength training in female distance runners: impact on running economy. J Strength Cond Res

1997;11:224-229.

27. Paavolainen L, Hakkinen K, Hamalainen I, Nummela A, Rusko H. Explosive strength training 

improves 5-km running time by improving running economy and muscle power. J Appl Physiol. 

1999;86:1527-1533.

28. Kelly C, Burnett A, Newton M. The effect of 

strength training on three-kilometer performance 

in recreational women endurance runners. J 

Strength Cond Res 2008;22:396-403.

29. Skovgaard C, Christensen P, Larsen S, Andersen T, 

Thomassen M, Bangsbo J. Concurrent speed endurance and resistance training improves performance, 

running economy, and muscle NHE1 in moderately 

trained runners. J Appl Physiol. 2014;117:1097-1109.

30. Grier T, Chervak M, McNulty V, Jones BH. Evaluation of the advanced tactical athlete conditioning 

and extreme conditioning programs in the 25th 

Infantry Division, Schofield Barracks, Hawaii. Injury Prevention Report. Aberdeen Proving Ground: 

United States Army Insitute of Public Health; 2010.

31. Knapik JJ, Rieger W, Palkoska F, Van Camp S, 

Darakjy S. United States Army physical readiness training: rationale and evaluation of the 

physical training doctrine. J Strength Cond Res. 

2009;23:1353-1362.

32. Warren M, Schmitz K. Safety of strength training 

in premenopausal women: musculoskeletal injuries 

from a two year randomized trial. Am J Health Promot. 2009;23:309-314.

33. Grier T, Chervak M, McNulty V, Jones BH. Extreme conditioning programs and injury risk in a 

US Army brigade combat team. US Army Med Dep 

J. October-December 2013:36-47.

34. Quatman C, Myer G, Khoury J, Wall E, Hewett T. 

Sex differences in “weightlifting” injuries presented to United States emergency rooms. J Strength 

Cond Res. 2009;23:2061-2067.

35. Kraemer W, Keuning M, Ratamess N, et al. Resistance training combined with bench-step aerobics 

enhances women’s health profile. Med Sci Sports 

Exerc. 2001;33:259-269.

36. Koplan JP, Powell KE, Sikes RK, Shirley RW, 

Campbell CC. An epidemiologic study of the benefits and risks of running. JAMA. 1982;248:3118-3121.

37. Marti B, Vader JP, Minder CE, Abelin T. On 

the epidemiology of running injuries. The 

1984 Bern Grand-Prix study. Am J Sports Med. 

1988;16:285-294.

38. Samet JM, Chick TW, Howard CA. Running-related mortality: a community survey. Ann Sports Med 

Res. 1982;1:30-34.

39. Rozzi S, Lephart S, Fu F. Effects of muscular fatigue on knee joint laxity and neuromuscular characteristics of male and female athletes. J Athl Train. 

1999;34:106-114.

40. Melnyk M, Gollhofer A. Submaximal fatigue of 

the hamstrings impairs specific reflex components 

and knee stability. Knee Surg Sports Traumatol Arthrosc. 2007;15:525-532.

41. Candau R, Belli A, Millet GY, George D, Barbier B, 

Rouillon JD. Energy cost and running mechanics 

during a treadmill run to voluntary exhaustion in 

humans. Eur J Appl Physiol. 1998;77:479-485.

42. Nyland JA, Shapiro R, Stine RL, Horn TS, Ireland 

ML. Relationship of fatigued run and rapid stop to 

ground reaction forces, lower extremity kinematics, 

and muscle activation. J Orthop Sports Phys Ther. 

1994;20:132-137.

43. Gerlach K, White S, Burton H, Dorn J, Leddy J, 

Horvath P. Kinetic changes with fatigue and relationship to injury in female runners. Med Sci 

Sports Exerc. 2005;37:657-663.

44. LeBris R, Billat V, Auvinet B, Chaleil D, Hammard L, Barrey E. Effect of fatigue on stride pattern continuously measured by an accelerometric 

gait recorder in middle distance runners. J Sports 

Med Phys Fitness. 2006;46:227-231.

THE EFFECTS OF CROSS-TRAINING ON FITNESS AND INJURY IN WOMEN
April – June 2015 31

THE ARMY MEDICAL DEPARTMENT JOURNAL

45. Yoshino K, Motoshige T, Araki T, Matsuoka 

K. Effect of prolonged free-walking fatigue 

on gait and physiological rhythm. J Biomech. 

2004;37(8):1271-1280.

46. Johnston R, Howard M, Cawley P, Losse G. Effect of lower extremity muscular fatigue on motor control performance. Med Sci Sports Exerc. 

1998;30:1703-1707.

47. Dickin D, Doan J. Postural stability in altered and 

unaltered sensory environments following fatiguing exercise of lower extremity joints. Scand J Med 

Sci Sports. 2008;18:765-772.

48. Baptista R, Scheeren E, Macintosh B, Vaz M. 

Low-frequency fatigue at maximal and submaximal muscle contractions. Braz J Med Biol Res. 

2009;42:380-385.

49. Wojtys E, Wylie B, Huston L. The effects of muscle 

fatigue on neuromuscular function and anterior tibial translation in healthy knees. Am J Sports Med. 

1996;24:615-621.

50. Sakai H, Tanaka S, Kurosawa H, Masujima 

A. The effect of exercise on anterior knee laxity in female basketball players. Int J Sports Med

1992;13:552-554.

Authors

Mr Grier is a Kinesiologist for the Injury Prevention 

Program of the Epidemiology and Disease Surveillance 

Portfolio, US Army Public Health Command, Aberdeen 

Proving Ground, Maryland.

Dr Canham-Chervak is a Senior Epidemiologist for the 

Injury Prevention Program of the Epidemiology and 

Disease Surveillance Portfolio, US Army Public Health 

Command, Aberdeen Proving Ground, Maryland.

Mrs Anderson is an Epidemiologist for the Injury Prevention Program of the Epidemiology and Disease Surveillance Portfolio, US Army Public Health Command, 

Aberdeen Proving Ground, Maryland.

Mr Bushman is an Exercise Physiologist for the Injury 

Prevention Program of the Epidemiology and Disease 

Surveillance Portfolio, US Army Public Health Command, Aberdeen Proving Ground, Maryland.

Dr Jones is a Program Manager for the Injury Prevention 

Program of the US Army Public Health Command, Aberdeen Proving Ground, Maryland.

Announcing

The 2015 Spurgeon Neel

Annual Award Competition

The Army Medical Department Museum Foundation is pleased to announce the 2015 Spurgeon 

Neel Annual Award competition for a paper of 5,000 words or less that best exemplifies the history, legacy, and traditions of the Army Medical Department.

Named in honor of Major General (Retired) Spurgeon H. Neel, first Commanding General of 

Health Services Command (now US Army Medical Command), the award competition is open to 

all federal employees, military and civilian, as well as nongovernmental civilian authors. More 

information about MG (Ret) Neel can be found at http://en.wikipedia.org/wiki/Spurgeon_Neel.

The AMEDD Museum Foundation will present a special medallion award and a $500 monetary 

prize to the winner at a Foundation-sponsored event early in 2016. The winning submission 

will be published in the AMEDD Journal during 2016.

All manuscripts must be submitted to the AMEDD Museum Foundation by September 30, 2015. 

At the time of submission, a manuscript must be original work and not pending publication in 

any other periodical. It must conform to the Writing and Submission Guidance of the AMEDD 

Journal, and must relate to the history, legacy, and/or traditions of the Army Medical Department. Manuscripts will be reviewed and evaluated by a six-member board with representatives 

from the AMEDD Museum Foundation, the AMEDD Center of History and Heritage, and the 

AMEDD Journal. The winning manuscript will be selected and announced in December 2015.

Submit manuscripts to amedd.foundation@att.net. Additional details concerning the Spurgeon 

Neel Annual Award may be obtained by contacting Mrs Sue McMasters at the AMEDD Museum 

Foundation, 210-226-0265.
32 http://www.cs.amedd.army.mil/amedd_journal.aspx

Military deployments can have a significant effect on 

Soldiers’ physical and/or mental well-being due to altered schedules, environmental conditions, and available resources during deployments. Physical training 

(PT), fitness levels, injury incidence, and health behaviors can be affected by these changes. Understanding 

how these fitness and health components are affected 

can help improve the readiness and effectiveness of deployed Soldiers.

Both men and women perform occupational tasks with 

varying physical demands during deployments. It is 

important that all Soldiers have the aerobic endurance 

and strength necessary to successfully complete missions without injury. The ability for a deployed unit to 

maintain a physical training program requires appropriate space, equipment, and time, which varies by location. Low levels of physical fitness have been shown to 

increase injury risk, which can limit unit readiness.1-3 It 

is essential to continue physical training, either with the 

unit, during personal time, or both.

In 2013, the US military announced that women would 

be eligible for combat roles previously only open to 

men.4 This announcement raised questions about the 

physical training requirements necessary for women entering these positions, and highlighted a need to better 

understand current physical training practices, both before and during deployment.5

 There have been few studies examining the physical training and fitness levels of 

Physical Training, Smoking, and Injury During

 Deployment: A Comparison of Men and

 Women in the US Army

Morgan K. Anderson, MPH, CPH

Tyson Grier, MS

Michelle Canham-Chervak, PhD

Timothy T. Bushman, MS

Bruce H. Jones, MD, MPH

Abstract

Purpose: To investigate changes in physical training (PT), fitness, and injury during deployment and identify 

differences between men and women.

Methods: Data were collected on male and female US Army Soldiers through self-reported surveys completed 

before and after deployment to Afghanistan. Changes in physical training activities, physical fitness, injury 

incidence, BMI, and smoking status were analyzed. Descriptive statistics were used to compare before deployment and deployment results and differences between men and women.

Results: Surveys were completed by 727 men and 43 women. The percentage of Soldiers engaging in unit PT 

running of 5 miles or more per week decreased by almost half for men and women. The percentage of Soldiers 

doing personal PT running of 5 miles or more per week and engaged in resistance training 3 or more days 

per week more than doubled for men and women during deployment. Cardiorespiratory endurance for women 

improved by 50 seconds (P=.06) and for men declined by 29 seconds (P<.01), while muscular endurance increased by 0.6 repetitions (P<.01) during deployment. Injury rates for men decreased, on average, 36.2 to 19.0 

injuries per 1,000 Soldiers per month (P=.01). Injury rates for women decreased on average from 42.6 to 14.0 

injuries per 1,000 Soldiers per month (P=.02). During deployment, BMI did not change for men or women and 

smoking increased 19% for men (P<.01), but did not increase for women.

Conclusion: Comparisons of physical training activities and health behavior among men and women before and 

during deployment suggests that increased resistance training could be recommended for women and smoking 

cessation for men. Given the potentially important role of personal PT in maintaining physical fitness in the 

deployment environment, future work should support provision of the necessary environment and equipment 

for Soldiers to perform personal PT effectively and safely on their own. Further, the physical training gaps 

between men and women should be addressed, with suggestions regarding where improvements can be made, 

especially for women interested in seeking combat positions with high physical demands.
April – June 2015 33

deployed Soldiers, and none that have included women. 

One study looking at 137 male combat arms Soldiers 

during a 13-month deployment showed upper and lower 

body strength improved, upper body power improved, 

aerobic performance declined, fat mass increased, and 

fewer Soldiers participated in aerobic exercise and 

sports during deployment.6 Another investigation which 

looked at changes in fitness and body composition after 

a 9-month deployment to Afghanistan showed decreases in aerobic capacity, upper body power, and body composition, with no change in lifting strength and vertical 

jump performance.7

With the average deployment lasting 9 months, Soldiers 

and leadership should understand the effects of deployment on fitness, health, and physical training practices.8

The focus of this investigation was to see how a 9-month 

deployment changed Soldiers’ physical training, injury 

incidence, health behaviors, and fitness levels, and to 

compare physical training practices of men and women 

before and during deployment.

Methods

Data Collected

A volunteer-based survey was administered to Soldiers 

in a light infantry brigade prior to their deployment in 

2011, and again when they returned from deployment in 

2013. The surveys obtained self-reported data on unit 

and personal PT, physical fitness, injury, body mass index (BMI), and tobacco use during the 6 months prior to 

deployment, and again during the 9 months of deployment (asked postdeployment). Participation in a variety 

of physical training activities was measured 

with questions pertaining to the frequency of 

resistance, sprint, cross-training, and running. 

The project was reviewed and approved by 

the US Army Public Health Command Public 

Health Review Board.

Physical training weekly running distance was 

calculated from reported average running frequency per week multiplied by average miles 

per run. Physical fitness was assessed using 

self-reported performance on the Army Physical Fitness Test (APFT), with the APFT push-up event 

and sit-up event reflecting muscular endurance and the 2 

mile run reflecting cardiovascular fitness.9 APFT scores 

consisted of a timed (2 minutes) push-up event, a timed 

(2 minutes) sit-up event and timed 2 mile run. Injury 

questions asked were pertaining to Soldiers most recent 

injury during the time-frame specified. Body mass index 

(BMI (kg/m2)) was calculated from self-reported height 

(meters) and weight (kg). Cigarette smokers were identified as those who had smoked at least 100 cigarettes in 

their lifetime and smoked at least one cigarette in the 30 

days prior to the survey administration date.

Data Analysis

Data were analyzed using SPSS, Version 19.0 (IBM 

Corp, Armonk, New York). Descriptive statistics for 

demographics were calculated. Means and standard 

deviations were calculated for all continuous variables. 

OpenEpi (http://www.openepi.com) was used for ANOVA, chi-square, and person-time rates. Chi-square and 

ANOVA tests were used to compare significant changes among before-deployment and during-deployment 

variables. Person-time rates were calculated for injury 

incidence. P values of 0.05 or less were considered significant changes, while P values between 0.06 and 0.10 

were considered marginally significant changes.

Results

Descriptive Statistics

Before- and during-deployment surveys were completed by 727 men and 43 women. The comparison of injury 

rates before and during deployment showed the average injury rate decreased from 36.2 to 19.0 injuries per 

1,000 Soldiers per month for men (P<.01) and decreased 

from 42.6 to 14.0 injuries per 1,000 Soldiers per month 

for women (P=.02) (Table 1). Prior to deployment, average age and BMI was 24.7 years and 25.8 kg/m2

 for 

men, and 25.2 years and 24.4 kg/m2 for women (Table 

2). Age and BMI did not significantly change during 

deployment for men or women. Incidence of smoking 

increased by 19% during deployment for men (P<.01), 

but did not change for women.

Personal and Unit Physical Training

For personal PT, resistance training participation of 3 or 

more days per week more than doubled for men, from 

33% before deployment to 77% during deployment, and 

increased 8 fold for women, from 5% before deployment 

to 40% during deployment. The percentage of personnel sprinting during personal PT increased slightly for 

men, from 50% to 67% reporting sprinting one or more 

days per week, but did not change for women during 

Table 1. Injury Rates Differences Before and During Deployment for Men 

and Women.

Before deployment

injury rate

(per 1,000 Soldiers

per month)

Deployment injury 

rate

(per 1,000 Soldiers 

per month)

P value, before

deployment

vs

deployment*

Male Soldiers

(n=727) 36.2* 19.0* <.01

Female Soldiers

(n=43) 42.6* 14.0* .02

P value,

male vs female* <.01 <.01

*P is calculated using 2 person-time rates z-score
34 http://www.cs.amedd.army.mil/amedd_journal.aspx

Table 2. Demographic, Physical Fitness, and Physical Training Differences Before and During Deployment for Men and Women.

Men (n=727) Women (n=43) % Difference

Predeployment

Between Sexes:

% Difference

Between Sexes:

Deployed Predeploy (mean±SD) Deployed (mean±SD)

P* %

Change

Predeploy

(mean±SD)

Deployed

(mean±SD)

P* %

Change

Age (years) 24.7±5.1 25.8±5.1 <.01† +4% 25.2±4.7 26.3±4.7 .28† +4% 4% 2%

BMI (kg/m2

) 25.8±3.3 26.0±3.2 .24† +<1% 24.4±2.8 24.5±2.5 .86† +<1% 6% 6%

Smokers (%) 47% 56% <.01† +19% 40% 38% .90‡ -5% 7% 18%

APFT

2 mile run (minutes) 14.34±1.33 14.82 ±1.40 <.01† +3% 17.83 ±2.14 16.99 ±1.78 .06† -5% 24% 15%

Sit-ups (repetitions) 69.8±10.7 69.5±9.9 .37† -<1% 66.8±13.4 69.1±14.2 .45† +3% 4% 1%

Push-ups (repetitions) 65.9±12.6 66.5±12.3 <.01† +1% 43.4±17.2 44.2±11.3 .80† +2% 52% 50%

Personal PT

Resistance Training (n) 723 720 43 43

None 31% 8%

<.01‡

-74% 51% 21%

<.01‡

-59% +20% +13%

≤1-2 days per week 36% 20% -44% 44% 40% -11% +8% +20%

≥3 days per week 33% 72% +119% 5% 40% +750% -28% -32%

Sprinting (n) 722 723 43 43

None 50% 33%

<.01‡

-34% 70% 35%

<.01‡

-50% +20% +2%

≤1-2 days per week 42% 57% +37% 26% 61% +136% -16% +4%

≥3 days per week 8% 10% +20% 5% 5% 0% -3% -5%

Running Mileage (n) 697 700 41 43

None 33% 12%

<.01‡

-64% 44% 14%

<.01‡

-67% +10% +2%

<5 miles per week 42% 29% -30% 49% 28% -40% +7% -1%

≥5 miles per week 25% 59% +134% 7% 58% +733% -18% -1%

Unit PT

Resistance Training (n) 708 723 41 43

None 11% 47%

<.01‡

+333% 20% 51%

.01‡

+175% +9% +4%

≤1-2 days per week 53% 16% -69% 56% 28% -48% +3% +12%

≥3 days per week 36% 37% +7% 24% 21% -10% -12% -16%

Sprinting (n) 709 725 42 43

None 10% 59%

<.01‡

+484% 17% 56%

<.01‡

+243% +7% -3%

≤1-2 days per week 72% 36% -49% 67% 44% -32% -5% +8%

≥3 days per week 18% 6% -68% 17% 0% -100% -1% -6%

Cross-Training (n) 704 722 38 43

None 21% 56%

<.01‡

+174% 37% 61%

.10‡

+86% +3% -4%

≤1-2 days per week 42% 35% -15% 45% 26% -35% +1% -4%

≥3 times per week 37% 7% -80% 19% 14% -14% -5% +8%

Running Mileage (n) 699 710 41 40

None 4% 54%

<.01‡

+117% 7% 50%

<.01‡

+578% +16% +5%

<5 miles per week 28% 17% -39% 29% 13% -75% +3% -9%

≥5 miles per week 68% 30% -56% 63% 38% -42% -18% +7%

*P<.10 is considered significant †ANOVA ‡Chi-square

PHYSICAL TRAINING, SMOKING, AND INJURY DURING DEPLOYMENT:

A COMPARISON OF MEN AND WOMEN IN THE US ARMY
April – June 2015 35

THE ARMY MEDICAL DEPARTMENT JOURNAL

deployment. The percentage of Soldiers running 5 or 

more miles per week during personal PT doubled for 

men (25% to 59%), and increased more than 8 times for 

women (7% to 58%).

For unit PT, resistance training participation of 3 or 

more days per week remained about the same for men 

during deployment (36% and 37%) and slightly decreased for women (24% to 21%). Participation in unit 

sprinting drills 3 or more days per week decreased for 

men (18% to 6%) and women (17% to 0%) during deployment. Participation in unit cross-training drills 3 or 

more days per week decreased for men (37% to 7%) and 

women (19% to 14%) during deployment. Unit running 

mileage of 5 miles or more per week decreased for both 

men (68% to 30%) and women (63% to 38%) during 

deployment (Table 2; Figures 1 and 2).

When comparing PT for men and women before deployment (Table 2), personal resistance training showed 

the largest difference between the 2 groups with 33% 

of men and 5% of women participating 3 or more days 

per week. The smallest difference between men and 

women prior to deployment was seen in unit sprinting 

with 68% of men and 63% of women performing some 

sort of sprint training 3 or more days per week. In the 

comparison of men and women during deployment (Table 2), personal resistance training showed the largest 

difference between the 2 groups with 72% of men and 

40% of women participating 3 or more days per week. 

The smallest difference between men and women during deployment was seen in personal running mileage 

with 59% of men and 58% of women participating 3 or 

more days per week.

Physical Fitness

During deployment, cardiorespiratory endurance improved for women by 0.84 minutes (50 seconds) (APFT 

2-mile) (P=.06). Cardiorespiratory endurance decreased for men by 0.48 minutes (29 seconds) (APFT 

2-mile) (P<.01) but their muscular strength improved by 

0.6 repetitions (APFT push-ups) (P<.01) during deployment (Table 2).

Comment

The focus of this investigation was to assess how a nine 

9-deployment affected Soldiers’ physical training activities, physical fitness, injury incidence, and health 

behaviors. It also showed differences between men and 

women. Deployment resulted in increases in personal 

physical training, decreases in unit physical training, 

improvement in physical fitness, reductions in reported 

injury incidence, and increases in smoking among men.

While deployed women saw a 50 second improvement 

in 2-mile run time, a measure of cardiorespiratory 

31%

36%

33%

72%

36%

53%

11%

47%

16%

37%

50%

57%

42%

33%

8% 10%

42%

42%

68%

37%

25%

28% 33%

4%

59% 56%

59%

17%

29%

30%

36% 35%

12%

54%

21%

18%

72%

10%

20%

8%

6% 7%

Personal

Resistance

Training

Personal

Sprinting

Personal

Running

Mileage

Unit

Resistance

Training

Unit

Sprinting

Unit

Running

Mileage

Cross

Training

(Unit)

PredeploymentPredeploymentPredeploymentPredeploymentPredeploymentPredeploymentPredeployment

During

Deployment

During

Deployment

During

Deployment

During

Deployment

During

Deployment

During

Deployment

During

Deployment

90%

80%

70%

60%

50%

40%

30%

20%

10%

0%

100%

Figure 1. Men’s physical training participation before and during deployment.

None ≤1-2 days per week ≥3 days per week ≥5 miles per week <5 miles per week
36 http://www.cs.amedd.army.mil/amedd_journal.aspx

endurance on the APFT, men’s run time performance 

declined by 29 seconds. Lester et al6 and Sharpe et al7

also showed cardiorespiratory endurance among men 

was negatively affected by deployments of 13 months 

and 9 months respectively. The reported increase in personal running mileage among both men and women during deployment appears to have had a positive effect for 

women. For men, personal running may not have been 

a sufficient replacement for the decrease in unit training. More men also initiated smoking while deployed 

which may have affected their aerobic fitness. Several 

studies have observed cigarette smoking to have a negative effect on aerobic and muscular fitness.9-13 A study 

of male Navy personnel observed smokers were almost 

30 seconds slower at the 1.5 mile run/walk, performed 6 

fewer curl-ups and 5 fewer push-ups on average, when 

compared to nonsmokers.11 The increase in cardiorespiratory endurance in women could be due to increased 

personal distance running and resistance training frequency during deployment. Past studies have reported 

a combination of strength and endurance training promotes increases in muscular and aerobic endurance.14,15

Muscular endurance, as measured by APFT push-up 

performance, improved for men during deployment. 

This improvement could be due to the increase in the 

rates of frequency in personal resistance training of 

3 or more days per week from 33% to 72% during 

deployment. Although women also increased the rates 

of personal time resistance training participation during 

deployment from 5% to 40% (Table 2, Figure 2), their 

muscular endurance fitness levels did not change. This 

could indicate that women desire to improve their muscular endurance, but are unfamiliar with appropriate resistance training exercises. Resistance training instruction and equipment geared towards women might help 

overcome these issues. The benefits of PT during deployment include reduction in injury risk, maintaining a 

healthy weight and improved circulation, balance, coordination, and bone/ligament strength.16,17 The American 

College of Sports Medicine recommends that men and 

women should perform 2 to 3 days of resistance training 

for each major muscle group, with 2 to 4 sets per muscle 

group to improve strength and power.18

When comparing physical training activities of men and 

women, similarities were seen in running mileage with 

their unit before deployment and during personal time 

during deployment. Physical training differences between men and women were seen in personal resistance 

training before deployment and during deployment. 

Both running and resistance training are crucial components to improving and maintaining Soldiers’ cardiovascular and muscular endurance. Resistance training 

during personal time and with the unit should be highly 

encouraged for women by unit leaders as it has shown 

44% 51%

28%

35%

70%

26%

67%

21%

40%

24%

60%

51%

56%

44%

40%

20%

44%

60%

37%

45%

28%

26%

5% 5% 5%

49% 58%

56%

18%

60%

37%

45%

14% 14%

14%

26%

18%

17%

17%

21%

7%

90%

80%

70%

60%

50%

40%

30%

20%

10%

0%

100%

Predeployment

During

Deployment

Personal

Resistance

Training

Personal

Sprinting

Personal

Running

Mileage

Unit

Resistance

Training

Unit

Sprinting

Unit

Running

Mileage

Cross

Training

(Unit)

PredeploymentPredeploymentPredeploymentPredeploymentPredeploymentPredeployment

During

Deployment

During

Deployment

During

Deployment

During

Deployment

During

Deployment

During

Deployment

None ≤1-2 days per week ≥3 days per week ≥5 miles per week <5 miles per week

Figure 2. Women’s physical training participation before and during deployment.

PHYSICAL TRAINING, SMOKING, AND INJURY DURING DEPLOYMENT:

A COMPARISON OF MEN AND WOMEN IN THE US ARMY
April – June 2015 37

THE ARMY MEDICAL DEPARTMENT JOURNAL

to improve occupational task performance.19 Gender differences in physical performance decreased in the repetitive box lift and the 2-mile loaded run when women 

participated in endurance and strength/power training.19

Another study looked at strength and cardiovascular 

training, and showed individuals who participated in 

both types of training had the largest percentage improvement in assigned occupational tasks (mannequin 

drag, lift and carry, and load carriage).14 Women benefit 

from resistance training, but participation is low in garrison compared to men. Encouraging similar physical 

training regimen between men and women might be 

an effective method for preparing men and women for 

combat and other physically demanding military occupational tasks.

Injury rates decreased during deployment for both men 

and women. Even though unit level PT decreased and 

personal PT participation increased, the combined frequency of unit and personal physical training during 

deployment stayed similar to that seen before deployment. The ability for Soldiers to train on their own while 

deployed allowed them more flexibility to train at their 

own pace and intensity level, which may explain why injury rates decreased among deployed Soldiers. A study 

by Knapik et al20 observed Soldiers that participated in 

similar ability groups for long-distance running had 

lower injury risk and equal or greater improvements in 

fitness as basic training progressed.

Cigarette use did not change during deployment for 

women, but increased by 19% for men. A study of 

48,304 US male and female service members by Smith 

et al21 showed smoking rates increased during deployment among those that had never smoked by 2%, and 

among those who had previously quit smoking by 53%. 

Smoking initiation was especially high during prolonged 

deployments, multiple deployments, and combat exposures. Another study showed that male and female Soldiers reported initiating smoking during deployment 

due to boredom (54%), social factors (24%), and stress 

(13%).22

Strengths and Limitations

Data were collected through self-reported surveys, 

which can be subject to recall bias as well as questions 

about honesty in answers and lack of comprehension of 

the questions. Prior analyses have found high correlations between actual and self-reported Army Physical 

Fitness Test data.23

Conclusion

During deployment, unit PT participation decreased, 

while personal PT participation increased for both men 

and women. Personal PT played a larger role in physical 

training compared to unit PT participation during deployment, which may have contributed to the decrease 

in injury rates, possibly due to more self-paced personal 

training. Body mass index remained similar for both 

men and women, while there was an increase in the 

number of men who began smoking. Comparisons of 

physical training activities and health behavior among 

men and women before and during deployment suggest 

that increased resistance training could be recommended for women and smoking cessation for men.

Information on personal PT activities described in this 

paper can be used to inform future unit PT and personal 

PT recommendations to improve fitness levels in garrison and during deployment. Given the potentially important role of personal PT in maintaining physical fitness in the deployment environment, future work should 

aim to provide the necessary tools for Soldiers to perform personal PT effectively and safely on their own. 

Addressing physical training gaps between men and 

women, such as the lack of resistance training among 

women in garrison, suggest where improvements can be 

made, especially for women looking to successfully fill 

combat positions with high physical demands.

References

1. Westphal KA, Friedl KE, Sharp MA, et al. Health, 

Performance, and Nutritional Status of U.S. Army 

Women during Basic Combat Training. Frederick, MD: US Army Medical Research and Material Command; 1995. Technical Report No. T96-2. 

Available at: http://www.dtic.mil/dtic/tr/fulltext/u2/

a302042.pdf. Accessed February 2, 2015.

2. Knapik JJ, Sharp MA, Canham-Chervak M, 

Hauret K, Patton JF, Jones BH. Risk factors for 

training-related injuries among men and women 

in basic combat training. Med Sci Sports Exerc. 

2001;33(6):946-954.

3. Grier TL, Morrison S, Knapik JJ, CanhamChervak C, Jones BH. Risk factors for injuries 

in the US Army Ordnance School. Mil Med. 

2011;176(11):1292-1299.

4. Brook TV, Michaels J. Officials: Panetta opens 

combat roles to women. USA Today [internet]. January 24, 2013. Available at: http://www.usatoday.

com/story/news/nation/2013/01/24/women-com

bat-change-panetta/1861995/. Accessed February 

2, 2015.

5. Dao J. In arduous officer course, women offer 

clues to their future in infantry. New York Times. 

February 18, 2013:A8. Available at: http://www.

nytimes.com/2013/02/18/us/marines-look-to-infantry-course-for-insight-on-women.html?page

wanted=all&_r=3&. Accessed February 2, 2015.
38 http://www.cs.amedd.army.mil/amedd_journal.aspx

6. Lester ME, Knapik JJ, Catrambone D, et al. Effect of a 13-month deployment to Iraq on physical fitness and body composition. Mil Med. 

2010;175(6):417-423.

7. Sharp MA, Knapik JJ, Walker LA, et al. Physical 

fitness and body composition following a 9-month 

deployment to Afghanistan. Med Sci Sports Exerc. 

2008;40(9):1687-1692. Available at: http://handle.

dtic.mil/100.2/ADA489599. Accessed February 2, 

2015.

8. Bacon LM. Army Announces switch to 9-month 

deployments. ArmyTimes [internet]. August 5, 

2011. Available at: http://www.armytimes.com/arti

cle/20110805/NEWS/108050304/Army-announces

-switch-9-month-deployments. Accessed February 

2, 2015.

9. Conway TL, Cronan TA. Smoking, exercise, and 

physical fitness. Prev Med. 1992;21(6):723-734.

10. Haddock CK, Pyle SA, Poston WSC, Bray RM, 

Stein RJ. Smoking and body weight as markers of 

fitness for duty among U.S. military personnel. Mil 

Med. 2007;172(5):527-532.

11. Macera CA, Arali HJ, MacGregor AJ, Rauh 

MJ, Han PP, Galarneau MR. Cigarette smoking, 

body mass index, and physical fitness changes 

among male navy personnel. Nicotine Tob Res. 

2011;13(10):965-971.

12. Reynolds KL, Heckel HA, Witt CE, et al. Cigarette 

smoking, physical fitness, and injuries in infantry 

soldiers. Am J Prev Med. 1994;10(3):145-150.

13. Bahrke MS, Baur TS, Poland DF, Connors DF. Tobacco use and performance on the US Army physical readiness test. Mil Med. 1988;153(5):229-235.

14. Hendrickson NR, Sharp MA, Alemany JA, et al. 

Combined resistance and endurance training physical capacity and performance on tactical occupational tasks. Eur J Appl Physiol. 2010;109:1197-1208.

15. Wilson JM, Marin PJ, Rhea MR, Wilson SMC, 

Loenneke JP, Anderson JC. Concurrent training: 

a meta-analysis examining interferences of aerobic and resistance exercise. J Strength Cond Res. 

2012;26(8):2293-2307.

16. Schmitz KH, Hannan PJ, Stovitz SD, Bryan 

CJ, Warren M, Jensen MD. Strength training 

and adiposity in premenopausal women: strong, 

healthy, and empowered study. Am J Clin Nutr. 

2007;86:566-572.

17. Williamson KB. Strength training for women [Women’s Heart Foundation Website]. 2007. Available 

at: http://www.womensheart.org/content/exercise

/strength_training.asp. Accessed February 2, 2015.

18. Garber CE, Blissmer B, Deschenes MR, et al. 

Quantity and quality of exercise for developing 

and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy 

adults: guidance for prescribing exercise. Med Sci 

Sports Exerc. 2011;43(7):1334-1359

19. Kraemer WJ, Mazzetti SC, Nindl BC, Gotshalk 

LA, Volek JS, Bush JA, Marx JO, et al. Effect of 

resistance training on women’s strength/power and 

occupational performances. Med Sci Sports Exerc. 

2001;33(6):1011-1025.

20. Knapik JJ, Scott SJ, Sharp MA, et al. The basis 

for prescribed ability group run speeds and distances in US Army basic combat training. Mil Med. 

2006;171(7):669-677.

21. Smith B, Ryan MAK, Wingard D, et al. Cigarette 

smoking and military deployment. Am J Prev Med. 

2008;35(6):539-546.

22. Boos CJ, Croft AM. Smoking rates in the staff of 

a military field hospital before and after wartime 

deployment. J R Soc Med. 2004;97(1):20-22.

23. Jones SB, Knapik JJ, Sharp MA, Darakjy S, Jones 

BH. The validity of self-reported physical fitness 

test scores. Military Medicine, 2007;172(2):115-120.

Authors

Mrs Anderson is an Epidemiologist for the Injury Prevention Program of the Epidemiology and Disease Surveillance Portfolio, US Army Public Health Command, 

Aberdeen Proving Ground, Maryland.

Mr Grier is a Kinesiologist for the Injury Prevention 

Program of the Epidemiology and Disease Surveillance 

Portfolio, US Army Public Health Command, Aberdeen 

Proving Ground, Maryland.

Dr Canham-Chervak is a Senior Epidemiologist for the 

Injury Prevention Program of the Epidemiology and 

Disease Surveillance Portfolio, US Army Public Health 

Command, Aberdeen Proving Ground, Maryland.

Mr Bushman is an Exercise Physiologist for the Injury 

Prevention Program of the Epidemiology and Disease 

Surveillance Portfolio, US Army Public Health Command, Aberdeen Proving Ground, Maryland.

Dr Jones is a Program Manager for the Injury Prevention 

Program of the US Army Public Health Command, Aberdeen Proving Ground, Maryland.
April – June 2015 39

As combat roles become open to women serving in the 

military, questions about their ability to maintain the 

physical demands and stay injury-free in these roles have 

been raised.1,2 Musculoskeletal injuries (MSK-I) and other noncombat illnesses are a leading cause of lost-duty 

time and morbidity among training and deployed military populations, particularly among women.3-8 Today, 

women comprise approximately 13% of the US armed 

forces9; however, they are more likely than men to suffer 

from MSK-I3,5-7,10-12 and be medically discharged from 

service due to their training-related injuries.13 Other risk 

factors for MSK-I and physical activity-related conditions (eg, heat stroke, exertional rhabdomyolysis) in 

women include older age, lower body mass/bone density, lower physical fitness levels, lower body mass index (BMI) and previous MSK-I history.6,10,14,15 High-risk 

psychological and behavioral factors, which may be inflated in the military,16 also differ by sex.17,18 Women, for 

example, report higher rates of disordered sleep,18 which 

may contribute to their increased risk for MSK-I.19 In 

contrast, men report higher rates of alcohol and tobacco 

use,16 which contributes to their MSK-I.7

Physical Fitness and Injury Reporting Among

 Active Duty and National Guard/Reserve

 Women: Associations with Risk and

 Lifestyle Factors

Josh B. Kazman, MS

Sarah de la Motte, PhD, MPH, ATC

Elizabeth M. S. Bramhall, MPH

Dianna L. Purvis, PhD

Patricia A. Deuster, PhD, MPH

Abstract

Objective: As more women enter the military, it is important to understand how different risks and lifestyle 

factors influence physical fitness and injury among women in both active duty (AD) and National Guard/Reserve (NG/R). Women in military service are less fit and more likely to suffer musculoskeletal injuries during 

physical training than men. They also use more medical care during deployment than men. Using data from 

the Comprehensive Soldier and Family Fitness Global Assessment Tool 2.0 (GAT 2.0), self-reported health and 

lifestyle and behavioral risk factors were analyzed in nondeployed Army personnel, with the goals of examining (1) service-component differences across traditional risk and lifestyle factors, and (2) correlates of physical 

performance and physical activity-related injury.

Methods: Self-report GAT 2.0 data included health risk factors (overall perceived health, sleep, diet, tobacco 

and alcohol use), self-reported health metrics (height, weight, Army Physical Fitness Test (APFT) scores), and 

history of physical activity-related injury. The GAT 2.0 was completed by 1,322 AD and 1,033 NG/R women, 

and APFT data were available for a subsample of 605 AD and 582 NG/R women.

Results: Initial analyses of GAT 2.0 data indicated that AD had higher rates of fair/poor perceived health, poor 

sleep, and unhealthy diet compared to NG/R women. However, AD women had a lower APFT fail rate (8%) 

than NG (27%) and R (28%). Active duty women were more likely to experience a physical injury in the past 

6 months (38%) than NG (19%) and R (22%) women, and more likely to seek medical care than NG/R women. 

Across all service components, predictive factors for APFT failure included high body mass index (BMI), fair/

poor health, and unhealthy diet. Predictive factors for physical injury included high BMI, fair/poor health, and 

binge drinking.

Conclusion: Our analyses suggest that AD women Soldiers are more physically fit than NG/R women Soldiers, 

which is accompanied by a greater prevalence of physical activity-related injuries. As women’s roles expand 

into combat military occupation specialties, a thorough understanding of service component differences will 

be critical to inform training programs, mitigate physical injury, and enhance force health protection and 

readiness.
40 http://www.cs.amedd.army.mil/amedd_journal.aspx

Service component differences further complicate 

MSK-I concerns in military women. During Operation 

Iraqi Freedom and Operation Enduring Freedom, over 

650,000 Army and Air National Guard (NG) Soldiers 

deployed, which represented over 30% of the fighting 

force.20 Even though active duty (AD) and NG troops 

may have similar physical fitness immediately prior to 

deployment,21 NG soldiers used greater medical care 

and suffered from more MSK-I during deployment than 

AD women.11 And even though women serving in the 

Army as AD, NG, or reserve (R) are expected to maintain similar levels of physical fitness, their levels of activity are likely different. For example, AD Soldiers typically spend 1-1.5 hours, 4 days per week participating 

in physical fitness training with their unit, whereas NG 

and R Soldiers are expected to individually maintain 

physical fitness standards.22 However, little is known 

about how these service components differ in terms of 

physical fitness, MSK-I, and other health factors outside 

of deployment.11,23,24

The Comprehensive Soldier and Family Fitness (CSF2)

Global Assessment Tool 2.0 (GAT 2.0) is an annual online survey of physical, emotional, social, family, and 

spiritual fitness in nondeployed Army personnel.25 The 

GAT 2.0 is part of a larger multifaceted program designed to build and improve psychological resilience 

and warfighter well-being.26 The GAT 2.0 includes all 

Army service components, so it provides a unique opportunity to assess a variety of risk factors among Army 

AD, NG, and R. Therefore, the objectives of the present 

study were to examine how traditional risk and lifestyle 

factors related to physical performance and to physical injury among female Soldiers across service components. Identifying key risk factors related to physical 

injury and performance in female AD, NG, and R Soldiers would be critical for revising training programs 

and implementing injury mitigation strategies.

Methods

As a key component of the Army’s CSF2 program, nondeployed Army soldiers are required to complete the 

GAT on an annual basis (while it is optional for their 

families and DoD civilians).25 The GAT is a self-report 

online survey that assesses 5 components of strength: 

social, emotional, family, spiritual and physical fitness.27 In 2012, 57 pilot questions were added to the 

original 105 questions in order to more accurately assess 

physical fitness, nutrition, and sleep quality. The present study consists of a subset of Army AD, NG and R 

female Soldiers (n=2,335) who completed the updated 

GAT over a 2-week period in July 2012. Fifty participants were excluded due to missing health behavior data, 

which allowed for a total sample size of 2,305 Army AD 

(n=1,014; 44%), NG (n=645; 28%), and R (n=646; 28%) 

women. Participants were on average 26.4±8.1 (17 to 58) 

years of age, and 15% were officers. Table 1 contains 

additional participant characteristics divided by service 

component (AD, NG, R).

Health and Behavioral Risk Factors

The GAT 2.0 assessment includes lifestyle health behaviors (sleep, diet, heavy alcohol use and tobacco use) and 

general health questions. Measures were dichotomized, 

as described below, based on available standards or previous research where available.

Body Mass Index. Self-reported height and weight 

were used to compute body mass index (BMI, weight 

(kg)·height (m)-2), which was then dichotomized at the 

cut point 27.5 kg/m2, based on Army Regulation 600-9.

28

Although low BMI has previously been reported to be a 

risk factor for MSK-I among women,6 only 1% of participants in our sample were underweight (BMI<18.5), 

and these women were included in the normal weight 

category.

Nutrition Behavior. Nutrition behavior was assessed by 

using a 5-question Healthy Eating Score (HES-5).29 This 

measure was derived from the more comprehensive US 

Department of Agriculture’s Healthy Eating Index,30 but 

with only 5 food category components: the frequency 

of fruit, vegetable, whole grain, dairy, and fish intake, 

answered by using a 6-point Likert-type scale (ranging from 0, “rarely or never”, to 5, “3 or more times per 

day”). The HES-5 was extensively analyzed in the larger 

CSF2 GAT 2.0 sample,29 and has adequate internal consistency (Cronbach α in present sample=0.74). Based on 

previous analyses,29 the HES-5 was dichotomized, such 

that participants with a sum score in the lowest quartile 

were coded as unhealthy eaters.

Sleep. Sleep was assessed with the 2-item31 version of the 

Pittsburgh Insomnia Rating Scale (PIRS2),32 which was 

also extensively analyzed in the larger CSF2 GAT 2.0 

sample.18 The 2 items ask about sleep over the past 7 days 

with a focus on how much a person was bothered by lack 

of energy due to poor sleep and perception of overall 

sleep satisfaction, each answered along separate 4-point 

Likert-type scales. The items were developed using 

item-response theory to efficiently screen for insomnia31

with an overall cutoff score that was used to dichotomize 

participants. The PIRS2 demonstrated adequate internal 

consistency (Cronbach α=0.81) in the present analysis.

Additional Health Behaviors. Additional health behaviors included tobacco and alcohol use. Tobacco was assessed by asking participants about their “use of tobacco 

PHYSICAL FITNESS AND INJURY REPORTING AMONG ACTIVE DUTY AND NATIONAL GUARD/RESERVE 

WOMEN: ASSOCIATIONS WITH RISK AND LIFESTYLE FACTORS
April – June 2015 41

THE ARMY MEDICAL DEPARTMENT JOURNAL

products (cigarettes, cigars, smokeless tobacco, chew, 

dipping, pinching) in the last year,” with responses dichotomized based on regular (≥4 times per week) use 

versus minimal (<4 times per week, no use, or quit in 

past year) use of tobacco products. Since only 1.4% of 

females reported use of smokeless tobacco, it was not 

feasible to distinguish between types of tobacco use. 

Heavy alcohol use was assessed with the question “Have 

you exceeded 5 alcoholic drinks on any single occasion 

during the past 3 months?” This is a common definition 

of binge drinking33 and has been used in previous military survey research.16

General Health. General health was measured with the 

single item, “How do you consider your general health?”, 

which was answered along a 4-point Likert-type scale 

(excellent, good, fair, and poor), to include “don’t know.” 

Using a single question to measure overall health has 

been shown to provide an efficient and reliable composite 

of both physical and mental health, or measure of global health.34 Although general health is broader than the 

other predictors above, and is often assessed as a health 

outcome, it has strong predictive power for injury risk35-37

and is a practical screening measure in general.34,38 As 

with previous research in this sample,18,29 responses to 

this question were dichotomized, with participants reporting “fair” and “poor” health categorized as “at risk.”

Outcome Variables

The primary health outcomes of interest from the GAT 

2.0 were self-reported physical fitness, self-reported 

physical activity-related injury in the previous 6 months, 

and medical care seeking for any physical activity-related injury.

Physical Fitness. Participants reported raw data scores 

from their most recent Army Physical Fitness Test 

(APFT, number of push-ups, number of sit-ups, and runtime in minutes and seconds), which were converted to a 

pass/fail score based on age-specific Army standards.22

Physical Injury Reporting and Medical Care Seeking Behaviors. Participants indicated whether they had experienced a “physical activity-related injury” over the past 

6 months. Examples of physical activity-related injuries 

included “joint sprains, muscle or tendon strains, concussion, broken bone, shin splints, heat stroke, and/or 

exertional rhyabdomyolysis.” Participants reporting a 

physical activity-related injury were then asked whether 

or not they “sought medical care for the reported injury.”

Statistical Analyses

Service component differences for all GAT 2.0 variables 

were compared using Pearson χ2 analyses. Pearson χ2

analyses were also used to test univariate relations between health/behavioral risk factor categories, including service component, and outcome measures. Among 

those participants who sustained a physical activityrelated injury, χ2 analyses were conducted to determine 

service-component differences in seeking medical care 

for that injury (eg, do injured AD seek medical care for 

their injuries more than injured NG?). For all univariate 

analyses, measures of effect size include Cramér’s v (suitable for ordinal or dichotomous variable analyses,39 such 

that a small effect=0.1, moderate=0.3, and large≥0.5) or 

Cohen’s d (for continuous variables, notably age, such 

that small effect=0.2, moderate=0.5, and large≥0.8).40

Multivariate logistic regression analyses with backwards-stepwise methodology were used to determine 

predictive health and behavioral risk factors for the following outcomes: (1) APFT pass/fail, (2) physical injury, 

and (3) seeking medical care for a physical injury. First, 

demographic variables (age, service component, and 

rank) were force-entered. Next, health and behavioral 

risk factors were individually selected using backwards 

stepwise entry, with a P value for the likelihood ratio 

set at 0.1. Interactions between Army service component 

(AD, NG, R) and significant predictors from multiple regression analysis were tested. All analyses were conducted using SPSS Version 22.0 (IBM Corp, Armonk, NY).

Results

Table 1 presents descriptive statistics for all participants 

by service component. Pearson χ2 analyses revealed several service component differences among all GAT variables. Active duty participants had higher rates of most 

health and behavioral risk factors. Active duty participants were 1.3 (95% CI, 1.05-1.55; P<.05) times more 

likely to report fair/poor general health than NG; 1.3 

(95% CI, 1.04-1.72, P<.05) and 1.4 (95% CI, 1.09-1.83; 

P<.05) times more likely to report poor sleep than NG 

and R, respectively; and 1.2 (95% CI, 1.05-1.47; P<.05) 

times more likely to report an unhealthy diet than NG. 

In contrast, NG were 1.7 (95% CI, 1.25-2.23; P<.001) 

and 1.5 (95% CI, 1.13-1.99; P<.01) times more likely to 

report binge drinking than AD and R, respectively.

Other notable descriptive findings included AD women 

reporting fewer APFT failures (8%) than NG (27%) and 

R (28%) women (χ2=87.7, v=0.25, P<.001); R participants being 4.3 (95% CI, 3.04, 6.14; P<.001) and NG 

participants 4.0 (95% CI, 2.81-5.71; P<.001) times more 

likely to fail APFT compared to AD women. Active 

duty women also reported higher physical injury rates 

(28%) than NG (19%) or R (22%) women (χ2=84.0, 

v=0.19, P<.001), such that AD women were 2.6 (95% 

CI, 2.04-3.28; P<.001) times more likely than NG and 
42 http://www.cs.amedd.army.mil/amedd_journal.aspx

2.1 (95% CI, 1.70-2.69; P<.001) times more likely than 

R women to report a physical injury in the previous 6 

months. Among those with reported physical activityrelated injuries (n=624), 80% of AD sought medical 

care for the injury, compared to 76% of NG and 67% of 

R (χ2=8.4, v=0.12, P<.05); the difference between AD 

and R was statistically significant.

Outcome Variables: Univariate and Multivariate 

Analyses

APFT Failure. Table 2 presents 

univariate and multivariate analyses with APFT pass/fail as the 

outcome variable. On the left of 

Table 2, participant characteristics are presented for those who 

passed versus those who failed 

their APFT; multivariate regression results are depicted on the 

right. Univariate analyses revealed several significant associations between predictor and outcome variables, the majority of 

which were retained in the multivariate model. Namely, female 

Soldiers who were younger, enlisted, NG or R, with high BMI, 

poor diet, and self-reported fair/

poor overall health were more 

likely to fail the APFT.

Physical Injury. Table 3 presents 

univariate and multivariate analyses with physical injury as the 

outcome variable. On the left of 

Table 3, participant characteristics are presented for those who 

reported a physical injury versus 

those who did not report a physical injury. Women with high 

BMI and self-reported fair/poor 

overall health and binge drinking 

were more likely to report experiencing a physical injury in the 

previous 6 months. 

Medical Care Seeking Behavior 

for Physical Injury. Table 4 presents univariate and multivariate 

analyses with seeking medical 

care for a physical injury as the 

outcome variable. On the left of 

Table 4, participant characteristics are presented for those who 

sought medical care for a physical injury versus those 

who did not seek medical care for a physical injury. Results similar to physical injury were noted, with the exception that BMI was not retained in the medical care 

model.

No significant interactions between any health and behavioral risk factors and multivariate outcomes were 

noted.

PHYSICAL FITNESS AND INJURY REPORTING AMONG ACTIVE DUTY AND NATIONAL GUARD/RESERVE 

WOMEN: ASSOCIATIONS WITH RISK AND LIFESTYLE FACTORS

Table 1. Participant Characteristics and Service Group Differences.

All Women

(N=2,305)

Active Duty

(n=1,014)

National 

Guard

(n=645)

Reserve

(n=646)

Effect

Size*

Age (years) 26.4±8.13 26.7±7.64a 25.2±7.65a,b 27.3±9.16b 0.01†

Height (m) 1.63±0.08 1.63±0.08 1.63±0.08 1.62±0.09

Weight (kg) 66.4±10.63 66.2±9.84 66.5±11.10 66.8±11.41

BMI (kg/m2) (n=1,758)

High (>27.5) 22% 20%

(30.7±3.4)

24%

(30.7±3.2)

23%

(31.4±3.6)

0.05

Normal (18.5-27.5) 78% 80%

(23.6±2.1)

76%

(23.3±2.3)

77%

(23.6±2.3)

Value 25.2±3.9 25.0±3.7 25.0±4.1 25.3±4.3

Military Status

Officer 15% 19%a 9%a 13%a 0.12‡

Enlisted 85% 81% 91% 87%

Health

Fair/Poor 21% 24%a 19%a 20% 0.06†

Good/Excellent 79% 76% 81% 80%

Sleep (n=2,058)

Poor sleep 15% 18%a,b 13%a 13%b 0.07†

Good sleep 85% 82% 87% 87%

Diet

Unhealthy 27% 29%a 23%a 27% 0.05†

Healthy 73% 71% 77% 73%

Tobacco Use

Smoker 16% 16% 18% 15% 0.03

Nonsmoker 84% 84% 82% 85%

Alcohol Use

Binged 12% 10%a 16%a,b 11%b 0.08‡

Did not binge 88% 90% 84% 89%

APFT (n=1,431)

Fail 18% 8%a,b 27%a 28%b 0.25‡

Pass 82% 92% 73% 72%

Physical Injury (n=2,219)

Injured 28% 38%a,b 19%a 22%b 0.19‡

Not injured 72% 62% 81% 78%

Care for Injury (n=2,076)

Sought care 25% 34%a,b 17%a 18%b 0.19‡

Did not seek care 75% 66% 83% 82%

NOTE: For pairwise comparisons, values within a row sharing a common superscript (a or b) are 

significantly different from each other at P<.05.

*Omnibus effect size with η2 was used for continuous variables, while Cramer’s v was used for all other 

ordinal variables.

†P<.05

‡P<.001
April – June 2015 43

THE ARMY MEDICAL DEPARTMENT JOURNAL

Comment

Female service members comprise approximately 13% 

of the US Armed Forces,9 but are much more likely than 

men to suffer from MSK-I, even when exercising under 

the same conditions.3-7,10-12 Previous studies have identified numerous risk factors for poor health outcomes and 

physical injury in female service members,3,6,12,41 but few 

have focused on differences between AD, NG and/or R 

female Soldiers. As combat roles across service components open to women, the state of their health and fitness 

is of prime concern.1,2 One study comparing 

AD and NG female Soldiers preparing for deployment found that they had similar levels 

of fitness.21 However, during deployment, NG 

Soldiers appeared to seek more medical care 

and suffer from MSK-I more than AD.11 No 

studies had previously examined these differences outside of the deployment cycle. Our 

results demonstrate differences in physical 

fitness (APFT pass/fail) and physical injury 

across service components among women. 

Among NG and R women, age, enlisted status, 

high BMI, poor diet, and overall poor health 

were significantly associated with APFT failure. However, despite these lower levels of 

fitness, our findings show NG or R females 

were less likely to suffer from physical injury 

in the previous 6 months than AD females.

Physical fitness is one of the most influential factors related to self-reported perceived 

health and physical injury.23 A study by Warr 

et al23 demonstrated that cardiovascular fitness (VO2max) had the largest influence on 

perceived health changes over the deployment of a NG unit, regardless of baseline fitness. It is important to note that our results 

indicate that female Soldiers with high BMI 

and poor health were more likely to fail their 

APFT. Women serving in Army AD, NG, or 

R are expected to maintain similar levels of 

physical fitness, but requirements and expectations about how that fitness is achieved and 

maintained vary greatly. NG/R females are 

required to train with their unit once a month, 

but outside of this, they are expected to maintain physical fitness standards on their own. 

Whereas Army guidelines related to physical 

fitness have been published as Field Manual 

7-22, NG/R Soldiers who are not within a 

structured environment may find it difficult 

to use this manual when daily physical training is not commonplace.

For other health and behavioral risk factors, AD females 

were more likely to report fair/poor health, poor sleep, 

and consuming an unhealthy diet compared to NG/R 

females. Having healthy food patterns should improve 

overall health and wellness, and be one approach for 

physical injury prevention.1 The finding of poorer eating 

in AD females is worrisome, as healthy dietary patterns 

can counteract glycogen depletion, restore energy balance, mitigate fatigue, and minimize muscle damage.1

In the present study, AD females were more likely to 

Table 2. Univariate and Multivariate Predictors of APFT Failure.

Univariate

(N=1,431)

Backwards

Stepwisea

(N=1,174)

Failed

APFT

(n=259)

Passed

APFT

(n=1,172)

Effect

Sizeb Adjusted OR(95% CI)

Age (years) 22.9±5.50 26.8±7.86 0.20c 0.9 (0.89, 0.94)c

Army Status

Active Duty 8% 92% 0.25c

National Guard 27% 73% 3.7 (2.50, 5.57)c

Reserve 28% 72% 4.9 (3.27, 7.43)c

Military Status

Officer 6% 94% 0.14c 1.8 (0.95, 3.29)

Enlisted 20% 80%

BMI (kg/m2) (n=1,174)

High (>27.5) 26% 74% 0.12c 2.2 (1.53, 3.21)c

Normal (18.5-27.5) 15% 85%

Health

Fair/Poor 24% 76% 0.08d 1.6 (1.12, 2.40)d

Good/Excellent 17% 83%

Sleep (n=1,267)

Poor sleep 20% 80% 0.01

Good sleep 18% 82%

Diet

Unhealthy 22% 78% 0.06d 1.6 (1.10, 2.25)d

Healthy 17% 83%

Tobacco Use

Smoker 23% 77% 0.06d –

Nonsmoker 17% 83%

Alcohol Use

Binged 20% 80% 0.02

Did not binge 18% 82%

Physical Injury (n=1,387)

Injured 15% 85% 0.04

Not injured 19% 81%

Care for Injury (n=1,296)

Sought care 17% 83% 0.02

Did not seek care 18% 82%

aMultiple backwards stepwise regression conducted, with demographic variables (age, 

Army status, military status) force-entered and significant health risks then entered 

stepwise.

bFor effect size, Cohen’s d was used for continuous variables (age), while Cramer’s v was 

used for all other ordinal variables.

cP<.001

dP<.05
44 http://www.cs.amedd.army.mil/amedd_journal.aspx

report physical injury than NG/R over the past 6 

months, and unhealthy diet, along with poor sleep 

and overall health, may be contributing factors.

In addition to AD status, predictive factors for 

physical injury in our study included high BMI, 

poor overall health, and binge drinking behaviors, which correspond to previously established 

risk factors in similar populations.3,10,42 Previous research has linked low BMI to MSK-I risk 

among women.6 In the present study, the number 

of women with low BMI was too small to determine its effect on any of study outcomes. Smoking behavior, which has previously been strongly 

linked to physical injury,7,43 had a weak effect on 

fitness and injury in univariate analyses, and became nonsignificant in multiple regression analysis. However, female Soldiers tend to use tobacco 

products less than male Soldiers, which may account for this finding.16

Of the 624 females who reported a physical injury in the previous six months, AD were slightly more likely to seek medical care (80%) than 

NG (76%) or R (67%). It is unclear whether this 

reflects differences in injury severity, access to 

medical care, or both. The lower rate of seeking 

medical care among injured R may warrant further investigation. Changes in fitness status over 

deployment appear to be a particularly strong 

risk factor for noncombat physical injury. In 

particular, NG male and female Soldiers who experienced declines in fitness during deployment 

were twice as likely to use medical resources for 

noncombat physical injuries than those who experienced improvements in fitness.23

Our study has several limitations. First, selfreport data are not always consistent with measured values, although the data are mixed.44,45

Importantly, the GAT 2.0 was rigorously developed, with simple measures of physical fitness, dietary 

patterns, health, and wellness, all of which have been 

previously validated. Second, the military occupational specialties (MOSs) of women in this cohort are not 

known. Particular MOSs may vary greatly in their physical and mental demands, and therefore exhibit diverse 

health and behavioral outcomes. Third, it is unclear as 

to whether these women had deployed in the previous 6 

months, and thus we cannot ascertain how deployment 

may have affected the service component differences 

in fitness and injury history. Lastly, we have no prior 

injury history information or specific diagnosis codes 

for physical injuries, both of which could provide more 

granularity with regard to injury risk factors specific to 

each service component. Despite these limitations, the 

GAT 2.0 data have allowed for the simultaneous investigation into the broad range of previously identified potential risk factors in a large population of female Soldiers. This is important for targeting risk factors.

In conclusion, our study is the first to examine service 

component differences in health, fitness, and behavioral risk factors for fitness and MSK-I in female service 

members. In particular, we simultaneously examined 

multiple, previously validated measures of physical fitness, and health and behavioral risk factors using the 

PHYSICAL FITNESS AND INJURY REPORTING AMONG ACTIVE DUTY AND NATIONAL GUARD/RESERVE 

WOMEN: ASSOCIATIONS WITH RISK AND LIFESTYLE FACTORS

Table 3. Univariate and Multivariate Predictors of Reported Physical 

Injury.

Univariate

(N=2,219)

Backwards

Stepwisea

(N=1,174)

Sought

Care

(n=624)

Did Not

Seek Care

(n=1,595)

Effect

Sizeb Adjusted OR(95% CI)

Age (years) 27.1±8.20 26.3±8.13 0.05c 1.0 (0.99, 1.02)

Army Status

Active Duty (ref) 22% 78% 0.19d

National Guard 18% 81% 0.3 (0.26, 0.46)d

Reserve 22% 78% 0.5 (0.35, 0.61)d

Military Status

Officer 26% 74% 0.02 1.3 (0.95, 1.88)

Enlisted 29% 71%

BMI (kg/m2) (n=1,699)

High (>27.5) 37% 63% 0.09d 1.4 (1.10, 1.90)d

Normal (18.5-27.5) 27% 73%

Health

Fair/Poor 43% 57% 0.18d 2.4 (1.83, 3.09)d

Good/Excellent 24% 76%

Sleep (n=1,980)

Poor sleep 44% 56% 0.13d –

Good sleep 27% 73%

Diet

Unhealthy 32% 68% 0.05c –

Healthy 27% 73%

Tobacco Use

Smoker 33% 67% 0.05c –

Nonsmoker 27% 73%

Alcohol Use

Binged 39% 61% 0.09d 1.6 (1.14, 2.17)d

Did not binge 27% 73%

APFT (n=1,387)

Fail 26% 74% 0.04

Pass 31% 69%

aMultiple backwards stepwise regression conducted, with demographic variables 

(age, Army status, military status) force-entered and significant health risks then 

entered stepwise.

bFor effect size, Cohen’s d was used for continuous variables (age), while Cramer’s v was used for all other ordinal variables.

cP<.05

dP<.001
April – June 2015 45

THE ARMY MEDICAL DEPARTMENT JOURNAL

GAT 2.0, a mandatory online reporting mechanism to 

assess the overall health of service members. As women are officially integrated into frontline combat roles, 

their performance during combat training may be determined by various risk factors. Our results show that 

service component is a key factor to consider as women 

transition into these roles. Overall, NG and R female 

Soldiers are more likely to have lower physical fitness 

(APFT pass rates), while women with high BMI and 

self-reported poor health are at greater risk for physical 

injury. These data lend credence towards the development of component-specific human performance optimization strategies for women as their roles in the military expand.

References

1. Epstein Y, Yanovich R, Moran DS, Heled Y. 

Physiological employment standards IV: integration of women in combat units physiological 

and medical considerations. Eur J Appl Physiol. 

2013;113(11):2673-2690.

2. Finestone AS, Milgrom C, Yanovich R, Evans 

R, Constantini N, Moran DS. Evaluation of the 

performance of females as light infantry soldiers. BioMed Res Int. 2014;Epub August 18, 

2014.

3. Altarac M, Gardner JW, Popovich RM, Potter 

R, Knapik JJ, Jones BH. Cigarette smoking 

and exercise-related injuries among young men 

and women. Am J Prev Med. 2000;18(suppl 

3):96-102.

4. Bijur PE, Horodyski M, Egerton W, Kurzon M, 

Lifrak S, Friedman S. Comparison of injury 

during cadet basic training by gender. Arch Pediatr Adolesc Med. 1997;151(5):456-461.

5. Darakjy S, Marin RE, Knapik JJ, Jones BH. 

Injuries and illnesses among armor brigade 

soldiers during operational training. Mil Med. 

2006;171(11):1051-1056.

6. Knapik J, Montain SJ, McGraw S, Grier T, 

Ely M, Jones BH. Stress fracture risk factors 

in basic combat training. Int J Sports Med. 

2012;33(11):940-946.

7. Knapik JJ, Sharp MA, Canham-Chervak M, 

Hauret K, Patton JF, Jones BH. Risk factors for 

training-related injuries among men and women in basic combat training. Med Sci Sports Exerc. 2001;33(6):946-954.

8. Reynolds KL, Heckel HA, Witt CE, et al. 

Cigarette smoking, physical fitness, and injuries in infantry soldiers. Am J Prev Med. 

1994;10(3):145-150.

9. Cawkill P, Rogers A, Knight S, Spear L. Women in 

Ground Close Combat Roles: The Experiences of 

other Nations and a Review of the Academic Literature. Porton Down, Salisbury, Wiltshire, UK: 

Defence Science and Technology Laboratory; 2009.

10. Grier TL, Knapik JJ, Canada S, Canham-Chervak 

M, Jones BH. Risk factors associated with selfreported training-related injury before arrival at 

the US Army Ordnance School. Public Health. 

2010;124(7):417-423.

11. Hartstein BH, Boor DD, Nystuen CM. Comparison 

of medical visits by active duty and National Guard 

soldiers at a forward deployed medical facility in 

Iraq. Mil Med. 2009;174(11):1167-1171.

Table 4. Univariate and Multivariate Predictors of Seeking Medical Care.

Univariate

(N=2,076)

Backwards

Stepwisea

(N=1,174)

Sought

Care

(n=509)

Did Not

Seek Care

(n=1,567)

Effect

Sizeb Adjusted OR(95% CI)

Age (years) 26.9±8.27 26.4±8.20 0.03 1.0 (1.00, 1.02)

Army Status

Active Duty 34% 66% 0.19c

National Guard 17% 87% 0.4 (0.26, 0.51)c

Reserve 18% 82% 0.4 (0.31, 0.54)c

Military Status

Officer 20% 80% 0.04d 1.3 (0.95, 1.88)

Enlisted 25% 75%

BMI (kg/m2) (n=1,591)

High (>27.5) 34% 66% 0.11c –

Normal (18.5-27.5) 22% 78%

Health

Fair/Poor 36% 64% 0.14c 1.8 (1.41, 2.29)c

Good/Excellent 21% 79%

Sleep (n=1,864)

Poor sleep 35% 65% 0.10c –

Good sleep 23% 77%

Diet

Unhealthy 27% 73% 0.03

Healthy 24% 76%

Tobacco Use

Smoker 29% 71% 0.04d –

Nonsmoker 24% 76%

Alcohol Use

Binged 32% 68% 0.07c 1.6 (1.18, 2.16)c

Did not binge 23% 77%

APFT (n=1,296)

Fail 24% 76% 0.02

Pass 26% 74%

aMultiple backwards stepwise regression conducted, with demographic variables 

(age, Army status, military status) force-entered and significant health risks then 

entered stepwise.

bFor effect size, Cohen’s d was used for continuous variables (age), while Cramer’s v was used for all other ordinal variables.

cP<.001

dP<.05
46 http://www.cs.amedd.army.mil/amedd_journal.aspx

12. Henderson NE, Knapik JJ, Shaffer SW, McKenzie 

TH, Schneider GM. Injuries and injury risk factors among men and women in US Army Combat 

Medic Advanced individual training. Mil Med. 

2000;165(9):647-652.

13. Springer BA, Ross AE. Musculoskeletal Injuries in Military Women. Fort Sam Houston, TX: 

The Borden Institute; 2011. Available at: http://

www.cs.amedd.army.mil/borden/FileDownload

public.aspx?docid=b42d1acd-0b32-4d26-8e22-

4a518be998f7. Accessed February 11, 2015.

14. Hauret KG, Jones BH, Bullock SH, Canham-Chervak M, Canada S. Musculoskeletal injuries description of an under-recognized injury problem among 

military personnel. Am J Prev Med. 2010;38(suppl 

1):S61-S70.

15. Jones BH, Knapik JJ. Physical training and exercise-related injuries. Surveillance, research and 

injury prevention in military populations. Sports 

Med. 1999;27(2):111-125.

16. Bray RM, Pemberton MR, Hourani LL, et al. 2008 

Department of Defense Survey of Health Related 

Behaviors Among Active Duty Military Personnel. Research Triangle Park, NC: RTI International; 2009. Available at: http://www.tricare.mil/

tma/2008healthbehaviors.pdf. Accessed February 

11, 2015.

17. Jacobson IG, Horton JL, Smith B, et al. Bodybuilding, energy, and weight-loss supplements 

are associated with deployment and physical activity in US military personnel. Ann Epidemiol.

2012;22(5):318-330.

18. Lentino CV, Purvis DL, Murphy KJ, Deuster PA. 

Sleep as a component of the performance triad: the 

importance of sleep in a military population. US 

Army Med Dep J. October-December 2013:98-108.

19. Finestone A, Milgrom C. How stress fracture incidence was lowered in the Israeli army: a 25-yr 

struggle. Med Sci Sports Exerc. 2008;40(suppl 

11):S623-S629.

20. National Guard Association of the United 

States. At a glance. National Guard Magazine. 

2012;66(4):52-82.

21. Warr BJ, Alvar BA, Dodd DJ, et al. How do they 

compare?: an assessment of predeployment fitness 

in the Arizona National Guard. J Strength Cond 

Res. 2011;25(11):2955-2962.

22. Field Manual 7-22: Army Physical Readiness 

Training. Washington, DC: US Department of the 

Army; 2012.

23. Warr BJ, Heumann KJ, Dodd DJ, Swan PD, Alvar 

BA. Injuries, changes in fitness, and medical demands in deployed National Guard soldiers. Mil 

Med. 2012;177(10):1136-1142.

24. Warr BJ, Scofield DE, Spiering BA, Alvar BA. Influence of training frequency on fitness levels and 

perceived health status in deployed National Guard 

soldiers. J Strength Cond Res. 2013;27(2):315-322.

25. Peterson C, Park N, Castro CA. Assessment for 

the U.S. Army Comprehensive Soldier Fitness program: the Global Assessment Tool. Am Psychol. 

2011;66(1):10-18.

26. Cornum R, Matthews MD, Seligman ME. Comprehensive soldier fitness: building resilience in 

a challenging institutional context. Am Psychol. 

2011;66(1):4-9.

27. Seligman ME. Building resilience. Harv Bus Rev. 

2011;89(4):100-106.

28. Army Regulation 600-9: The Army Body Composition Program.Washington, DC: US Dept of the 

Army; 2013.

29. Purvis DL, Lentino CV, Jackson TK, Murphy 

KJ, Deuster PA. Nutrition as a component of the 

performance triad: how healthy eating behaviors 

contribute to soldier performance and military 

readiness. US Army Med Dep J. October-December 

2013:66-78.

30. Guenther PM, Reedy J, Krebs-Smith SM. Development of the Healthy Eating Index-2005. J Am Diet 

Assoc. 2008;108(11):1896-1901.

31. Moul DE, Mai E, Shablesky M, et al. The 2-item 

and 20-item versions of the Pittsburgh Insomnia 

Rating Scale (PIRS): design, methods and initial 

modeling. Paper presented at: Annual Meeting 

of the World Psychiatric Association; 2009; Melbourne, Australia.

32. Moul DE, Pilkonis PA, Miewald JM, Carey TJ, 

Buysse DJ. Preliminary study of the test-retest 

reliability and concurrent validities of the Pittsburgh Insomnia Rating Scale (PIRS). Sleep. 

2002;25:A246-A247.

33. Canagasaby A, Vinson DC. Screening for hazardous or harmful drinking using one or two 

quantity-frequency questions. Alcohol Alcohol.

2005;40(3):208-213.

34. Hays RD, Bjorner JB, Revicki DA, Spritzer KL, 

Cella D. Development of physical and mental health 

summary scores from the patient-reported outcomes measurement information system (PROMIS) global items. Qual Life Res. 2009;18(7):873-880.

35. Cunningham R, Carter K, Connor J, Fawcett J. 

Does health status matter for the risk of injury? N Z 

Med J. 2010;123(1327):35-46.

36. Mattila VM, Jormanainen V, Sahi T, Pihlajamäki H. An association between socioeconomic, 

health and health behavioural indicators and 

fractures in young adult males. Osteoporos Int. 

2007;18(12):1609-1615.

PHYSICAL FITNESS AND INJURY REPORTING AMONG ACTIVE DUTY AND NATIONAL GUARD/RESERVE 

WOMEN: ASSOCIATIONS WITH RISK AND LIFESTYLE FACTORS
April – June 2015 47

THE ARMY MEDICAL DEPARTMENT JOURNAL

37. Rice VJ, Mays MZ, Gable C. Self-reported 

health status of students in-processing into military medical advanced individual training. Work. 

2009;34(4):387-400.

38. DeSalvo KB, Bloser N, Reynolds K, He J, Muntner 

P. Mortality prediction with a single general selfrated health question. A meta-analysis. J Gen Intern Med. 2006;21(3):267-275.

39. McHugh ML. The chi-square test of independence. 

Biochem Med. 2013;23(2):143-149.

40. Cohen J. Statistical Power Analysis for the Behavioral Sciences. 2nd ed. Hillsdale, NJ: Lawrence 

Erlbaum Associates; 1988.

41. Evans R, Reynolds K, Creedon J, Murphy M. Incidence of acute injury related to fitness testing of U.S. 

Army personnel. Mil Med. 2005;170(12):1005-1011.

42. Ivković A, Franić M, Bojanić I, Pećina M. Overuse injuries in female athletes. Croat Med J. 

2007;48(6):767-778.

43. Knapik JJ, Swedler DI, Grier TL, et al. Injury reduction effectiveness of selecting running shoes 

based on plantar shape. J Strength Cond Res. 

2009;23(3):685-697.

44. Keith NR, Clark DO, Stump TE, Callahan CM. 

Validity of self-reported fitness across black and 

white race, gender, and health literacy subgroups. 

Am J Health Promot. 2014 [March 26 Epub ahead 

of print].

45. Lassale C, Peneau S, Touvier M, et al. Validity of 

web-based self-reported weight and height: results 

of the Nutrinet-Sante study. J Med Internet Res. 

2013;15(8):e152.

Authors

Mr Kazman, Dr de la Motte, Ms Bramhall, Dr Purvis, 

and Dr Deuster are with the Consortium for Health 

and Military Performance, Department of Military and 

Emergency Medicine, Uniformed Services University of 

the Health Sciences, Bethesda, Maryland.
48 http://www.cs.amedd.army.mil/amedd_journal.aspx

As women enter into previously closed military occupational specialties,1

 they are likely to be exposed more to 

challenging and extreme conditions. For example, exercise in extreme environments could increase their risk 

for exertional heat illness (EHI)2 and exertional heat 

stroke (EHS), the most extreme type of EHI and a fatal threat to Warfighters,3-6 athletes,7-9 and others who 

engage in physically demanding jobs.10 EHS occurs during physical exertion, typically in a hot and humid environment, and is characterized by a rise in core body 

temperature (usually 40°C or more), accompanied by 

central nervous system dysfunction (eg, delirium, convulsions, coma) and sometimes multiple organ system 

failure.11 Although EHS continues to be a significant 

threat to Warfighters’ health, force readiness, and operational resources,3,5 in most cases it is preventable, 

given our understanding of predisposing risk factors 

and proper implementation of safeguards.5,12-15 Key risk 

factors include dehydration, lack of acclimatization, recent illness,16,17 certain classes of medication,18 and prior 

Women and Exertional Heat Illness:

 Identification of Gender Specific Risk Factors

Josh B. Kazman, MS Danit Atias, PhD

Dianna L. Purvis, PhD Stephanie Van Arsdale, MS

Yuval Heled, PhD Patricia A. Deuster, PhD, MPH

Peter Lisman, PhD

Abstract

Objective: With the expanding role of women into previously closed combat military occupational specialties, 

women will likely be exposed more to challenging and extreme conditions. Physical work or exercise in extreme environments could increase the risk for exertional heat illness (EHI) and exertional heat stroke (EHS), 

the most severe type of EHI. Although men have higher rates of EHS than women, women have slightly higher 

rates of other EHI. Women may respond differently to exertion in the heat than men, as they typically have 

higher percentage of body fat (BF%) and lower aerobic power. Further, published pilot-data using the Israeli 

heat tolerance test (HTT) indicate that women are more likely to be classified as heat intolerant than men. The 

objectives of the present study were to (1) compare male and female classification patterns of heat tolerance, 

and (2) identify EHI risk factors that might account for the relationship between heat tolerance classification 

and sex.

Methods: Fifty-five male and 20 female participants were recruited from military and university communities to participate in a standardized HTT. Subjects underwent measures to calculate anthropometric variables 

(BF%, body surface area, and waist circumference), a maximal oxygen uptake test to assess aerobic power 

(VO2max), and a standardized HTT, which consisted of treadmill walking at 5 km/h at a 2% grade for 120 minutes at 40°C and 40% relative humidity. Heat intolerance was defined as attaining a maximum heart rate (HR) 

greater than 150 bpm or a core body temperature (Tc) more than 38.5°C. Separate hierarchical regressions were 

conducted using categorical (heat tolerant/intolerant) and continuous (physiological strain index, maximum 

HR, Tc) HTT outcomes. Risk factors were identified with and without controlling for sex.

Results: Women were 3.7 (95% CI, 1.21-11.24) times more likely to be heat intolerant than men (χ2=6.85, P<.01). 

Compared to men, women had significantly higher BF% and lower body surface area, waist circumference, and 

VO2max. All heat intolerant participants had lower VO2max and higher BF% than those who were classified as 

heat tolerant. When VO2max and BF% were entered into regression equations to predict HTT outcomes, sex became nonsignificant; VO2max predicted maximum HR and physiological strain index after controlling for sex.

Conclusion: The present study found that differences between men and women in heat tolerance classification 

are largely explained by VO2max. The higher rates of heat intolerance among women likely correlate with 

higher EHI risk, and underscore the need to understand the physiological and thermoregulatory differences 

between men and women. As lower aerobic power is a major risk factor for EHI, maximizing the aerobic power 

of women will be critical to force health protection and readiness as they integrate into combat military occupational specialties.
April – June 2015 49

EHS.3,13,14,16,17,19 Additionally, poor aerobic power and 

high percentage of body fat, two of the strongest risk 

factors for EHI in the military,20-22 may be of particular 

concern for women.

Since men in combat military training typically engage 

in more physically demanding activities under many environmental conditions than women, the prevalence of 

EHS is higher in men than women.3,4,23,24 In 2013, 324 

cases of EHS and 1,701 additional EHI were reported 

in the US armed forces, which represented a decline in 

EHI over the previous few years.3 The incidence rate 

of EHS was higher among men (0.24 per 1,000 personyears) than women (0.15). However, for all other EHI, 

women had a higher rate (1.30) than men (1.19). Thus, 

when baseline rates are corrected for gender participation, women have a slightly higher incidence of EHI (not 

EHS) than men, both in the military3,4,25 and in the general population.23,24

Although men and women thermoregulate internal temperature in a similar manner, key sex differences exist 

in how they respond to heat.26,27 Most notably, women 

have a higher baseline core temperature,28,29 especially 

during the luteal phase of the menstrual cycle.30,31 Thus, 

women begin to sweat at a higher core temperature than 

men.32 Women typically have a lower body surface area, 

but a higher body surface area-to-mass ratio than men, 

which may provide more efficient body heat dissipation in certain environments (eg, very humid weather).33

Taken together, these differences may place women at 

a slight advantage in hot and humid climates, and a 

slight disadvantage in hot and dry climates, relative to 

men.32,33 However, the net effect of these sex differences 

on EHI risk is generally considered to be negligible, especially in comparison to larger differences in aerobic 

power and anthropometrics, particularly percentage of 

body fat.26,30,31

One approach to assessing the capacity to thermoregulate is to expose individuals to a designated heat challenge during exercise, and the Israeli heat tolerance test 

(HTT) is one valuable tool for use in the laboratory. The 

HTT, designed over decades of iterative studies, is used 

as a clinical test to guide return to duty decisions for 

Warfighters in the Israeli Defense Force (IDF) who have 

suffered an EHS event.5,34 Between 2008 and 2010, 26% 

of men and 67% of women in the IDF who had been diagnosed with EHS (or EHS was suspected) were classified as heat intolerant by their criteria,35 which suggests 

sex differences.

Importantly, the HTT was originally developed using 

male Warfighters. Thus, if their HTT is to be used in 

our military, and particularly as women enter combat 

military occupational specialties, it will be necessary to 

know how they respond to the HTT, with and without 

a prior EHI. Additionally, the IDF did not have data on 

either aerobic power or body composition,35 which could 

be key in assessing risk of EHI.20-22,36 Thus, the purposes 

of the present study were to examine the responses of 

men and women to the HTT and to compare their classification results. Additionally, we assessed both aerobic 

power and body composition to help explain any sex differences observed with the HTT.

Methods

Subjects

Fifty-five male and 20 female participants were recruited from military and university communities to participate in a standardized HTT. Inclusion criteria included: 

(1) aged 18 to 45 years; (2) waist circumference less than 

39.4 inches (100 cm); (3) systolic and diastolic blood 

pressure below 140 mmHg and 90 mmHg, respectively; 

(4) no previous history of malignant hyperthermia; (5) 

not pregnant or lactating; (6) not anemic; (7) not using 

glucose-lowering agents, prednisone, or beta blockers; 

and (9) not presently being treated for any mental health 

disorder. Participants included those with and without 

a history of EHI. Participants who had a previous clinically documented EHS (n=20, of which 19 were male) 

were tested 6 weeks or more after their EHS. Each participant underwent a thorough telephone health screen 

and on-site medical examination to ensure that inclusion criteria were met. All participants were informed of 

the study’s purposes and procedures, and then provided 

written consent prior to participation. Approval was obtained from the Uniformed Services University Institutional Review Board, and the data presented herein are 

a subset of a larger study.

Baseline Screening and Anthropometric Testing

Participants underwent a medical examination, several 

anthropometric evaluations (body mass, height, waist 

circumference, and percentage of body fat), and a maximal aerobic graded exercise test to assess aerobic power. 

After completion of a medical history and other questionnaires, physiological measures of heart rate (HR), 

blood pressure (BP) (Criticare Systems Inc.; Waukesha, 

WI) and electrocardiographic activity (Philips StressVue Testing System with Trackmaster Full Vision Inc. 

Treadmill, Waltham, MA) were obtained at rest. Participant body mass was measured with a calibrated metric 

scale to the nearest 0.1 kg, and height was measured 

to the nearest 0.1 cm while the participant was wearing light clothing and no shoes. Body mass index was 

calculated from height and mass, and waist circumference was determined with a tape measure by standard 
50 http://www.cs.amedd.army.mil/amedd_journal.aspx

techniques.37 Body surface area and surface-to-mass ratio were calculated by standard methods.38

Percentage of body fat was determined using 2 techniques: skinfold measurements and bioelectrical impedance analysis (BIA). Skinfolds were used to allow comparison with previous analyses from the present study36

and similar research.39,40 The BIA was used due to concern about reliability/validity of skinfold measurements, 

especially for sex comparisons. Skinfold thickness was 

quantified with a skinfold caliper (Cambridge Scientific 

Industries Inc, Cambridge, MD) at 4 sites (biceps, triceps, subscapular, and suprailiac) on the right side of 

the body and BF% was computed by using the Durnin 

and Womersley calculation.41 In order to combine data 

from a previous pilot study,36 3 skinfold sites were used 

for 36% of participants based on ACSM guidelines,37

using chest, triceps, and subscapular for men, and triceps, abdomen, and suprailiac for women. The BIA was 

conducted using RJL Quantum II (RJL Systems, Clinton Township, Michigan), with participants lying down, 

arms at a 30° angle from body, and legs not touching. 

Based on recent research comparing BIA equations to 

estimate BF% among a military sample,42 equations 

published by Segal et al43 were selected (using the equations generalized across body fat levels). The correlation 

between the skinfold and BIA-derived BF% values was 

0.76 (P<.001).

During the second visit, subjects underwent a standardized HTT, which consisted of walking on a treadmill 

for 2 hours in an environmental chamber as described 

below.

Determination of VO2max

The VO2max was determined by a maximal aerobic 

graded exercise test on a motorized treadmill through 

indirect calorimetry. Expired respiratory gases were 

collected continuously and analyzed by open-circuit 

spirometry (Oxycon Mobile portable system, Viasys 

Healthcare Inc, Yorba Linda, CA). The test used in this 

study, adapted from a protocol previously described 

by our laboratory,44 consisted of a 5-minute warm-up 

(5.0 km/h and a 2.0% grade) followed by a running portion, at a constant speed of 7.7-13.7 km/h (based on HR 

achieved during warm-up), with incline starting at 0% 

and increasing 2.5% every 2 minutes, until the subject 

could no longer continue or VO2 plateaued with an increase in workload.

Heat Tolerance Testing

All HTTs were conducted in the morning with participants wearing shorts and athletic shoes; none wore a tshirt, but women wore a sports bra. The HTT consisted 

of walking on a treadmill at 5.0 km/hr at a 2% grade 

for 2 hours at 40°C and 40% relative humidity. Women were tested between days 3 and 9 of their follicular phase. To ensure adequate hydration before testing, 

urine specific gravity was measured with a hand held 

refractometer. If urine specific gravity was 1.02 units 

or more, the participant was provided water to hydrate 

until it was less than 1.02. Participants were instructed to void their bladder, and then nude body mass was 

measured. From this point on, all urine was collected in 

a 3.0 L polypropylene collection container. During the 

HTT, participants were permitted to hydrate with water 

ad libitum (up to one L/hr). Core temperature (Tc) was 

measured by using a rectal thermometer inserted 10 cm 

beyond the anal sphincter; skin temperature was measured with skin sensors placed at 4 different sites (shoulder, chest, thigh, and calf). The Tc was measured using 

either a thermistor-based system (64% of participants) 

(MEAS Temperature Probes (Measurement Specialties Inc, Dayton, OH) with Sensor Interface Box Model 

93200 (Deban Enterprises Inc.; Beavercreek, OH)) or a 

thermocouple system for more recent participants (Type 

T Thermocouples with Thermes WiFi, Physitemp, Clifton, NJ). The HR was assessed by a Polar HR monitor 

(Polar Team 2 Pro, Polar USA Inc, Lake Success, NY). 

The HR, Tc and skin temperatures were continuously 

monitored and recorded throughout the test; the physiological strain index was calculated from changes in final 

and baseline HR and Tc, as suggested by Moran et al.45

Physiological strain index values range from 0-10, and 

are classified as follows: minimal (values of 0-2), low 

(3-4), moderate (5-6), high (7-8), and very high (9-10) 

strain. Sweat rate was estimated based on the difference 

in nude body mass before and after the test corrected 

for fluid intake and urine output. Most HTTs were conducted in the summer (49%), followed by the fall (24%), 

spring (20%), and winter (7%). Baseline and maximum 

physiological measures for HR and Tc did not differ by 

season.

The HTT was discontinued if any participant met one of 

the following criteria: (1) Tc greater than 39.5°C; (2) HR 

above 170 bpm; (3) experienced nausea, weakness, or 

dizziness; or (4) requested early test termination. Heat 

intolerance was defined as Tc greater than 38.5°C, HR 

above 150 bpm, or failure to plateau,5,34 with the latter 

defined by a rise in Tc of greater than 0.45°C during the 

second hour of the HTT.46

Data Analyses

Sample characteristics are provided for men and women in Table 1, with independent-samples t tests used to 

identify differences between men and women, and heat 

tolerant vs heat intolerant participants. Cohen’s d is used 

WOMEN AND EXERTIONAL HEAT ILLNESS: IDENTIFICATION OF GENDER SPECIFIC RISK FACTORS
April – June 2015 51

THE ARMY MEDICAL DEPARTMENT JOURNAL

as a measure of effect size (small effect=0.2; moderate=0.5; and large>0.8).

Logistic regression models were developed to predict 

HTT performance. For the regression models, sex was 

entered into a first block, and additional predictors were 

entered into a second one. The primary HTT outcome 

was heat tolerance classification (with heat intolerance 

defined as Tc>38.5°C or HR>150 bpm). To allow for 

a more granular assessment of heat tolerance, logistic 

regressions were also conducted to predict elevated Tc

(>38.5°C) and elevated HR (>150 bpm) separately.

Linear regression models were developed to predict continuous HTT outcomes. These additional models, even 

though similar to those above, were run because cutoffs 

for heat tolerance are being debated47 and dichotomization reduces statistical power, especially with small 

sample sizes. Continuous HTT outcomes included maximal values for physiological strain index, HR, and Tc.

Results

Demographic, anthropometric, and aerobic power characteristics are presented in Table 1. As expected, women 

had lower VO2max, body surface area, waist circumference, and body mass index and higher body surface 

area-to-mass ratio and BF% compared to men. Women 

were also 3.68 times more likely to be classified as heat 

intolerant than men (95% CI, 1.21, 11.24; χ2=6.85, P<.01, 

d=0.63), such that 45% of women (9 out of 20) were intolerant, compared to 18% of men (10 out of 55). Sex differences in other HTT outcomes are presented in Table 

2 and graphically in Figures 1 and 2. During the HTT, 

women demonstrated higher maximum HR than men 

(t

73=2.27, P<.01, d=0.76); in contrast, sex differences 

between maximum Tc did not reach statistical significance (t

73=0.71, P>.05).

Heat intolerant participants (34% of sample) had lower 

VO2max (t

73=2.28, P<.05, d=0.60) and higher BF% than 

heat tolerant ones, shown in Table 3. However, group differences in BF% were statistically significant for skinfold BF% (t

73=2.30, P<.05, d=0.57), but not for BIA 

BF% (t

73=1.51, P=.15). Because VO2max and BF% were 

strongly correlated (skinfold: r=-0.55; BIA: r=-0.56; 

P<.001), they were assessed in separate regression models to predict HTT outcomes. For each regression, sex 

was entered into a first block (Block 1), followed by either VO2max (Block 2A), skinfold BF% (Block 2B), or 

BIA BF% (Block 2C).

In the logistic regression models (Table 4, column 1), 

sex initially predicted heat tolerance, however its effect 

became nonsignificant when VO2max and BF% were entered into the model. In the linear regression models, sex 

was related to maximum HR when it was the only variable; its effect also became nonsignificant in subsequent 

blocks. Meanwhile, the standardized beta-coefficients 

for VO2max as predictors of HRmax (assessed dichotomously and continuously) and maximal physiological 

strain index were much greater than sex (maximum HR: 

VO2max=-0.48 vs sex=0.14 and physiological strain index: VO2max=-0.34 vs sex=0.03). On the other hand, 

skinfold BF% only exceeded sex in relation to maximum HR (sex=0.14 vs skinfold BF%=0.28), and this 

did not hold for BIA BF% (sex=0.15 vs BIA BF%=0.03).

Comment

Our results suggest that although women are classified 

as heat intolerant to a greater extent than men, VO2max

appears to account for most, if not all, of this sex difference. When heat tolerance was broken down into 2 

components, HR and Tc, the sex findings held for HTT 

outcomes related to HR, but not Tc. Thus, cardiovascular 

strain is far more important than thermal strain. This 

Table 2. Physiological Measurements (mean±SD) During HTT 

by Sex.

Variable Women Men All

(n=20) (n=55) (n=75)

Core Temperature, Tc (°C)

Baseline Tc 37.1±0.4 36.9±0.4 37.0±0.4

Max Tc 38.1±0.4 38.1±0.4 38.1±0.4

∆Tc (over min 60-120) 0.26±0.19 0.28±0.11 0.27±0.18

Heart rate, HR (bpm)

Baseline HR 76±15.0 68±12.1* 70±13.3

Max HR 137±20.1 122±20.2† 126±21.1

∆HR (over min 60-120) 7.5±7.2 4.6±8.2 5.3±8.0

Physiological strain index 5.2±1.4 4.7±1.3 5.3±8.0

Sweat rate (L/h) 0.81±0.28 1.10±0.31† 1.03±0.33

*P<.05

†P<.01

Table 1. Participant Characteristics (mean±SD) by Sex.

Variable Women Men All

(n=20) (n=55) (n=75)

Age (yrs) 28.6±5.2 28.7±6.3 28.7±6.0

Height (cm) 163.8±5.5 178.3±6.6* 174.4±9.0

Weight (kg) 63.8±7.5 84.3±11.2* 78.8±13.8

BMI (kg/m2) 23.8±2.5 26.5±3.0* 25.8±3.1

Body surface area (m2) 1.69±0.11 2.02±0.16* 1.93±0.21

Body surface/mass

(m2

·kg-1·102

)

2.67±0.16 2.41±0.18* 2.48±0.21

Skinfold BF% 28.4±5.1 18.7±5.1* 21.3±6.7

BIA BF% 30.1±21.6 21.6±5.1* 23.8±6.2

Waist circumference (cm) 72.4±4.8 84.6±7.0* 81.4±8.5

VO2max (ml·kg-1

·min-1

) 45.3±6.8 52.3±7.4* 50.5±7.8

BIA=bioelectrical impedance analysis

*P<.05
52 http://www.cs.amedd.army.mil/amedd_journal.aspx

finding contributes to the literature by suggesting that a relatively fit, representative sample of 

a military population can be risk stratified for a 

military setting by participating in an HTT.5 As 

women are integrated into combat military occupational specialties, risk profiles for exertional and physical injuries must be determined to 

assist in developing gender-specific training requirements,2

 as combat exposures will be gender neutral. The present study results suggest 

that when standard risk factors are controlled 

for, particularly aerobic power, women do not 

appear to be at greater risk for EHI than men.

Aerobic power and BF% serve key roles in thermoregulation,48 risk for EHI,14,19-21 and military 

performance.49 Importantly, poor aerobic power and high BF% are the 2 most studied risk 

factors for EHI.20-22 Even though aerobic power 

and body fat are strongly negatively correlated, 

they may both directly relate to EHI risk.21,22

Individuals with poor aerobic power need to 

work at a higher relative intensity for a given 

workload than individuals with high aerobic 

power. This increases their relative physiological strain, which, in turn, decreases peripheral 

blood flow, hinders thermoregulation, and increases heat absorption.14,50 Higher body fat 

also increases metabolic heat and hinders heat 

dissipation.7,14 Since aerobic power and BF% 

also differ by sex, it is important to clarify their 

independent contributions to thermoregulation, 

especially as women are officially integrated 

into combat roles. In fact, proposed algorithms 

to stratify EHI risk typically include aerobic 

power and percentage of body fat.22,51 These 

algorithms are useful screening tools for warfighters and athletes. But a full HTT is often 

warranted among EHS patients,5 particularly 

when gradual return to physical activity may 

be problematic.19,52

Laboratory exercise studies have consistently demonstrated that sex differences in thermoregulation in the 

heat become minimal after controlling for aerobic power 

and body fat.32,39,40,53,54 Other demographic differences in 

heat thermoregulation, such as age, may be explained by 

these factors as well.55,56 Nevertheless, previous studies 

have used relatively small sample sizes and varied protocols, which make comparisons difficult. Protocols differ 

in exercise type (eg, walking, cycling), acclimatization 

procedures, and test conditions, depending on the particular research aims. Results from most studies indicate 

that women are not at a thermoregulatory disadvantage 

compared to men when matched for body composition 

and when performing tasks appropriate for their aerobic 

power level. In the military, fitness and body composition standards are often relative to sex, and in some 

military occupational specialties, physically demanding 

tasks cannot be customized to the Warfighter’s sex. Certainly in the deployed setting, task assignment cannot be 

based on gender.

Combat fitness, as defined by Epstein et al,2 is an individual’s ability to effectively perform military-oriented 

tasks and be able to accomplish all aspects of a combat 

mission, while staying healthy and uninjured. Combat 

fitness requires not only the traditional aspects of fitness 

Core Temperature (°C)

Time (minutes)

0 20 40 60 80 100 120

38.0

38.5

39.0

37.0

37.5

36.0

36.5 Women (n=20)

Men (n=55)

Figure 1. Mean core body temperature response to the heat tolerance 

test displayed by sex.

Women (n=20)

Men (n=55)

Time (minutes)

Heart Rate (BPM) 120

130

140

100

110

80

90

0 20 40 60 80 100 120

Figure 2. Mean heart rate response to the heat tolerance test displayed 

by sex.

WOMEN AND EXERTIONAL HEAT ILLNESS: IDENTIFICATION OF GENDER SPECIFIC RISK FACTORS
April – June 2015 53

THE ARMY MEDICAL DEPARTMENT JOURNAL

(cardiovascular endurance, muscular strength, and 

flexibility), but also neuromuscular motor (handeye coordination, agility, speed, and power) and 

environmental (heat acclimatization) fitness. To 

partially address these questions, each service and 

operational specialty is reevaluating occupational 

fitness requirements for gender neutrality, while at 

the same time maximizing successful outcomes, 

regardless of whether the service member is male 

or female.

Thermoregulatory differences between men and 

women can likely be attributed to physical characteristics rather than other inherent metabolic/

regulatory differences.2 Given that women are at higher 

risk for EHI, efforts should focus on improving intrinsic 

and extrinsic modifiable risk factors. On average, when 

matched for age, men have greater lean body mass and 

less fat mass compared to women.57 A smaller body 

mass and higher BF% will increase Tc.

58 Additionally, 

when compared to men, women have lower relative and 

absolute aerobic power, which may contribute to earlier 

fatigue compared to men.2 Clearly, sex differences in 

performance variables, such as muscle mass and VO2max, affect combat fitness. Cardiovascular and resistance training programs for women can improve physical performance through increases in strength, power, 

and endurance.59 The challenge of operating in hot 

environments is compounded by the use of protective 

gear and body armor, which inhibit sweat evaporation 

and heat dissipation, and increase thermoregulatory and 

cardiovascular strain. Although performance requirement criteria may become gender-neutral for certain 

combat military occupational specialties, new training 

practices will be needed to help overcome modifiable 

sex differences.

Limitations to the present study include the sample 

size and debate regarding the IDF HTT. The number of 

women in the present study was larger than some previous studies,32,33,35,39,40,53,54 but still somewhat limited. Future studies should include a greater number of female 

subjects to allow for more robust sex comparisons and 

the use of other statistical techniques such as propensity 

score matching/adjustment.60 In addition, there is controversy with regard to the construct of heat tolerance in 

general61 and the standardized use of the HTT in particular.62 Alternatives to the IDF HTT include measuring 

heat tolerance over the course of a multiday acclimation 

protocol,62 or customizing a HTT’s exercise intensity to 

the individual being tested.63 Since many of the EHI patients in the study visited the laboratory from other locations and were on temporary physical activity restrictions, it was not feasible to assess and control for heat 

acclimation status. More advanced techniques to measure BF% would have also benefitted the study due to 

concerns about validity and reliability of skinfolds and 

to a lesser degree BIA, which often vary across sex.42

Additionally, other key variables, such as fluid and salt 

losses, may be important to consider.64

The IDF HTT remains the most widely used 

and clinically useful test to assess Warfighter return to duty following EHS,5,52 as 

it simulates the conditions of many military 

EHI scenarios.65 Importantly, it correlates 

with risk factors for EHS in the military,36

for men and women. As women are integrated into combat military occupational 

specialties, their risk for EHS will increase, 

and physicians will have to decide whether 

to return them to duty following such an 

event. The IDF HTT can help, but research 

on how women perform has been lacking. 

Based on the present study and previous 

work by Druyan et al,35 women demonstrate 

a much higher failure rate on the test. As 

Table 4. Adjusted Odds Ratios (95% CI) from Hierarchical Logistic Regression Predicting Dichotomous HTT Outcomes.

Independent Variable HTT Outcome

Heat Tolerant Core >38.5°C HR >150 BPM

Block 1

Gender 3.7 (1.21-11.24)* 2.0 (0.56-6.90) 3.5 (0.98-12.56)

Block 2A

Gender 2.5 (0.75-8.54) 1.7 (0.43-6.86) 1.5 (0.35-6.47)

VO2max (ml·kg-1

·min-1) 0.9 (0.87-1.02) 0.9 (0.90-1.07) 0.9 (0.76-0.96)†

Block 2B

Gender 2.2 (0.49-9.87) 1.1 (0.18-6.63) 1.8 (0.33-10.16)

Skinfold BF% 1.1 (0.95-1.18) 1.1 (0.98-1.31) 1.0 (0.89-1.13)

Block 2C

Gender 3.5 (0.82-15.09) 2.0 (0.39-10.54) 1.6 (0.30-8.19)

BIA BF% 1.0 (0.90-1.12) 1.0 (0.88-1.13) 1.1 (0.96-1.27)

BIA indicates bioelectrical impedance analysis.

*P<.05

†P<.01

Table 3. Characteristics (mean±SD) of Heat Tolerant versus Heat 

Intolerant Participants.

Independent Variable HTT Outcome

Heat Tolerant

(n=56)

Heat Intolerant

(n=19)

t

VO2max (ml·kg-1

·min-1) 51.6±7.5 47.0±7.9 2.28*

Skinfold BF% 20.3±6.1 24.3±7.6 2.30*

BIA BF% 23.2±5.4 25.7±8.2 1.51

BMI (kg/m2) 25.9±3.0 25.2±3.4 0.89

Body surface area (m2) 1.96±0.21 1.85±0.19 1.93

Body surface/mass (m2

·kg-1·102

) 2.46±0.21 2.54±0.22 1.55

Waist circumference (cm) 82.4±8.4 78.2±7.9 1.92

BIA indicates bioelectrical impedance analysis.

*P<.05
54 http://www.cs.amedd.army.mil/amedd_journal.aspx

with any high stake test, it is important to determine 

whether group differences are due to underlying differences in the latent variable.66 Since the sex differences appear mostly attributable to aerobic power and 

perhaps BF%, they likely reflect women’s increased 

risks for EHI. These findings should not be surprising 

to those familiar with human thermoregulation research, 

as they are consistent with a long line of previous research.26-29,32,33,39,40 In the present context, however, these 

results will be crucial for physicians tasked with interpreting IDF HTT scores for men and women, and may 

inform broader military policy.

References

1. Dempsey ME, Panetta LE. Memorandum: Elimination of the 1994 Direct Ground Combat Definition and Assignment Rule. Washington, DC: US 

Dept of Defense, US Joint Chiefs of Staff; January 24, 2013. Available at: http://www.defense.gov/

news/WISRJointMemo.pdf. Accessed January 26, 

2015.

2. Epstein Y, Yanovich R, Moran DS, et al. Physiological employment standards IV: integration of women in combat units physiological 

and medical considerations. Eur J Appl Physiol. 

2013;113(11):2673-2690.

3. Armed Forces Health Surveillance Center. Heat injuries, active component, U.S. Armed Forces, 2013. 

MSMR. 2014;21(3):10-13.

4. Carter R III, Cheuvront SN, Williams JO, et al. 

Epidemiology of hospitalizations and deaths from 

heat illness in soldiers. Med Sci Sports Exerc. 

2005;37(8):1338-1344.

5. Epstein Y, Druyan A, Heled Y. Heat injury prevention-a military perspective. J Strength Cond Res. 

2012;26(suppl 2):S82-S86.

6. Rav-Acha M, Hadad E, Epstein Y, et al. Fatal exertional heat stroke: a case series. Am J Med Sci. 

2004;328(2):84-87.

7. Casa DJ, Guskiewicz KM, Anderson SA, et al. National Athletic Trainers’ Association position statement: preventing sudden death in sports. J Athl 

Train. 2012;47(1):96-118.

8. Coris EE, Ramirez AM, Van Durme DJ. Heat illness in athletes: the dangerous combination of heat, 

humidity and exercise. Sports Med. 2004;34(1):9-16.

9. Mueller FO, Cantu RC. Twenty-ninth Annual Report for the National Center for Catastrophic Sports 

injury Research: Catastrophic Football Injuries. 

2012.

10. Xiang J, Bi P, Pisaniello D, et al. Health impacts 

of workplace heat exposure: an epidemiological review. Ind Health. 2014;52(2):91-101.

11. Bouchama A, Knochel JP. Heat stroke. N Engl J 

Med. 2002;346(25):1978-1988.

12. Booker RJ, Bricknell MC. Heat illness–recent developments. J R Army Med Corps. 2002;148(1):11-18.

13. Casa DJ, Armstrong LE, Kenny GP, et al. Exertional heat stroke: new concepts regarding cause 

and care. Curr Sports Med Rep. 2012;11(3):115-123.

14. Cleary M. Predisposing risk factors on susceptibility to exertional heat illness: clinical decision-making considerations. J Sport Rehabil. 

2007;16(3):204-214.

15. Epstein Y, Shani Y, Moran DS, et al. Exertional heat 

stroke–the prevention of a medical emergency. J 

Basic Clin Physiol Pharmacol. 2000;11(4):395-401.

16. Carter R III, Cheuvront SN, Sawka MN. A case 

report of idiosyncratic hyperthermia and review of 

U.S. Army heat stroke hospitalizations. J Sport Rehabil. 2007;16(3):238-243.

17. Epstein Y. Heat intolerance: predisposing factor or residual injury?. Med Sci Sports Exerc. 

1990;22(1):29-35.

18. Lopez RM, Casa DJ. The influence of nutritional 

ergogenic aids on exercise heat tolerance and hydration status. Curr Sports Med Rep. 2009;8(4):192-199.

19. Armstrong LE, Casa DJ, Millard-Stafford M, et al. 

American College of Sports Medicine position stand. 

Exertional heat illness during training and competition. Med Sci Sports Exerc. 2007;39(3):556-572.

20. Bedno SA, Li Y, Han W, et al. Exertional heat 

illness among overweight U.S. Army recruits 

in basic training. Aviat Space Environ Med. 

2010;81(2):107-111.

21. Gardner JW, Kark JA, Karnei K, et al. Risk factors predicting exertional heat illness in male 

Marine Corps recruits. Med Sci Sports Exerc. 

1996;28(8):939-944.

22. Wallace RF, Kriebel D, Punnett L, et al. Risk factors for recruit exertional heat illness by gender 

and training period. Aviat Space Environ Med. 

2006;77(4):415-421.

23. Kerr ZY, Casa DJ, Marshall SW, et al. Epidemiology of exertional heat illness among U.S. high 

school athletes. Am J Prev Med. 2013;44(1):8-14.

24. Nelson NG, Collins CL, Comstock RD, et al. Exertional heat-related injuries treated in emergency 

departments in the U.S., 1997-2006. Am J Prev 

Med. 2011;40(1):54-60.

25. Dellinger AM, Kachur SP, Sternberg E, et al. Risk 

of heat-related injury to disaster relief workers in 

a slow-onset flood disaster. J Occup Environ Med. 

1996;38(7):689-692.

WOMEN AND EXERTIONAL HEAT ILLNESS: IDENTIFICATION OF GENDER SPECIFIC RISK FACTORS
April – June 2015 55

THE ARMY MEDICAL DEPARTMENT JOURNAL

26. Kenney WL. A review of comparative responses 

of men and women to heat stress. Environ Res. 

1985;37(1):1-11.

27. Stephenson LA, Kolka MA. Thermoregulation in 

women. Exerc Sport Sci Rev. 1993;21:231-262.

28. Heikens MJ, Gorbach AM, Eden HS, et al. Core 

body temperature in obesity. Am J Clin Nutr.

2011;93(5):963-967.

29. Hoffmann ME, Rodriguez SM, Zeiss DM, et al. 24-h 

core temperature in obese and lean men and women. Obesity (Silver Spring). 2012;20(8):1585-1590.

30. Charkoudian N, Stachenfeld NS. Reproductive hormone influences on thermoregulation in women. 

Compr Physiol. 2014;4(2):793-804.

31. Marsh SA, Jenkins DG. Physiological responses to 

the menstrual cycle: implications for the development of heat illness in female athletes. Sports Med. 

2002;32(10):601-614.

32. Shapiro Y, Pandolf KB, Avellini BA, et al. Physiological responses of men and women to humid 

and dry heat. J Appl Physiol Respir Environ Exerc 

Physiol. 1980;49(1):1-8.

33. Shapiro Y, Pandolf KB, Avellini BA, et al. Heat 

balance and transfer in men and women exercising 

in hot–dry and hot–wet conditions. Ergonomics. 

1981;24(5):375-386.

34. Moran DS, Erlich T, Epstein Y. The heat tolerance test: an efficient screening tool for evaluating susceptibility to heat. J Sport Rehabil. 

2007;16(3):215-221.

35. Druyan A, Makranz C, Moran D, et al. Heat tolerance in women–reconsidering the criteria. Aviat 

Space Environ Med. 2012;83(1):58-60.

36. Lisman P, Kazman JB, O’Connor FG, et al. Heat 

tolerance testing: association between heat intolerance and anthropometric and fitness measurements. 

Mil Med. 2014;179(11):1339-1346.

37. American College of Sports Medicine. ACSM’s 

Guidelines for Exercise Testing and Prescription. 9th ed. Baltimore, MD: American College of 

Sports Medicine; 2014.

38. Dubois D. Clinical calorimetry: a formula 

to estimate the appropriate surface area if 

height and weight be known. Arch Intern Med. 

1916;67(1):160-165.

39. Havenith G, Luttikholt VG, Vrijkotte TG. The relative influence of body characteristics on humid heat 

stress response. Eur J Appl Physiol Occup Physiol. 

1995;70(3):270-279.

40. Havenith G, van Middendorp H. The relative influence of physical fitness, acclimatization state, anthropometric measures and gender on individual 

reactions to heat stress. Eur J Appl Physiol Occup 

Physiol. 1990;61(5-6):419-427.

41. Durnin J, Womersley J. Body fat assessed from total 

body density and its esimation from skinfold thickness: measurements on 481 men and women aged 

from 16 to 72 years. Br J Nutr. 1974;1974(1):77-97.

42. Aandstad A, Holtberget K, Hageberg R, et al. Validity and reliability of bioelectrical impedance analysis and skinfold thickness in predicting body fat in 

military personnel. Mil Med. 2014;179(2):208-217.

43. Segal KR, Van Loan M, Fitzgerald PI, et al. Lean 

body mass estimation by bioelectrical impedance 

analysis: a four-site cross-validation study. Am J 

Clin Nutr. 1988;47(1):7-14.

44. Kyle SB, Smoak BL, Douglass LW, et al. Variability of responses across training levels to 

maximal treadmill exercise. J Appl Physiol. 

1989;67(1):160-165.

45. Moran DS. Stress evaluation by the physiological 

strain index (PSI). J Basic Clin Physiol Pharmacol. 

2000;11(4):403-423.

46. Amit D, Itay K, Ran Y, et al. Refining the distinction between heat tolerant and heat intolerant individuals during a heat tolerance test. J Therm Biol. 

2013;38:539-542.

47. O’Connor FG, Casa DJ, Bergeron MF, et al. American College of Sports Medicine Roundtable on exertional heat stroke–return to duty/return to play: 

conference proceedings. Curr Sports Med Rep. 

2010;9(5):314-321.

48. Epstein Y, Roberts WO. The pathopysiology of heat 

stroke: an integrative view of the final common pathway. Scand J Med Sci Sports. 2011;21(6):742-748.

49. Nindl BC, Castellani JW, Warr BJ, et al. Physiological Employment Standards III: physiological 

challenges and consequences encountered during 

international military deployments. Eur J Appl 

Physiol. 2013;113(11):2655-2672.

50. Rowell LB. Human cardiovascular adjustments 

to exercise and thermal stress. Physiol Rev. 

1974;54(1):75-159.

51. Eberman LE, Cleary MA. Development of a heatillness screening instrument using the Delphi panel 

technique. J Athl Train. 2011;46(2):176-184.

52. Kazman JB, Heled Y, Lisman PJ, et al. Exertional 

heat illness: the role of heat tolerance testing. Curr 

Sports Med Rep. 2013;12(2):101-105.

53. Gagnon D, Dorman LE, Jay O, et al. Core temperature differences between males and females during 

intermittent exercise: physical considerations. Eur 

J Appl Physiol. 2009;105(3):453-461.

54. Sawka MN, Toner MM, Francesconi RP, et al. 

Hypohydration and exercise: effects of heat acclimation, gender, and environment. J Appl Physiol 

Respir Environ Exerc Physiol. 1983;55(4):1147-1153.
56 http://www.cs.amedd.army.mil/amedd_journal.aspx

55. Best S, Caillaud C, Thompson M. The effect of 

ageing and fitness on thermoregulatory response 

to high-intensity exercise. Scand J Med Sci Sports. 

2012;22(4):e29-e37.

56. Tankersley CG, Smolander J, Kenney WL, et al. 

Sweating and skin blood flow during exercise: effects of age and maximal oxygen uptake. J Appl 

Physiol. 1991;71(1):236-242.

57. Friedl KE. Body composition and military performance–many things to many people. J Strength 

Cond Res. 2012;26(suppl 2):S87-S100.

58. Mora-Rodriguez R. Influence of aerobic fitness on 

thermoregulation during exercise in the heat. Exerc Sport Sci Rev. 2012;40(2):79-87.

59. Kraemer WJ, Mazzetti SA, Nindl BC, et al. Effect 

of resistance training on women’s strength/power 

and occupational performances. Med Sci Sports 

Exerc. 2001;33(6):1011-1025.

60. Beal SJ, Kupzyk KA. An introduction to propensity scores: what, when, and how. J Early Adolesc. 

2014;34(1):66-92.

61. Armstrong LE, Maresh CM. The induction and 

decay of heat acclimatisation in trained athletes. 

Sports Med. 1991;12(5):302-312.

62. Johnson EC, Kolkhorst FW, Richburg A, et al. Specific exercise heat stress protocol for a triathlete’s 

return from exertional heat stroke. Curr Sports 

Med Rep. 2013;12(2):106-109.

63. Jones DM, Green MS, Heaney JH, et al. Heat and 

hypoxia cause additive increases in heat shock 

protein 72 during submaximal exercise. Med Sci 

Sports Exerc. 2012;44(S5):759.

64. Hori S. Index for the assessment of heat tolerance. J 

Hum Ergol (Tokyo). 1978;7(2):135-144.

65. Epstein Y, Moran DS, Shapiro Y, et al. Exertional 

heat stroke: a case series. Med Sci Sports Exerc. 

1999;31(2):224-228.

66. Warne RT, Yoon M, Price CJ. Exploring the various interpretations of “test bias”. Cultur Divers 

Ethnic Minor Psychol. 2014;20(4):570-582.

Authors

Mr Kazman, Dr Purvis, Dr Lisman, Ms Van Arsdale, 

and Dr Deuster are with the Department of Military and 

Emergency Medicine, Uniformed Services University of 

the Health Sciences, Bethesda, Maryland.

Dr Heled and Dr Atias are with the Institute of Military 

Physiology, Heller Institute of Medical Research, Sheba 

Medical Center, Tel HaShomer, Israel.

WOMEN AND EXERTIONAL HEAT ILLNESS: IDENTIFICATION OF GENDER SPECIFIC RISK FACTORS
April – June 2015 57

Iron, a nutrient found in food sources of both vegetable 

(nonheme) and animal (heme) origin, is an essential mineral that confers function in a number of biological processes, to include physical and cognitive performance,1

immunity,2 and energy metabolism.3 Iron deficiency (ID, 

reduced iron stores) and iron deficiency anemia (IDA, reduced iron stores coupled with diminished hemoglobin) 

are a worldwide public health concern, affecting billions 

of individuals.4 Additionally, poor iron status has been 

associated with decreased physiological and cognitive 

performance in both civilian and military populations.5,6

Recent data from the United States and the United 

Kingdom indicate an ID prevalence of 16% and 21%, 

respectively, among premenopausal women,7-9 and approximately 2% to 5% among males aged 12-69 years.9

Although poor iron status is less common in males than 

females, athletes and others, including Warfighters who 

engage in strenuous physical activity, are known to be 

at increased risk for decrements in iron status. Such 

declines may be caused by several contributing factors 

including hemolysis and iron sequestration due to the 

effects of inflammation.10,11

Iron deficiency, with or without the presence of anemia, 

may reduce both physical work capacity and cognitive 

performance. As the vast majority of body iron is distributed in hemoglobin and developing erythroid cells,3

poor iron status impairs physiological performance as 

iron is required for oxygen transport to peripheral tissues.10 Although there is evidence that physical activities such as military training may cause declines in iron 

status12-15 resulting in an increased prevalence of ID and 

IDA, the definitive mechanism remains unknown.

Effects of Basic Combat Training on Iron

 Status in Male and Female Soldiers:

 A Comparative Study

MAJ Ran Yanovich, ISDF COL Sonya J. Cable, SP, USA

J. Philip Karl, PhD, RD Andrew J. Young, PhD

Einat Yanovich, PhD Stefan M. Pasiakos, PhD

Laura J. Lutz, MS, RD James P. McClung, PhD

Kelly W. Williams, PhD

Abstract

Objective: Iron is an essential micronutrient known to affect physical and cognitive performance. Studies 

indicate a significant reduction in iron status in female Soldiers immediately following military training, 

although the comparative effects of military training on iron status between male and female Soldiers have not 

been examined. The objective of this study was to compare the longitudinal effects of US Army basic combat 

training (BCT) on iron status indicators in a group of male and female Soldiers.

Methods: A total of 154 male and female Soldiers (89 and 65, respectively) completed the study. Blood was 

collected at 4 time-points during BCT (weeks 0, 3, 6, 9) and dietary iron intake was assessed at weeks 0 and 

9. Iron status indicators included hemoglobin, serum ferritin (SF), soluble transferrin receptor (sTfR), and 

transferrin saturation (TS).

Results: Iron status was greater in male Soldiers than female Soldiers, as hemoglobin and SF levels were higher 

(P<.05) and sTfR levels were lower (P<.05) in males as compared to females at each time-point. Despite a 

mean increase of greater than 25% in iron intake (mg/day) among both male (15±13 to 20.2±14.4) and female 

Soldiers (12.8±9.7 to 16±6.2) over the course of BCT, iron status declined in both groups. As compared to 

baseline, SF declined (P<.05) by 21% and 47%, sTfR increased (P<.05) by 17% and 30%, and TS declined 

(P<.05) by 23% and 54% in male and female Soldiers, respectively, over the course of BCT.

Conclusions: These data indicate that although dietary iron intake improves, iron status declines in both male 

and female Soldiers during BCT, and the decline in female Soldiers is of a greater magnitude. Future studies 

should aim to determine the mechanism by which iron status declines during military training, with a focus on 

functional outcomes affecting Soldier health and performance.
58 http://www.cs.amedd.army.mil/amedd_journal.aspx

Iron status has been reported to decline during military 

training in recent studies among female Soldiers,16,17

however, reports investigating changes in iron status 

during military training among male Warfighters are 

limited.15,18 Further, dietary iron intake has not been assessed during initial military training. As such, the objective of the present study was to evaluate and compare 

sex differences in dietary iron intake, iron status, and 

inflammatory responses during US Army basic combat 

training (BCT) in an effort to determine whether changes in iron levels are similar between the sexes, and to 

quantify the relative contribution of dietary iron intake 

to iron homeostasis during military training.

Methods

This study was approved by the Human Use Review 

Committee at the US Army Research Institute of Environmental Medicine and conducted at Fort Jackson, 

South Carolina. Human subjects participated in this 

study after providing their free and informed voluntary consent. The study was conducted in compliance 

with Army Regulation 70-2519 and US Army Medical 

Research and Materiel Command Regulation 70-2520 

on the use of volunteers in research. The data presented 

in this manuscript were collected in association with a 

larger study investigating the effects of military training 

on cardiometabolic risk.21

Volunteers

A total of 209 Soldiers (118 male, 91 female) volunteered 

for this longitudinal study during a 10-week BCT course. 

Baseline data (time-point 1) were collected within one 

week of arrival at BCT (week 0), followed by 3 additional data collections as follows: weeks 3, 6, and 9 (timepoints 2, 3, and 4, respectively). During BCT, volunteers 

were engaged in physical and military specific training. 

Physical training requirements include aerobic activities 

such as road marching with weighted packs, obstacle 

courses, distance running, and sprinting. Energy costs 

associated with BCT have been published previously.22

Anthropometric (height, weight, body mass index 

(BMI), and body fat percentage) characteristics were determined at baseline and week 9. Weight was recorded 

to the nearest 0.01 kg on a calibrated digital scale (A&A 

Scales, Prospect Park, NJ), and height was measured to 

the nearest 0.01 cm using a stadiometer (Creative Health 

Products, Plymouth, MI). Body mass index was calculated by dividing the individual’s weight by the square of 

his/her height (kg•m-2). As previously reported,21 skinfold thickness was assessed at the chest, triceps, and subscapular sites for men, and at the triceps, suprailiac, and 

abdominal sites for women using Lange calipers (Beta 

Technology, Santa Cruz, CA). Body fat percentage was 

calculated from body density using 3-site skinfold equations.23-25 Body composition was assessed under similar 

experimental conditions (fasted, similar attire) by the 

same trained technician.

Dietary iron intake was assessed using a validated food 

frequency questionnaire (FFQ) (Block 2005 FFQ; NutritionQuest, Berkeley, CA) administrated by registered 

dietitians. The FFQ was administered at baseline and at 

the end of BCT to estimate usual dietary intake prior to 

and during the 10-week training course. Mean daily iron 

intake was calculated from the USDA Food and Nutrient 

Database for Dietary Studies version 1.0 (http://www.

ars.usda.gov/Services/docs.htm?docid=12089). Notably, 

dietary supplements are not permitted during BCT.

Blood samples were collected at each time-point after 

an overnight fast. Samples were obtained through antecubital venepuncture into tubes containing the appropriate anticoagulants, including EDTA for the collection of samples used in whole-blood assays (Vacutainer; 

Becton-Dikinson, Franklin Lakes, NJ). Hemoglobin 

was determined in whole blood using a hematology analyzer (Medonic CA 620, Boule Medical AB, Stockholm, 

Sweden). Serum was isolated, frozen, and shipped to the 

Pennington Biomedical Research Center (Baton Rouge, 

LA) for iron status indicator assays. Serum ferritin (SF) 

was measured using an automated immunoassay instrument (Siemens Medical Solutions, USA, Inc, Malvern, PA) and soluble transferrin receptor (sTfR) was 

determined using a commercially available immunoassay (Quantikine IVD, R&D Systems Inc, Minneapolis, 

MN). Serum iron and total iron-binding capacity were 

measured using the DXC 600 Pro system (Beckman 

Coulter, Fullerton, CA). Transferrin saturation (TS) was 

determined by dividing serum iron by total iron binding capacity. Serum interleukin 6 (IL-6) concentrations 

were measured with a multiplex assay with a lower detectable limit of 0.6 pg/mL (Milliplex MAP, Millipore, 

Billerica, MA) and high sensitivity C-reactive protein 

(hsCRP) concentrations were measured with an automated immunoassay instrument with a lower detectable 

limit of 0.2 mg/L (Siemens Medical Solutions USA Inc).

Data were analyzed with SPSS Version 20.0 (IBM Corp, 

Armonk, NY). Normal distribution of variables was determined using the Shapiro-Wilks test. Descriptive statistics are presented as the mean (±SD). Comparisons of 

anthropometric measures and dietary iron intake were 

made using Student’s t-tests. Two-factor repeated measures analysis of variance (ANOVA) was used to test 

main effects of sex and time and biomarker by time interactions. When a significant interaction was observed 

(time X group interaction= T X G), post hoc analyses 

EFFECTS OF BASIC COMBAT TRAINING ON IRON STATUS IN MALE AND FEMALE SOLDIERS:

A COMPARATIVE STUDY
April – June 2015 59

THE ARMY MEDICAL DEPARTMENT JOURNAL

with Bonferroni adjustments were conducted to identify those differences. Correlations between changes 

in dietary iron intake and indicators of iron status were 

performed using Spearman’s rho. Differences between 

percentage changes in iron status between groups were 

computed using Student’s t tests. Significance level was 

set at P<.05.

Results

A total of 89 male and 65 female volunteers (75% and 

71%, respectively) completed the 4 data collection timepoints throughout BCT. There were no significant differences in age, anthropometrics, or any of the baseline 

biomarkers between those who completed the study and 

those who did not. As shown in Table 1, in comparison 

to men, women were shorter, weighed less, had a lower 

BMI, and had a greater body fat percentage (P<.05). 

Over the course of BCT, men lost weight and reduced 

BMI whereas women did not, although both men and 

women experienced reduced (P<.05) body fat.

At baseline (week 0), significant differences in iron status 

were observed between sexes. In comparison to females, 

males had greater levels of hemoglobin (P<.05) and SF 

(P<.05), coupled with reduced sTfR levels (P<.05).

Throughout the course of BCT, there were significant 

changes in many of the biochemical indicators of iron 

status in both male and female Soldiers, shown in Table 2, suggesting a decline in iron status. Changes in 

the iron status indicators SF, sTfR, and TS differed between men and women during BCT (interaction P<.05). 

Changes in female Soldiers were apparent by week 3, as 

SF levels had decreased by 34% (P<.05), sTfR levels 

had increased 26% (P<.05), and TS decreased by 37% 

(P<.05). Hemoglobin and SF in male Soldiers declined 

and sTfR increased at week 3 (P<.05), although TS was 

not affected. Declines in iron status persisted through 

the training period, as all status indicators were significantly affected (P<.05) in both male and female Soldiers by week 6.

Similarly, at the end of BCT (week 9), all indicators of 

iron status (with the exception of hemoglobin in female 

Soldiers) had declined significantly in both male and female Soldiers as compared to baseline. The magnitude 

of this decline was significantly greater (P<.05) in female Soldiers in comparison with male Soldiers as reflected by sharper declines in SF and TS coupled with a 

steeper increase in sTfR (Figure 1).

Inflammatory biomarkers did not change over the course 

of BCT (data not shown; P>.05).

Dietary Iron Intake

Dietary iron intake increased in both male (35%, P<.05) 

and female Soldiers (25%, P<.05) over the course of 

BCT. By week 9, iron intake was significantly greater 

(P<.05) in male Soldiers as compared to female Soldiers 

(20.2±13.0 mg/day vs 16.0±6.2 mg/day, respectively).

At the start of BCT, daily iron intake among men was 

188% of the Recommended Dietary Allowance (RDA)26

(15.0 mg/day vs 8 mg/day, respectively). Women did not 

Table 1. Volunteer demographics and anthropometrics (mean±SD): males, n=89; 

females, n=65.

Week 0 Week 9 Effect

Age (years)

Males 23.1±5.4

Females 23.1±6.0

Height (cm)

Males 176.1±7.0*

Females 162.8±5.8

Weight (kg)

Males 83.5±15.9* 79.8±11.9*† T X G

Females 66.2±8.5 66.3±7.5

BMI (kg•m-2)

Males 26.9±4.6* 25.7±3.3† T X G

Females 25.0±2.8 25.0±2.3

Body fat (%)

Males 14.2±4.9* 12.3±3.5*† T X G

Females 26.6±5.7 22.6±5.0†

*Significant differences between males and females 

(P<.05).

†Significantly different from baseline (P<.05).

T X G indicates time X group interaction (P<.05).

Table 2. Longitudinal changes (mean±SD) in iron status indicators during BCT 

among male and female Soldiers: hemoglobin (Hgb), serum ferritin (SF), soluble 

transferrin receptor (sTfR), and transferrin saturation (TS).

Week 0 Week 3 Week 6 Week 9 Effect

Hgb (g/dL)

Males (n=77) 14.7±0.8* 14.1±0.8*† 13.9±0.8*† 14.0±0.9*† T X G

Females (n=56) 12.7±0.9 12.4±1.0† 12.3±1.0† 12.4±1.2

SF (ng/mL)

Males (n=84) 129.5±79.8* 121.5±81.3*† 105.7±68.6*† 101.9±66.3*† T X G

Females (n=65) 35.6±27.1 23.4±16.1† 20.2±13.4† 18.9±14.2†

sTfR (nmol/L)

Males (n=82) 16.8±3.6* 19.7±4.8*† 19.7±4.6*† 19.6±4.7*† T X G

Females (n=65) 18.9±7.2 23.9±8.4† 24.6±8.6† 24.6±8.5†

TS (%)

Males (n=89) 31.6±11.7 31.4±11.6* 25.3±9.7*† 24.1±10.5*† T X G

Females (n=65) 28.5±13.8 18.0±9.1† 15.8±7.9† 13.2±6.3†

*Significant differences between males and females (P<.05).

†Significantly different from baseline (P<.05).

T X G indicates time X group interaction (P<.05).
60 http://www.cs.amedd.army.mil/amedd_journal.aspx

meet dietary recommendations, as intake met only 71% 

of the requirement (12.8 mg/day vs 18 mg/day, respectively). Daily iron intake increased in both male and female Soldiers over the course of BCT. By the end of the 

course, overall daily iron intake met 253% and 89% of 

the RDA for men and women, respectively (Figure 2). 

Although there were no correlations between changes 

in dietary iron intake and indicators of iron status in 

male Soldiers, there was a significant negative association (P<.05) between changes in dietary iron intake and 

change in SF in female Soldiers.

Comment

The objective of this study was to evaluate changes in 

iron status, markers of inflammation, and dietary iron 

intake during a 10-week US Army BCT course among 

male and female Soldiers. The major finding of the 

study was that iron status declined in both sexes during 

military training, regardless of improvements in dietary 

iron intake. Although several studies have examined 

iron status among military recruits on induction day,27,28

and throughout military training courses,18,29 this is the 

first study to comprehensively examine differences between the sexes in iron intake and metabolism during 

initial military training in the US Army.

While both men and women experienced a significant 

decline in iron status during BCT, the influence of 

BCT on iron status was more pronounced among females. Data from the current study indicate that the activities associated with military training may contribute 

to declines in iron status, as iron intake significantly 

increased over the course of BCT, and most Soldiers 

were meeting dietary requirements for iron. Improved 

dietary iron intake during BCT was a novel finding, as 

previous studies have not assessed micronutrient intake 

during the training course. Although the relative contribution of particular food items to iron intake was not 

assessed, previous work indicates that dietary patterns 

(reflective of nutrient density) improve in Soldiers during BCT as compared to the period prior to enlistment, 

especially among individuals who enter military service 

with the least favorable eating habits.30

Decreases in iron status have been observed previously 

among physically active populations.31 As observed in 

our study population, decreases in SF and TS coupled 

with an increase in sTfR were evident in both male and 

female Soldiers, although the decrement experienced in 

female Soldiers was nearly double that experienced by 

their male counterparts. These differences between the 

sexes are reflective of previous studies conducted with 

integrated military platoons or professional athletes, although limited data are available with regards to iron 

status in males.32,33 These studies indicated a greater 

prevalence of overuse injuries and sharper declines in 

hematological parameters during BCT and physical 

training periods among females exposed to the same 

absolute physical demands as males.31,34,35 It is possible 

that female Soldiers experience a relatively higher physiological strain in comparison to their male counterparts 

when exposed to similar absolute strains, which may 

contribute to the declines in iron status.36

As previously described in the scientific literature, the 

inflammatory response to exercise is mediated by the 

increased expression of several cytokines, including 

EFFECTS OF BASIC COMBAT TRAINING ON IRON STATUS IN MALE AND FEMALE SOLDIERS:

A COMPARATIVE STUDY

35

30

25

20

15

10

5

0

40

Female

Male

RDA Week 0 Week 9

Iron Intake (mg/day)

Figure 2. Daily iron intake (mg/day) at the beginning (week 0) 

and the end (week 9) of BCT among males (n=89) and females 

(n=65) in comparison to the Recommended Dietary Allowance 

(for males and females aged 19-30 years). Note: significant effects of time and group (P<.05).

*

*

*

*

20

0

-20

-40

-120

-100

-80

80

-60

60

40

Percentage

Female

Male

Hgb SF sTfR TS

Figure 1. Percentage changes (week 0 vs week 9) in iron status 

indicators during BCT in male and female Soldiers: hemoglobin 

(Hgb), serum ferritin (SF), soluble transferrin receptor (sTfR), 

and transferrin saturation (TS). Note: * indicates significant differences between males and females (P<.05).
April – June 2015 61

THE ARMY MEDICAL DEPARTMENT JOURNAL

IL-6, and acute phase proteins such as CRP, and is correlated with the intensity of the activity.37 Hepcidin, a 

key regulator of iron homeostasis, increases in response 

to the inflammation associated with exercise and results 

in the sequestering of iron in enterocytes and macrophages, preventing iron from becoming available for 

incorporation into proteins and enzymes that support 

physical performance and energy metabolism.11 A recent study conducted on 12 physically active women 

(aged 19 to 32 years) found that hepcidin was increased 

3 hours after either a 60-minute or 120-minute run at 

65% of maximal oxygen uptake (VO2max), while IL-6 

levels increased immediately after the end of the exercise bout.38 In the current study, elevations in hsCRP 

and IL-6 occurred over time in both male and female 

Soldiers, although increases were not statistically or 

clinically significant. These findings were contrary to 

our hypothesis; a greater inflammatory response to BCT 

may have been expected in female Soldiers given the 

greater decrement in iron status markers. However, the 

short half-life of acute phase proteins and cytokines 

may cause difficulties in assessing the physiological 

influence of these markers when collected chronically, 

especially following an overnight fast.11 Recent studies 

have demonstrated the acute effects of military training 

on the IL-6 and hepcidin response in male personnel 

during intense operational exercises,15 although future 

studies should more carefully investigate the nature of 

this response to activities encountered during BCT in 

both male and female Soldiers.

Despite the data demonstrating a considerable decrease 

in iron status in this study population regardless of dietary iron intake, the functional consequences of poor 

iron status and effective countermeasures to prevent 

declines in iron status remain unclear. It appears that 

the decline in iron status is of much greater concern 

for female Soldiers, as male Soldiers began the training 

course with more robust iron stores, and experienced an 

attenuated decline in iron status as compared to female 

Soldiers. Although this study did not assess the relationship between iron status and physical or cognitive 

performance, previous studies have demonstrated a relationship between declines in iron status and running 

performance and mood in female Soldiers.14,16 Further, 

effects of both IDA and iron deficiency without anemia 

on physical performance have been noted in civilian 

populations.6 Effects of iron deficiency without anemia could be of significant operational concern during 

military training, especially in female Soldiers, as the 

observed declines in SF and TS coupled with increases 

in sTfR could approach values known to affect performance. The relationship between declining iron status and performance in male Soldiers during military 

training has not been studied and may warrant further 

exploration.

Dietary countermeasures may be effective for preventing declines in iron status during military training as 

indicated by recent studies demonstrating the efficacy of 

both iron supplements14 and fortified foods39 for attenuating the decline in iron status in female Soldiers during 

BCT. However, data from the present study indicate that 

consuming iron at levels well beyond the RDA through 

the diet during BCT does not protect against declines 

in iron status. As such, questions remain regarding the 

mechanism by which iron status declines in response to 

military training, which may drive the development of 

effective nutritional or pharmacologic methods for preventing the negative consequences of poor iron status in 

Warfighters during training. Future studies should address limitations of the current study, to include further 

exploration of the mechanism responsible for the decline 

in iron status including the incorporation of a more detailed panel of proinflammatory cytokines, assessment 

of activities the day prior to blood collection, and greater 

control for menstrual phase in female volunteers. Lastly, 

future studies should assess iron status in both male and 

female Soldiers during periods subsequent to BCT, such 

as advanced individual training, including associations 

with physical and cognitive performance, with a focus 

on female Soldiers that may begin these activities with 

degraded iron status.

Acknowledgements

The authors have no potential conflicts of interest.

This project was funded by the US Army Medical Research and Materiel Command. The study sponsor had 

no role in study design, collection, analysis, and interpretation of data; writing the report, nor the decision to 

submit the report for publication.

We thank the Soldier volunteers that participated in the 

study as well as the Command staff at Fort Jackson, 

South Carolina, for allowing access to the Soldiers.

References

1. Murray-Kolb LE, Beard JL. Iron treatment normalizes cognitive functioning in young women. Am J 

Clin Nutr. 2007;85(3):778-787.

2. Ward RJ, Crichton RR, Taylor DL, Della Corte L, 

Srai SK, Dexter DT. Iron and the immune system. J 

Neural Transm. 2011;118(3):315-328.

3. Jian W, Kostas P. Regulation of cellular iron metabolism. Biochem J. 2011;15:434(3):365-381. 

4. Stoltzfus R. Defining iron-deficiency anemia in 

public health terms: a time for reflection. J Nutr. 

2001;131(2S-2):565S-567S.
62 http://www.cs.amedd.army.mil/amedd_journal.aspx

5. Zimmermann MB, Hurrell RF. Nutritional iron deficiency. Lancet. 2007;370:511-520.

6. McClung JP, Murray-Kolb LE. Iron nutrition and 

premenopausal women: effects of poor iron status 

on physical and neuropsychological performance. 

Annu Rev Nutr. 2013;33:271-288.

7. Looker AC, Dallman PR, Carroll MD, Gunter EW, 

Johnson CL. Prevalence of iron deficiency in the 

United States. JAMA. 1997;277(12):973-6.

8. Heath AL, Fairweather-Tait SJ. Clinical implications of changes in the modern diet: iron intake, absorption, and status. Best Pract Res Clin Haematol. 

2002;15:225-241.

9. Centers for Disease Control and Prevention. Iron 

deficiency: United States, 1999-2002. MMWR 

Morb Mortal Wkly Rep. 2002;51(50):897-899.

10. Shaskey DJ, Gren GA. Sports haematology. Sports 

Med. 2000;29:27-38.

11. Gaffney-Stomberg E, McClung JP. Inflammation 

and diminished iron status: mechanisms and functional outcomes. Curr Opin Clin Nutr Metab Care. 

2012;15:605-613.

12. Magazanik A, Weinstein Y, Dlin RA, Derin M, 

Schwartzman S, Allalouf D. Iron deficiency caused 

by 7 weeks of intensive physical exercise. Eur J 

Appl Physiol Occup Physiol. 1988;57(2):198-202.

13. Wilkinson JG, Martin DT, Adams AA, Lieberman 

M. Iron status in cyclists during high-intensity 

interval training and recovery. Int J Sports Med. 

2002;23(8):544-548. 

14. McClung JP, Karl JP, Cable SJ, Williams KW, Nindl 

BC, Young AJ, Lieberman HR. Randomized, double-blind, placebo-controlled trial of iron supplementation in female Soldiers during military training: effects on iron status, physical performance, 

and mood. Am J Clin Nutr. 2009;90(1):124-131.

15. McClung JP, Martini S, Murphy NE, et al. Effects 

of a 7-day military training exercise on inflammatory biomarkers, serum hepcidin, and iron status. 

Nutr J. 2013;12:141.

16. McClung JP, Karl JP, Cable SJ, Williams KW, 

Young AJ, Lieberman HR. Longitudinal decrements in iron status during military training in female Soldiers. Br J Nutr. 2009;102(4):605-609.

17. Yanovich R, Merkel D, Israeli E, Evans RK, Erlich 

T, Moran DS. Anemia, iron deficiency, and stress 

fractures in female combatants during 16 months. 

J Strength Cond Res. 2011;25(12):3412-3421.

18. Moran DS, Heled Y, Arbel Y, Israeli E, Finestone 

AS, Evans RK, Yanovich R. Dietary intake and 

stress fractures among elite male combat recruits. 

J Int Soc Sports Nutr. 2012;13:9(1):6.

19. Army Regulation 70-25: Use of Volunteers as Subjects of Research. Washington, DC: US Dept of the 

Army; January 1990.

20. US Army Medical Research and Development Command Regulation 70-25: Use of Human Subjects in 

Research, Development, Testing and Evaluation. 

Fort Detrick, MD: US Army Medical Research and 

Development Command; May 1989 [updated July 

2003].

21. Pasiakos SM, Karl JP, Lutz LJ, et al. Cardiometabolic risk in US Army recruits and the effects of 

basic combat training. PloS One. 2012;7:e31222.

22. Simpson K, Redmond JE, Cohen BS, et al. Quantification of physical activity performed during US 

Army Basic Combat Training. US Army Med Dep J. 

October-December 2013:55-65. 

23. Heyward VH. Evaluation of body composition. 

Current issues. Sports Med. 1996;22:146-156. 

24. Jackson AS, Pollack ML. Generalized equations 

for predicting body density of men. Br J Nutr.

1978;40:497-504.

25. Jackson AS, Pollack ML, Ward A. Generalized 

equations for predicting body density of women. 

Med Sci Sports Exerc. 1980;12:175-181.

26. Food and Nutrition Board, Institute of Medicine.

Dietary Reference Intakes for Vitamin A, Vitamin 

K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, 

Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy 

Press; 2001.

27. Merkel D, Huerta M, Grotto I, et al. Prevalence 

of iron deficiency and anemia among strenuously trained adolescents. J Adolesc Health. 

2005;37(3):220-223.

28. Israeli E, Merkel D, Constantini N, Yanovich R, Evans RK, Shahar D, Moran DS. Iron deficiency and 

the role of nutrition among female military recruits. 

Med Sci Sports Exerc. 2008;40(suppl 11):S685-S690.

29. Merkel D, Huerta M, Grotto I, et al. Incidence of 

anemia and iron deficiency in strenuously trained 

adolescents: results of a longitudinal follow-up 

study. J Adolesc Health. 2009;45:286-291.

30. Lutz LJ, Gaffney-Stomberg E, Scisco JL, Cable 

SJ, Karl JP, Young AJ, McClung JP. Assessment of 

dietary intake using the healthy eating index during military training. US Army Med Dep J. OctoberDecember 2013:91-97.

31. Beard J, Tobin B. Iron status and exercise. Am J 

Clin Nutr. 2000;72(suppl 2):594S-597S.

32. Sinclair LM, Hinton PS. Prevalence of iron deficiency with and without anemia in recreationally active men and women. J Am Diet Assoc. 

2005;105(6):975-978.

EFFECTS OF BASIC COMBAT TRAINING ON IRON STATUS IN MALE AND FEMALE SOLDIERS:

A COMPARATIVE STUDY
April – June 2015 63

THE ARMY MEDICAL DEPARTMENT JOURNAL

33. Merkel D, Moran DS, Yanovich R, Evans RK, 

Finestone AS, Constantini N, Israeli E. The association between hematological and inflammatory 

factors and stress fractures among female military recruits. Med Sci Sports Exerc. 2008;40(suppl 

11):S691-S697.

34. Yanovich R, Evans R, Israeli E, et al. Differences 

in physical fitness of male and female recruits in 

sex-integrated army basic training. Med Sci Sports 

Exerc. 2008;40(suppl 11):S654-S659.

35. Nindl BC, Scofield DE, Strohbach CA, Centi AJ, 

Evans RK, Yanovich R, Moran DS. IGF-I, IGFBPs, 

and inflammatory cytokine responses during sexintegrated Israeli Army basic combat training. J 

Strength Cond Res. 2012;26(suppl 2):S73-S81.

36. Epstein Y, Yanovich R, Moran DS, Heled Y. 

Physiological employment standards IV: integration of women in combat units physiological 

and medical considerations. Eur J Appl Physiol. 

2013;113:2673-2690.

37. Pedersen BK. Exercise and cytokines. Immunol 

Cell Biol. 2000;78(5):532-535.

38. Newlin MK, Williams S, McNamara T, Tjalsma H, 

Swinkels DW, Haymes EM. The effects of acute 

exercise bouts on hepcidin in women. Int J Sport 

Nutr Exerc Metab. 2012;22(2):79-88.

39. Karl JP, Lieberman HR, Cable SJ, Williams KW, 

Young AJ, McClung JP. Randomized, double-blind, 

placebo-controlled trial of an iron-fortified food 

product in female Soldiers during military training: relations between iron status, serum hepcidin, 

and inflammation. Am J Clin Nutr. 2010;92:93-100.

Authors

MAJ Yanovich is the deputy director of the Israeli Defense Forces’ Institute of Military Physiology, The Heller 

Institute of Medical Research Sheba Medical Center, TelHashomer, Israel.

Dr Karl is a principal investigator within the Military 

Nutrition Division of the US Army Research Institute of 

Environmental Medicine, Natick, MA.

Dr Yanovich is a principal investigator within the Zinman College of Physical Education and Sport Sciences, 

Wingate Institute, Israel.

Ms Lutz is a project manager within the Military Nutrition Division of the US Army Research Institute of Environmental Medicine, Natick, MA.

Dr Williams is a research physiologist within the Knowledge Preservation Program at the US Army Research Institute of Environmental Medicine administered by the 

Oak Ridge Institute for Science and Education.

COL Cable is Chief of the Nutrition Care Division, Womack Army Medical Center, Fort Bragg, NC.

Dr Young is a research physiologist within the Knowledge Preservation Program at the US Army Research Institute of Environmental Medicine administered by the 

Oak Ridge Institute for Science and Education.

Dr Pasiakos is a principal investigator within the Military Nutrition Division of the US Army Research Institute of Environmental Medicine, Natick, MA.

Dr McClung is a principal investigator within the Military Nutrition Division of the US Army Research Institute of Environmental Medicine, Natick, MA.

Articles published in the Army Medical Department Journal are indexed 

in MEDLINE, the National Library of Medicine’s (NLM’s) bibliographic 

database of life sciences and biomedical information. Inclusion in the 

MEDLINE database ensures that citations to AMEDD Journal content will 

be identified to researchers during searches for relevant information using any 

of several bibliographic search tools, including the NLM’s PubMed service.
64 http://www.cs.amedd.army.mil/amedd_journal.aspx

Women currently comprise 15% of the total active duty 

population and 10% of brigade units.1 The number of 

female war veterans from current military conflicts is 

expected to rise accordingly.2 While the study of the female veterans as a distinct population lags behind the 

study of the overall veteran population, there is evidence 

that the female veteran reacts to combat trauma differently than males.3

 This is consistent with several reports 

in the literature describing sexual dimorphism in outcomes in the civilian trauma population.4,5 Evidence 

from prior wars suggests that female veterans have 

higher incidence of reproductive health issues compared 

to females who never served in the military.6,7 Outside 

of the physical toll of trauma, mental health outcomes 

also differ between men and women in the civilian 

trauma literature. Posttraumatic stress disorder (PTSD) 

rates are higher for women in civilian accidents and for 

women who witness death or injury versus men.8,9 Some 

studies support that female veterans experience similar 

rates of PTSD compared to male veterans.10,11 However, the most common cause of evacuation of deployed 

women service members from both recent wars in Iraq 

and Afghanistan was and is mental health condition.12,13

A recent publication on disability following combat injuries highlights the importance and frequent nature of 

orthopaedic related disability.14 This is certainly so for 

service members with combat related amputations and 

the ensuing disability related to the amputation. The disability outcomes for female veterans, including females 

with combat related amputations specifically, have not 

been determined. We aim to determine what differences exist, if any, in the disability profiles of women 

who sustained a combat related amputation versus male 

veterans with amputations. Because mental health disorders such as PTSD are known to adversely affect outcomes following trauma and because the PTSD rates for 

female veterans may be higher than for male veterans, 

differences in male and female disability profiles for 

both physical and mental health conditions may exist.15

Based on prior literature that supports different mental 

health outcomes and a variable reaction to trauma, we 

Female Combat Amputees Have Higher Rates

 of Posttraumatic Stress Disorder Disability

MAJ Jessica C Rivera, MC, USA

CPT (P) Chad A. Krueger, MC, USA

LTC (P) Anthony E Johnson, MC, USA

Abstract

Background: The civilian trauma literature suggests that the sexes differ in physical and mental health outcomes 

following traumatic injury. In order to determine if the reaction to combat injury is different between the sexes 

in a specific war wounded population, service members with amputations, we examined the disability profiles 

of male and female amputees.

Methods: All US combatants who sustained a major extremity amputation between October 2001 and July 2011 

were examined for demographic and injury information from the Department of Defense Trauma Registry and 

for disability outcomes in the service specific Physical Evaluation Boards. The proportions of women versus 

men with various disabling conditions were compared using Fisher’s Exact Test and the mean disability ratings 

for each condition were compared using student’s t tests.

Findings: Among 1,107 amputees, 21 were female. There was no difference in the average age, military rank, or 

Injury Severity Score between the sexes. While the most common military occupation of male amputees was 

infantry service, the most common occupation for the female amputee was military police. The overall disability 

ratings between females and males were not different (82% for females, 75% for males). Female amputees had 

more frequent disability from posttraumatic stress disorder (PTSD, 8/21 [38%] vs 168/818 [17%]). Disability 

ratings from PTSD tended to also be higher in women.

Conclusions: Outside of variable occupational descriptions, both male and female amputees were exposed to 

explosions resulting in their injuries. Consistent with many civilian trauma and veterans’ population studies, 

female amputees have higher frequencies of disability from PTSD. These results support the need for additional 

effort and attention directed towards optimizing physical and mental fitness following deployment in order to 

reduce disability and promote return to duty. Because certain conditions, such as PTSD, may be more or less 

common in men versus women veterans, postdeployment fitness may need to be tailored in a gender specific way.
April – June 2015 65

hypothesize that female amputees will have different 

disability profiles compared to male amputees.

Methods

This study was conducted in accordance with a research 

protocol approved by the Brooke Army Medical Center 

Institutional Review Board. All military patients who 

sustained a major limb amputation between October of 

2001 and July 2011 were queried in the Department of 

Defense Trauma Registry (DoDTR, Joint Base San Antonio Fort Sam Houston, Texas) for demographic and 

injury information to include age, sex, military rank, 

mechanism of injury, and Injury Severity Score (ISS). 

Major limb amputation was defined as an amputation 

occurring proximal to the carpus in the upper extremity 

and proximal to the tarsal bones in the lower extremity. 

Injury and demographic data were cross-checked for the 

female amputees in the Military Orthopaedic Trauma 

Registry (MOTR, Joint Base San Antonio Fort Sam 

Houston, Texas). We then queried the resultant subjects 

in the service specific Physical Evaluation Board databases which are maintained separately for the Army, Air 

Force, and Navy (including Marine Corps). The Physical 

Evaluation Board (PEB) is responsible for determining 

an ill or injured service member’s fitness for duty after 

an adequate period of recovery which is determined by 

the various treating physicians. If the service member 

is not able to perform his or her 

active duty job description, the 

PEB helps determine if the service member should be medically 

separated or retired from the military, or be retained temporarily 

for additional treatment or recovery. The high physical demands 

of military service make the PEB 

determinations important following orthopaedic injury.

Subjects with complete DoDTR injury data who were 

medically retired or separated from active duty service 

by the PEB were included in this analysis. For service 

members who are medically retired by the PEB, the 

diagnoses that affect their inability to return to duty 

are called “unfitting” or disabling conditions. Each 

disabling condition is also assigned a percentage on a 

continuous spectrum from 0% to 100% to reflect how 

much that individual condition contributes to the service member’s inability to perform his or her active 

duty position. For example, for a service member with 

a transtibial amputation, the PEB assigned a percent 

disability to the amputation diagnosis of 40%. This indicates that the amputation diagnosis detracts 40% of 

military fitness and readiness for that service member’s 

ability to perform his or her job. The percent disability can therefore be evaluated on a spectrum of severity. 

The disability rating for each of the separate conditions 

is totaled according to the Veterans Affairs (VA) Schedule for Rating Disabilities formula to yield a total percent disability. While the PEB rating is different from 

the service connected disability designation a veteran 

receives from the VA, the VA rating scheme is used by 

the PEB for this Department of Defense disability rating.

We present demographic and injury descriptions compared between the sexes. The proportions of related 

disabling conditions between men and women were 

compared using Fisher’s Exact Test. The mean percent 

disabilities (continuous variables from 0% to 100% reflecting a disability spectrum) per group of disabling 

conditions were compared between the sexes using unpaired student’s t tests. Calculations were performed using Graph Pad Prism 6 software (GraphPad Software, 

Inc, La Jolla, CA).

Results

Of the 1,107 amputees who were evaluated by the PEB, 

21 were female and 986 were male. Average age, median military rank, and average ISS were not different 

between the sexes as shown in Table 1. A majority of 

both women and men sustained their amputations in a 

battle injury of explosion mechanism. One female sustained a 

transtibial amputation in a nonbattle machinery accident. The 

distribution of amputation sites 

were also similar with the majority of amputations being of the 

lower extremities as illustrated 

in the Figure. Because of certain 

restrictions on women serving in 

direct combat roles, job descriptions for males and females did differ as most male 

amputees served in infantry units. Ten of the females 

with amputations served as Military Police, 4 in supply/

transport, 3 as mechanics, 2 in human resources, one as 

an explosive ordinance officer, and one as an aviation 

officer. All of the female amputees served in the Army.

The frequencies of orthopaedic related disabling conditions were not different between the sexes. Outside of 

the disability received for the amputation diagnoses, 

posttraumatic arthritis was the most common condition 

affecting male amputees and the second most common 

condition affecting female amputees. Among the nonorthopaedic conditions, female amputees had a higher 

proportion of PTSD related disability compared to male 

amputees, with PTSD being the most common disabling 

Table 1. US Military Combatants with Major Extremity Amputations who underwent Physical 

Evaluation Board Review, October 2001–July 

2011 (N=1,007)

Women

(n=21, 2%)

Men

(n=986, 98%)

Age (mean±SD) 27±5 25±5

Rank (median, range) E-6 (E3-O3) E-7 (E1-O6)

Battle Injury 20, 95% 976, 99%

ISS (mean±SD) 19±7 21±10
66 http://www.cs.amedd.army.mil/amedd_journal.aspx

condition in women aside from the amputations themselves as shown in Table 2.

The overall disability ratings and the percent disability 

rating assigned to upper extremity amputations tended to 

be higher for women but not significantly so as shown in 

Table 3. The average percent disability ratings assigned 

to individual orthopaedic and nonorthopaedic conditions 

were also not different for males versus females, shown 

in Table 4. While all females were deemed unfit for duty 

and eligible for medical retirement based on their disability ratings, 3 women were able to continue on active 

duty in a limited or altered job description through a 

Continuation on Active Duty (COAD) appeals process. 

Females who COAD were of average age 23 years old 

and enlisted rank E-4, while the 89 males who returned 

to duty or were able to COAD were of average age 28 

and enlisted rank E-7. None of the women who were 

COAD were assigned disability related to PTSD; and 

only one male who was COAD had a PTSD disability.

Comment

Among a population of wounded service members 

who sustained similar injuries by similar mechanisms, 

a comparison of resultant disabilities is possible. We 

found that general demographics in this specific injured 

population, with the expected differences in job description, are similar for male and female combat amputees. 

Consistent with prior literature in the civilian population, 

we found that female amputees have a higher proportion of PTSD diagnoses compared to similarly injured 

males. The disability percentage ratings, however, were 

not different between the sexes. The high proportion of 

posttraumatic arthritis being similar between the sexes 

is notable, though, as idiopathic osteoarthritis is more 

common in females than males.16-18

Current literature on the veteran population is mixed regarding the presence or absence of difference in rates of 

PTSD in male and female veterans. Haskell et al found 

that the female sex was negatively correlated with a positive screen for PTSD or VA service connected disability 

for PTSD, while other studies have found no difference 

between the sexes.10,11,19 However, studies that account 

for other levels of interpersonal trauma, prior history of 

trauma, and sexual trauma in the military indicated that 

personal history and type of trauma exposure contributed to higher rates of PTSD and depression in female 

veterans.20-23 A recent study of homeless veterans found 

that homeless women were more likely than men to have 

PTSD, but were less likely to have substance abuse and 

incarceration histories.24 Studies of PTSD rates use variable methods for measuring and diagnosing PTSD, making a firm conclusion about dimorphism in PTSD rates 

difficult.25

We found a higher rate (40%) of PTSD in our cohort 

than previously published or expected based on recent epidemiologic studies of veterans.26,27 We believe 

this study shows a true difference in the frequency of 

PTSD among female service members when the injury 

mechanism and injury pattern are considered. Because 

of the similarities across the board in our male and 

Table 2. Service Disqualifying Conditions per Sex

Women

N=21

(n, %N)

Men

N=986

(n, %N)

P

Value

PTSD 8, 40% 168, 17% .0193

Scar 4, 20% 89, 9% .1207

TBI 4, 20% 99, 10% .2605

Arthritis 7, 35% 247, 25% .4453

Back Pain 1, 5% 20, 2% .3605

Abdomen/Pelvic Condition 1, 5% 20, 2% .3605

General Pain 1, 5% 30, 3% .4849

Muscle Condition 2, 10% 79, 8% .6832

Nerve-Loss of Function 3, 15% 150, 15% 1

Two-tailed P value calculated using Fisher’s Exact Test.

PTSD indicates posttraumatic stress disorder; TBI, traumatic 

brain injury.

One Subject:

bilateral upper

extremity

amputation

One Subject:

transfemoral

& contralateral

transtibial

amputation

3 Subjects:

bilateral

amputations at

or below the

transtibial level

2 Subjects:

transradial

amputations

7 Subjects:

transfemoral

amputations

6 Subjects:

amputations at

or below the

transtibial level

One Subject:

shoulder

disarticulation

Amputation levels of 21 female amputees.

FEMALE COMBAT AMPUTEES HAVE HIGHER RATES OF

POSTTRAUMATIC STRESS DISORDER DISABILITY
April – June 2015 67

THE ARMY MEDICAL DEPARTMENT JOURNAL

female cohorts, the comparison of frequencies is useful. Additionally, in order for a condition to be deemed 

a disabling condition, the service member must have 

undergone an adequate time for treatment and recovery 

and have undergone subspecialty evaluation and diagnosis, making this rate of persistent PTSD reflective of 

physician diagnosed disorders rather than self-reported 

incidences. The disability percentages were not different among the sexes, suggesting that the severity of the 

injuries and resultant disability are no different, even in 

light of frequency differences for PTSD.

Other studies on female veterans demonstrate other possible sex differences following trauma. Female veterans 

from multiple prior wars have reported increased issues 

in reproductive health including higher incidence of 

birth defects, higher incidence of severe premenstrual 

symptoms, and a more difficult time becoming pregnant.6,7,28 Other studies demonstrate higher rates of anxiety and depression among female service members.19,29

One study by Nunes et al demonstrated higher rates of 

psychological diagnoses in civilian female amputees 

versus males.30 Other studies have found that female 

veterans have more pain disorders and higher healthcare 

utilization for pain versus male veterans.31,32 Our study 

did not demonstrate higher frequencies of other mental 

health diagnoses, pain disorders, or gynecological problems in this cohort. In this small population of amputees, 

however, this likely reflects the conditions that are evident to the PEB a relatively short time following injury, 

whereas some issues may arise later or be amplified 

with time as suggested in some studies published from 

the VA.

One unique finding about this small population of female amputees is the number and characteristics of the 

women who were able to return to an active duty role 

through the COAD process. COAD is an appeals process that allows select service members to be retained 

on active duty in limited or altered job roles despite 

being deemed medically unfit by the PEB. Prior studies on return to duty after a variety of orthopaedic 

injuries have found that the service members who 

were able to continue on active duty in some fashion 

were typically older and higher rank.33-35 This makes 

the 3 female amputees on COAD unique as their average age was 23 and median military rank E-4. We 

speculate that the ability for these young soldiers to 

continue active duty service in a new job description 

is related to job descriptions which might be amenable to an altered level of physical activity. For example, the most common job description for the male 

amputee, infantry, would rarely be achievable for the 

duties required of the young, junior-enlisted infantryman.36 The new job roles to which the COAD soldiers 

returned to duty were not available for analysis. However, the absence of PTSD may also have contributed to 

these women’s ability and desire to return to duty.

Our study does have several limitations. For one, the 

PEB results and disposition are unique to the military 

and may be difficult to extrapolate to civilian trauma 

setting. We believe that with the rising number of combat veterans from our most current wars, military related disability will become an increasingly important 

issue in the VA and in treatment centers outside the 

VA. Furthermore, the PEB system serves as essentially 

a workman’s compensation system comparable to that 

found in the civilian trauma environment. Secondly, our 

data is limited to retrospective evaluations which limits 

our ability to demonstrate causation. We have attempted 

to limit the deficiencies in this data as best as possible by 

validating the demographic and injury information in 

our Military Orthoapedic Trauma Registry which was 

designed specifically for capture of orthopaedic specific 

injury, treatment, and complication information. Finally, 

our most concerning limitation is the small sample size 

of female amputees making statistical inference difficult when comparing the sexes. While this remains the 

largest cohort of female amputees to be reported from 

the most comprehensive combat injury registry available, this is a limitation of the patient population, but we 

Table 4. Mean Disability Ratings per Condition (range)

Women Men P

Value

PTSD 49% (10%-80%) 44% (0-70%) .5553

Nerve-Loss of Function 45% (10%-80%) 33% (0-40%) .4636

Muscle Condition 40% (40%) 29% (0-70%) .4142

Arthritis 33% (10%-40%) 22% (0-40%) .2527

TBI 30% (10%-40%) 40% (0-100%) .4968

Scar 27% (10%-50%) 30% (0-70%) .3893

Back Pain 20% 13% (0-20%) n/a

Abdomen/Pelvic Condition 20% 58% (0-80%) n/a

General Pain 0% 15% (0-30%) n/a

Disability ratings assigned as a continuous variable between 0 and 100%.

Two tailed P value comparing means were calculated using student’s t test.

PTSD indicates posttraumatic stress disorder; TBI, traumatic brain injury.

Table 3. Mean Overall Disability Ratings (range)

Women Men P

Value

Upper Extremity Amputation 85%

(70%-100%)

76%

(40%-100%) .2933

Lower Extremity Amputation 66%

(40%-100%)

65%

(40%-100%) .9781

Overall Combined Disability 82%

(40%-100%)

75%

(40%-100%) .2042

Disability ratings assigned as a continuous variable between 0 and 100%.

Two tailed P value comparing means were calculated using student’s t test.
68 http://www.cs.amedd.army.mil/amedd_journal.aspx

believe the information is useful by further supporting 

other military and civilian amputee literature.

Summary

In a cohort of recent combat veterans with similar injury mechanisms and patterns over a 10-year span, the 

disability profiles between female and male amputees is 

not entirely different. Female amputees are more likely 

to have PTSD as a service disqualifying condition than 

male amputees, though the severity of the PTSD is not 

statistically different between the sexes. Proportions and 

severities of the orthopaedic disabling conditions were 

not different between the sexes. There appears to be a 

demographic difference in female amputees who were 

able to continue on active duty which may be related to 

military occupation specific factors. These findings in a 

small cohort of female military amputees add additional 

information on the importance of understanding differences in response to combat injury for both physical and 

mental disorders such as PTSD in the female veteran 

population.

References

1. A Profile of Women Veterans Today [internet]. 

Women’s Health Services, US Department of 

Veterans Affairs; 2013. Available at: http://www.

womenshealth.va.gov/WOMENSHEALTH/docs/

ProfileSheet_073113_508c.pdf. Accessed April 22, 

2014.

2. Resnick EM, Mallampalli M, Carter CL. Current 

challenges in female veterans’ health. J Womens 

Health. 2012;21:895-900.

3. Cross JD, Johnson AE, Wenke JC, Bosse MJ, Ficke 

JR. Mortality in female war veterans of Operations 

Enduring and Iraqi Freedom. Clin Orthop Relat 

Res. 2011;469:1956-1961.

4. Haider AM, Crompton JG, Oyetunji T, et al. Females have fewer complications and lower mortality following trauma then similarly injured males: 

a risk adjusted analysis of adults in the National 

Trauma Data Bank. Surgery. 2009;146:308-315.

5. Wohltmann CD, Franklin GA, Boaz MSN, et al. A 

multicenter evaluation of whether gender dimorphism affects survival after trauma. Am J Surg. 

2001;181:297-300.

6. Kang HK, Li B, Mahan CM, Eisen SA, Engel CC. 

Health of US veterans of 1991 Gulf War: a follow-up survey in 10 years. J Occup Environ Med. 

2009;51:401-410.

7. Kang H, Magee C, Mahan C, et al. Pregnancy outcomes among U.S. Gulf War veterans: a population 

based survey of 30,000 veterans. Ann Epidemiol. 

2001;11:504-511.

8. Olff M, Langeland W, Draijer N, Gersons BP. Gender differences in posttraumatic stress disorder. 

Psychol Bull. 2007;133:183-204.

9. Tolin DF, Foa EB. Sex differences in trauma 

and posttraumatic stress disorder: a quantitative review of 25 years of research. Psychol Bull. 

2006;132:959-992.

10. Hoge CW, Auchterlonie JL, Milliken CS. Mental 

health problems, use of mental health services, 

and attrition from military service after returning 

from deployment to Iraq or Afghanistan. JAMA. 

2006;295:1023-1032.

11. Fear NT, Jones M, Murphy D, et al. What are the 

consequences of deployment to Iraq and Afghanistan on the mental health of the UK armed forces? 

A cohort study. Lancet. 2010;375:1728-1797.

12. Medical evacuations from Afghanistan during 

Operation Enduring Freedom, active and reserve 

component, U.S. Armed Forces, 7 October 2001-31 

December 2012. MSMR. 2013;20:2-8.

13. Medical evacuation from Operation Iraqi Freedom. Operation New Dawn, active and reserve 

components, U.S. armed forces, 2003-2011. MSMR. 

2012;19:18-21.

14. Cross JC, Ficke JR, Hsu JR et al. Battlefield orthoapedic injuries cause the majority of long-term 

disabilities. J Am Acad Orthop Surg. 2011;19(suppl 

1):S1-S7.

15. Starr AJ, Smith WR, Frawley WH, et al. Symptoms 

of posttraumatic stress disorder after orthopaedic 

trauma. J Bone Joint Surg Am. 2004;86:1115-1121.

16. Hanna FS, Teichtahl AJ, Wluka AE, et al. Women 

have increased rates of cartilage loss and progression of cartilage defects at the knee than men: a 

gender study of adults without clinical knee osteoarthritis. Menopause. 2009;16:666-670.

17. Kopec JA, Rahman MM, Berthelot, et al. Descriptive epidemiology of osteoarthritis in British Columbia, Canada. J Rheumatol. 2007;34:386-393.

18. Felson DT, Naimark A, Anderson J, Kazis L, Castelli W, Meenan RF. The prevalence of knee osteoarthritis in the elderly. The Framingham Osteoarthritis Study. Arthritis Rheum. 1987;30:914-918.

19. Haskell SG, Gordon KS, Mattocks K, et al. Gender differences in rating of depression, PTSD, pain, 

obesity, and military sexual trauma among Connecticut war veterans of Iraq and Afghanistan. J 

Womens Health. 2010;19:267-271.

20. Fontana A, Rosenheck R, Desai R. Female veterans of Iraq and Afghanistan seeking care from 

VA specialized PTSD programs: comparison with 

male veterans and female war zone veterans of previous eras. J Womens Health. 2010;19:751-757.

FEMALE COMBAT AMPUTEES HAVE HIGHER RATES OF

POSTTRAUMATIC STRESS DISORDER DISABILITY
April – June 2015 69

THE ARMY MEDICAL DEPARTMENT JOURNAL

21. Hassija CM, Jakupcak M, Maguen S, Shipherd JC. 

The influence of combat and interpersonal trauma 

on PTSD, depression, and alcohol misuse in U.S. 

Gulf War and OEF/OIF women veterans. J Trauma 

Stress. 2012;25:216-219.

22. Kang H, Dalager N, Mahan C, Ishii E. The role of 

sexual assault on the risk of PTSD among Gulf War 

veterans. Ann Epidemiol. 2005;15:191-195.

23. Wolfe J, Erickson DJ, Sharkansky EJ, King DW, 

King LA. Course and predictors of posttraumatic stress disorder among Gulf War veterans: 

a prospective analysis. J Consult Clin Psychol. 

1999;67:520-528.

24. Tsai J, Rosenheck RA, Kane V. Homeless female 

US veterans in a national supported housing program: comparison of individual characteristics 

and outcomes with male veterans. Psychol Serv. 

2014;11:309-316.

25. Street AE, Vogt D, Dutra L. A new generation of 

women veterans: stressors faced by women deployed to Iraq and Afghanistan. Clin Psych Rev. 

2009;29:685-694.

26. Gates MA, Holowka DW, Vasterling JJ, Keane TM, 

Marx BP, Rosen RC. Posttraumatic stress disorder 

in veterans and military personnel: epidemiology, screening, and care recognition. Psychol Serv. 

2012;9:361-382.

27. Gradus JL. Epidemiology of PTSD [internet]. National Center for PTSD, US Department of Veterans Affairs; January 30, 2014. Available at: http://

www.ptsd.va.gov/professional/PTSD-overview/

epidemiological-facts-ptsd.asp. Accessed April 23, 

2014.

28. Cohen BE, Maguen S, Bertenthal D, Shi Y, Jacoby 

V, Seal KH. Reproductive and other health outcomes in Iraq and Afghanistan women veterans using VA health care: association with mental health 

diagnoses. Womens Health Issues. 2012;22:461-471.

29. Wells TS, Leard Mann CA, Fortuna SO, et al. A 

prospective study of depression following combat 

deployment in support of the wars in Iraq and Afghanistan. Am J Public Health. 2010;100:90-99.

30. Nunes MA, de Barros N, Miranda F, Baptista-Silva 

JC. Common mental disorders in patients undergoing lower limb amputation: a population-based 

sample. World J Surg. 2012;36:1011-1015.

31. Haskell SG, Brandt CA, Krebs EE, Skanderson 

M, Kerns RD, Goulet JL. Pain among Veterans of Operations Enduring Freedom and Iraqi 

Freedom: do women and men differ? Pain Med. 

2009;10:1167-1173.

32. Haskell SG, Ning Y, Krebs E, et al. Prevalence of 

painful musculoskeletal conditions in female and 

male veterans in 7 years after return from deployment in Operation Enduring Freedom/Operation 

Iraqi Freedom. Clin J Pain. 2012;28:163-167.

33. Cross JD, Stinner DJ, Burns TC, Wenke JC, Hsu 

JR, Skeletal Trauma Research Consortium. Return 

to duty after type III open tibia fracture. J Orthop 

Trauma. 2012;26:43-47.

34. Krueger CA, Wenke JC. Initial injury severity and 

social factors determine ability to deploy after combat-related amputation. Injury. 2014;45:1231-1235.

35. Stinner DJ, Burns TC, Kirk KL, Ficke JR. Return to duty rates of amputee soldiers in the current conflicts in Afghanistan and Iraq. J Trauma. 

2010;68:1476-1479.

36. Belisle JG, Wenke JC, Krueger CA. Return-to-duty-rates among US military combat-related amputees in the global war on terror: job description matters. J Trauma Acute Care Surg. 2013;75:279-286.

Authors

MAJ Rivera is with the US Army Institute of Surgical 

Research, San Antonio Military Medical Center, Texas.

CPT (P) Krueger is with the Department of Orthopaedics and Rehabilitation, Brooke Army Medical Center, 

San Antonio, Texas.

LTC (P) Johnson is Chairman, Department of Orthopaedics and Rehabilitation, Brooke Army Medical Center, 

San Antonio, Texas.
70 http://www.cs.amedd.army.mil/amedd_journal.aspx

The United States has been involved in armed conflicts 

in Iraq and Afghanistan over the last 12 years,1 and during this time there have been changes in the nature and 

severity of casualties, especially as compared to previous US conflicts.2-4 There is previous literature which 

addressed treatment of casualties based on mechanism 

of injury such as blast injuries that have been common 

in these conflicts due to the use of improvised explosive devices.2,4,5 Further studies looked into prevention 

of injury including body armor and eye protection3 and 

further treatment of severe extremity trauma through 

the use of tourniquets.6,7 Less research has focused 

on identifying differences in the individuals being injured. There are some studies looking specifically at 

demographic information, especially when comparing 

military branches.8,9 However, there is very little that 

can be found from any investigation into casualty differences between the sexes.

Some studies in the civilian trauma literature indicate 

that there is a difference in survival rates for women 

versus men with similar injury patterns.10 Both animal 

studies and retrospective reviews of civilian trauma 

data have indicated that women may have a biological advantage when it comes to surviving trauma,10-12

at least if there are no medical complications after the 

sustained trauma. This is in contrast to Cross et al who 

studied mortality in combat which indicated that female 

Comparison of Female and Male

 Casualty Cohorts from Conflicts

 in Iraq and Afghanistan

CPT Christina Hylden, MC, USA

LTC (P) Anthony E. Johnson, MC, USA

MAJ Jessica C. Rivera, MC, USA

Abstract

Although there has been interest in the literature regarding the casualties within the recent US military conflicts in 

Iraq and Afghanistan, very little to date has looked specifically at a difference between the sexes. As the role of the 

female Soldier has changed over the years, so have the risk and the nature of the female casualty. Combat injuries in 

women are an important medical consideration that has yet to be studied. For the purposes of this study, the following 

questions pertained:

Do female and male casualties from the US military in recent conflicts differ in age, service, rank, military 

operation, or other demographic characteristics?

Do female and male casualties from the US military in recent conflicts differ in their injury characteristics such 

as Injury Severity Score (ISS), Abbreviated Injury Score (AIS), injury type (blunt versus penetrating), injury 

cause (mechanism of injury), and injury date?

The Department of Defense Trauma Registry (DoDTR) was queried, returning results for 425 female and 14,982 male 

subjects who sustained musculoskeletal injuries from October 2003 (beginning of hostilities in Iraq) to December 

2012.

The female and male cohorts were compared and analyzed for significance in demographics (age, service, rank, and 

military operation) and injury characteristics (ISS, AIS, injury type, injury cause, and injury date).

Female casualties differ from their male counterparts in that they are slightly younger (F=26.11, M=27.83 years; 

P<.001), proportionally more female casualties were in the Army (F=81.5%, M=72.2%; P<.001), and proportionally 

more women were injured during Operation Iraqi Freedom (F=75.6%, M=63.2%; P<.001).

Female casualties showed on average lower ISS (F=7.49; M=9.68; P<.001) and lower AIS specific to the skeletal 

anatomic region (F=2.06; M=2.36; P<.001); however when broken down into battle versus nonbattle injury, the 

difference disappeared. Women were less likely to be injured in battle (F=33.1%; M=70.9%; P<.001) and less likely 

to be injured due to an explosive device (F=27.7%, M=55.2%; P<.001).

Women comprised 2.75% of the DoDTR casualties during the studied time frame and were less likely to be involved 

in explosions or during battle. The ISS were significantly different when comparing battle and nonbattle injuries for 

both of the sexes. However, since men were more likely to be injured in battle, their total ISS mean was higher.
April – June 2015 71

casualties with battle injuries of a similar severity to 

their male counterparts were more likely to die of their 

injuries.13 This disparity indicates that more research is 

needed to further understand the impact that sex may 

have on wartime casualty survival.

Women currently serve in the military in many countries around the world including Israel, which is the only 

nation that mandates service for all citizens, men and 

women alike.14 Today women comprise approximately 

15% of the US military,15,16 and their contributions are 

recognized as vital to readiness. This has not always 

been the case. Prior to and during World War II, women 

serving in support roles for the troops were not considered to be a part of the military itself. This changed 

in 1948 when federal legislation mandated that women 

would be part of the US military services.16 The first matriculation of women at military academies occurred in 

1976, and a small contingent of women was deployed to 

Grenada in 1983.16 During the first Gulf War (1990-1991), 

approximately 40,000 women were deployed. However, 

this effort was soon followed in 1994 by a Pentagon policy that established a ban on assignment of women to 

ground combat units considered to be “front-line” positions.16 Despite this, current conflicts have demonstrated 

that women’s invaluable contributions to the military 

are no longer required only behind the front lines of 

fighting as in previous wars. The Secretary of Defense 

acknowledged this fact in 2013 when he lifted the 1994 

prohibition, allowing women to hold direct combat positions, including infantry and even potentially special 

forces roles.15,17

Given these changes in the role of the female service 

member, it is more important than ever to learn if there 

are any differences between the sexes in casualty treatment and/or survival. In order to provide the best care, 

physicians must not only look at the injuries sustained 

but also the individual being treated. We do not yet 

know what the differences might be between men and 

women injured during conflict.13

For the purposes of this study, the following questions 

pertained:

3⁄4 Do female and male casualties from the US military 

in recent conflicts differ in age, service, rank, military operation, or other demographic characteristics?

3⁄4 Do female and male casualties from the US military 

in recent conflicts differ in their injury characteristics such as Injury Severity Score (ISS), Abbreviated Injury Score (AIS), injury type (blunt versus 

penetrating), injury cause (mechanism of injury), 

and injury date?

Methods

This retrospective study of existing data was conducted 

under and in accordance with a protocol approved by 

the US Army Institute of Surgical Research Institutional 

Review Board. We performed a retrospective collection 

of casualty data, which was then placed into one of 2 

cohorts, females and males. These cohorts were then 

compared with a variety of characteristics.

We studied male and female service members who 

served and were injured in Operation Iraqi Freedom 

(OIF), Operation Enduring Freedom (OEF) in Afghanistan, or Operation New Dawn (OND) between October 

2003 (the beginning of hostilities in Iraq) and December 2012. The Department of Defense Trauma Registry 

(DoDTR) was queried for all musculoskeletal related 

casualties, defined as any injury related to bone, joint, 

or muscle in the upper extremities, lower extremities, 

or the spine. This search resulted in the identification 

of 425 female and 14,982 male subjects who met the 

criteria. All female and male casualties identified were 

included.

Age, branch of military service, military rank, military 

operation (OIF, OEF, or OND), ISS, body-specific AIS, 

injury type, injury cause, and injury date were collected from the DoDTR on each subject. Each subject was 

also marked as either injured either during battle or in a 

nonbattle related incident. The body-specific AIS scores 

rate the severity of injury to 6 different body regions: (1) 

the head, neck, and cervical spine; (2) the face; (3) the 

chest and thoracic spine; (4) the abdomen and lumbar 

spine; (5) the extremities and bony pelvis; and (6) external injuries to the integument.

Because the casualty data is entered into the DoDTR 

consecutively as information of casualties is received 

and processed, the data pulled from this database provides a consecutive sample of all casualties for the above 

defined time period. Less than 1% of the male subjects 

were missing information on cause of injury (had “other” listed), while this information was complete for all 

female subjects.

Using IBM SPSS Statistics Version 19.0 (IBM Corp, 

Armonk, NY), the female and male cohorts were compared and analyzed for significance in demographics 

(age, service, rank, and military operation) and injury 

characteristics (ISS, AIS, injury type, injury cause, and 

injury date). We used the Shapiro-Wilk test to determine whether the data were randomly distributed. The 

variables were not normally distributed among men, 

so a nonparametric test was required; the Spearman 
72 http://www.cs.amedd.army.mil/amedd_journal.aspx

rank correlation was used. This was used to compare 

age, combined ISS, individual AIS values between the 

groups male and female. Contingency tests (Pearson χ2

and Fisher’s Exact Test) were used to compare proportions of the male and female groups in military branch, 

battle and nonbattle injuries, and explosion versus nonexplosion mechanisms of injury.

The study population is comprised of all active duty, activated reservist, and National Guard service members 

in the US military, with all branches included: Army, 

Marine Corps, Navy, Air Force, and Coast Guard. As in 

the study parameters, there are 425 females and 14,982 

males. They ranged in age from 18 to 60 years and included military ranks from E-1 through O-9.

Results

The collected data revealed that women comprised 

2.75% of the overall casualties. Female casualties were 

on average slightly younger with a mean age of 26.11 

(range 18-55) years, while males have a mean age of 

27.83 (range 18-60) years with a P<.001. Among the 

military branches, the Army as a whole had the greatest 

percentage of both men and women, depicted graphically in Figure 1. However, with a χ2 comparison, it was 

shown that a greater proportion of female casualties 

were from the Army (81.5%) while a greater proportion 

of male casualties were from the Marine Corps (21.2%) 

(P<.001), When comparing casualties in each conflict, 

again a higher percentage of female and male casualties 

were in Operation Iraqi Freedom (females at 75.6% and 

males at 63.2%). A χ2 analysis showed that proportionally more female casualties were in OIF while OEF produced more male casualties (P<.001).

The analysis of the injury characteristics also showed 

several statistical differences. All subjects, both male 

and female, showed higher Injury Severity Scores (ISS), 

with a higher score being related with more severe injury, in battle-related trauma (mean 11.53, range 1-75) 

as compared to nonbattle injury (mean 5.20, range 1-59) 

(P<.01). Women on average showed lower ISS but only 

when comparing the mean of all casualties together 

(P<.01). Mean ISS for females was 7.49 with a range 

from 1 to 50; mean ISS for men was 9.68 with a range 

from 1 to 75. Both sexes averaged higher ISS in battle 

injuries (F=12.01, M=11.52) as compared to nonbattle 

injuries (F=5.28, M=5.19) (P<.001). Females also averaged a lower AIS specific to the skeletal anatomic region 

for all casualties together (F=2.06; M=2.36) (P<.03). In 

comparing battle versus nonbattle-related injury, women were less likely to be injured in battle than the male 

casualties with 33.1% of female and 70.9% of male casualties being recorded as battle-related. As shown in 

Figure 2, women were less likely to be injured due to 

an explosive device; 27.7% of female casualties were 

related to an explosion as compared to 55.2% of male 

casualties. However, the most common cause of battlerelated injury for both sexes was an explosion, and the 

most common cause of nonbattle injury for both sexes 

was a fall. No differences were found between the sexes 

when comparing date of injury.

Comment

This study endeavored to address in quantifiable metrics 

the overarching question: are female casualties different 

from their male counterparts? This does not address female and male Soldiers or other service members pre-injury, but rather questions if their injuries were sustained 

and/or treated differently in any way. Previous information presented on female mortalities in the US military 

indicated that the casualty death rate in women may be 

higher than that of men.13 There are also earlier studies looking specifically at psychiatric illness, some of 

which suggested that women may be more likely to exhibit signs of psychiatric illness during deployment.18-20

However, we were not able to find any studies directly 

addressing questions involving comparisons of cause 

and severity of physical trauma between the sexes.

This study had several limitations. First, we were able to 

identify only basic information about the service members and their injuries with descriptors of general injury 

characteristics such as blunt versus penetrating, but not 

identify specific injury patterns such as type or number 

of fractures. Therefore we do not know what elements 

Army Marine Corps Air Force Navy

Men

Women

73%

82%

3%

8%

3% 4%

21%

6%

80%

90%

70%

60%

50%

30%

20%

10%

0%

40%

Figure 1. Distribution by gender of all casualties examined in 

the study across the military services.

COMPARISON OF FEMALE AND MALE CASUALTY COHORTS

FROM CONFLICTS IN IRAQ AND AFGHANISTAN
April – June 2015 73

THE ARMY MEDICAL DEPARTMENT JOURNAL

contributed to the final ISS assigned each casualty. Second, the significant difference in sample size (by a factor 

of 100) between our 2 cohorts makes a subtype analysis 

of specific causes of injury less reliable. As demonstrated above, a comparison of mean ISS between the sexes 

in battle and nonbattle injuries individually reveals no 

statistical difference between the sexes. However, because of the number of males injured in battle, the mean 

ISS as a whole does show statistical significance. Third, 

the study is not inclusive of all casualties but rather focused on musculoskeletal trauma. Many of the subjects 

in the database had other injuries as well (abdominal, facial, etc), but they were not included in the study if they 

did not have a musculoskeletal diagnosis. This limits the 

generalizability of our data to all casualties.

The percentage of casualties who are female in our study 

was 2.75%, which is consistent with previous papers that 

showed 2.4% of deaths and 1.9% of casualties were female.9,13 One previous study showed the female case fatality rate for OEF to be higher than OIF, but this is not 

directly comparable to our investigation of total casualty 

comparison between the conflicts.

The difference shown in age with females being slightly 

younger may be due to the age range, in that there are 

fewer women past the age of 40 still within the military.9,21 This may also explain the discrepancy in casualty 

percentage between the sexes in the Army versus Marine 

Corps, since the Marine Corps has the lowest percentage of women of any of the US military branches.9,21,22

The fighting tactics used by the military in Iraq and Afghanistan are inherently different due to the nature of the 

battle and the terrain. As a result, it can be hypothesized 

that there were potentially more special forces troops 

in Afghanistan than Iraq. This could contribute to the 

difference seen in casualty rates between OIF and OEF 

since women were not allowed to be assigned to direct 

combat roles during the entire studied timeframe, including special forces and other specialized ground troops.

Regarding injury characteristics, there is no related previous study to which we can compare our results. The 

previous work on female mortalities showed high ISS 

scores for those who died (mean of 24.5), but there was 

no male cohort comparison in that study.13 Cross et al 

did show that 39.5% of female casualties were injured in 

battle, which is consistent with the 33.1% of female injuries incurred in battle in our study.13 When looking at the 

mean ISS between the sexes, there is a statistical difference with males showing higher ISS on a whole. However, when this is broken down into battle and nonbattle 

groups, there is no statistical difference in the mean 

between men and women. What appears to be more 

Figure 2. Distribution of the most common causes of injury 

to male and female servicemembers respectively. GSW 

indicates gunshot wound; MVC, motor vehicle collision.

28%

21%

12%

10%

8%

2%

3%

4%

4%

4%

4%

Women

Men

55%

17%

7%

2%

3%

4%

5%

1%

2%

Crush

Blunt Object

Bullet/GSW

Knife

Explosive

Fall

Other

Machinery

MVC

Unknown

Sports
74 http://www.cs.amedd.army.mil/amedd_journal.aspx

important is that both sexes show significantly higher 

mean ISS when they sustain battle related injury compared to nonbattle injury. The difference demonstrated 

comparing all females to all males is due to a higher 

percentage of males injured in battle related incidents.

Further research to investigate any differences is still 

needed. The same pool of data is being used to agematch males and females for a cohort study where more 

specific injury patterns can be compared between the 

sexes.

Conclusions

The statistical analysis comparing female to male US 

military casualties from the recent conflicts in Iraq and 

Afghanistan showed differences between the sexes in relation to both demographics (age and service) and injury 

characteristics (ISS, AIS, and MOI). Females comprised 

2.75% of the DoDTR casualties during the studied timeframe and were less likely to be involved in explosions 

or during battle. Thus, this population has received little 

attention in the literature to date. Despite lower rates of 

battle-related and explosion-type injuries, female casualties sustained similar ISSs when broken down into battle and nonbattle means. The main difference found in 

ISS is not in comparing the sexes but comparing battle 

and nonbattle injuries. When our data is paired with previous evidence that the case fatality rate may be higher 

for females, it is apparent that additional investigation 

is required to further study the effect of battle and nonbattle injuries among our female casualty population.

References

1. Belmont PJ, Goodman GP, Zacchilli M, Posner M, 

Evans C, Owens BD. Incidence and epidemiology 

of combat injuries sustained during “the surge” portion of Operation Iraqi Freedom by a US Army brigade combat team. J Trauma. 2010;68(1):204-210.

2. Holcomb J, Caruso J, McMullin N, Wade CE, 

Pearse L, Oetien-Gerdes L, Champion HR, 

Lawnick M, Farr W, Rodriguez S, Butler F. Causes 

of death in US Special Operations Forces in the 

global war on terrorism: 2001-2004. US Army Med 

Dep J. January-March 2007:24-37.

3. Holcomb JB, Stansbury LG, Champion HR, Wade 

C, Bellamy RF. Understanding combat casualty 

care statistics. J Trauma. 2006;60:397-401.

4. OwensB, Kragh J, Macaitis J, Svoboda S,Wenke 

J.Characterization of extremity wounds in Operation Iraqi Freedom and Operation Enduring Freedom. J Orthop Trauma. 2007;21:254-257.

5. Ramasamy A, Harrisson SE, Clasper JC, Stewart 

MP. Injuries from roadside improvised explosive 

devices. J Trauma. 2008;65:910-914.

6. Kragh JF Jr. Use of tourniquets and their effects on 

limb function in the modern combat environment. 

Foot Ankle Clin. 2010;15:23-40.

7. Stansbury L, Lalliss S, Branstetter J, Bagg M, Holcomb J. Amputations in US military personnel in 

the current conflicts in Afghanistan and Iraq. J Orthop Trauma. 2008;22:43-46.

8. Maynard C. The association of state per capita income and military service deaths in the Vietnam 

and Iraq wars. Popul Health Metr. 2009;7:1. Available at: http://www.pophealthmetrics.com/con

tent/7/1/1. Accessed March 17, 2015.

9. Zouris JM, Wade AL, Magno CP. Injury and illness casualty distributions among U.S. Army and 

Marine Corps personnel during Operation Iraqi 

Freedom. Mil Med. 2008;173(3):247-252.

10. Haider AH, Crompton JG, Oyetunji T, et al. Females have fewer complications and lower mortality following trauma than similarly injured males: 

a risk adjusted analysis of adults in the National 

Trauma Data Bank. Surgery. 2003;146:308-315.

11. Frink M, Pape HC, van Griensven M, Krettek C, 

Chaudry IH, Hildebrand F. Influence of sex and 

age on MODS and cytokines after multiple injuries. 

Shock. 2007;27:151-156.

12. George RL, McGwin G, Windham ST, Melton SM, 

Metzger J, Chaudry IH, Rue LW. Age-related gender differential in outcome after blunt or penetrating trauma. Shock. 2003;19:28-32.

13. Cross JD, Johnson AE, Wenke JC, Bosse MJ, Ficke 

JR. Mortality in female war veterans of operations 

enduring freedom and Iraqi freedom. Clin Orthop 

Relat Res. 2011;469(7):1956-1961.

14. Feldinger LG. Skirting history. The Jerusalem Post. 

September 18, 2008. Available at: http://www.jpost.

com/Magazine/Features/Skirting-history. Accessed September 12, 2014.

15. Lopez TC. Army to open 33,000 positions to female Soldiers in April. Army News Service [online]. 

January 27, 2014. Available at: http://www.army.

mil/article/118930/Army_to_open_33_000_posi

tions_to_female_Soldiers_in_April/. Accessed 

September 12, 2014.

16. Women in the military. Norfolk Daily News [online]. June 18, 2013. Available at: http://norfolk

dailynews.com/interactive/onlineextras/womenin-the-military/article_a21c355a-d822-11e2-87e3-

001a4bcf6878.html. Accessed September 12, 2014.

17. Fischel J. Military leaders lift ban on women in 

combat roles. FoxNews.com [online]. January 24, 

2013. Available at: http://www.foxnews.com/poli

tics/2013/01/24/panetta-opens-combat-roles-towomen/. Accessed September 12, 2014.

COMPARISON OF FEMALE AND MALE CASUALTY COHORTS

FROM CONFLICTS IN IRAQ AND AFGHANISTAN
April – June 2015 75

THE ARMY MEDICAL DEPARTMENT JOURNAL

18. Bond EF. Women’s physical and mental health sequellae of wartime service. Nurs Clin North Am. 

2004;39(1):53-68.

19. Goodman GP, DeZee KJ, Burks R, Waterman BR, 

Belmont PJ Jr. Epidemiology of psychiatric disorders sustained by a U.S. Army brigade combat 

team during the Iraq War. Gen Hosp Psychiatry. 

2011;33(1):51-57.

20. Street AE, Vogt D, Dutra L. A new generation of 

women veterans: stressors faced by women deployed to Iraq and Afghanistan. Clin Psych Rev. 

2009;29:685-694.

21. Abramson L. West Point women: a natural pattern 

or a camouflage ceiling?. National Public Radio

[online]. October 22, 2013. Available at: http://

www.npr.org/2013/10/22/239260015/west-pointwomen-a-natural-pattern-or-a-camouflage-ceiling. 

Accessed September 12, 2014.

22. Ogilvie P. Sisters in arms: breaking down barriers and rising to the challenge. Army.mil [online]. 

September 3, 2013. Available at: http://www.army.

mil/article/110447/Sisters_in_Arms__Breaking_

down_barriers_and_rising_to_the_challenge/. Accessed September 12, 2014.

Authors

CPT Hylden is with the Department of Orthopaedics and 

Rehabilitation, Brooke Army Medical Center, San Antonio, Texas.

LTC (P) Johnson is Chairman, Department of Orthopaedics and Rehabilitation, Brooke Army Medical Center, 

San Antonio, Texas.

MAJ Rivera is with the US Army Institute of Surgical 

Research, San Antonio Military Medical Center, Texas.
76 http://www.cs.amedd.army.mil/amedd_journal.aspx

The number of women in the military has steadily increased since the Selective Service draft ended in 1973 

and now comprises 15% of the active duty military 

population and 10% of the deployed population.1 Congress mandated that, starting in January 2016, military 

women would be afforded the same opportunities for 

combat assignments as men. As a result, women could 

be serving in the most austere conditions. Women will 

compete with men for these once restricted combat assignments under the same physical and performance 

standards. In order to ensure the health and well-being 

of women as they progress in military roles and/or optimize their health in their current military roles, military health care professionals and leaders should consult 

current evidence-based knowledge on women’s health 

issues and care. The research that is currently available 

is typically published in peer reviewed journals, yet is 

not readily accessible to military care providers and decision makers. The Military Women’s Health Research 

Interest Group (MWHRIG) was founded to address the 

lack of a consolidated review.

In 2008, four officers (2 Army Nurse Corps, one Navy 

Nurse Corps, and one Air Force Nurse Corps) identified 

the need to compile all peer reviewed research publications on military women’s health issues and care in the 

past decade to promote awareness in the professional 

military community. The initial goal of the MWHRIG 

was to identify and grade existing research and build a 

database with the results that could be searchable and 

accessible to military clinicians and leaders charged 

with making evidence-based decisions. To advance the 

science of military women’s health, the next steps were 

to perform a systematic review of the published literature, examine utilization of the Military Healthcare System (MHS), and identify the gaps in knowledge. Finally, 

they strove to create a military women’s health research 

agenda that would guide future research. Not only is it 

paramount that research be available, but it must also 

be highly relevant to guide decision-making as the Department of Defense (DoD) embarks on this significant 

demographic shift and force multiplier.

Establishing the Purpose of the MWHRIG

The MWHRIG founders first established the need for 

the systematic review and gap analysis efforts with a 

strong position paper. The MWHRIG foundational paper was entitled, “A Call to Action for Evidence-Based 

Military Women’s Health Care: Developing a Women’s 

Health Research Agenda that Addresses Sex and Gender 

in Health and Illness.”2 The article highlighted female 

gender-specific deployment and in-garrison health care 

disparities based on the Armed Forces Health Surveillance Center’s Medical Surveillance Monthly Reports 

from 2007-2009. These reports identified health effects 

related to deployment to Operation Iraqi Freedom and 

Operation Enduring Freedom, as well as utilization 

trends by female service members within the MHS. 

The article emphasized the dearth of scientific-based 

information relevant to military women’s occupational 

risks, training requirements, and gender-specific health 

promotion programs. It was concluded that this absence 

Creating and Sustaining a Military

 Women’s Health Research Interest Group

Lt Col Candy Wilson, NC, USAF LTC (Ret) Nancy Steele, AN, USA

COL Lori Trego, AN, USA Megan Foradori, MSN, RN

CAPT Jacqueline Rychnovsky, NC, USN

Abstract

In 2008, four doctorate military nurse scientists representing the triservices (Army, Navy, and Air Force) identified 

a common interest in the health and care of all women in the armed forces. For 7 years, the team’s shared vision 

to improve servicewomen’s health inspired them to commit to a rigorous schedule of planning, developing, and 

implementing an innovative program that has the capability of advancing scientific knowledge and influencing 

health policy and practice through research. The ultimate goal of the Military Women’s Health Research Interest 

Group (MWHRIG) is to support military clinicians and leaders in making evidence-based practice and policy 

decisions. They developed a 4-pronged approach to cultivate the science of military women’s healthcare: evaluate 

the existing evidence, develop a research agenda that addresses gaps in knowledge, facilitate the collaboration of 

multidisciplinary research, and build the bench of future researchers. The MWHRIG has been a resource to key 

leaders; its value has been validated by multiservice and multidisciplinary consultations. However, the journey to 

goal attainment has only been achieved by the enduring commitment of these MWHRIG leaders and their passion to 

ensure the health and wellbeing of the many women who serve in the United States military. This article describes 

their journey of dedication.
April – June 2015 77

of information could contribute to the lack of essential preventive medicine and interventions to improve 

the health, safety, and performance of military women. 

The authors postulated that there may be a requirement for changes in policies that reflect gender specific 

health care needs of women, particularly as they move 

into expanded military roles. The article described the 

need for a concerted effort to synthesize the literature 

on women’s health care needs and thus designated the 

genesis of the MWHRIG. The role of the MWHRIG in 

conducting a comprehensive identification of gaps in 

knowledge about military women’s health issues and 

the subsequent development of research priorities were 

described. The ultimate goal was to identify gaps in the 

literature to inform future research and policy changes.

While the primary objectives of the MWHRIG were 

to systematically conduct an extensive literature review and evaluate published articles related to military 

women’s health, they also endeavored to create an online searchable database of the reviewed literature. A 

centralized online repository will be vital in supporting 

military women’s health needs through evidence-based 

practice and policies. This database will assist scientists 

with research proposal development and funding efforts 

by providing a search for the state of the science on any 

given women’s health topic relevant to service women.

Building the Team

Realizing that implementing a systematic review of a decade’s worth of literature that is relevant to the health of 

women in all of the military services would require support, the MWHRIG reached out to the Veterans Administration (VA) Greater Los Angeles Health Services Research and Development (HSR&D) Center of Excellence 

Agenda Planning Group for guidance in the systematic 

review process. In 2006, the VA Greater Los Angeles 

HSR&D Center of Excellence had conducted a systematic review and developed an online database for veteran 

women’s health research that the MWHRIG felt was appropriate to replicate. Since the MWHRIG envisioned 

an analysis with goals comparable to the VA Women’s 

Health Research Agenda,

3

 they contacted the VA’s 

Agenda Planning Group for guidance in the systematic 

review process. Besides the expertise in the review process, the MWHRIG hoped to foster collaboration with 

the VA HSR&D that would enhance the possibility for 

combined efforts in the future. With the initial guidance 

from the VA women’s health research agenda leaders, 

the MWHRIG adopted a similar 4-step approach to conducting the review of the literature and gap analysis.

In addition to developing a research agenda, the MWHRIG initiated simultaneous efforts to create a community 

of scientists dedicated to advancing military women’s 

health through research. They enacted 2 avenues of 

approach to cultivate the science of military women’s 

healthcare: facilitate the collaboration of multidisciplinary research, and build the bench of future scientists. 

With the original four military nurse scientists identified 

as MWHRIG Core Leaders, the MWHRIG built a team 

by recruiting the most experienced research scientists in 

the United States who conducted and published research 

studies about U.S. military women’s health. With volunteer members from every military service, as well as the 

VA, and academia, the MWHRIG developed a base of 

64 Subject Matter Experts (SMEs) whom they could employ in the conduct of the systematic review of literature.

Supporting Agencies

In the fall of 2008, the MWHRIG Core Leaders met 

with representatives from the Triservice Nursing Research Program (TSNRP),* a component of the Office 

of Research at the Uniformed Services University of the 

Health Sciences in Bethesda, Maryland, to discuss the 

group’s purpose and planned goal attainment. The goals 

of the MWHRIG meshed seamlessly with the mission 

and strategic goals of the TSNRP, which are to facilitate 

nursing research, optimize the health of military members, expand the cadre of military researchers, build an 

infrastructure to support nursing research, and foster 

collaborative research. It was at this meeting that the 

MWHRIG’s vision for cataloging and grading research 

to identify gaps in military women’s health and facilitate future research became a possibility. In order to 

substantiate their efforts, the MWHRIG created a charter and developed a timeline for achieving milestones. 

A year later, TSNRP agreed to sponsor the group in its 

ambitious endeavor and the TSNRP Resource Center 

Program Manager joined the team. The TSNRP Resource Center assisted the MWHRIG by lending infrastructure to support and sustain the efforts of the MWHRIG, technology to support strategic communication of 

research interest group members, and the coordination 

for the development of partnerships with academic and 

other research institutions.

As the core leaders initiated the first phase of the systematic review—gather and catalog all peer reviewed 

literature on military women’s health research from 

2000-2010—they requested assistance from several 

talented Army, Navy and Air Force medical librarians. 

Given the volume and workload this generated, TSNRP 

recognized the group’s need for the technical support of 

a research group program coordinator. As a result, TSNRP utilized the Henry M. Jackson Foundation to hire a 

*http://www.usuhs.mil/tsnrp/AboutTSNRP/WhoWeAre/

mission.php
78 http://www.cs.amedd.army.mil/amedd_journal.aspx

master’s prepared civilian nurse with extensive research 

experience as the program coordinator. In addition to 

the program coordinator provision, TSNRP financially 

supported the MWHRIG core leaders to attend research 

courses and conferences, telecommunications, interactive video conference lines for frequent virtual meetings, licenses for technical tools for work flow support, 

and logistical costs for dissemination of key MWHRIG 

products.

The team reached out to their partners for guidance on 

the database development. The Research Programming 

Department at RAND Corporation had assisted the VA 

Women’s Health Research Agenda Planning Group with 

their data collection for the systematic review. According to a senior research programmer analyst at RAND 

(E. Roth, oral communication, November 2, 2010), they 

used web-based systematic review program designed 

specifically for the screening and data extraction phases 

of a systematic review when collecting their VA women’s health research article reviews. The MWHRIG program coordinator developed a comprehensive cost-benefit analysis for TSNRP and the MWHRIG proposed 

acquisition of the program. This critical component of 

the systematic review process was funded by TSNRP. 

The online data management tool allowed the core leaders and SMEs to access the uploaded full text article 

and input their review and grade determination. Instead 

of cataloging individually scanned review documents, 

which presented a data management nightmare for the 

program coordinator, the on-line system served as a real-time repository to input the systematic reviews. The 

on-line system allowed the team to export the evaluations to set the foundation for a searchable database.

Creating a searchable database for military researchers 

and leaders to query specific topics required information technology (IT) experts. With an introduction and 

coordination through the TSNRP Resource Center, the 

Uniformed Services University of the Health Sciences 

(USUHS) IT department provided the needed technical 

support to develop the website repository. Permission to 

use the coding behind the VA’s systematic review database was granted (P. Shekelle, oral communication, June 

7, 2013). Meeting with the research interest group program coordinator, the USUHS IT developers created an 

interface adapted from the VA’s online interface coding. 

The Military Women’s Health Research Literature database was created from work group systematic review 

data collection spreadsheets and served as the backbone 

for importing the data from the systematic review software. This program was created so that the MWHRIG 

database would mirror the VA Women’s Health literature database making future collaboration possible.

Accomplishments of the MWHRIG

The Systematic Review

With the development of multiple synergistic relationships, the MWHRIG was able to accomplish 16 milestones as shown in the Figure. The most prominent 

product is the systematic review. A 3-level screening 

process was used to evaluate a decade’s worth of scientific literature on military women’s health issues. Article searches were completed using predetermined title 

search criteria for Level 1, abstract approval criteria for 

Level 2, and grading and analysis criteria for Level 3. 

Articles advanced to Level 3 review if all four of the 

core leaders agreed the article fit the project inclusion 

criteria based on the predetermined criteria used for the 

Level 2 screening. The MWHRIG garnered the support 

of the SMEs from the military, academic, and civilian 

research communities to grade the level of evidence and 

quality of the research studies. Both a core leader and 

a SME reviewed and graded each article. Finally, the 

same core leader established congruency between the 

2 reviews and research quality grades. Once completed, 

these data were ready for upload into the searchable database, ultimately depicted as an article summary with a 

complete citation on the website. Following the completion of the database, the MWHRIG was able to draw the 

evidence tables from the systematic review program and 

produce the systematic review summary.

Encouraging Collaboration in Military Women’s Health

In order to boost collaboration, the MWHRIG engaged 

in a multimedia approach to develop a community of research scientists with a common desire to improve military women’s health and healthcare. First, the MWHRIG 

created a handbook, Military Women’s Health Researchers Guide, now in its 6th version, which lists all of the 

MWHRIG members and SMEs, including their abbreviated curriculum vitae and publications as relevant to 

military women’s health research. The guide serves to 

connect multidisciplinary research scientists with similar interests or subject matter expertise in collaborative 

efforts to develop and conduct research. The TSNRP 

Resource Center funded production of hard copies of 

the guide, as well as various marketing products, such 

as business and information cards for dissemination 

at conferences and scientific meetings. Second, in order to promote the connections among those interested 

in advancing evidence-based women’s health care, the 

MWHRIG then created a Facebook page* where current 

events, publications, and news about military women’s 

health are posted. The Facebook page fosters connections among both seasoned and aspiring researchers, 

links appropriate SMEs for areas of research interest, 

*https://www.facebook.com/pages/Military-Womens-HealthResearch-Interest-Group/117532448302481

CREATING AND SUSTAINING A MILITARY WOMEN’S

HEALTH RESEARCH INTEREST GROUP
April – June 2015 79

THE ARMY MEDICAL DEPARTMENT JOURNAL

and provides the contact information to requesting an 

electronic version of the guide. Finally, in support of the 

MWHRIG, TSNRP developed a webpage for research 

interests groups, and, based on the success of the MWHRIG, inaugurated 3 more research interest group webpages (behavioral health, en route care, and anesthesia).

With support from the TSNRP through the Henry M. 

Jackson Foundation, MWHRIG members have presented or participated in various research, development, and 

collaborative forums, such as the VA Women’s Health 

Services Research Conference, the Department of Defense Panel at the National Training Summit on Women 

Veterans, the Women in the Military Service for America, the Association of Military Surgeons of the United 

States Annual Meetings, the first Women in Combat 

Symposium, and multiple national women’s health conferences. The MWHRIG has contributed valuable evidence on military women’s health issues to guide the 

initiatives of the US Army Office of The Surgeon General’s Women’s Health Task Force and the Office of the 

Assistant Secretary of Defense for Health Affairs Women’s Health Issues Working Group. The MWHRIG has 

been a resource to key proponents for the advancement 

of military women’s health. It has been consulted by the 

US Government Accountability Office4,5 on 2 reports 

on the health of servicewomen and by the Defense Department Advisory Committee on Women in the Services for their 2012 report6

 and recommendations on the 

health of deployed servicewomen.

Strength Through the Team Characteristics

In addition to the research experience of this team, over 

time we determined a key strength of the MWHRIG 

leadership is their firsthand experiences while serving 

on active duty. They are personally familiar with the 

triumphs and struggles military women face throughout the course of a military career which included many 

psychosocial adaptations to multiple duty station relocations, personal illnesses, illnesses of family members, 

births, deaths, loss of friendships and support systems, 

promotions with added responsibilities, the threat of 

war, adaptation to field assignments, geographical separations from family, and the eventual transition into the 

VA system upon retirement. The 4 nurse scientists are 

also licensed independent providers, one midwife and 

3 nurse practitioners. The fact that these researchers are 

also clinicians helps them critique the science and its 

Timeline of Progress for the Military Women’s Health Research Interest Group

Publish the MWH

Research Agenda

Foster Collaborative

Efforts in New Research 

that Address the MWH 

Research Agenda

Conduct Research that 

Addresses the MWH 

Research Agenda

FUTURE

Beta Test Website 

Repository

Completed 511 Level 

2 Screeners

Completed 320 Level 

3 Reviews

Obtained Utilization 

Data

Conducted Gap 

Analysis

Drafted Systematic 

Review

2014

Initiated Web-based 

Review Software

Conducted Article 

Level 2 Screeners

Began Level 3

Grading of the 

Literature

Designed Online

Research 

Repository

2013

Gathered Literature

Conducted Level 1 

Article Screening of 

1411 Titles

Used Subject Matter 

Experts in Review of 

Literature

Designed Online

Communities 

(Facebook & TSNRP 

Website)

2011

Conducted Article 

Level 2 Screeners

Reviewed Exisiting 

Utilization Data

Planned Gap Analysis

Developed a

Dissemination Plan 

for Products

Began Mentorship 

of New MWH 

Researchers

2012

Developed a Charter

Identified Core 

Leaders

Began Visionary 

Manuscript

2009

Published Manuscript

Recruited Project 

Manager

Collaborated With 

VA Health Services 

Research and

Development

Recruited Subject 

Matter Experts

Published First MWH 

Researcher Guide

2010
80 http://www.cs.amedd.army.mil/amedd_journal.aspx

potential contribution to women’s healthcare. Over the 

course of five years, the four core leaders experienced a 

total of 12 permanent changes of station (PCS) moves of 

which five were outside of the continental United States 

(OCONUS), 5 in-theater deployments to austere settings, and numerous temporary duty assignments. The 

multiple international assignments of group members 

led to scheduling challenges due to multiple time zones 

with up to a 14-hour time difference. Many meetings 

were conducted after or before the duty day in order 

to accommodate all members. Our TSNRP sponsored 

program coordinator was critical in the success of the 

project. She kept scheduled weekly conference lines, 

created meeting agendas, provided review updates, and 

emailed reminders to complete pending tasks.

Future of the MWHRIG

As of the time of this publication, goals for the immediate future are anticipated to be complete, including the 

completion and publication of the systematic review of 

the military women’s health research from 2000 through 

2010, as well as the debut of the online database. A followup review of literature published from 2011 through 2014 

is already under way. Long term goals include obtaining support for the maintenance of the article repository 

and allocating responsibility as an enduring requirement 

to ensure that the evidence base on military women’s 

health issues continues to be expanded. Marketing strategies are required for the multidisciplinary and triservice use of these valuable resources, as well as continued 

literature input and subject matter expertise. We hope 

the Facebook community will continue to grow strong 

and be the meeting place for innovative research as inspired by the military women’s health research agenda.

Summary

The creation and sustainment of this team has been made 

possible by the vision and drive of 4 military nurse scientists who felt passionately about the advancement of 

women’s health for the support of the inclusion of women 

in combat roles. The products this team has generated 

and continue to develop will be a sound resource to inform lawmakers and military leaders about the research 

gaps that must be identified and explored to fully support women as they forge new paths within the DoD. The 

MWHRIG will continue to be valuable resource to the 

triservice research community and military leaders.

Acknowledgement

The authors thank the TriService Nursing Research Program for its support of the Military Women’s Health Research Interest Group. This work would not have been 

possible without the financial and administrative support 

provided by the Program.

References

1. Women’s Research and Education Institute. Women in the Military: Where They Stand. 8th ed. 

2013. Available at: http://www.wrei.org/WIM_

Book_2013.html. Accessed November 24, 2014.

2. Trego L, Wilson C, Steele N. A call to action for 

evidence-based military women’s health care: developing a women’s health research agenda that addresses sex and gender in health and illness. Biol 

Res Nurs. 2010;12:171-177.

3. Yano EM, Bastian LA, Frayne SM, et al. Toward 

a VA women’s health research agenda: setting evidence-based priorities to improve the health and 

health care of women veterans. J Gen Intern Med. 

2006;21:S93-S101.

4. US Government Accountability Office. Military 

Personnel: DOD Has Taken Steps to Meet the 

Health Needs of Deployed Servicewomen, but Actions Are Needed to Enhance Care for Sexual Assault Victims. Washington, DC: US Government 

Accountability Office; January 29, 2013. Report 

GAO-13-182. Available at: http://www.gao.gov/as

sets/660/651624.pdf. Accessed March 23, 2015.

5. US Government Accountability Office. DOD 

Health Care: Domestic Health Care for Female 

Service Members. Washington, DC: US Government Accountability Office; January 29, 2013. Report GAO-13-205. Available at: http://www.gao.

gov/assets/660/651620.pdf. Accessed March 23, 

2015.

6. Defense Department Advisory Committee on 

Women in the Services. 2012 Report. Washington, 

DC: US Dept of Defense; 2012. Available at: http://

dacowits.defense.gov/ReportsMeetings.aspx. Accessed November 24, 2014.

Authors

Lt Col Wilson is with the USAF Acupuncture Center, 

Joint Base Andrews, Maryland.

COL Trego is with the Center for Nursing Science and 

Clinical Inquiry, Brooke Army Medical Center, San Antonio Military Medical Center, Texas.

CAPT Rychnovsky is with the Naval Health Research 

Center, San Diego, California.

LTC (Ret) Steele is an Associate Professor, Brooks College of Health School of Nursing, University of North 

Florida, Jacksonville, Florida.

Ms Foradori is the Research Interest Group Coordinator 

for the Triservice Nursing Research Program, The Henry 

M. Jackson Foundation for the Advancement of Military 

Medicine, Pittsburgh, Pennsylvania.

CREATING AND SUSTAINING A MILITARY WOMEN’S

HEALTH RESEARCH INTEREST GROUP
April – June 2015 81

History

A man 19 years of age with a history of complex dextrotransposition of the great arteries (d-TGA) repaired during infancy presented with intermittent palpitations at 

rest. He denied orthopnea, edema, paroxysmal nocturnal dyspnea, and exertional chest pain.

His cardiac history is significant for d-TGA with a ventricular septal defect (VSD) and sub-valvular and valvular pulmonary stenosis palliated with a balloon septostomy on day of life zero and right modified BlalockTaussig shunt at 10 days of age followed by a completion Rastelli repair at 10 months of age with VSD patch 

and placement of a right ventricle to pulmonary artery 

conduit. His postoperative course was complicated by 

left ventricular outflow tract obstruction secondary to 

restriction at the VSD and intermittent high-grade AV 

block, for which he had a pacemaker implanted. The 

pacemaker was subsequently removed at 4 years of 

age after resumption of normal sinus rhythm, however, he has retained epicardial leads. He has subsequently required multiple revisions of the pulmonary 

outflow shunt and pulmonary arteries, the last of which 

was performed at 14 years of age. Otherwise, he had 

been stable without symptoms for the past 5 years. His 

physical exam was significant for a grade III/VI harsh, 

crescendo-decrescendo systolic murmur at the left and 

right upper sternal borders and a widely split S2 with 

a prominent P2 component. Jugular venous distention, 

edema, heaves, and extra heart sounds were all absent. 

Electrocardiogram showed normal sinus rhythm with a 

right bundle branch block.

Echocardiography and cardiac computed tomography 

angiography were ordered to evaluate patency of his 

cardiovascular structures, given his history of congenital heart disease, prior pulmonary artery stenosis requiring arterioplasty, retained epicardial lead, and the symptoms described.

Imaging Findings

Figure 1 presents the volume rendered cardiac CT angiography image oriented in the left anterior oblique, cranial projection demonstrating the Rastelli conduit (open 

arrow) arising from the right ventricular (RV) free wall 

and anastomosing at the main pulmonary artery (not 

visualized). The left anterior descending (LAD) coronary artery (solid arrow) arises from the aorta (Ao) and 

courses in the anterior interventricular groove between 

the RV and left ventricle (LV). The lack of a branch vessel from the Ao origin coursing in the atrioventricular 

groove suggests an anomalous course of the left circumflex coronary artery. Figure 2 is a multiplanar reformat 

which demonstrates a repaired ventricular septal defect 

(arrow). The course of the Rastelli graft (1) immediately 

deep to the sternum is appreciated and the anastomosis 

with the main pulmonary artery is well visualized. The 

atrophic right pulmonary artery (*) is also seen coursing superior to the aortic root. Additionally, a mildly obstructive left ventricular outflow tract (LVOT) is shown 

(2) with good appreciation of the misalignment of the 

aorta with respect to the LVOT. Figure 3 is an axial image which shows the bifurcation of the main pulmonary 

artery (1). The size disparity between the normal left 

pulmonary artery (2), measuring 17 mm, and the atrophied right pulmonary artery (*), measuring 9 mm, is 

better appreciated. The left-sided aortic course (3) is appreciated, which is secondary to the leftward origin of 

the ascending aorta compared with normal anatomy.

Figures 4 and 5 depict apical 3- and 5-chamber views 

showing turbulence across the LVOT beginning below 

the aortic valve (in the baffle between VSD and aorta). 

Figure 6 is a high-parasternal-short-axis view showing turbulence in the RV-PA conduit. Conduits such as 

these are often difficult to visualize by echocardiography due to anatomical position, body habitus, or surgical 

scarring.

Complex d-TGA Status Post Rastelli Repair

 Presenting with Palpitations: Cardiac CTA

 Imaging Findings and Discussion of

 Long-Term Outcomes

Capt Ross Pinson, MC, USAF

MAJ Dustin Thomas, MC, USA

Maj S. Jared Bentley, MC, USAF
82 http://www.cs.amedd.army.mil/amedd_journal.aspx

Comment

Transposition of the great arteries (TGA) is an uncommon congenital heart disease with a reported incidence 

of 2.3/10,000 births.1 D-transposition (d-TGA) is a cyanotic lesion characterized by inappropriate ventriculoarterial connections leading to parallel pulmonary and 

systemic circulations that is best surgically corrected 

very early in life.

Patients with d-TGA are dependent upon intracardiac 

blood mixing for survival, usually through an atrial 

septal defect, VSD, or patent ductus arteriosus.2 Early, 

frequently severe, cyanosis is a common presenting sign, 

however, if there is adequate mixing, visible cyanosis 

maybe under recognized and the patient may present 

with signs of heart failure due to pulmonary over circulation within a few weeks of life.

Palliative procedures are often initially performed, including the Rashkind catheter-directed balloon septostomy and the modified Blalock-Taussig shunt (if there is 

inadequate pulmonary blood flow in the setting of pulmonary outflow tract obstruction). The Rashkind procedure attempts to increase intracardiac blood mixing 

through balloon dilation of an atrial septal defect.3 The 

modified Blalock-Taussig shunt is a systemic-to-pulmonary artery shunt that uses a PTFE interposition graft 

between the innominate artery and the right branch pulmonary artery (with left aortic arch) to palliate until definitive correction can be achieved.4

Atrial switch operations, the Senning and Mustard procedures, were developed around 1960 and became the 

standard operative correction. These procedures created 

an intracardiac baffle to direct deoxygenated blood from 

the right atrium to the left ventricle for oxygenation via 

the pulmonary circulation. Then oxygenated pulmonary 

venous return is directed through the tricuspid valve for 

distribution via the right ventricle to the systemic circulation. Several long-term complications were seen with 

these operations, including sinus node dysfunction, arrhythmias, tricuspid regurgitation, and right ventricular 

COMPLEX D-TGA STATUS POST RASTELLI REPAIR PRESENTING WITH PALPITATIONS:

CARDIAC CTA IMAGING FINDINGS AND DISCUSSION OF LONG TERM OUTCOMES

Figure 2. Multiplanar reformat demonstrating a repaired ventricular septal defect (arrow), the Rastelli graft (1) immediately 

deep to the sternum, and the anastomosis with the main pulmonary artery is well visualized. The atrophic right pulmonary 

artery (*) is also seen coursing superior to the aortic root 

and a mildly obstructive left ventricular outflow tract (LVOT) 

is shown (2) with evidence of aortic root misalignment with 

respect to the LVOT.

Figure 1. Volume rendered image oriented in the left anterior 

oblique, cranial projection demonstrating the Rastelli conduit 

(open arrow) arising from the right ventricular (RV) free wall 

and anastomosing at the main pulmonary artery (not visualized). The left anterior descending coronary artery (solid arrow) arises from the aorta (Ao) and courses in the anterior 

interventricular groove between the RV and left ventricle (LV).
April – June 2015 83

THE ARMY MEDICAL DEPARTMENT JOURNAL

failure.5 An arterial switch procedure, developed by Jatene in 1975, offered a more definitive method of correction by transection and translocation of the great vessels, 

translocation of the coronary arteries, and establishment 

of “normal” ventriculoarterial connections.6

About 13% of d-TGA is complicated by the presence of 

pulmonary outflow tract obstruction. The Rastelli operation was developed in patients with complex d-TGA 

and concomitant pulmonic outflow tract obstruction and 

a large VSD. This procedure allows the left ventricle to 

develop as the systemic ventricle, patches the VSD to 

direct blood flow from LV through the aorta, closes the 

congenitally stenotic pulmonic valve, and uses a grafted 

conduit between the right ventricle and pulmonary artery to direct blood to the lungs for oxygenation.7

Regardless of the type of surgical correction, all patients 

should have annual clinical evaluation.5 Postoperative 

imaging evaluation of complex d-TGA cases involves 

assessment of the pulmonic and systemic outflow tracts, 

branch pulmonary arteries, conduit (if present) and coronary arteries (if they were involved in the procedure).8,9

Imaging by echocardiogram can be obtained as needed 

for anatomic and hemodynamic assessment.5 Echocardiography can have limitations such as poor windows 

due to obesity or scarring and lack of definition of 

Figure 4. Apical 3- and 5-chamber views showing turbulence across the LVOT beginning below the aortic valve (in the baffle between 

VSD and aorta).

Figure 3. Axial image showing the bifurcation of the main pulmonary artery (1). The size disparity between the normal left 

pulmonary artery (2), measuring 17 mm, and the atrophied 

right pulmonary artery (*), measuring 9 mm, is better appreciated. The left-sided aortic course (3) is appreciated, which is 

secondary to the leftward origin of the ascending aorta compared with normal anatomy.
84 http://www.cs.amedd.army.mil/amedd_journal.aspx

thoracic great vessels. Although cardiac magnetic resonance imaging (MRI) improves upon these limitations, 

it may be contraindicated in patients with pacemakers 

or significant amounts of retained metal. Patients who 

need further imaging in addition to echocardiography, 

and have contraindications to MRI can be evaluated using cardiac computed tomography angiography.8,9

Given the rarity of these complex lesions and the relatively recent development of new procedures and their 

variations such as the Nahkaido and Réparation à l’Etage 

Ventriculaire procedures, data on long-term outcomes of 

Rastelli repair for complex d-TGA is still being compiled. Studies suggest that earlier corrective surgery is 

associated with reduced morbidity and mortality.10 According to Brown et al who followed 40 patients with 

complex d-TGA corrected with the Rastelli operation 

from 1988 to 2008, freedom from death or cardiac 

transplant was 90% at 20 years postoperation.11 Horer 

et al published data on 39 patients with complex d-TGA 

treated with Rastelli operation from 1977-2004. Their 

data showed freedom from death or transplantation at 

20 years was 57.5%±15.1%.12 Between 41% and 78% of 

patients with Rastelli repair will require reoperation for 

conduit replacement with stenosis and right ventricular 

outflow tract obstruction being the most common justification for replacement.11,12 A permanent pacemaker 

was implanted for complete AV block or sick sinus syndrome in 14% to 25% of patients by 20 years postoperation.11,12 Right bundle branch block at 20 years was seen 

in 64% to 77.5% of patients.11,12 The vast majority (96% 

to 97%) of patients were NYHA Class I or II at final 

follow-up with 3% experiencing Class III symptoms.11-13

Other long-term issues encountered by patients statuspost arterial switch operation are reduced exercise tolerance (85% of predicted), aortic regurgitation (21%), and 

reduced systemic ventricular function (7%).14

References

1. Reller MD, Strickland MJ, Riehle-Colarusso T, 

Mahle WT, Correa A. Prevalence of congenital 

heart defects in metropolitan Atlanta, 1998-2005. J 

Pediatr. 2008;153(6):807-813.

COMPLEX D-TGA STATUS POST RASTELLI REPAIR PRESENTING WITH PALPITATIONS:

CARDIAC CTA IMAGING FINDINGS AND DISCUSSION OF LONG TERM OUTCOMES

Figure 5. Apical 3- and 5-chamber views showing turbulence across the LVOT beginning below the aortic valve (in the baffle between 

VSD and aorta).
April – June 2015 85

THE ARMY MEDICAL DEPARTMENT JOURNAL

2. Goor DA, Edwards JE. The spectrum of transposition of the great arteries: with specific reference to 

developmental anatomy of the conus. Circulation. 

1973;48(2):406-415.

3. Rashkind WJ, Cuaso CC. Transcatheter closure of patent ductus arteriosus. Pediatr Cardiol. 

1979;1(1):3-7.

4. Singh SP, Chauhan S, Choudhury M, Malik 

V, Hote MP, Devagourou V. Modified Blalock 

Taussig shunt: comparison between neonates, infants and older children. Ann Card Anaesth. 2014; 

17(3):191-197.

5. Warnes CA. Transposition of the great arteries. 

Circulation. 2006;114(24):2699-2709.

6. Jatene AD, Fontes VF, Paulista PP, de Souza 

LC, Neger F, Galantier M, Souza JE. Successful 

anatomic correction of transposition of the great 

vessels: a preliminary report. Arq Bras Cardiol. 

1975;28(4):461-464.

7. Rastelli GC. A new approach to the “anatomic” 

repair of transposition of the great arteries. Mayo 

Clin Proc. 1969;44(1):1-12.

8. Dos L, Pen V, Silversides C, Provost Y, Oechslin E, 

Horlick E, Paul N. Images in cardiovascular medicine. Cardiac magnetic resonance imaging and 

multidetector computed tomography scan illustrating Damus-Kaye-Stansel operation. Circulation. 

2007;115(18):e440-e442.

9. Han BK, Lesser JR. CT imaging in congenital 

heart disease: an approach to imaging and interpreting complex lesions after surgical intervention 

for tetralogy of fallot, transposition of the great arteries, and single ventricle heart disease. J Cardiovas Comput Tomogr. 2013;7(6):338-353.

10. Anderson BR, Ciarleglio AJ, Hayes DA, Quaegebeur JM, Vincent JA, Bacha EA. Earlier arterial 

switch operation improves outcomes and reduces 

costs for neonates with transposition of the great 

arteries. J Am Coll Cardiol. 2014;63(5):481-487.

11. Brown JW, Ruzmetov M, Huynh D, Rodefeld MD, 

Turrentine MW, Fiore AC. Rastelli operation for 

transposition of the great arteries with ventricular 

septal defect and pulmonary stenosis. Ann Thorac 

Surg. 2011;91(1):188-194.

Figure 6. High-parasternal-short-axis view showing turbulence in the RV-PA conduit. Conduits such as these are often difficult 

to visualize by echocardiography due to anatomical position, body habitus, or surgical scarring.
86 http://www.cs.amedd.army.mil/amedd_journal.aspx

12. Hörer J, Schreiber C, Dworak E, Cleuziou J, Prodan Z, Vogt M, Holper K, Lange R. Long-term results after the 

Rastelli repair for transposition of the great arteries. Ann Thorac Surg. 2007;83(6):2169-2175.

13. Marcelletti C, Mair DD, McGoon DC, Wallace RB, Danielson GK. The Rastelli operation for transposition of the 

great arteries. Early and late results. J Thorac Cardiovasc Surg. 1976;72(3):427-434.

14. Ruys TP, van der Bosch AE, Cuypers JA, et al. Long-term outcome and quality of life after arterial switch operation: a prospective study with a historical comparison. Congenit Heart Dis. 2013;8(3):203-210.

Authors

Capt Pinson is an Internal Medicine Resident with the San Antonio Uniformed Services Health Education Consortium, 

Brooke Army Medical Center, Joint Base San Antonio Fort Sam Houston, Texas.

MAJ Thomas is with the Department of Cardiology, Brooke Army Medical Center, Joint Base San Antonio Fort Sam 

Houston, Texas.

Maj Bentley is with the Department of Pediatric Cardiology, Brooke Army Medical Center, Joint Base San Antonio Fort 

Sam Houston, Texas.

COMPLEX D-TGA STATUS POST RASTELLI REPAIR PRESENTING WITH PALPITATIONS:

CARDIAC CTA IMAGING FINDINGS AND DISCUSSION OF LONG TERM OUTCOMES
October – December 2014 87

Borden Institute’s latest publication was authored by 

Norman Camp, a retired Army psychiatrist who led a 

psychiatric unit during the war in Vietnam. The result 

is a story that is both scholarly and intensely personal, 

reflecting Dr Camp’s keen interest in presenting the big 

picture of this after action review, yet also filled with anecdotes and case histories that illustrate his perspectives 

and opinions, as well as the points of view of many of his 

professional colleagues who served in the conflict. The 

cover is dramatic, the presentation is first class, and the 

pages are replete with illustrations and correspondence 

from the Vietnam era. The story is presented in a fresh 

way—from a psychiatrist’s point of view—although it is 

now nearly 50 years since the war was fought.

The American ground war in Vietnam lasted from 1965 

to 1973. Just as the current Army has evolved in response to social issues over the past decade, the Army 

of the 1960s and 1970s reflected ongoing changes in the 

culture of the time. This was a time of upheaval—worsening racial tensions, widespread use of illicit drugs, 

and, of course, the antiwar movement—all coinciding 

in ways that posed threats to our social institutions, including the US Army. At home, the many aspects of 

this cultural change provoked intense media scrutiny 

and political controversy. Although Army morale remained high for the first few years, as the war dragged 

on and the Army became increasingly draftee dependent, these tensions strongly influenced those serving 

in Vietnam. The effects were manifest as a growing 

inability or unwillingness to accept the risks of combat or to acknowledge military authority, and lessening 

tolerance for the hardships of an assignment in Vietnam. 

Matters became substantially worse in 1970 when a 

heroin epidemic spread quickly among the lower ranks, 

an unprecedented problem that seriously undermined 

Soldier health, morale, and military preparedness. The 

cost of a small package of heroin in Vietnam, which in 

American had a street value of hundreds of dollars, was 

less than the cost of a package of cigarettes.

Dr Camp has set the stage for his discussion by describing the dramatic political and military events of 

1968, the de facto turning point in the war; the pre-Tet 

years of 1963 to 1967 which encompassed the conflict’s 

buildup under Lyndon Johnson; and the 1969 to 1973 

post-Tet years during which Richard Nixon directed the 

withdrawal from combat. The war’s bloodiest year was 

1968, with more than 16,000 American casualties. On 

January 31, 1968, Viet Cong guerillas and North Vietnamese army elements broke the Tet (Lunar New Year) 

truce, launching coordinated attacks on cities and towns 

throughout South Vietnam. The attacks were followed 

by the month-long effort by US forces to retake Hue, a 

historic city on the border with North Vietnam, as well 

as American resistance during a prolonged siege of the 

US Marine combat base at Khe Sahn. In the month of 

May alone, more than 2,000 Americans were killed 

across South Vietnam. Although there were few tactical gains for the communist forces, the political gains 

were substantial. According to some, US media reports 

of these events as defeats for US forces led to the loss of 

political and popular support for the war, and the call for 

an end to the fighting became louder and clearer. Lyndon Johnson had proposed the end of aerial bombing 

and the start of peace negotiations in March 1968, and 

Americans began pulling out of Vietnam in mid-1969. 

The recognition that there could be no US victory in the 

conflict caused a powerful negative reaction, in both the 

country and the Army. The troops’ commitment in the 

A New Offering from the

Borden Institute History Series

US Army Psychiatry

in the

Vietnam War

Norman M. Camp, MD

COL (Ret) US Army Medical Corps

LTC Daniel E. Banks, USA

COL (Ret) Hershell L. Moody, USA
88 http://www.cs.amedd.army.mil/amedd_journal.aspx

build-up years evolved into worsening morale, apathy, 

destructive behavior, and a breakdown in discipline.

Among many aspects of the war that placed the mental 

health of American service members at risk in Vietnam 

were the following:

` The opposition Vietnamese forces included the 

North Vietnamese army, who staged relatively conventional attacks, and the Viet Cong, who were 

most active and fought a guerilla/counterinsurgency war built on terrorizing citizens living in the villages of South Vietnam. Many South Vietnamese 

were too intimidated by the Viet Cong to become 

American allies. The enemy was elusive but often 

unable to deliver sustained direct fire. American 

Soldiers located in forward bases ventured “outside of the wire” to engage the enemy in searchand-destroy missions. There was no way to control 

territory. The war had evolved into a protracted, 

bloody, mainly guerrilla conflict, and the American 

fight became a war of attrition measured in “body 

counts” and “kill ratios.” 

` In the United States, Americans had become increasingly divided. The rising civil rights and black 

power movements, the emerging youth counterculture (illustrated by the protests at the Democratic 

National Convention in 1968), and an American 

public that increasingly showed dissatisfaction with 

the war were met “head on” by conservative members of the population who opposed these ideas. 

The members of the US military were caught in the 

middle.

` Instead of deploying as a unit as the Army does today, individuals deployed in fixed, individual, oneyear assignments. The result was a constant shuffle 

of Soldiers in and out of theater and in and out of 

units, making it more difficult for Soldiers to bond 

and serve as a team. Furthermore, officers would 

often lead for shorter time periods, typically 3 to 6 

months. These rotations were intended to give each 

officer a taste of command, but the policy actually 

resulted in diminished leadership continuity and 

unit cohesiveness.

` The previsouly mentioned decision to begin peace 

talks while the battle raged sent mixed messages to 

those in the fight. No matter how intensely Soldiers 

embraced the mission, there was to be no victory, 

only a brokered peace agreement. The result was a 

dramatic loss of morale. Soldiers clearly and openly 

expressed concerns regarding the reason for the 

fight when there could be no victory. Perhaps this 

was best exemplified by the abbreviated message 

sent by the “UUUU” graffiti throughout the war 

zone: “We are the Unwilling, led by the Unqualified, doing the Unnecessary, for the Ungrateful.” 

` Changes in American culture also affected psychiatrists and the care they provided. Over the course 

of the war, approximately one-third of the Army 

psychiatrists deployed to Vietnam were military 

trained, while two-thirds were civilian trained. The 

great majority were recent graduates of psychiatry training programs, with relatively little military experience. Perhaps this combination of psychiatrists with relatively little military background, 

coupled with the cultural changes that occurred in 

the Army as the war raged, led to the dramatic increase in rates for psychiatric out-of-country evacuation (1.9/1,000 Soldiers in 1965; 2.3/1,000 in 1968; 

108/1,000 Soldiers in 1972).

` Vietnam veterans returned to an unwelcoming society. Much has been written about the many episodes of rejection by the American public of returning Soldiers. Yet the impact was even more insidious, affecting troops still in action as well. Psychiatrists practicing in Vietnam after 1968 recognized 

that the Soldiers still in the fight perceived blame 

from their countrymen back home, and this had an 

adverse effect on morale.

In one of the Borden Institute’s strongest productions, 

the author has addressed a complicated subject and identified and discussed many of the tragic human and psychological aspects of the Vietnam conflict in a thoughtful manner. Dr Camp has taken the time to present cases 

of Soldiers with behavioral issues that show the situation these men faced, and how he and his colleagues attempted to make their lives better and remain true to 

Army values. This is a story about events that have been 

in the American military consciousness for more than 

a generation, with many of these ideas bubbling below 

the surface for years and only now being presented. We 

applaud Dr Camp and his fellow Vietnam War psychiatrists for addressing these issues and providing quality 

care to our fellow Soldiers.

Author

LTC Banks is the Director of the Borden Institute, Joint 

Base Fort Sam Houston, Texas.

COL (Ret) Moody, a Vietnam War Veteran, is a retired 

Army Medical Service Corps officer.

US ARMY PSYCHIATRY IN THE VIETNAM WAR

A NEW OFFERING FROM THE BORDEN INSTITUTE HISTORY SERIES
October – December 2014 89

THE ARMY MEDICAL DEPARTMENT JOURNAL

This book is available in PDF and will soon be available in iPad and Kindle formats for download on your electronic reader. The book can be ordered at no cost by those on active duty, in the 

National Guard, and in the Reserve by following the instructions on the Borden Institute website, 

http://www.cs.amedd.army.mil/borden/. It will soon be available for purchase from the US Government Printing Office.
90 http://www.cs.amedd.army.mil/amedd_journal.aspx

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