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Load Carriage in Military Operations: A Review of Historical, Physiological, Biomechanical, and Medical Aspects

Chapter 11

LOAD CARRIAGE IN MILITARY 

OPERATIONS: A REVIEW OF HISTORICAL, 

PHYSIOLOGICAL, BIOMECHANICAL, 

AND MEDICAL ASPECTS

JOSEPH KNAPIK, ScD*; and KATY REYNOLDS, MD†

INTRODUCTION

HISTORICAL PERSPECTIVE

Loads Carried During Various Historical Periods

19th- and 20th-Century Efforts to Study Load Carriage

Historical Perspective

Body Stature and Body Mass as Factors in Load Carriage

PHYSIOLOGICAL AND BIOMECHANICAL ASPECTS OF LOAD CARRIAGE 

Load Distribution

Backpacks and Double Packs

Load Carriage on the Feet, on the Thighs, and in the Hands

Rifle Carriage

Body Armor

Load Carriage Using Carts and Motorized Vehicles

Physiological Factors Associated With Load Carriage

Physical Training and Load Carriage

Gender Differences

Predicting the Energy Cost of Carrying Military Loads

MEDICAL PROBLEMS ASSOCIATED WITH LOAD CARRIAGE 

Foot Blisters

Metatarsalgia 

Stress Fractures

Knee Pain

Low Back Injuries

Rucksack Palsy

Meralgia Paresthetica

INFLUENCE OF LOAD CARRIAGE ON THE PERFORMANCE OF OTHER TASKS 

SUMMARY

*Major (Ret), Medical Service Corps, US Army; Research Physiologist, Injury Prevention Program, US Army Public Health Command (Provisional), 

5158 Blackhawk Road, Aberdeen Proving Ground, Maryland 21005-5425

†Colonel (Ret), Medical Corps, US Army; currently, 8820 Burning Tree Road, Pensacola, Florida 32514
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Military Quantitative Physiology: Problems and Concepts in Military Operational Medicine

INTRODUCTION

the Falkland Islands War (1982) and US Army troops 

in both Grenada (1983) and Afghanistan (1999–2010) 

emphasizes that overloading troops is still a problem 

in modern warfare.5–7

The purpose of this chapter is to review the historical, physiological, biomechanical, and medical aspects 

of load carriage. Practical suggestions are offered for 

reducing the stress of loads on service members and 

for preventing and treating common load carriagerelated injuries. Reviews on other aspects of load 

carriage are available in the works of Haisman8 and 

Knapik et al.9,10

Because of mission requirements or the limited 

transportation assets of some types of units, service 

members must often depend on their personal mobility to move individual equipment. The carrying 

of loads by troops is an important aspect of military 

operations that can become critical in some situations. 

Overloading with ammunition and equipment can 

lead to excessive fatigue and impair the ability to fight. 

Military historians can cite numerous examples when 

heavy loads directly or indirectly resulted in reduced 

performance, unnecessary deaths, and lost battles 

(Exhibit 11-1).1–4 The experience of British troops in 

HISTORICAL PERSPECTIVE 

Loads Carried During Various Historical Periods 

Figure 11-1 shows loads that were carried by various 

military units in history, with emphasis on more recent 

times. Lothian11 provided data on ancient military 

units. Until about the 18th century, troops carried loads 

that seldom exceeded 15 kg as they marched. Extra 

equipment was often moved by auxiliary transport, 

including assistants, horses, carts, and camp followers. The extra equipment often consisted of weapons 

and protection used by troops when they went into 

battle (eg, swords and shields). After the 18th century, 

auxiliary transport was deemphasized, and more disciplined armies required troops to carry their own loads. 

The latter-day service member often carried more 

equipment during the march and less when in contact 

with hostile forces.2 It should be noted that most of the 

loads provided in Figure 11-1 are from estimates and 

literary sources. The only actually measured values 

are those from the Joint Readiness Training Center (in 

Fort Chaffe, Ark) and Operation Enduring Freedom 

(Afghanistan).

19th- and 20th-Century Efforts to Study Load Carriage 

European Efforts

After the Crimean War, a British “Committee 

Appointed to Inquire into the Effects of the Present 

System of Carrying Accouterments, Ammunition and 

Kit of the Infantry Soldier” recommended that soldier 

loads be reduced to 21 kg through the elimination of 

“necessaries,” especially underclothing.2,4 Studies at 

the Frederick Wilhelm Institute in 1895 showed that, 

if the weather was cool, soldiers could tolerate marching 24 km with a load mass of 22 kg. In warm weather, 

this test caused “minor disturbances,” from which the 

men recovered in 1 day.2 In 1908, a “Committee on the 

Physiological Effects of Food, Training, and Clothing 

of the Soldier” developed a much-improved load carriage system that was used in World War I. In 1920, the 

Hygiene Advisory Board of the British Army recommended that the soldier’s load should not exceed 18 to 

20 kg or one third of his body weight while marching. 

With the development of indirect calorimetry, Cathcart 

and colleagues12 were able to study the energy cost of 

two men marching at a variety of paces and with a 

variety of load masses. They found that energy cost 

per mass carried was lowest when subjects carried a 

mass equal to 40% of their body mass.

US Efforts 

There is little information about US efforts to study 

load carriage formally before World War II, if these 

efforts even existed. Under the direction of the Quartermaster General, Captain HW Taylor developed 

a soldier “payload plan.” This was an attempt to 

unburden the soldier by providing him with only the 

items needed for combat. There were also attempts to 

develop segmented packs: if the tactical situation permitted, a portion of the pack containing nonessential 

equipment could be left behind.13

World War II led to many situations in which soldiers 

had to carry loads for long distances. Figure 11-2 shows 

American soldiers marching to relieve troops in the 

Ardennes Forest during the Battle of the Bulge. Figure 

11-3 shows a training exercise in which a modern airman is being transported using a two-man carry, not an 

uncommon situation in World War II. Figure 11-4 shows 
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Load Carriage in Military Operations: A Review of Historical, Physiological, Biomechanical, and Medical Aspects

EXHIBIT 11-1 

HEAVY LOADS IN MILITARY HISTORY

Omaha Beach, France (1944)

“In the initial assault waves at Omaha Beachhead there were companies whose men started ashore, each with four 

cartons of cigarettes in his pack—as if the object of the operation was trading with the French. Some never made the 

shore because of the cigarettes. They dropped into deep holes during the wade-in, or fell into the tide nicked by a bullet. Then they soaked up so much weight they could not rise again. They drowned. Some were carried out to sea but 

the great number were cast up on the beach. It impressed the survivors unforgettably—that line of dead men along 

the sand, many of whom had received but trifling wounds. . . . No one can say with authority whether more men died 

directly from enemy fire than perished because of the excess weight that made them easy victims of the water. . . . 

This almost cost us the beachhead. Since it is the same kind of mistake that armies and their commanders have been 

making for centuries, there is every reason to believe it will happen again.”(1)

Grenada (1986)

“Unfortunately too few commanders enforced load discipline. Consider this soldier’s observation: ‘We attacked to 

secure the airhead. We were like slow moving turtles. My rucksack weighed 120 pounds. I would get up and rush for 

10 yards, throw myself down and couldn’t get up. I’d rest for 10 or 15 minutes, struggle to get up, go 10 more yards, 

and collapse. After a few rushes, I was physically unable to move and I am in great shape. Finally, after I got to the 

assembly area, I shucked my rucksack and was able to fight, but I was totally drained.’ Consider another soldier’s 

telling comment: ‘I was scared I was going to get killed because I couldn’t really run with that rucksack on.’ Even allowing for some exaggeration by the soldiers, no one can doubt they were overloaded.”(2)

Saudi Arabia and Iraq (1990)

“During Operation Desert Shield, a brigade conducted a live fire training assault to seize a bridge. The brigade commander noticed that the equipment the soldiers were carrying was interfering with the mission. At the after action 

review he directed the battalion commanders to investigate the weight the soldiers carried in their battalions. At the 

brief back one commander indicated that the average soldier in his battalion carried more than 100 pounds.

At Christmas 1990 the 2d Brigade, 82d Airborne Division was conducting training far to the South of the front. During 

this relatively peaceful time, and especially as a result of the holiday, the soldiers had accumulated many items they 

could not take into combat. When the order came for the brigade to spearhead the French 6th Light Armored Division’s 

attack into Iraq, the chain of command took steps to care for the soldier’s personal effects and excess baggage. They 

made a list of what a soldier would carry on his person (fighting load), what he would carry in his rucksack (approach 

march load), what he would carry in his A-bag (sustainment load), and what would go in his B-bag (contingency load). 

Items that did not fit in these categories, the soldier shipped home. . . . The battalions that entered the Euphrates River 

Valley had learned a valuable lesson as a result of their earlier training attack on the bridge. Although their fighting and approach march loads were still heavy, they knew better how to manage them. When units arrived at their 

landing zones, the battalions secured their rucksacks (approach march load) with a minimum guard force while the 

rest of the soldiers occupied their positions. As soon as practicable, soldiers went back, a few at a time, to retrieve the 

rucksacks. In at least one instance, a unit placed excess ammunition and water in kick-out bundles that could then be 

taken forward and stored in a central location for further distribution.”(3)

Afghanistan (2002)

“We had extreme difficulty moving with all of our weight. If our movement would have been to relieve a unit in contact or a time sensitive mission we would not have been able to move in a timely manner. It took us 8 hours to move 5 

clicks. With just the vest [Interceptor hard body armor] and LBV [Enhanced Tactical Load Bearing Vest or the MOLLE 

vest] we were easily carrying 80 lbs. Throw on the ruck and you’re sucking.”(4)

Data sources: (1) Marshall SLA. The Soldier’s Load and the Mobility of a Nation. Quantico, Va: Marine Corps Association; 1950. (2) Dubik 

JM, Fullerton TD. Soldier overloading in Grenada. Mil Rev. 1987;67:38–47. (3) Porter SC. The soldier’s load. Infantry. 1992;May–

June:19–22. (4) Comments from the 187th Regiment First Sergeant, Operation Anaconda, 2002.
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Military Quantitative Physiology: Problems and Concepts in Military Operational Medicine

Fig. 11-1. Loads carried on the march by various infantry units throughout history. Inf: infantry; JRTC: Joint Readiness Training Center (Ft Chaffee, Ark); OEF: Operation Enduring Freedom; WWI: World War I; WWII: World War II. 

Data sources: Dean CE. The Modern Warrior’s Combat Load. Dismounted Operations in Afghanistan April–May 2003. Ft Leavenworth, Kan: Army Center for Lessons Learned; 2004. Downs F. The Killing Zone: My Life in the Vietnam War. New York, NY: 

Berkley Publishing Group; 1978. Holmes R. Acts of War. The Behavior of Men in Battle. New York, NY: MacMillan and Co, 

1985. Joint Readiness Training Center. Unpublished data collected on units participating in exercises at the Joint Readiness 

Training Center, 1988. Lothian NV. The load carried by the soldier. J R Army Med Corps. 1922;38:9–24. Porter SC. The soldier’s 

load. Infantry. 1992;May–June:19–22. 

an infantryman transporting loads by mules in Burma. 

Presumably drawing on many of the experiences from 

World War II, US Army Field Board No. 3 (Fort Benning, 

Ga) performed a number of studies from 1948 to 1950. 

Board members noted that previous work had ignored 

the individual soldier’s mission within the military unit. 

In studying individual positions, they found that loads 

ranged from 25 kg for the rifleman to 50 kg for the ammunition carrier. In cooperation with the Office of The 

Surgeon General, the Board estimated how load masses 

should be reduced to make the soldier more combat effective. Metabolic data and stress placed on soldiers in 

combat were considered. Based on a literature review, 

the Board determined that the energy available for 

marching (with the basal metabolic rate subtracted) 

could not exceed 3,680 kcal/day. They recommended 

that a rifleman carry 18 kg in the worst conditions; 25 

kg was recommended as the maximum march load.14

About a decade later, the US Army Infantry Combat 

Developments Agency15,16 reinforced the weight recommendations of US Army Field Board No. 3. The agency 

recommended a load of 18 kg (or 30% body weight) 

for a conditioned fighting soldier and 25 kg (or 45% 

body weight) for a marching soldier. They developed 

the idea of “load echeloning” and defined a fighting 

load and an existence load. 

In 1987, the US Army Development and Employment Agency (ADEA; Fort Lewis, Wa) further developed the concept of load echeloning.17 They called the 

load carried by a soldier the combat load, defined as 

the mission-essential equipment required by soldiers 

to fight, survive, and complete their combat mission. 

The combat load was further divided into a fighting 

load and an approach march load. The fighting load was 

carried when enemy contact was expected or stealth 

was necessary. It consisted of the soldier’s clothing, 

load-bearing equipment, helmet, weapon, rations, 

bayonet, and ammunition. The approach march load 

was carried in more prolonged operations. It included 

the combat load plus a pack, sleeping roll, extra clothing, extra rations, and extra ammunition. Current 

US Army doctrine recommends 22 kg (or 30% body 

weight) for the fighting load and 33 kg (or 45% body 

weight) for the approach march load.18

ADEA studied nine light infantry jobs that soldiers 

might have to perform in a worst-case situation. The 

loads carried by soldiers in these positions are shown 

in Table 11-1. ADEA17 proposed five approaches for 

lightening soldier loads:

1. development of lighter weight components—

however, technical developments were 

expected to reduce loads by only 6% overall 

(see Table 11-1);19

50

40

30

20

10

0

Estimated Load Mass (kg)

Greek

Hoplites

Roman

Legions

Byzantine

Infantry

Anglo

Saxon

Freemen

English

Pikemen

Napoleonic

Wars

US

Civil

War

British

Crimean

War

JRTC

US

Vietnam

British

on 

Somme

WWI

US

Marines

Korea

US Inf

Desert

Shield

Wingate's

Chindits

WWII

Estimated load masses carried on the march

Estimated total mass of all equipment soldiers took OEF
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Load Carriage in Military Operations: A Review of Historical, Physiological, Biomechanical, and Medical Aspects

2. use of the soldier load-planning model: 

a computer program that aided the commander to tailor loads through a risk analysis 

based on the mission, enemy, terrain, troops, 

and time;

3. development of specialized, load-carrying 

equipment (including items such as handcarts and all-terrain vehicles);

4. reevaluation of current doctrine that might 

affect load carriage (eg, an increased emphasis on marksmanship to reduce ammunition 

loads); and 

5. development of special physical training 

programs to condition soldiers to develop 

more physical capability for load carriage.

The first study of loads actually carried in combat 

was performed with a light infantry brigade (the 82nd 

Airborne Division) engaged in a low-intensity conflict 

in the deserts and mountains of Afghanistan during 

spring 2003. A team of infantrymen was dedicated 

to the data collection effort and also served to augment the combat forces. Loads were inventoried and 

weighed with digital scales on 15 separate occasions 

involving seven combat missions from April 4, 2003 

to May 5, 2003. The loads carried by soldiers in each 

of the 29 duty positions are shown in Table 11-2. The 

emergency approach march load was defined as the 

load that was carried in foot operations when the terrain was “impassable to vehicles or where ground/

air transportation resources are not available.” It was 

noted that recent improvements in ballistic protection 

(interceptor body armor, advanced combat helmet) had 

increased soldier survivability, but had decreased mobility and endurance. Body armor and the protective 

helmet accounted for roughly 31% of the fighting load.5

Historical Perspective 

Many of the approaches proposed more recently 

for reducing soldier loads5,17 are not new. For example, 

commanders and individual soldiers have practiced 

load tailoring throughout history. Iphicrates of Ancient 

Fig. 11-2. American soldiers marching to relieve troops 

encircled in the Ardennes Forest during the Battle of the 

Bulge.

Photograph: Courtesy of Olive-Drab.com. From http://www.

olive-drab.com/od_history_ww2_ops_battles_1944bulge.

php.

Fig. 11-4. Mars Task Force mule skinners (2nd Battalion, 

475th Infantry Regiment) lead mules through the swift river 

that impeded their progress to Bhamo, Burma, November 

17, 1944.

Photograph: Courtesy of Olive-Drab.com. From http://

www.olive-drab.com/od_army-horses-mules_ww2.php. 

Fig. 11-3. An airman being transported using a two-man 

carry in a training exercise. 

Photograph: Reproduced from US Air Force link photo 

library at http://www.af.mil/shared/media/photodb/

photos/070515-F-4127S-706.jpg. 
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Military Quantitative Physiology: Problems and Concepts in Military Operational Medicine

Greece armed his infantry with only a wooden shield, 

lance, and sword. They defeated a Spartan force of 

heavily equipped Hoplites, presumably because of 

their greater agility. The Hoplites carried a load of 

about 37 kg into battle. In the 17th century, Gustavus 

Adolphus of Sweden lightened his soldiers’ loads 

by removing armor and shortening weapons. In the 

Boer Wars, the British Army carried only arms, ammunition, water, and a haversack—a total weight of 

11 kg.2 Soldiers in battle have often reduced loads 

on their own initiative. During the highly successful 

Shenandoah campaign, the Confederate troops under 

Stonewall Jackson discarded extra clothing, overcoats, 

and knapsacks. They carried only rifles, ammunition, 

food, a blanket (or rubber sheet), and the clothing they 

wore.2,3 American paratroopers entering Normandy 

in 1944 exited the aircraft with a load of about 36 kg. 

However, once on the ground, they quickly discarded 

equipment they considered unnecessary.3

A wide variety of load-carrying systems have also 

been used throughout history. The Greek Hoplites used 

helots (serfs in ancient Sparta) to carry their equipment 

on the march. Carts and packs were used by Roman 

legions. Oliver Cromwell’s armies used “pack boys.” 

Napoleon used carts whenever possible to relieve his 

soldiers of their march loads. Camp followers also carried much of the soldiers’ load during various wars.1,2

Physical training has been used to improve marching with loads. Roman legionnaires are estimated to 

have performed road marching three times per month 

at a rate of about 5 km/h carrying a 20-kg pack over a 

32-km distance. In Cromwell’s army (circa 1640), pay 

was contingent on marching 24 km on a regular basis. 

During World War I, the French Chasseurs (infantry), 

carrying a “light kit,” marched more than 13 to 18 

km two times per week. Recruit training in Germany 

during World War I included taking an initial 10-km 

march, with 1 km added weekly until recruits were 

marching 20 km with a “full kit.”2 McMichael20 gives a 

brief description of the training of Wingate’s Chindits 

(from the Burmese word “chinthe” [or lions]—also 

known as “Wingates’ Raiders”), who fought as light 

infantry during the Central Burma campaign in World 

War II. “They were loaded with huge 34-kg packs and 

marched unmercifully through man-killing terrain.”20

These soldiers performed a 225-km road march just 

before their deployment to Burma. Units within the 

US Army’s 10th Mountain Division routinely road 

marched with their fighting loads about three times per 

month. Training guidance prescribed a quarterly road 

march of 40 km (7 min/km [or 11 min/mile] pace) and 

a yearly road march of 161 km in 5 days.21

Body Stature and Body Mass as Factors in 

Load Carriage 

A service member’s height and weight might be 

an important factor in load carriage.2,22 Larger service 

members might be able to carry heavier loads by 

virtue of their greater bone and muscle mass.23–25 It 

has been estimated that humans have increased their 

height about 10 cm since the Industrial Revolution, 

possibly because of better nutrition.26 Table 11-3 provides a summary of the heights and weights of various 

groups derived from a variety of sources. Before the 

British Crimean War, only minimum standards were 

available. US samples show a progressive increase 

in height, weight, and body mass index since the 

American Civil War. The increase in weight is apparently attributable to an increase in fat-free mass, with 

TABLE 11-1

WORST CASE LOADS AND PROJECTED WEIGHTS BECAUSE OF NEW TECHNOLOGIES (INCLUDING 

CLOTHING AND PERSONAL EQUIPMENT) FOR NINE US ARMY LIGHT INFANTRY POSITIONS

US Army Development and Expected Weights

Position Employment Agency Worst-Case Loads (kg) Because of New Technologies (kg)

Assistant Dragon Gunner 76 74

Assistant Machine Gunner 69 59

Radio Telephone Operator 68 64

Dragon Gunner 64 61

Rifleman 62 64

Squad Automatic Weapon Gunner 59 57

Platoon Leader 58 54

Machine Gunner 58 53

Grenadier 56 53

Data source: Sampson J. Technology Demonstration for Lighting the Soldier’s Load. Natick, Mass: US Army Natick Research and Development 

Laboratory; 1988. Technical Report TR-88/027L. 
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Load Carriage in Military Operations: A Review of Historical, Physiological, Biomechanical, and Medical Aspects

TABLE 11-2

AVERAGE LOADS CARRIED BY LIGHT INFANTRY SOLDIERS DURING DISMOUNTED 

OPERATIONS IN AFGHANISTAN IN APRIL AND MAY 2003

Emergency Approach

Duty Position Fighting Load (kg) Approach March Load (kg) March Load (kg)

Rifleman 29 43 58

M203 Grenadier 32 48 62

Automatic Rifleman 36 50 64

Antitank Specialist 31 45 59

Rifle Team Leader 29 43 59

Rifle Squad Leader 28 43 58

Forward Observer 26 41 58

Forward Observer Radio/Telephone Operator 27 39 54

Weapons Squad Leader 28 45 60

M240 Machine Gunner 37 51 60

M240B Assistant Gunner 32 55 67

M240B Ammunition Bearer 31 53 65

Rifle Platoon Sergeant 28 41 54

Rifle Platoon Leader 28 42 53

Platoon Medic 25 42 54

Radio/Telephone Operator 29 45 No data

Mortar Section Leader 26 50 68

Mortar Squad Leader 28 58 65

60-mm Mortar Gunner 29 49 61

60-mm Mortar Assistant Gunner 25 55 No data

60-mm Mortar Ammunition Bearer 24 46 No data

Rifle Company Communication Chief 31 50 No data

Fire Support Officer 25 42 No data

Fire Support Noncommissioned Officer 24 41 65

Sapper Engineer 27 43 60

Company Executive Officer 27 42 No data

Company First Sergeant 29 41 57

Company Radio/Telephone Operator 29 44 59

Rifle Company Commander 30 44 50

Average 29 46 60

Data source: Dean CE. The Modern Warrior’s Combat Load. Dismounted Operations in Afghanistan, April–May 2003. Ft Leavenworth, Kan: Army 

Center for Lessons Learned; 2004.

temporal changes in body fat less consistent. Data on 

the general US population suggest that body weight 

and body mass index have been progressively increasing since 1980.27,28 Data on Army recruits suggest that 

the increase in weight is accounted for by about equal 

increases in fat-free mass and body fat.29

PHYSIOLOGICAL AND BIOMECHANICAL ASPECTS OF LOAD CARRIAGE 

Although historical studies are useful to show that 

the problems of load carriage have been with the 

military for a considerable time, it is physiological and 

biomechanical research conducted during the last 70 

years that have developed some practical methods to 

reduce load stress on service members. Many general 

principles and techniques have emerged, but studies 

do not reveal a single way of carrying loads that applies to all situations. Commanders must consider the 

mission, environment, time, and terrain to adjust the 

service members’ burdens.

Load Distribution

There are many ways to carry loads, and the technique used depends on the characteristics of the load 

(size, shape, mass, etc), how far the load may be carried, previous experience, and the equipment available 
310

Military Quantitative Physiology: Problems and Concepts in Military Operational Medicine

to the service member.30 Figure 11-5 illustrates techniques of carrying loads that have been directly 

investigated for individual soldiers.30–37 Team-lifting 

techniques can assist in moving larger loads, as shown 

in Figures 11-6 and 11-7.

Two load-carrying systems currently available to 

individual US soldiers include (1) the All-Purpose 

Lightweight Individual-Carrying Equipment (ALICE) pack and (2) the Modular Lightweight LoadCarrying Equipment (MOLLE) pack. The ALICE pack 

is more than 35 years old, having been introduced 

TABLE 11-3

PHYSICAL CHARACTERISTICS OF SOLDIERS AND RECRUITS

Sample Height (cm) Weight (kg) Body Mass Index (kg/m2) Fat-Free Mass (kg) Body Fat (%)

French Samples

French (Crimean War)(1) 163 56 21.1 NA NA

French (Post-WWI)(1) 163 NA NA NA NA

British Samples

British (Post-WWI)(1) 168 59 20.9 NA NA

British recruits (1978)(2) 175 70 22.9 NA NA

British infantry (1976)(2) 175 73 23.8 NA NA

US Samples 

US male soldiers (1864)(3) 171 64 21.9 53* 16.9*

US male soldiers (1919)(3) 172 66 22.3 55* 15.7*

US male soldiers (1946)(3) 174 70 23.1 60* 14.4*

US male soldiers (1976)(4) 175 73 23.8 59† 19.5†

US male soldiers (1984)(3) 174 76 25.1 63‡ 17.3‡

US male soldiers (1986)(5) 177 76 24.2 NA NA

US male soldiers (1988)(6) 176 76 24.5 63* 15.9*

US male soldiers (1989)(7) 178 77 24.4 64‡ 15.9‡

US male soldiers (2004)§ 177 81 25.7 NA NA

US male soldiers (2005)(8) 178 83 26.4 68¥ 17.7¥

*Estimated from circumference measures.(9)

†Estimated from skinfolds.(10)

‡Estimated from densiometry.(11)

§

Previously unpublished data, Fort Campbell, Kentucky. 

¥

Estimated from dual X-ray absorptiometry.(12)

NA: not available; WWI: World War I

Data sources: (1) Lothian NV. The load carried by the soldier. J R Army Med Corps. 1921;37/38:241–263, 342–351, 448–458. (2) Vogel JA, Crowdy 

JP. Aerobic fitness and body fat of young British males entering the Army. Eur J Appl Physiol. 1978;40:73–83. (3) Friedl KE. Body composition 

and military performance: origins of the Army standards. In: Marriott BM, Grumstrup-Scott J, eds. Body Composition and Military Performance. 

Washington, DC: National Academies Press; 1992. (4) Vogel JA, Patton JF, Mello RP, Daniels WL. An analysis of aerobic capacity in a large 

United States population. J Appl Physiol. 1986;60:494–500. (5) Knapik J, Drews F. Influence of a Specific Light Infantry Physical Training Program 

on Physical Fitness. Carlisle Barracks, Pa: US Army Physical Fitness Research Institute, US Army War College; 1987. Technical Report T3-87. 

(6) Reynolds KL, White JS, Knapik JJ, Witt CE, Amoroso PJ. Injuries and risk factors in a 100-mile (161-km) infantry road march. Prev Med. 

1999;28:167–173. (7) Knapik JJ, Staab J, Bahrke M, et al. Relationship of Soldier Load Carriage to Physiological Factors, Military Experience and 

Mood States. Natick, Mass: US Army Research Institute of Environmental Medicine; 1990. Technical Report T17-90. (8) Sharp M, Knapik JJ, 

Walker LM, et al. Changes in physical fitness and body composition following 9 months deployment to Afghanistan. Med Sci Sports Exerc. 

2008;40:1687–1692. (9) Vogel JA, Kirkpatrick JW, Fitzgerald PI, Hodgdon JA, Harman EA. Derivation of Anthropometry Based Body Fat Equations 

for the Army’s Weight Control Program. Natick, Mass: US Army Research Institute of Environmental Medicine; 1988. Technical Report 17-88. 

(10) Durnin JV, Womersley J. Body fat assessed from total body density and its estimate from skinfold thickness: measurements on 481 men 

and women aged 16 to 72 years. Br J Nutr. 1974;32:77–97. (11) Fitzgerald PI, Vogel JA, Miletti J, Foster JM. An Improved Portable Hydrostatic 

Weighing System for Body Composition. Natick, Mass: US Army Research Institute of Environmental Medicine; 1988. Technical Report T4/88. 

(12) Lohman TG. Dual energy X-ray absorptiometry. In: Roche AF, Heymsfield SB, Lohman TG, eds. Human Body Composition. Champaign, 

Ill: Human Kinetics; 1996.

within the 1973 to 1974 time frame. The ALICE pack 

is durable, stable with heavy loads, and provides 

ventilation to the back because the external frame 

holds the rucksack away from the body; however, 

adjustment is limited. Studies completed in 199538 

showed the need for a modular system, with better 

equipment compatibility and features for fitting special equipment. Studies39 resulted in the development 

and improvement of the MOLLE pack, which was 

adopted by the Marine Corps in 1999 and by the Army 

in 2001.40 The MOLLE pack (Figure 11-8) is an entire 
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Load Carriage in Military Operations: A Review of Historical, Physiological, Biomechanical, and Medical Aspects

Backpacks and Double Packs 

Where the load is carried on the body will affect 

both energy cost and gait mechanics. Loads can be 

transported with the lowest energy cost (ie, most 

efficiently) when they are carried on the head.35,42

However, this method is impractical for military operations because it requires a long training time to learn 

how to use effectively, is useful only on unobstructed 

horizontal terrain, and produces a high profile (greater 

body signature). A more practical choice is to carry a 

load as close as possible to the center of mass of the 

body.43–45 In this regard, the backpack and double pack 

methods (Figure 11-9) have been shown to have a 

lower energy cost than most other forms of load carriage.36,37,46,47 Nonetheless, a backpack places most of 

the load on the back and produces a forward inclination of the trunk and head that becomes greater as the 

load increases.48–51 The forward inclination keeps the 

load-plus-body center of mass over the feet (the base 

of support), but this leads to repetitive contractions 

(and stress) of low back muscles.52,53 Just standing with 

a backpack increases postural sway (anterior-posterior, 

medial-lateral center of pressure excursions) in a linear 

manner as the load increases.54 On the other hand, the 

double pack produces fewer deviations from normal 

walking than does a backpack, including less forward 

lean of the trunk.49,55 With the double pack, increasing load produces a reduction in stride length and 

an increase in stride frequency that is more desirable 

because it can reduce stress on the bones of the foot. 

In contrast, stride length becomes longer as backpack 

loads increase, which by the same line of reasoning, 

could be potentially harmful.30

Double packs can be useful in some military situations (eg, medics carrying their aid bags on the front 

of their bodies), but backpacks appear to provide 

greater versatility in military situations. Double packs 

can inhibit movement and limit the field of vision in 

front of the body, making it difficult to see obstructions and traps. They can be burdensome to don and 

doff; doffing can be very important when sudden or 

unexpected enemy contact occurs. The double pack can 

also induce ventilatory impairments30 and greater heat 

stress symptoms,56 compared with the backpack. The 

double pack can restrict tasks, such as firing weapons 

and donning protective masks.

Service members can take advantage of what has 

been learned from the double pack by distributing the 

load more evenly over the torso. Although it is difficult 

to make the load equal on the front and back of the 

body, both the ALICE and MOLLE systems allow a part 

of the load to be moved forward onto the load-carrying 

vest. Doing this might be expected to reduce energy 

cost, improve body posture, and reduce injuries.

Fig. 11-5. Methods of load carriage investigated in various 

studies.

Illustration: Courtesy of SURVIAC (Survivability/Vulnerability Information Analysis Center; Wright-Patterson Air 

Force Base, Ohio)/ARL (US Army Research Laboratory; 

Adelphi, Md)/Booz Allen (McLean, Va).

system that consists of a main pack with an external 

frame, butt pack, and load-bearing vest. The main 

pack has pouches and a sleeping bag compartment 

attached to the external frame. The external frame 

is a lightweight plastic polymer that is anatomically 

contoured. A patrol pack can be detached and used 

separately. The vest has removable pockets to accommodate different objects. Padded shoulder straps, 

waist belt, and strap adjustments allow for better load 

distribution, and the soldier can shift the load to different anatomical locations. An intermediate system 

between the ALICE pack and the MOLLE pack was 

the Integrated Individual Fighting System that was introduced in 1988. The Integrated Individual Fighting 

System had a large internal frame pack and a tactical 

load vest, with pockets that allowed more flexibility 

than the ALICE system; however, the internal frame 

pack was unstable with heavy loads (more than 36 

kg) and was prone to breakage.40,41
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Military Quantitative Physiology: Problems and Concepts in Military Operational Medicine

Fig. 11-6. An Army relief team carries an Army tent in a box to a waiting truck following a major earthquake on November 

23, 1980. The men are from the 1st Battalion, 509th Infantry Regiment, Vicenza, Italy.

Photograph: Reproduced from DefenseImagery.mil. Image DF-SN-82-06152.

Pack Frames and Hip Belts 

Pack frames and hip belts reduce shoulder stress. 

The shoulder straps of a pack exert pressure on the 

skin, which can be measured with transducers under 

the straps.57 Shoulder pressure is considerably lower 

with a pack frame incorporating a wide hip belt, compared with a pack frame without a hip belt. In one 

study, 10 kg carried in a frameless pack resulted in a 

peak pressure of 203 mm Hg; the same mass carried 

in a pack with a frame and wide hip belt resulted in a 

peak pressure of only 15 mm Hg. The pack with the 

frame and hip belt produced less electromyographic 

activity in the trapezius muscle, also suggesting less 

stress in the shoulder area.57 

When a pack frame and hip belt are used for a load 

between 14 and 41 kg, the proportion of the load supported on the hips and lower back is 30% and the load 

on the shoulders is 70%, regardless of the load mass. 

There is a consistent anterior force exerted on the lower 

back that might increase stress in this area.58 There is 

some suggestion that experienced individuals adjust 

their walking posture to reduce forces and force fluctuations in the shoulder straps.59 Rigid rods attached 

to both sides of the pack and extending into the hip 

belt transfer about 14% of the vertical load from the 

upper torso to the pelvis.60

Internal frame packs have supporting structures 

(metal and plastic) inside the fabric of the pack and 

keep the pack closer to the center of mass of the body. 

External frame packs have the supporting structure on 

the outside of the pack, and the pack is usually farther 

away from the center of mass of the body. There is 

conflicting information regarding whether the internal 

frame pack has a lower energy cost than the external 

frame pack.61,62 There is no difference in perceived exertion between external and internal frame packs when 

walking on level, even terrain.61 However, perceived 

exertion over rough terrain is lower with the internal 

frame pack.63 

Subjective reports of discomfort vary, depending 

on the design of the pack system. For backpacks with 

and without frames, the majority of discomfort appears 

to be in the neck and shoulder region, although foot 

discomfort can also be substantial, presumably because 

of the development of hot spots and blisters.64,65 For 
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Load Carriage in Military Operations: A Review of Historical, Physiological, Biomechanical, and Medical Aspects

Although both high- and low-load placements 

bring about forward body lean (knees, hips, shoulders, and head are farther forward), this effect is 

greater for low placements. This is because the lower 

load is closer to the ankles, which requires more forward body rotation to bring the pack center of mass 

over the feet.72 The additional forward body rotation 

tends to bring the body’s center of mass over the front 

half of the foot, which could increase the likelihood 

of foot strain and injury.

Nonetheless, placement of the load high in the pack 

tends to destabilize posture to a greater extent than 

lower placements, especially among tall men, as measured by the amount of body sway while standing with 

Fig. 11-7. Marines carry a stretcher bearing a sniper victim 

on Guadalcanal in World War II.

Photograph: Reproduced from the National Archives and 

Records Administration, Archival Research Catalog. From: 

http://www.pbs.org/thewar/at_war_timeline_1942.htm.

Fig. 11-8. Soldier wearing the Modular Lightweight LoadCarrying Equipment (MOLLE) pack. The MOLLE pack is 

an entire modular system that includes a main pack with 

an external frame, butt pack, and load-bearing vest. A patrol 

pack can be detached and used separately. The vest has removable pockets to accommodate different objects. Padded 

shoulder straps, waist belt, and strap adjustments allow for 

better load distribution, and the soldier can shift the load to 

different anatomical locations. 

a backpack with a hip belt, discomfort is localized to 

the midtrunk and upper legs.66 Overall, when a portion of the load is carried on the waist through use 

of a hip belt, there is less subjective discomfort than 

there is with shoulder load carriage.67 When walking 

uphill, individuals give higher ratings for balance and 

ease of gait for packs with hip belts that pivot in the 

sagittal plane.68

Placement of Load in the Backpack 

The location of load in the backpack can affect 

energy cost, subjective comfort, and body mechanics. 

Using both internal and external frame packs, higher 

energy costs were associated with a load that was lower 

in the pack and farther away from the body; lower 

energy costs were associated with loads placed higher 

in the pack and closer to the body (Figure 11-10).69,70

However, another study using an external frame pack 

and similar methodology found no difference in energy 

cost with load placements.71 A more even distribution 

of loads using a rack system within the pack resulted 

in considerably lower ratings of discomfort in the neck, 

shoulders, and lower back.63 
314

Military Quantitative Physiology: Problems and Concepts in Military Operational Medicine

the load.73 Dynamic moments are about 40% greater 

with high-back placement, an affect attributed to the 

greater rotational inertia of the high load.74

A low- or midback load placement might be preferable for stability on uneven terrain, particularly during 

unexpected stumbles, when high-load placement can 

necessitate relatively high-muscle forces to maintain 

postural stability. The high-load placement might be 

best for even terrain because it keeps body posture with 

a load most similar to that without a load.72

Strap Adjustments 

Although not tested experimentally, it is reasonable 

to assume that shifting loads from one part of the body 

to another during a march can improve soldier comfort 

and allow loads to be carried for longer periods of time. 

Load shifting is accomplished with some pack systems 

using various strap adjustments. Strap adjustments can 

redistribute the load to other muscles or other portions 

of previously loaded muscles. Portions of the body 

subjected to high-load pressures for long periods of 

time can suffer discomfort, circulatory occlusion, and 

paresthesis.30,67,75 

Some rucksacks have sternum straps that are attached horizontally across both shoulder straps at 

midchest level. When the sternum strap is tightened, 

it pulls the shoulder straps toward the midline of the 

body so that pressure is shifted more medially. When 

the sternum strap is loosened, the shoulder straps 

move laterally, and the load is also shifted laterally.

Most pack systems with hip belts and shoulder 

straps have adjustments that presumably allow more 

of the load to be placed on the hips or shoulders. 

When the shoulder strap tension is reduced (straps 

loosened), more of the load is placed on the hips. With 

the shoulder straps tighter, more of the load is placed 

on the shoulders.

Some pack systems have load-lifter straps that attach 

the top of the shoulder straps to the pack frame. When 

the strap is tightened, the top of the load is pulled more 

anteriorly over the base of support; however, when the 

strap is loosened, the top of the load falls more posteriorly. Other strap adjustments that shift load pressures, center the pack, and improve lumbar support 

can further improve soldier mobility and comfort.68

Load Carriage on the Feet, on the Thighs, and 

in the Hands 

Loads can be carried in places other than the torso, 

although other body positions result in higher energy 

expenditure. Loads carried on the feet result in an energy cost five to seven times higher than an equivalent 

load carried on the upper body.44,76,77 The increase in 

energy expenditure is 7% to 10% for each kilogram 

added to the foot.44,76–79 This finding suggests that 

footwear should be as light as possible, compatible 

with durability requirements.

Loads carried on the thigh result in energy costs 

Fig. 11-10. Effects of load distribution within the pack on 

energy cost. A high and more anterior load results in a lower 

energy cost than a low and more posterior load.

Data source: Reproduced with permission from Obusek 

JP, Harman EA, Frykman PN, Palmer CJ, Bills RK. The 

relationship of backpack center of mass to the metabolic 

cost of load carriage. Med Sci Sports Exerc. 1997;29:S205.

Pack

Lower Energy Cost

Higher Energy Cost

 = Center of Load Mass

Pack

Frame

Fig. 11-9. A Marine with a double pack at a forward operating 

base. The marine is from the 26th Marine Expeditionary Unit 

and is boarding for a flight back to Kandahar, Afghanistan, 

in support of Operation Enduring Freedom.

Photograph: Reproduced from DefenseImagery.mil. From 

http://www.defenseimagery.mil. VIRIN: 020212-M7370C-126. Photographer: CWO2 William D. Crow, USMC.
315

Load Carriage in Military Operations: A Review of Historical, Physiological, Biomechanical, and Medical Aspects

that are lower than foot carriage, but greater than 

torso carriage. For each kilogram added to the thighs 

(at about midthigh level), the increase in energy cost 

is about 4%.80,81 When load masses are carried on the 

thighs (compared with the feet), less mechanical work 

is performed because of reduced inertia of the body 

segments; therefore, changes in gait with increasing 

thigh load are minimal.80

Carriage of loads in the hands also results in a 

higher energy cost than with torso carriage36,46,76 and 

produces greater cardiovascular strain.82 Hand carriage 

is more efficient than foot carriage because the energy 

cost of carrying loads on the ankles exceeds that of 

carrying loads in the hands by five to six times if the 

hand load is carried close to the body.44 This is likely 

related to the fact that leg swing is an essential part 

of walking, whereas arm swing is a secondary aspect 

of gait that can be greatly reduced without affecting 

walking speed. For hand carriage tasks (eg, transporting a stretcher), the use of simple shoulder straps or 

more complex harness systems considerably reduce 

cardiovascular stress and result in more subjective 

comfort.83,84

Rifle Carriage 

A rifle will almost always be carried in dismounted 

military training and operations. Rifle carriage restricts arm swing, adds weight, and moves the center 

of mass more anteriorly. During rapid walking (5.4 

km/h), a 4.4-kg rifle (a loaded M16A2 weighs 4.0 kg) 

has minimal, but significant, effects on human gait. 

There are increases in forces produced at heel strike 

(ground impact forces, about 5%), forces to decelerate 

the body (maximum breaking forces, about 1%), and 

side-to-side forces (mediolateral impulse, about 12%). 

Many of these changes are less because of the mass of 

the rifle and more associated with the restriction of 

arm movement, which increases the movement of the 

body center of mass.85,86

Body Armor 

Individual body armor is commonly worn by soldiers to protect against small arms fire and explosive 

devices. The system currently used is the Interceptor 

Multipurpose Body Armor System, consisting of two 

major components: (1) an outer tactical vest (OTV) and 

(2) small arms protective inserts. The OTV is composed 

of a Kevlar weave and provides protection from 9-mm 

bullets and fragmentation. The OTV has a removal 

collar, throat protector, and groin protector. The small 

arms protective inserts are silicon carbide/boron carbide plates worn in the front and back of the OTV, and 

provide protection from rifle and machine gun fire. 

Studies87,88 indicated that additional protection was 

needed and subsequently developed enhancements 

included deltoid and axillary protectors providing 

fragmentation and projectile protection over and under 

the arms (Figure 11-11). A medium-sized vest without 

deltoid and axillary protectors and other vest attachments weighs about 13 kg.89,90

As might be expected, the wearing of body armor 

(compared with no body armor) increases perceived 

exertion, the energy cost of walking, vertical ground 

reaction forces, and loading rate (change in force over 

time from heel strike to peak impact force)91,92; men 

and women respond in a similar manner.93 As walking velocity increases, the increase in energy cost and 

relative exercise intensity (%V

•

O2max) is not linear, but 

rather the increase is exponential.92 A vest increases 

heat stress (core temperature, body heat storage) 

during prolonged (2–4 hours) walking, independent 

of the increase in energy cost, and a spacer garment 

(to presumably provide “passive cooling”) may not 

mitigate this heat stress.94 Soldiers returning from 

deployment report deployment-related increases in 

musculoskeletal pain, with 24%, 29%, and 27% of 

soldiers attributing neck, back, and upper extremity 

pain, respectively, to the wearing of individual body 

armor.89 

Load Carriage Using Carts and Motorized Vehicles 

Military personnel seldom consider using wheeled 

carts to transport loads, but for some missions, this 

can be an option. In a field trial of three manually operated load carts, both positive and negative aspects 

emerged. On the positive side, the tested carts were 

Fig. 11-11. (Left) Interceptor Multipurpose Body Armor 

System with removable collar, throat protector, and groin 

protector. (Center) Deltoid and (right) axillary protectors, 

respectively.

Photographs: Courtesy of GlobalSecurity.org. From http://

www.globalsecurity.org/military/systems/ground/interceptor.htm.
316

Military Quantitative Physiology: Problems and Concepts in Military Operational Medicine

generally durable; able to carry or exceed their rated 

loads (91–181 kg); and were effectively used on flat 

terrain, in barrier construction, and in resupply. On 

the negative side, the carts created problems on rugged terrain: they were noisy in brush or rocky areas, 

thus reducing tactical surprise; and equipment could 

get caught in the wheels of some carts.95

A combat load cart appropriate for military operations should have a low center of gravity, a wide wheel 

base, and a large wheel size.96,97 Compared with body 

carriage, energy cost was reduced by 88% when a 50-

kg load was pushed in a cart on a smooth surface.97

Pulled carts (rather than pushed) seem to be easier to 

control on uneven terrain and also result in considerable energy cost-savings.96 Over mixed terrain (paved 

road, dirt road, field, and rough trail), a cart pulled by a 

hip belt resulted in 54% faster march times (compared 

with a rucksack) over a 3.2-km distance.98 This latter 

cart, specifically developed for military operations, is 

available.

Besides carts, removing much of the load burden 

from the soldier can be achieved through the use of 

a wide variety of motorized vehicles. Systems that 

have carried soldier equipment in rugged areas in 

Afghanistan have included the Military Gator (or 

M-Gator; John Deere Company, Moline, Ill) and the 

Polaris Sportsman Military Vehicle (Polaris Industries, 

Inc, Medina, Minn). The Military Gator is a two-seat, 

six-wheel squad vehicle that can carry up to a 550-kg 

load and runs on JP8 fuel (Figures 11-12 and 11-13). 

The Polaris Sportsman Military Vehicle is a four-wheel, 

all-terrain vehicle that can carry one person and a load 

up to 204.1 kg (Figure 11-14).99,100 Of course, there will 

still be terrain that will not be suitable for carts or 

motorized vehicles of any type, and soldiers will be 

personally required to bear the load.5

Physiological Factors Associated With Load Carriage 

Several studies have examined associations between 

load carriage and various physiological factors using 

very similar methods. Subjects were administered a series of physiological tests to measure physical characteristics, body composition, muscular strength, anaerobic 

capacity, and aerobic capacity. Subjects were asked to 

complete a given distance as rapidly as possible while 

carrying various load masses. Trip completion times 

were correlated with these physiological measures.

Using univariate correlations, early studies demonstrated low (r = 0.2–0.6), but statistically significant, relationships between trip completion times and aerobic 

capacity, back and lower body strength, and fat free 

mass.23,101,102 More recent studies using multivariate 

techniques generally confirm that aerobic fitness, fat 

free mass, and leg/back strength are important physiological factors associated with load carriage performance and changes in load carriage performance.24,25

These studies provide clues as to the components of 

physical fitness that should be trained to improve load 

carriage performance.

Physical Training and Load Carriage 

Appropriately designed physical training can 

improve service members’ load carriage capabilities. 

Walking with backpack loads over several weeks 

Fig. 11-12. The Military Gator. This is a two-seat, six-wheel 

squad vehicle that can carry up to a 550-kg load and runs 

on JP8 fuel.

Photograph: Courtesy of Olive-Drab.com. From http://

www.olive-drab.com/idphoto/id_photos_m-gator.php.

Fig. 11-13. US Army soldiers assigned to the 86th Combat 

Support Hospital using a Military Gator to transport a litter patient at an undisclosed location in Iraq, in support of 

Operation Iraqi Freedom.

Photograph: Reproduced from DefenseImagery.mil. From 

http://www.defenseimagery.mil. ID: DF-SD-04-01753. Photographer: SSGT Quinton T. Burris, US Air Force. 
317

Load Carriage in Military Operations: A Review of Historical, Physiological, Biomechanical, and Medical Aspects

results in a decrease in the energy cost of carrying the 

load.103 Australian military recruits with high initial 

aerobic capacity (predicted V

•

O2max = 51 • mL • kg–1 • 

min–1) further improved their aerobic fitness by engaging in regular backpack load carriage. Loads were progressively increased during the 11-week basic training 

program, and improvements in aerobic capacity were 

similar to those of a control group performing the traditional recruit training program involving running.104

Twelve-week physical training programs involving a combination of aerobic training (running) and 

resistance training improved the speed at which 

men completed a 3.2-km distance carrying 46 kg,105

and women completed a 5-km distance carrying 19 

kg,106 even when these load carriage tasks were not 

included in the training program. It is interesting that 

neither running nor resistance training alone improved 

march speed,105 suggesting that both aerobic capacity 

and muscle strength must be trained to improve road 

marching capability. When regular road marching 

with loads (at least twice a month) was included in a 

training program that also involved running and resistance training, service members marched faster than 

if march training was not included.107 Substantial improvements in load-carrying performance were found 

when civilian women were trained with a combination 

of resistance training, running, and load-carrying.108

Gender Differences 

Compared with men, women walk with shorter 

stride length and greater stride frequency. As loads 

increase, women’s stride length decreases, whereas 

men’s stride length does not show significant change. 

With increasing load, women also show a more pronounced linear increase in the time that both feet are 

on the ground (double support time) than do men. To 

bring the center of the load mass over the feet (base 

of support), women tend to hyperextend their necks 

and bring their shoulders farther forward than do men, 

possibly to compensate for less upper body strength. 

Many of these differences between men and women 

persist even when differences in body size and composition are taken into account.40,50

When men and women were asked to complete 

a 10-km road march as quickly as possible carrying 

loads of 18 kg, 27 kg, and 36 kg (using ALICE packs), 

men were about 21% faster, regardless of load. On 

systematically administered questionnaires, women 

commented more often than men that the pack straps 

were uncomfortable, that the pistol belts fit poorly, and 

that the rucksacks (ALICE packs) were unstable. An 

independent predictor of march time (when gender 

was included in the equation) was acromial breadth 

(shoulder breadth). Because pack systems have been 

designed primarily based on the anthropometry of 

men, these data suggest that pack systems designed 

considering the anthropometry of women can lessen 

the time gap between men and women.109 Studies with 

the MOLLE pack suggest that the well-padded hip 

belt allows a better transfer of the load to the hips so 

that women can use the stronger muscles of the legs 

to carry the load.40,58 This might assist in improving 

female load carriage performance.

Predicting the Energy Cost of Carrying 

Military Loads 

Studies conducted on treadmills for short periods 

of time show that energy cost increases in a systematic 

manner, with increases in body mass, load mass, velocity, grade, or a combination of these items.110–116 Type of 

terrain also influences energy cost, as shown in Figure 

11-15.96,117,118 Pandolf and colleagues119 expanded on the 

work of Givoni and Goldman120 to develop an equation 

(1) to predict the energy cost of load carriage:

(1) Mw = 1.5 • W + 2.0 • (W + L) • (L/W)

2

 + T •

(W + L) • (1.5 • V2 + 0.35 • V • G),

where Mw = metabolic cost of walking (Watts), W = 

body mass (kg), L = load mass (kg), T = terrain factor 

Fig. 11-14. Polaris Sportsman Military Vehicle. It is a fourwheel, all-terrain vehicle that can carry one person and a 

load up to 204.1 kg.

Photograph: Courtesy of Justin Burke, Marketing Manager, 

Polaris Defense, Medina, Minn. From http://www.polarisindustries.com.
318

Military Quantitative Physiology: Problems and Concepts in Military Operational Medicine

velocity or walk rate (m/sec), and G = slope or grade (%).

The Pandolf equation has been independently 

validated using a range of loads and body masses.121

However, the equation has several limitations. First, it 

does not predict accurately the energy cost of downhill 

walking.122,123 Downhill walking energy cost approximates a U-shape when plotted against grade: it initially 

decreases, then begins to increase.124–126 The lowest 

energy cost occurs between –5% to –15%, depending 

on individual gait characteristics.124,126 Santee and colleagues126 developed an empirical model to predict the 

energy cost of downhill walking. The model assumes 

that the initial reduction in downhill walking energy 

cost is from the negative work of gravity, but that this 

is reduced by the eccentric action of the muscles to decelerate the body and energy absorbed by the muscles 

and joints. Equation (2) is as follows:

(2) Wtd = Wl + (2.4 (mt • g • h • s–1) • 0.3(α/7.65)),

where Wtd = total metabolic cost (Watts), Wl = metabolic 

cost of level walking (Watts), mt = total load mass (kg), 

g = acceleration caused by gravity (9.8 m/s2), and α = 

grade or slope for negative work.

A second limitation of the Pandolf equation might 

be that it does not account for increases in energy cost 

over time. In studies used to develop the equation, 

energy cost was examined for short periods, usually 

less than 30 minutes. Most studies127–129 have shown 

that the energy cost of prolonged (≥2 h) load carriage 

at a constant speed increased over time at higher 

loads, or speeds or both. Energy cost also increases 

over time during downhill walking with loads.129

Whether or not energy expenditure increases over 

time is important, because the individual carrying 

the load might become more easily fatigued if energy 

cost does increase.

Fig. 11-15. Effects of terrain on energy cost. Energy cost increases about 8% on a dirt road and about 24% for moving 

through light brush. Much heavier brush requiring the use of 

arms and more lifting of the legs to move over downed trees 

and brush can increase energy cost by 60%. Going through 

swampy land or walking on sand almost doubles energy 

cost. Walking in snow without the use of snowshoes can 

considerably increase energy cost 3 or 4 times, depending on 

the depth and quality of the snow. This increase in energy cost 

with deeper snow is presumably because of the extra energy 

needed to raise the legs. Numbers after the snow estimates are 

the depth of depression the shoe makes in the snow.

Data sources: Haisman MF, Goldman RF. Effect of terrain 

on the energy cost of walking with back loads and handcart 

loads. J Appl Physiol. 1974;36:545–548. Pandolf KB, Haisman 

MF, Goldman RF. Metabolic energy expenditure and terrain 

coefficients for walking on snow. Ergonomics. 1976;19:683–

690. Soule RG, Goldman RF. Terrain coefficients for energy 

cost prediction. J Appl Physiol. 1972;32:706–708.

40

30

20

10

0

VO2 (mL/kg/min)

Treadmill

Paved Road

Dirt Road

Light Brush

Heavy Brush

Swamp

Sand

Snow (10 cm)

Snow (20 cm)

(1.0 = blacktop road, 1.1 = dirt road, 1.2 = light brush, 

1.5 = heavy brush, 1.8 = swampy bog, 2.1 = loose sand, 

snow [dependent on depth of depression {T = 1.30 + 

0.082 • D, where D = depression depth in cm}]),117 V = 

MEDICAL PROBLEMS ASSOCIATED WITH LOAD CARRIAGE 

Injuries associated with load carriage, although 

generally minor, can adversely affect an individual’s 

mobility and thus reduce the effectiveness of an entire 

unit. Tables 11-4 and 11-5 show the results of two studies that recorded acute injuries during military road 

marching operations.130,131 Foot blisters, back problems, 

and metatarsalgia were the most common marchrelated injuries. These injuries are similar to those selfreported by recreational hikers who generally carry 

lighter loads, but the relative frequency is somewhat 

different.132–134 Table 11-6 summarizes common load 

carriage-related injuries, as well as prevention and 

treatment strategies.

Foot Blisters 

Foot blisters are the most common load carriage–

related injury65,131,135–137 (Figure 11-16). They result from 

friction between the socks and skin,138–140 a product of 

point pressures exerted by the boot and the foot. Blisters 

can cause extreme discomfort, prevent service members 

from completing marches, and lead to many days of 

limited activity.131,141,142 If they are not properly managed, especially in field conditions, they can progress to 

more serious problems, such as cellulitis or sepsis.141,143

Heavy loads increase blister incidence,109,137,144

possibly by increasing pressure on the skin and causing 
319

Load Carriage in Military Operations: A Review of Historical, Physiological, Biomechanical, and Medical Aspects

TABLE 11-4 

INJURIES AMONG 355 INFANTRY SOLDIERS DURING A 20-KM MAXIMAL EFFORT ROAD MARCH

During March* Totals

 Soldier

Injury Soldier Continued March (n) Did Not Continue March (n) 1–12 Days Post-march (n)† N %

Foot blisters 16 0 19 35 38

Back pain/strain 5 7 9 21 23

Metatarsalgia 1 1 9 11 12

Leg strain/pain 0 0 7 7 8

Sprains 1 1 4 6 7

Knee pain 0 0 4 4 4

Foot contusion 0 1 1 2 2

Other 1 2 2 5 5

Total 24 12 55 91 100

*From medics and physician during the march.

†From medical records after the march.

Data source: Knapik J, Reynolds K, Staab J, Vogel JA, Jones B. Injuries associated with strenuous road marching. Mil Med. 1992;157:64–67.

TABLE 11-5

INJURIES AMONG 218 INFANTRY SOLDIERS DURING A 5-DAY, 161-KM ROAD MARCH

During March* Totals

 Soldier

Injury Soldier Continued March (n) Did Not Continue March (n) 1–15 Days Post-march (n)† N %

Foot blisters 43 3 3 49 48

Metatarsalgia 8 2 9 19 19

Back pain/strain 4 1 1 6 6

Sprains 2 3 0 5 5

Knee pain 3 1 3 7 7

Ingrown toenail 0 3 0 3 3

Stress fracture 0 1 0 1 1

Other 8 3 1 12 12

Total 68 17 17 102 100

*From physician’s assistants at fixed medical sites along the march.

†From medical records after the march.

Data source: Reynolds KL, White JS, Knapik JJ, Witt CE, Amoroso PJ. Injuries and risk factors in a 100-mile (161-km) infantry road march. 

Prev Med. 1999;28:167–173.

more movement of the foot inside the boot through 

higher propulsive and breaking forces.49,145 Rifle carriage alone has minor effects on maximal breaking and 

propulsive forces.85 Other blister risk factors include 

tobacco use, low aerobic fitness, and ethnicity other 

than black.130,146

When loads are very heavy (>61 kg), the double 

pack has been shown to demonstrate a lower blister 

incidence than the backpack,147 suggesting that better load distribution can reduce blisters. Spenco shoe 

insoles (Spenco Medical Corporation, Inc, Waco, Tex) 

have also been shown to reduce foot blister incidence, 

possibly because they absorb frictional forces in anteroposterior and mediolateral directions.148–150 Regular physical training with load carriage induces skin 

adaptations that reduce the probability of blisters.140

Thus, blisters can be less of a problem in units that 

march regularly; however, sudden increases in march 
320

Military Quantitative Physiology: Problems and Concepts in Military Operational Medicine

TABLE 11-6 

SUMMARY OF COMMON LOAD CARRIAGE-RELATED INJURIES WITH PREVENTION AND 

TREATMENT STRATEGIES*

Injury Signs and Symptoms Prevention Treatment

Foot blisters Elevated area, lighter 

in color than surrounding skin, and filled with 

fluid; pain, burning, 

warmth, and erythema

1. Use acrylic, nylon, or polyester inner sock; use thick, 

snug, dense-weave outer 

sock with inner sock

2. Use Spenco† insoles

3. Utilize antiperspirants

4. Make sure that load distribution is more evenly around 

the body center of mass

5. Reduce load mass

6. Precondition feet through 

physical training and road 

march practice

7. Improve aerobic fitness 

8. Cease smoking/tobacco use

9. Cover skin when hot spots 

appear

Intact blister: drain, leave top 

in place, and use light pressure 

dressing

Torn blister: remove top, use 

antibiotic ointment, and put 

on surgical bandage 

Use hydrogel or hydrocolloid 

dressings; also polyurethane 

films

Metatarsalgia Pain, swelling on sole of 

foot

1. Precondition feet through 

physical training and road 

march practice

2. Reduce load mass

RICE‡

Antiinflammatory medication§

Stress fractures Persistent, bony pain; 

well-circumscribed 

palpable area of bony 

tenderness

1. Cease smoking/tobacco use

2. Precondition feet and legs 

through physical training 

and road march practice

RICE

Antiinflammatory medication

Knee pain Pain, swelling, crepitus, 

and instability

1. Perform lower extremity

 strengthening 

2. Perform lower extremity 

stretching

RICE

Antiinflammatory medication

Low-back pain Pain, muscle spasm, and 

neurological symptoms

1. Be sure that load distribution is more evenly around 

the body center of mass

2. Reduce load mass

3. Perform trunk and abdominal strengthening

RICE

Antiinflammatory medication

Rucksack palsy Upper extremity numbness, paralysis, and 

cramping; scapular 

winging

1. Use framed rucksack

2. Utilize hip belt on rucksack

3. Employ load shifting via 

strap adjustments

RICE

Antiinflammatory medication

Meralgia paresthetica Pain, paresthesia, and 

weakness in the anterolateral thigh

1. Use properly fitted body 

armor

2. Avoid compressing thighs 

with lower edge of body 

armor

Reduce body armor wear

Antiinflammatory medication

*See text for full descriptions and applications.

†

Spenco Medical Corporation, Inc, Waco, Tex.

‡

RICE: Rest, Ice, Compression, Elevation. §

Antiinflammatory medication refers to aspirin or a nonsteroidal antiinflammatory drug.

Data sources: Knapik JJ, Reynolds KL, Duplantis KL, Jones BH. Friction blisters: pathophysiology, prevention and treatment. Sports Med. 

1995;20:136–147. Jones BH, Reynolds KL, Rock PB, Moore MP. Exercise related musculoskeletal injuries: risks, prevention and care. In: 

Durstine JL, King AC, Painter PL, et al, eds. ACSM’s Resource Manual for Guidelines for Exercise Testing and Prescription. Philadelphia, Pa: Lea 

and Febiger; 1993.
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Load Carriage in Military Operations: A Review of Historical, Physiological, Biomechanical, and Medical Aspects

intensity or distance will probably make blisters more 

likely, regardless of training regularity.

Moist skin increases frictional forces and probably 

increases blister incidence.140,141,151 Acrylic socks decrease 

the number and size of blisters,152 possibly by conducting sweat away from the foot.153 A nylon sock worn 

inside a wool sock reduces the incidence of blisters on 

soldiers who are road marching.154,155 Polyester socks 

alone, or a thin polyester sock worn inside thicker socks 

(that are either wool-polypropylene or cotton-wool), reduce foot blister incidence during military training.156,157

Antiperspirants also reduce foot sweating,158,159 and 

some anecdotal reports and case studies suggest they 

might be effective in reducing blisters.160–162 A 20% solution of aluminum chloride hexahydrate in an anhydrous 

ethyl alcohol base (eg, Drysol, Person & Covey, Inc, 

Glendale, Calif) was effective in reducing the likelihood of march-related blisters when the preparation 

was applied to the entire foot for at least three nights 

before a march.163Once the antiperspirant effect has been 

achieved, it can be maintained with applications once 

per week.164 However, many individuals report irritant 

dermatitis using this preparation,163 which can require 

the application of a topical steroid. Other options in this 

case include using a lower concentration preparation 

(eg, Xerex, Person & Covey, Inc, Glendale, Calif), changing the treatment schedule (using the same number of 

applications, but over a longer period of time), or discontinuing use. Antiperspirants in emollient bases are 

not effective in reducing blisters, presumably because 

emollients interfere with the antiperspirant effect.165

Soldiers typically experience areas of friction known 

as “hot spots,” the subjective experience of which is a 

localized warm or burning sensation. This presumably 

preblister stage is characterized as a local red (erythema) and tender area (Figure 11-17). When hot spots 

are detected, blisters may be avoided by shielding the 

affected area with a low-friction skin covering. Various 

skin coverings have been examined for their coefficients of friction (μ), and lower μ values may be more 

effective in reducing blister incidence. Tested skin coverings (with μ values in brackets) include the following:

• Bursatec (Bursatec, Mexico City, Mexico)[0.57], 

• Dr. Scholl’s Moleskin Plus (Schering-Plough 

HealthCare Products, Inc, Memphis, Tenn) 

[0.69],

• Moleskin [0.94], 

• Band-AidBrand Adhesive Bandages (Johnson 

& Johnson Consumer Companies, Inc, New 

Brunswick, NJ) [1.01], 

• Band-Aid Plastic Bandages [1.03], 

• Spenco 2nd Skin Blister Pad [1.04], 

• New-Skin (Prestige Brands, Inc, Irvington, 

NY) [1.05], 

• Nexcare Comfort Bandage (3M Company, St 

Paul, Minn) [1.08], 

• Dr. Scholl’s Blister Treatment [1.20], 

• Band-Aid Blister Block [1.37], and 

• Tegaderm (3M Company, St Paul, Minn) 

[1.54].166

Fig. 11-16. Friction blisters on the feet.

Photograph: Courtesy of Wikimedia Commons. From 

http://commons.wikimedia.org/wiki/File:Friction_Blisters_On_Human_Foot.jpg. 

Fig. 11-17. A “hot spot” on the medial aspect of a soldier’s 

foot during a road march.
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Military Quantitative Physiology: Problems and Concepts in Military Operational Medicine

Another option is a doughnut pad or covering 

(eg, DuoDERM, ConvaTec, Inc, Skillman, NJ), which 

should be applied to reduce friction and possible blister 

development.167

There are few studies of blister treatment, and care is 

based on clinical experience and common sense. Small 

blisters (<5 mm) are usually self-limiting and should 

not be drained unless they are painful, because of the 

risk of infection.168 A small, doughnut-shaped moleskin 

pad can be placed over the blister to prevent rupture. If 

the blister is larger than 5 mm and on a weight-bearing 

area, it should be drained. To promote blister-top adhesion and healing, blister drainage should occur at the 

proper time. For blisters less than 24 hours old, several 

punctures should be made with a sterile needle or a 

no. 11 surgical blade (Figure 11-18). For older blisters, 

a single puncture is recommended.169 Tops should 

be kept in place to serve as functional dressings.170 A 

pressure dressing (eg, gauze pad and adhesive tape) 

can be applied to ensure that the blister roof adheres to 

the underlying tissue. If the top of the blister is almost 

completely torn off, it should be removed171 and the 

site treated as an open wound. In addition to antiseptic 

treatments (eg, antibiotic ointment), a surgical bandage 

should be applied.169 For smaller blisters, a doughnutshaped moleskin pad affixed with a porous adhesive 

knit cover (eg, Coverlet, BSN-Jobst, Charlotte, NC) will 

protect the blister as shown in Figure 11-19; for larger 

blisters, a larger dressing will be needed.162,164 Hydrogel dressings (Figure 11-20) (eg, Spenco 2nd Skin) or 

polyurethane films (eg, Tegaderm) can be affixed to 

the blister and covered with a pad and tape.169,172 Hydrocolloid dressings, such as DuoDERM (ConvaTec, 

Inc), can also be helpful in allowing mobility173 and 

promoting healing.172,174,175 

Metatarsalgia 

Metatarsalgia is a descriptive term for nonspecific, 

painful overuse injury of the foot. The usual symptom 

is localized tenderness on the sole of the foot under 

the second or third metatarsal head (Figure 11-21). 

Sutton176 reported a 20% incidence of metatarsalgia 

during a strenuous 7-month Airborne Ranger physical 

training program that included regular load carriage. 

One study131 reported a 3.3% incidence of metatarsalgia after a single, strenuous 20-km walk with soldiers 

carrying 45 kg. 

Metatarsalgia is usually associated with foot strain 

caused by rapid changes in the intensity of weightbearing activity.177 Walking with heavy loads can 

be a predisposing factor for metatarsalgia, because 

this might cause the foot to rotate anteroposteriorly 

around the distal ends of the metatarsal bones for 

more prolonged periods of time, thus resulting in more 

mechanical stress in this area.49

Treatment is conservative and includes rest, use of 

ice packs, elevation of the foot, and antiinflammatory 

medications. A metatarsal pad can be used. If symptoms persist, despite these conservative measures, 

further evaluation for more serious problems (eg, 

fractures, tumors) is warranted.178

Fig. 11-19. Treatment for smaller blisters. A doughnutshaped moleskin pad affixed with a porous adhesive cover 

(eg, Coverlet, BSN-Jobst, Charlotte, NC) will protect the 

blister.

Illustration: Reproduced from the US Army Research Institute of Environmental Medicine (Natick, Mass).

Antiseptic

ointment

Adhesive

cover

Doughnut moleskin pad

Fig. 11-18. Friction blisters showing suggested puncture 

sites to drain the blister. For blisters less than 24 hours old, 

several punctures should be made with a sterile needle or a 

no. 11 surgical blade.

Illustration: Courtesy of Heidi Moncrief, Healthwise, Inc, Boise, Idaho. From http://64.143.176.9/library/healthguide/

en-us/images/media/medical/hw/hwkb17_072.jpg.
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Load Carriage in Military Operations: A Review of Historical, Physiological, Biomechanical, and Medical Aspects

Stress Fractures 

Lower extremity stress fractures are common in 

military recruits179–184 and have also been reported in 

trained soldiers.184 During the Central Burma campaign in World War II, 60 stress fracture cases were 

reported in one infantry unit during a 483-km road 

march.185

Stress fractures are attributable to repetitive 

overloading of bones during activities, such as road 

marching. The most common areas of involvement 

are the lower extremities, especially the tibia, tarsals, 

and metatarsals.179,185–190 For metatarsal stress fractures, 

tenderness is generally localized on the dorsal side of 

the metatarsal shafts, which distinguishes the pain 

from metatarsalgia (Figure 11-22). Figure 11-23 shows 

X-ray films of a metatarsal stress fracture when the 

patient first presented and 3 weeks later. Generally, a 

period of time is necessary before stress fractures are 

apparent on X-ray films. 

Demonstrated risk factors for stress fractures include the following: 

• female gender,179,184,191–194

• white ethnicity,179,195–197

• older age,179,196,197

• taller body stature,182

• high foot arches,198,199

• low aerobic fitness,192,196

• prior physical inactivity,182,196,197 

• older running shoes,197 

• genu varus,200 and 

• cigarette smoking.195,201 

Other factors that might increase risk include load 

carriage distance184,202 and walking style.182,203 

A number of interventions have been tested in an effort to reduce the incidence of stress fractures.191,197,204–210

All studies were conducted in basic combat training. 

Successful interventions include reduced running 

mileage,204 neoprene boot insoles,206 and calcium/vitamin D supplementation.211,212 A multiple intervention 

Fig. 11-20. Other ways of protecting blisters. Hydrogel dressings such as Spenco 2nd Skin (Spenco Medical Corporation, 

Waco, Tex) or a polyurethane film such as Tegaderm (3M 

Company, St Paul, Minn) can be afixed to the blister and 

covered with a pad and tape.

Illustration: Reproduced from the US Army Research Institute of Environmental Medicine (Natick, Mass).

Adhesive tape

Gauze pad

Hydrogel dressing

Fig. 11-21. Sites of metatarsalgia. The usual symptom is localized tenderness on the sole of the foot under the second or 

third metatarsal head. 

Illustration: Reproduced from the US Army Research Institute of Environmental Medicine (Natick, Mass).

Sites of

tenderness

Sole of foot

Fig. 11-22. Symptom of metatarsal stress fracture. Tenderness 

is generally localized on the dorsal side of the metatarsal 

shafts, which distinguishes the pain from metatarsalgia.
324

Military Quantitative Physiology: Problems and Concepts in Military Operational Medicine

study in Australian basic training demonstrated that 

reducing march speed, allowing trainees to march at 

their own step length (rather than marching in step), 

running and marching in more widely spaced formations, running on grass, and reducing running mileage were successful in reducing female pelvic stress 

fractures.205

Stress fracture treatment includes a long period of 

rest, use of ice packs, and antiinflammatory medications. If the patient has to be mobile, crutches are 

necessary.

Knee Pain 

Knee pain is another condition that has been associated with load carriage. Dalen and colleagues213

reported a 15% incidence of knee pain (17 cases of 

114 subjects) during their load carriage study. Knapik 

and colleagues131 reported only a 0.6% incidence of 

knee pain (2 cases of 335 subjects) following a single 

strenuous walk, but the two cases resulted in a total 

of 14 days of disability.

Knee pain is difficult to diagnose. Various disorders include patellofemoral pain syndrome, patellar 

tendonitis, bursitis, and ligamentous strain. These 

conditions can arise from an abrupt increase in road 

marching mileage or intensity or from climbing hills 

if service members have not been conditioned for 

this activity. Treatment includes rest, use of ice packs, 

and antiinflammatory medications. Quadriceps and 

hamstring strengthening and stretching exercises, 

along with heel cord stretching, may be important to 

prevent recurrence.214

Low Back Injuries 

Low back injuries can pose a significant problem 

during load carriage. In one study,131 50% of the soldiers who were unable to complete a strenuous 20-km 

walk reported problems associated with their backs. 

Dalen and colleagues213 reported frequent problems 

with back strain during a 20- to 26-km walk. Low back 

injuries are difficult to define because the pain might 

result from trauma to a variety of structures, including 

spinal discs, the ligaments connecting the vertebral 

bodies, nerve roots, or supporting musculature.177

Heavy loads can be a risk factor for back injuries.137

This could be because heavier loads lead to changes 

in trunk angle, which can stress back muscles,52,53,215 or 

because heavier loads do not move in synchrony with 

the trunk,53,216 thus causing cyclic stress of the back 

muscles, ligaments, and spine.52,53 Framed packs exert 

a consistent anterior force on the lower back, and it 

has been suggested that this force could contribute to 

low back pain and soreness.58 Walking with a frameless pack for a relatively short period of time (18 min) 

results in a greater anterior curvature of the spine, 

which could result in moments of greater posteriorcompressive/anterior-tensile forces on intervertebral 

discs.217 The double pack can help reduce the incidence 

of back problems because it results in a more normal 

posture and eliminates prolonged bending of the 

back.49,58 Thus, better load distribution could reduce 

back injuries. Also, a general overall strengthening and 

warm-up program involving the back, abdomen, hamstrings, and hip muscles can assist in prevention.177

Rucksack Palsy 

Rucksack palsy is a disabling injury that has 

been widely reported in association with load carriage.75,176,218–225 The incidence of rucksack palsy was 

reported to be, respectively, 1.2/1,000 and 0.2/1,000 

in US Army basic training when wearing a rucksack 

alone versus a rucksack with a frame and hip belt218; 

the incidence in Finnish basic training was reported 

to be 0.5/1,000 recruits.226 It is hypothesized that the 

shoulder straps of a backpack or the top portion of 

individual body armor when in certain postures can 

cause a traction injury of the C5 and C6 nerve roots of 

the upper brachial plexus. In minor cases, compression 

results in entrapment of the long thoracic nerve. Symptoms include numbness, paralysis, and cramping, 

and minor pain in the shoulder girdle, elbow flexors, 

and wrist extensors. Long thoracic nerve injuries usually present with “scapular winging” (Figure 11-24) 

because of weakness of the serratus anterior muscle. 

Sensorimotor deficits from rucksack palsy injuries 

Fig. 11-23. X-ray films of a metatarsal stress fracture when 

the patient first presented to the clinician (left) and 3 weeks 

later (right). 

Photographs: Courtesy of Keith G Hauret, MSPH, MPT.
325

Load Carriage in Military Operations: A Review of Historical, Physiological, Biomechanical, and Medical Aspects

are usually temporary, but, in some cases, can result 

in a chronic condition. Nerve conduction studies and 

electromyographic studies might be necessary to document this condition.218,221

Use of a backpack frame and hip belt have been 

demonstrated to reduce the incidence of rucksack 

palsy,218 presumably by reducing pressure on the shoulders.57,58 Hypothetical risk factors for rucksack palsy 

include heavy loads, improper load distribution, and 

longer carriage distances.137,218 Height, weight, body 

mass index, or aerobic fitness were not risk factors in 

Finnish basic training.226

Meralgia Paresthetica 

Meralgia paresthetica is an abnormal condition 

characterized by pain and paresthesia in the outer 

anterolateral thigh. It is caused by a compression of 

the lateral femoral cutaneous nerve, a sensory nerve 

branch of the L2/L3 spinal area. A recent report of two 

cases of this disorder suggests that when soldiers are 

wearing body armor and are seated for long periods, 

the lower edge of the body armor may compress the 

inguinal region, thus resulting in a compression of the 

lateral femoral cutaneous nerve and leading to pain 

and paresthesia. Symptoms generally resolve with 

removal of the chronic compression.227

Fig. 11-24. Scapular winging.

Photograph: Courtesy of Dwaipayan Chakraborti. From 

http://en.wikipedia.org/wiki/File:Wingingofscapula.jpg.

INFLUENCE OF LOAD CARRIAGE ON THE PERFORMANCE OF OTHER TASKS 

A significant consideration from a military perspective is how well service members are able to 

perform military tasks during load carriage. Load 

mass, load volume, and load distribution seem to 

be important variables. As the mass increases, there 

are systematic decrements in the performance of 

specific tasks (eg, short sprints, agility runs, ladder 

climbs, and obstacle courses).67,228 The decrement in 

performance of such tasks is estimated at about 1% 

per kilogram load.67 Loads of greater volume will inhibit movement under obstacles. The distribution of 

the load within the backpack can also influence performance of specific tasks.67 Wearing of individual 

body armor (10 kg) results in increased perceived 

exertion and decrements in pull-up performance, 

flexed arm hang time, and maximal stair-stepping 

ability,91 which may be relevant to some soldier 

tasks like climbing over obstacles and movements 

in urban buildings.

In some operations, service members are required 

to walk long distances and perform critical military 

tasks at the completion of the march. Very strenuous marches (maximal speed with loads of 34–61 

kg over 10- to 20-km distances) lead to postmarch 

decrements in marksmanship and grenade-throwing 

distance.64,109,144 Decrements in marksmanship are 

presumably attributable to small movements of the 

rifle, resulting from fatigue of the upper body muscle 

groups, fatigue-induced tremors, or elevated heart 

rate or respiration.64,144,229 The decrements in grenadethrowing distance might be from nerve entrapment 

syndrome218,221 or pain in the shoulder area, both 

resulting from pressure of the rucksack straps. Lower 

body muscular power (as measured by the vertical 

jump and Wingate’s Anaerobic Test [which measures 

anaerobic capacity using a bicycle ergometer]) and 

muscle strength do not appear to be adversely affected 

by prolonged pack load carriage.64,109,144,230

SUMMARY 

There are several ways to improve military load 

carriage. The techniques most available to unit commanders are load reduction, load redistribution, and 

physical training. Load reduction can be accomplished 

by tailoring the load to the specific objective and by 

using special load-handling devices. Commanders 

must make realistic risk analyses and then take only the 

equipment necessary for the mission. Special combat 

load carts are available that could be useful in special 

situations (eg, marches on unobstructed terrain or in 
326

Military Quantitative Physiology: Problems and Concepts in Military Operational Medicine

close resupply operations).

Load redistribution can be accomplished by placing 

equipment more evenly around the torso. Current load 

carriage systems have attachment points and pockets 

that can be useful for moving some items from the rucksack to the front of the body. Items carried on the front of 

the body should be those likely to be needed suddenly 

or needed often. The most advantageous distribution 

of the load in the pack might depend on the type of 

terrain. On roads or well-graded paths, placement of 

heavy items high in the pack is preferable for maintaining a more upright body posture and reducing low back 

problems. On uneven terrain, a more even distribution 

of the load within the pack is more helpful to maintain 

stability. Load reduction and redistribution can reduce 

energy cost, decrease injuries, and improve performance 

on tasks following load carriage.

Physical training that includes aerobic exercise, 

resistance exercise, and road marching should be performed on a regular basis. Appropriate programs can 

be tailored to unit needs based on previously successful 

programs. Road marching should be conducted at least 

twice each month, with loads that service members 

will be expected to carry in unit operations (this could 

be in place of regular physical training). Load and 

distance should be increased gradually over sessions 

until a maintenance level has been achieved. New unit 

members should be given time to adapt through the 

same gradual program. Regular physical training has 

been shown to increase march performance and might 

reduce injuries.

To some extent, the selection and proper use of 

equipment can assist in reducing load-carrying stress. 

The MOLLE pack has a frame with a well-padded hip 

belt that reduces pressure on the shoulders, results 

in less perceived strain, and reduces the incidence of 

some injuries. Frames and hip belts can improve service members’ performance on tasks requiring use of 

the upper body. Equipment such as the sternum strap 

on the MOLLE packs reduces stress by allowing pressure to be distributed to other parts of the body. The 

MOLLE pack also provides some ventilation across 

the back because of its external frame construction. 

New load carriage technologies that are being tested 

and will become available will use many of the ideas 

and principles discussed in this chapter. 

It is desirable to reduce load carriage-related injuries 

that impair performance, cause discomfort and disability, and result in a loss of manpower. The use of 

hip belts can reduce the incidence of rucksack palsy. 

Keeping the feet dry using an acrylic, polypropylene, 

or nylon inner socks combined with wool or woolpolypropylene outer socks will reduce the incidence 

of blisters. Antiperspirants (applied for at least three 

consecutive days before a march) and frequent changes 

of socks can also be helpful. Blister incidence can be 

reduced by using Spenco insoles (Spenco Medical 

Corporation) and by distributing the load more evenly 

around the torso (both of which can reduce frictional 

forces around the foot). Physical training directed at 

improving aerobic fitness, along with regular load 

carriage marches, can reduce the incidence of stress 

fractures and blisters. In basic training, stress fractures 

can also be controlled by using neoprene insoles, limiting running mileage, allowing trainees to march at 

their own stride length, and using more widely spaced 

formations.

Making loads lighter, improving load distribution, 

using appropriate physical training, selecting proper 

equipment, and choosing specific techniques directed 

at injury prevention will all facilitate load carriage. 

Suitable changes will allow service members to continue missions at lower energy costs and with fewer 

injuries, and be better able to perform other tasks.

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