A Human Factors Evaluation of Exoskeleton 

Boot Interface Sole Thickness 

by Angela C. Boynton and Harrison P. Crowell III 

ARL-TR-3812 June 2006 

Approved for public release; distribution is unlimited.
NOTICES 

Disclaimers 

The findings in this report are not to be construed as an official Department of the Army position 

unless so designated by other authorized documents. 

Citation of manufacturer’s or trade names does not constitute an official endorsement or 

approval of the use thereof. 

DESTRUCTION NOTICE⎯Destroy this report when it is no longer needed. Do not return it to 

the originator. 
Army Research Laboratory 

Aberdeen Proving Ground, MD 21005-5425 

ARL-TR-3812 June 2006 

A Human Factors Evaluation of Exoskeleton 

Boot Interface Sole Thickness 

Angela C. Boynton and Harrison P. Crowell III 

Human Research and Engineering Directorate, ARL 

Approved for public release; distribution is unlimited.
ii 

REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining 

the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for 

reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, 

VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not 

display a currently valid OMB control number. 

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 

1. REPORT DATE (DD-MM-YYYY)

 June 2006 

2. REPORT TYPE 

Final 

3. DATES COVERED (From - To) 

 January 2003 through March 2003 

5a. CONTRACT NUMBER 

5b. GRANT NUMBER 

4. TITLE AND SUBTITLE 

 

 A Human Factors Evaluation of Exoskeleton Boot Interface Sole Thickness 

5c. PROGRAM ELEMENT NUMBER 

5d. PROJECT NUMBER 

 62716AH70 

5e. TASK NUMBER 

6. AUTHOR(S) 

 Angela C. Boynton and Harrison P. Crowell III (both of ARL) 

5f. WORK UNIT NUMBER 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

 U.S. Army Research Laboratory 

 Human Research and Engineering Directorate 

 Aberdeen Proving Ground, MD 21005-5425

8. PERFORMING ORGANIZATION 

 REPORT NUMBER 

ARL-TR-3812

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) 

11. SPONSOR/MONITOR'S REPORT 

 NUMBER(S) 

12. DISTRIBUTION/AVAILABILITY STATEMENT 

 Approved for public release; distribution is unlimited. 

13. SUPPLEMENTARY NOTES 

14. ABSTRACT 

The purpose of this study was to identify potential human factors issues related to the sole thickness of an exoskeleton boot 

interface. Twelve Soldiers were evaluated in three footwear conditions (no additional sole, 1-inch sole, and 2-inch sole). 

Lower extremity biomechanics were assessed for walking, running, squatting, and kneeling with the use of a force plate and 

motion capture system. Mobility performance was assessed with five obstacles on a mobility-portability course. 

Participants also provided subjective feedback on each footwear condition’s comfort, stability, and difficulty during the 

biomechanics and mobility assessments. Results indicate that an exoskeleton could incorporate a boot interface as thick as 2 

inches without substantially impacting the human factors issues evaluated in this study. 

15. SUBJECT TERMS

 biomechanics; exoskeleton; human factors 

16. SECURITY CLASSIFICATION OF:

19a. NAME OF RESPONSIBLE PERSON

 Angela C. Boynton 

a. REPORT 

Unclassified 

b. ABSTRACT 

Unclassified 

c. THIS PAGE 

Unclassified 

17. LIMITATION 

OF ABSTRACT 

SAR 

18. NUMBER 

OF PAGES 

65 19b. TELEPHONE NUMBER (Include area code) 

 410-278-3621 

Standard Form 298 (Rev. 8/98) 

Prescribed by ANSI Std. Z39.18
iii 

Contents 

List of Figures v

List of Tables vi

Acknowledgments vii

Executive Summary 1

1. Introduction 3

2. Objectives 4

3. Methodology 4

3.1 Participants ......................................................................................................................4 

3.2 Apparatus.........................................................................................................................5 

3.2.1 Clothing...............................................................................................................5 

3.2.2 Force Plate (Advanced Mechanical Technology, Inc., Newton, MA) ................5 

3.2.3 Motion Analysis System (Motion Analysis Corporation, Santa Rosa, CA) .......6 

3.2.4 Visual3D Movement Analysis Software (D-Motion, Inc., Rockville, MD) .......8 

3.2.5 U.S. Army Research Laboratory (ARL) Mobility-Portability Course................8 

3.3 Procedures .....................................................................................................................10 

3.3.1 Volunteer Consent.............................................................................................10 

3.3.2 Training .............................................................................................................10 

3.3.3 Data Collection..................................................................................................11 

3.4 Experimental Design .....................................................................................................11 

3.4.1 Independent Variables.......................................................................................11 

3.4.2 Dependent Variables .........................................................................................12 

3.4.3 Statistical Analysis ............................................................................................12 

4. Results 13

4.1 Biomechanical Variables...............................................................................................13 

4.2 Obstacle Completion Times ..........................................................................................15 

4.3 Comfort, Stability, and Difficulty Questionnaire Responses........................................16 
iv 

5. Discussion 16

6. Conclusions 18

7. References 19

Appendix A. Three-Dimensional Biomechanics Terminology (from Hamill & 

 Knutzen, 2003) 21

Appendix B. Comfort, Stability, and Difficulty Questionnaire 23

Appendix C. Biomechanical Variables Data Tables 25

Distribution List 52
v 

List of Figures 

Figure 1. Overboot and sole setup. ................................................................................................ 6 

Figure 2. Walking, running, squatting, and kneeling on the walkway and force plate.................. 7 

Figure 3. Reflective marker placement (red used for the neutral trial only, black used for 

neutral and motion trials) ........................................................................................................ 8 

Figure 4. Obstacles on ARL’s mobility-portability course.......................................................... 14 

Figure 5. Mean values for squat/kneel group biomechanical variables significantly affected 

by footwear condition. .......................................................................................................... 14 

Figure 6. Mean values for obstacle times significantly affected by trial..................................... 15 

Figure 7. Mean values for questionnaire responses across footwear conditions. ........................ 16 

Figure A-1. Planes of motion and axes of rotation. ..................................................................... 21 

Figure A-2. Joint motion terminology. ........................................................................................ 22 

Figure D-1. Joint angles (degrees) over one stride of walking: (Blue=Baseline, Green= 

1-inch Sole, Red=2-inch Sole), N=12, 0%=Begin Stance, vertical lines=Begin Swing, 

100%= End Swing. ...............................................................................................................36 

Figure D-2. Joint moments (Nm/kg) over one stride of walking: (Blue=Baseline, Green= 

1-inch Sole, Red=2-inch Sole), N=12, 0%=Begin Stance, vertical lines=Begin Swing, 

100%= End Swing. ...............................................................................................................37 

Figure D-3. Joint powers (W/kg) over one stride of walking: (Blue=Baseline, Green= 

1-inch Sole, Red=2-inch Sole), N=12, 0%=Begin Stance, vertical lines=Begin Swing, 

100%= End Swing. ...............................................................................................................38 

Figure D-4. Joint angle (degrees) over one stride of running: (Blue=Baseline, Green= 

1-inch Sole, Red=2-inch Sole), N=12, 0%=Begin Stance, vertical lines=Begin Swing, 

100%= End Swing. ...............................................................................................................39 

Figure D-5. Joint moments (Nm/kg) over one stride of running: (Blue=Baseline, Green= 

1-inch Sole, Red=2-inch Sole), N=12, 0%=Begin Stance, vertical lines=Begin Swing, 

100%= End Swing. ...............................................................................................................40 

Figure D-6. Joint powers (W/kg) over one stride of running: (Blue=Baseline, Green=1-inch 

Sole, Red=2-inch Sole), N=12, 0%=Begin Stance, vertical lines=Begin Swing, 100%= 

End Swing.............................................................................................................................41 

Figure D-7. Ground reaction forces (N/BW) over one stride of walking and running: 

(Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12, 0%=Begin Stance, 

vertical lines=Begin Swing, 100%=End Swing....................................................................42 

Figure D-8. Joint angles (degrees) over one cycle of squatting: (Blue=Baseline, Green= 

1-inch Sole, Red=2-inch Sole), N=12...................................................................................43 

Figure D-9. Joint moments (Nm/kg) over one cycle and squatting: (Blue=Baseline, Green= 

1-inch Sole, Red=2-inch Sole), N=12...................................................................................44 

Figure D-10. Joint powers (W/kg) over one cycle of squatting: (Blue=Baseline, Green= 

1-inch Sole, Red=2-inch Sole), N=12...................................................................................45 

Figure D-11. Joint angles (degrees) over one cycle of right kneeling: (Blue=Baseline, 

Green=1-inch Sole, Red=2-inch Sole), N=12.......................................................................46 
vi 

Figure D-12. Joint moments (Nm/kg) over one cycle of right kneeling: (Blue=Baseline, 

Green=1-inch Sole, Red=2-inch Sole), N=12.......................................................................47 

Figure D-13. Joint powers (W/kg) over one cycle of right kneeling: (Blue=Baseline, 

Green=1-inch Sole, Red=2-inch Sole), N=12.......................................................................48 

Figure D-14. Joint angles (degrees) over one cycle of left kneeling: (Blue=Baseline, 

Green=1-inch Sole, Red=2-inch Sole), N=12.......................................................................49 

Figure D-15. Joint moments (Nm/kg) over one cycle of left kneeling: (Blue=Baseline, 

Green=1-inch Sole, Red=2-inch Sole), N=12.......................................................................50 

Figure D-16. Joint powers (W/kg) over one cycle of left kneeling: (Blue=Baseline, 

Green=1-inch Sole, Red=2-inch Sole), N=12.......................................................................51 

Figure D-17. Ground reaction forces (N/BW) over one cycle of squatting, right kneeling, 

and left kneeling: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12..............52 

List of Tables 

Table 1. Participants’ physical characteristics (N = 12). ............................................................... 5 

Table 2. Obstacle completion times (seconds). ........................................................................... 15 

Table C-1a. Temporal-spatial variables, joint angles and ground reaction forces for walking... 25 

Table C-1b. Joint moments and powers for walking. .................................................................. 26 

Table C-2a. Temporal-spatial variables, joint angles and ground reaction forces for running. .. 27 

Table C-2b. Joint moments and powers for running.................................................................... 28 

Table C-3a. Cycle time, joint angles, and ground reaction forces for squatting.......................... 29 

Table C-3b. Joint moments and powers for squatting. ................................................................ 30 

Table C-4a. Cycle time, joint angles, and ground reaction forces for right kneeling.................. 31 

Table C-4b. Joint moments and powers for right kneeling.......................................................... 32 

Table C-5a. Cycle time, joint angles, and ground reaction forces for left kneeling. ................... 33 

Table C-5b. Joint moments and powers for left kneeling............................................................ 34 
vii 

Acknowledgments 

The authors wish to thank Michael Mungiole of the U.S. Army Research Laboratory’s (ARL’s) 

Computational and Information Sciences Directorate (CISD), Nathan Jarboe of ARL’s Human 

Research and Engineering Directorate (HRED), and John Jansen of the Oak Ridge National 

Laboratory for their technical review of this report. The authors also wish to thank Jock 

Grynovicki of ARL’s HRED for his statistical input and Nancy Nicholas of ARL’s CISD for 

technically editing this report.
viii 

INTENTIONALLY LEFT BLANK
1 

Executive Summary 

Development of a wearable, anthropomorphic, powered exoskeletal device intended to increase the 

speed, strength, and endurance of Soldiers in combat situations is currently being funded by the 

Defense Advanced Research Projects Agency (DARPA) through the Exoskeletons for Human 

Performance Augmentation (EHPA) program. The exoskeleton boot interface, an integral component of the system, is expected to incorporate a 1- to 2-inch-thick sole for the containment of 

force sensors, thus creating a substantial offset of the Soldier’s foot from the ground. Very little 

published data exist regarding human factors issues related to footwear sole thickness; therefore, 

the objective of this investigation was to identify any biomechanical, mobility performance, and 

subjective assessment issues related to the additional sole thickness of an exoskeleton boot interface. In this investigation, the examined biomechanical variables included three-dimensional (3-D) 

angles, moments, and powers at the right hip, knee, and ankle joints during walking, running, 

squatting, and right and left kneeling. The measured mobility performance variables were stride 

time, stride length, velocity, and percent stance during walking and running; cycle time during 

squatting and right and left kneeling; and time to negotiate obstacles. The subjective assessments 

included ratings of comfort, stability, and difficulty during walking, running, squatting, kneeling, 

and negotiating obstacles. There were three footwear conditions: baseline (no additional thickness 

added to the boot sole), 1 inch of thickness added to the boot sole, and 2 inches of thickness added 

to the boot sole. The results of this investigation will provide critical guidance to the DARPA 

EHPA program for the development of an exoskeleton boot interface that is safe, comfortable, and 

functional and may also result in substantial savings of time and money for the EHPA program. 

Twelve male Soldiers stationed at Aberdeen Proving Ground (APG), Maryland, participated in 

this study. Rubber overboots with detachable wooden soles were used to create the three sole 

conditions. For each of the three footwear conditions, 3-D positions of reflective markers placed 

on the participants’ boots and at several anatomical locations were tracked by six high-resolution 

video cameras as participants walked, ran, squatted, kneeled on their right knees, and kneeled on 

their left knees on a force plate surrounded by a raised walkway. Sixty-four biomechanical 

variables for walking and running and 61 biomechanical variables for squatting and kneeling 

were calculated from the ground reaction force and 3-D marker data. Individual completion 

times under the three sole conditions were collected for five obstacles (log balance, elevated up 

and down, tires, house, and zig-zag) on the U.S. Army Research Laboratory (ARL) mobilityportability course at APG. Subjective assessments of comfort, stability, and difficulty during 

walking, running, squatting, right and left kneeling and negotiating the five obstacles during the 

three sole conditions were obtained via a questionnaire with a six-point rating scale. 

All participants were first briefed about the objectives of this investigation and procedures to be 

followed and were then asked to sign a statement of informed consent and to complete a medical 
2 

status form. After they signed the volunteer agreement, height, weight, and shoe size were 

measured and recorded for each participant. Before data collection for each sole condition, 

participants were trained to walk, run, squat, and kneel on the force plate and to negotiate each of 

the five obstacles correctly and were then permitted to practice until they were able to perform 

each movement comfortably. 

With the Statistical Package for the Social Sciences (SPSS) 12.0 for Windows1 (SPSS, Inc., 

Chicago, IL), the data were analyzed by multivariate analyses of variance. For those main and 

interactive effects found to be statistically significant (Wilks’ λ ≤ 0.05), a univariate analysis of 

variance was performed on each dependent variable with a significance level of 0.05. Dependent 

variables found to be significantly affected were further analyzed by a Sidak post hoc test for 

multiple comparisons to identify differences between levels of the main or interactive effect in 

question. 

Twelve of the 61 squatting and kneeling biomechanical variables were found to be significantly 

affected by footwear condition, but this had no impact on the ability of the participants to correctly 

perform those movements. Responses to the comfort, stability, and difficulty questionnaire were 

also found to be significantly affected by footwear condition; however, the actual differences in 

mean ratings of comfort, stability, and difficulty for the baseline and 2-inch conditions are 

relatively small. Based on the results of this investigation, it appears that the exoskeleton boot 

interface could incorporate a sole as thick as 2 inches without substantial impact on any of the 

human factors issues investigated. 

 1Windows is a trademark of Microsoft.
3 

1. Introduction 

In 2000, the Defense Advanced Research Projects Agency (DARPA) issued a Broad Agency 

Announcement (BAA) soliciting proposals on Exoskeletons for Human Performance 

Augmentation (EHPA). In this BAA, DARPA outlined requirements for the development of 

wearable, anthropomorphic, powered exoskeletal devices to increase the speed, strength, and 

endurance of Soldiers in combat situations. Supplemental material to the BAA states that “the 

developed system should be ergonomic and must consider a variety of human factors,” and “to 

the greatest extent possible, human agility must be maintained and even enhanced.” The EHPA 

program is currently in the component development stage. 

The exoskeleton boot interface is an integral part of the exoskeleton system. The boot interface 

will serve as one of two or three connection points between the Soldier and the exoskeleton, as 

well as being the only interface between the exoskeleton system and the ground. It has also been 

proposed that force sensors be incorporated into the exoskeleton boot interface so that it will also 

serve as part of the exoskeleton’s control system. Several concepts for the exoskeleton boot 

interface’s design have been proposed. In all cases, the boot interface incorporates approximately 

a 1- to 2-inch thick sole that will attach to the bottom of the boot, thus substantially offsetting the 

Soldier’s foot from the ground. 

Very little published research exists regarding human factors issues related to the sole thickness 

of footwear. A few studies have been conducted concerning the effects of shoe sole hardness 

and thickness on foot position awareness, stability (Robbins, Waked, Gouw, & McClaran, 1994; 

Robbins, Waked, Allard, McClaran, & Krouglicof, 1997) and joint position sense (Sekizawa, 

Sandrey, Ingersoll, & Cordova, 2001). In both studies conducted by Robbins et al., foot position 

awareness and stability were found to be related, and shoes with thin, hard soles were found to 

provide better stability than those with soft, thick soles. Similarly, Sekizawa et al. found that 

joint position sense is affected by shoe sole thickness but only in dorsiflexion. 

Our investigation sought to identify, through biomechanical evaluation, human performance 

evaluation, and subjective assessment, potential human factors issues related to the thickness of 

the boot interface’s sole. Identification of such issues early in the project will provide critical 

guidance in the development process and may result in substantial savings of time and money for 

the EHPA program. 
4 

2. Objectives 

The overall objective of this investigation was to identify potential human factors issues related 

to the additional sole thickness of an exoskeleton boot interface. This was accomplished through 

analyses of biomechanical data, subjective assessments of comfort, stability, and difficulty, and 

observations of ability to negotiate obstacles in three footwear conditions: baseline (no 

additional sole thickness), 1-inch sole, and 2-inch sole. 

The results of this investigation allowed us to 

a. determine the effects of sole thickness on three-dimensional (3-D) lower limb joint angles, 

moments, and powers during walking, running, squatting, and kneeling; 

b. determine the effects of sole thickness on stride length, stride time, velocity, and percent 

stance during walking and running; 

c. determine the effects of sole thickness on cycle time for squatting and kneeling; 

d. determine the effects of sole thickness on perceptions of comfort, stability, and difficulty 

during walking, running, squatting, kneeling, and negotiating obstacles; 

e. determine the effects of sole thickness on obstacle completion times; and 

f. provide guidance to the DARPA EHPA program for the development of an exoskeleton 

boot interface that is safe, comfortable, and functional. 

3. Methodology 

3.1 Participants 

Twelve male Soldiers, stationed at Aberdeen Proving Ground (APG), Maryland, were recruited 

for participation in this investigation. Only male participants were used in this investigation, 

based on the fact that the exoskeletal system is being developed initially for combat Soldiers 

only. A summary of the participants’ physical characteristics is presented in table 1. All 

participants were briefed about the objectives of this investigation, procedures to be followed, 

and risks associated with their participation. Before participating in this investigation, 

participants read and signed a statement of informed consent2

. To eliminate the possibility of 

any illness or injury that could increase the risk to the participant or bias the data, participants 

were also asked to complete a medical status form. 

 2The investigators have adhered to the policies for protection of human subjects as prescribed in AR 70-25.
5 

Table 1. Participants’ physical characteristics (N = 12). 

 Mean ± SD Range 

Age (yr) 21 ± 3 18 to 30 

Height without shoes (cm) 172.5 ± 8.6 162.5 to 190.5 

Body mass (kg) 76.0 ± 9.1 61.2 to 93.0 

Shoe size (U.S. men’s) 10 ± 1 7 to 11.5 

3.2 Apparatus 

3.2.1 Clothing 

All participants wore their own physical training (PT) shorts and t-shirt or battle dress uniform 

(BDU) and standard issue combat boots throughout this investigation. Rubber overboots and 

plywood soles 1 inch and 2 inches thick were used to produce the experimental conditions. In 

the footwear conditions incorporating additional sole thickness, the rubber overboots had loop 

Velcro3 placed on their bottoms to allow for secure attachment of the 1- and 2-inch soles. Each 

1- and 2-inch sole was constructed from an appropriate thickness of plywood that had been 

shaped to the bottom of the rubber overboot, cut into two segments at a point coinciding with the 

metatarsophalangeal (MP) joint, topped with hook Velcro and covered with tread identical to that 

of the rubber overboots. This construction resulted in soles that were easy to attach and remove, 

lightweight, flexible and provided adequate traction. Several different sized pairs of 1- and 

2-inch soles were constructed in order to accommodate various foot sizes. Also, in order to 

eliminate differences in footwear condition weight, lead insoles were inserted into the rubber 

overboots for the baseline sole condition, and the wooden soles for the 2-inch sole condition 

were partially hollowed so that both footwear conditions weighed the same as the 1-inch sole 

condition. Photographs of the overboot and sole setup are shown in figure 1. The U.S. Army 

Developmental Test Command issued a safety release for the overboots and soles, and its 

recommendations were followed throughout this study. Participants were also required to wear a 

personal armored system for ground troops (PASGT) helmet throughout training and obstacle 

negotiation on the mobility-portability course. 

3.2.2 Force Plate (Advanced Mechanical Technology, Inc. [AMTI], Newton, MA) 

A 1.22-m (4-ft) square AMTI force plate was used in this investigation to collect ground reaction 

force data for the right foot as subjects walked, ran, squatted, and kneeled on their right and left 

knees (figure 2). The force plate was surrounded by several solid platforms to create a level 

walkway along which the participants could walk and run. With strain gauge sensors, the force 

plate measures vertical and horizontal ground reaction forces (GRFs) (to approximately 17,800 N 

and 8,900 N, respectively), as well as torques about the vertical axis, at a maximum sampling rate 

of 1,000 Hz. The three GRF channels (Fx, Fy, Fz) have resolutions of 0.714, 0.722, and 3.052 

Newtons, and the torque channels (Mx, My, Mz) have resolutions of 0.718, 0.714, and 0.315 

Newton-meter. In this investigation, the force plate data were sampled at a rate of 120 Hz. 

 3Velcro is a registered trademark of Velcro USA, Inc.
6 

Figure 1. Overboot and sole setup. 

3.2.3 Motion Analysis System (Motion Analysis Corporation, Santa Rosa, CA) 

The Motion Analysis System, which consists of six high-resolution video cameras and the 

EVaRT 4.0 Motion Capture software package, is capable of collecting and tracking the 3-D 

positions of reflective markers in real time. The EvaRT software can additionally collect data 

from analog devices (force plate, in this case) and synchronize them with the marker position 

data. In this investigation, the six cameras were arranged around a force plate and walkway, and 

reflective markers were placed on the participants’ boots as well as at several anatomical 

positions (figure 3). Marker position data were collected at a rate of 60 Hz, with an accuracy of 

approximately 1.5 ±0.5 mm. The synchronized marker position and force plate were exported to 

a .c3d file for analysis via Visual3D Movement Analysis software (C-Motion, Inc., Rockville, 

Maryland). 
7 

 

Walking Running

Squatting

Right Kneeling Left Kneeling

Figure 2. Walking, running, squatting, and kneeling on the walkway and force plate. 
8 

Base of Rib Cage

Upper Thigh

Mid Thigh

Lower Thigh

Upper Shank

Mid Shank

Lower Shank

Left ASIS

Right ASIS

Lateral Condyle

Medial Condyle

Medial Malleolus

Lateral Malleolus

Toe

Heel

R. 5th Metatarsal

Top of Foot

L. 5th Metatarsal

Base of Rib Cage

Upper Thigh

Mid Thigh

Lower Thigh

Upper Shank

Mid Shank

Lower Shank

R. 5th Metatarsal

Toe

Heel

Left ASIS

Right ASIS

Lateral Condyle

Lateral Malleolus

Top of Foot

Figure 3. Reflective marker placement (red used for the neutral trial only, black used for neutral and motion 

trials). 

3.2.4 Visual3D Movement Analysis Software (C-Motion, Inc., Rockville, MD) 

The Visual3D software package uses a flexible 6 degree-of-freedom model to perform kinematic 

and kinetic (inverse dynamic) analyses on synchronized motion capture and analog data. Threedimensional lower limb joint angles were calculated during walking, running, squatting, and 

kneeling; stride length, stride time, velocity, and percent stance during walking and running; and 

cycle time during squatting and kneeling with the use of the marker position data. Threedimensional lower limb joint torques and powers were also calculated during walking, running, 

squatting, and kneeling with the use of the synchronized marker position and force plate data. 

Diagrams detailing the planes of motion, axes of rotation, and terminology used to describe joint 

motion are presented in appendix A. 

3.2.5 U.S. Army Research Laboratory (ARL) Mobility-Portability Course 

The ARL mobility-portability course at APG is approximately 500 m long and consists of 20 

pairs of identical obstacles, thus allowing two subjects to negotiate the course simultaneously 

without interfering with one another. Negotiation of the obstacles requires running, jumping, 

climbing, and crawling. It has been shown that the movements performed by Soldiers 

negotiating obstacles on this course allow for identification of human factors issues associated 

with individual equipment (Hanlon et al., 1984; Hanlon, Hickey, & Ortega, 1990). In this part of 

the investigation, objective data (time to complete obstacle), observations, and participant 

feedback were collected to determine if differences resulting from the various footwear 

conditions exist in the negotiation of five selected obstacles. Obstacle completion times were 
9 

measured with mechanical stopwatches. The five obstacles used in this investigation were the 

log balance, elevated up and down, tires, house, and zig-zag (figure 4). 

 

 

 Log Balance Elevated Up and Down 

 

 

 

 Tires 

 

 

 

 House Zig-zag 

Figure 4. Obstacles on ARL’s mobility-portability course. 
10 

3.3 Procedures 

3.3.1 Volunteer Consent 

The volunteers were first briefed about the objectives of this investigation, procedures to be 

followed, and the potential risks associated with their participation. Proper procedures for 

walking, running, squatting, and kneeling on the right and left knees were demonstrated. A video 

of a Soldier negotiating each of the five obstacles was also shown to the volunteers. They were 

given an opportunity to examine the overboots and soles. Any questions they had regarding their 

participation were then answered. The volunteer agreement affidavit was read aloud to them by 

the investigator as they followed. They were then asked individually whether they chose to 

participate in this investigation. After consenting to participate, each volunteer, along with the 

investigator, initialed the bottom of each page and answered and signed the last page of the 

volunteer agreement affidavit. As part of the affidavit, permission to obtain the participant’s 

Armed Services Vocational Aptitude Battery (ASVAB) scores was also requested. After 

completing the affidavits, volunteers completed the medical status form and were assigned 

participant numbers to preserve anonymity and for use in identification throughout data 

collection. 

3.3.2 Training 

3.3.2.1 Biomechanics 

Participants were individually trained to walk and run across the force plate, as well as squat and 

kneel on the force plate, before data were collected for each of the three footwear conditions. In 

order to eliminate force plate targeting during the walking and running trials, starting positions 

that allowed the subject’s right foot to land squarely near center of the force plate without modification of gait were first identified. They were then given an opportunity to practice walking 

and running across the force plate. Participants were considered trained for walking and running 

when they were able to place their feet in the proper location on the force plate for three 

consecutive passes. After participants had been trained to walk and run across the force plate, 

they were also given an opportunity to practice squatting and kneeling on the force plate. 

Participants were considered trained for squatting and kneeling when they felt capable of 

performing the movements in a consistent manner. Following training, participants were 

provided with a 15-minute break. 

3.3.2.2 Obstacle Negotiation 

Participants were trained to negotiate five obstacles on the mobility-portability course. They 

were first instructed in the proper method for negotiating each obstacle and were then given an 

opportunity to familiarize themselves with negotiating each obstacle in the three footwear 

conditions before data collection. Participants were considered trained when they felt confident 

in their ability to negotiate each obstacle properly. Following training, participants were 

provided with a 15-minute break. 
11 

3.3.3 Data Collection 

3.3.3.1 Biomechanics 

For each of the three footwear conditions, motion and force plate data were collected for the 

right leg of each participant as he performed five movements (walking, running, squatting, 

kneeling on left knee, kneeling on right knee). Footwear conditions were presented to each 

participant according to a Latin square counterbalancing scheme. Before the motion trials for 

each footwear condition, a neutral (standing) trial was collected to be used later in building the 

Visual3D model. During the walking and running trials, the participant proceeded along the 

walkway at a self-selected speed, striking the center of the force plate with his right foot as he 

passed over it. During the squatting, kneeling on the left knee, and kneeling on the right knee 

trials, the participant began and ended in a standing position with his right foot flat on the force 

plate and left foot flat on the walkway. When kneeling on the left knee, the participant moved 

down into a kneeling position while keeping his right foot on the force plate and placing his left 

knee on the walkway. When kneeling on the right knee, the participant moved down into a 

kneeling position while keeping his left foot on the walkway, right foot on the force plate and 

placing his right knee on the walkway. Following the data collection period for each footwear 

condition, the participant was asked to complete part A of the comfort, stability, and difficulty 

questionnaire (see appendix B). Each data collection period lasted for approximately 15 minutes 

and was followed by a 15-minute break. 

3.3.3.2 Obstacle Negotiation 

The ability of each participant to negotiate five obstacles on the mobility-portability course was 

assessed for each of the three footwear conditions. As with the biomechanical data collection, 

footwear conditions were presented to the participants according to the counterbalancing scheme. 

Participants negotiated each of the five obstacles, while observers recorded the time required for 

the participants to negotiate each obstacle and any footwear-related problems encountered. After 

negotiating each of the five obstacles, participants were asked to complete part B of the comfort, 

stability, and difficulty questionnaire. 

3.4 Experimental Design 

3.4.1 Independent Variables 

The independent variables in this investigation were footwear condition, trial during which the 

footwear condition was presented, and movement performed. Footwear condition consisted of 

three levels: no additional sole thickness, 1-inch sole, and 2-inch sole. Trials consisted of three 

levels: first, second, and third. Movement consisted of five levels for the biomechanical 

analysis (walking, running, squatting, kneeling on the right knee, and kneeling on the left knee) 

and five levels for the obstacle negotiation (log balance, elevated up and down, tires, house, and 

zig-zag). 
12 

3.4.2 Dependent Variables 

The following dependent variables were calculated from the biomechanical data for each of the 

three footwear conditions: 

a. peak 3-D joint angles at the ankle, knee, and hip (degrees); 

b. peak 3-D joint moments at the ankle, knee, and hip (Newton-meters/kilogram); 

c. peak 3-D joint powers at the ankle, knee, and hip (watts/kilogram); 

d. peak ground reaction forces normalized to body weight (Newtons/body weight)4

; 

e. stride length (meters), walking and running trials, 

f. stride time (seconds), walking and running trials, 

g. velocity (meters/second), walking and running trials, 

h. percent stance, walking and running trials; and 

i. cycle time (seconds), squatting and kneeling trials. 

The dependent variable associated with obstacle negotiation was time. With respect to the 

questionnaire, the dependent variable was the participant’s response to each question.

3.4.3 Statistical Analysis 

All statistical analyses were performed with the Statistical Package for the Social Sciences 

(SPSS) 12.0 for Windows5 (SPSS, Inc., Chicago, IL). The biomechanical variables, obstacle 

completion times, and questionnaire responses were analyzed by multivariate analyses of 

variance (MANOVAs). A Wilks’ λ value of 0.05 or less was considered statistically significant. 

For those main and interactive effects found to be statistically significant, a univariate analysis of 

variance (ANOVA) was performed on each dependent variable, and the results were considered 

statistically significant for p-values of 0.05 or less. Dependent variables found to be significantly 

affected were further analyzed via a Sidak post hoc test to identify differences between levels of 

the main or interactive effect in question. The significance level of the Sidak post hoc test was 

adjusted for multiple comparisons according to the formula 1-(1-α)

1/k, in which α is equal to 

overall significance level and k is the number of comparisons. Therefore, given an overall 

significance level of 0.05 and 3 comparisons, the calculated adjusted significance level was 

0.017. 

 4

Body weight has units of Newtons; it is calculated when weight in kilograms is multiplied by acceleration 

attributable to gravity (9.81 meters/second2

)

5Windows is a trademark of Microsoft.
13 

4. Results 

4.1 Biomechanical Variables 

Summaries of the biomechanical data for walking, running, squatting, and right and left kneeling 

under each of the three footwear conditions are given in appendix C, tables C-1 through C-5, 

respectively. Stride time, stride length, velocity, percent stance and cycle time are reported as 

mean values. Ground reaction forces, and 3-D joint angles, moments, and powers are reported as 

means of the peak values. Plots of mean ground reaction forces, and 3-D joint angles, moments 

and powers over one stride or cycle of each movement are presented in appendix D. 

Based on the number of variables measured, data for the five movements were divided into two 

groups: walk/run and squat/kneel. A MANOVA with main effects for movement, footwear 

condition, trial and participant, and interaction effects for movement*footwear condition, 

movement*trial and footwear condition*trial, was performed on each group. For the walk/run 

group, a statistically significant effect was found only for movement (p = 0.016) and participant 

(p = 0.000). Since these effects were expected, no further analyses were conducted. However, 

for the squat/kneel group, in addition to movement (p = 0.000) and participant (p = 0.000), a 

statistically significant main effect was identified for footwear condition (p = 0.028). Each of the 

biomechanical variables for the squat/kneel group was independently analyzed for footwear 

condition effects by an ANOVA with Sidak post hoc test. 

Of the 61 biomechanical variables analyzed for the squat/kneel group, 12 were identified as 

being significantly affected by footwear condition. Their mean values and post hoc analysis 

results are presented graphically in figure 5. Cycle time, peak ankle abduction, peak ankle 

external rotation, and peak ankle dorsiflexor moment all tend to increase with increasing sole 

thickness, but only the 2-inch condition mean was found to differ significantly from the baseline 

mean. Peak hip flexion, peak knee flexion, and peak knee extensor moment also tend to increase 

with increasing sole thickness, and both the 1- and 2-inch condition means were found to differ 

significantly from the baseline mean but not from each other. Peak ankle adduction and peak 

ankle internal rotation both tend to decrease with increasing sole thickness; however, only the 

baseline and 2-inch condition means were found to be significantly different from one another. 

No difference in condition means was identified for peak hip extension, peak ankle abductor 

moment, or peak ankle adductor moment. 
14 

*based on post hoc analyses, indicated mean differs significantly from baseline mean 

Figure 5. Mean values for squat/kneel group biomechanical variables significantly affected by footwear condition.

CycleTime, p=0.028

3.153.203.253.303.353.403.453.503.55

Baseline 1-inch 2-inch

Time (seconds)

* 

Hip Flexion, p=0.000

64656667686970717273

Baseline 1-inch 2-inch

Angle (degrees)

Hip Extension, p=0.043

0123456

Baseline 1-inch 2-inch

Angle (degrees)

Knee Flexion, p

120122124126128130

Baseline 1-i

Angle (degrees)

Ankle Adduction, p=0.002

0.00.51.01.52.02.53.03.54.0

Baseline 1-inch 2-inch

Angle (degrees)

Ankle Abduction, p=0.022

13.013.514.014.515.015.516.016.517.017.5

Baseline 1-inch 2-inch

Angle (degrees)

Ankle Ext. Rotation, p=0.011

02468

1012

Baseline 1-inch 2-inch

Angle (degrees)

Ankle Int. Rotation

01234567

Baseline 1-in

Angle (degrees)

Knee Extensor, p=0.000

1.151.201.251.301.351.401.45

Baseline 1-inch 2-inch

Moment (Nm/kg)

Ankle Dorsiflexor, p=0.009

0.000.020.040.060.080.100.120.140.160.18

Baseline 1-inch 2-inch

Moment (Nm/kg)

Ankle Abductor, p=0.034

0.000.050.100.150.200.25

Baseline 1-inch 2-inch

Moment (Nm/kg)

Ankle Adductor, 

0

0.010.020.030.040.05

Baseline 1-

Moment (Nm/kg)

* 

* * 

* * 

* 

* 

* * 

14
15 

4.2 Obstacle Completion Times 

Mean obstacle completion times under each of the three footwear conditions are shown in 

table 2. Obstacle completion times were analyzed by a MANOVA with main effects for 

footwear condition, trial and participant, and interaction effect for footwear condition*trial. A 

statistically significant effect was identified for trial (p = 0.034) and participant (p = 0.000). 

Footwear condition was not found to significantly affect obstacle completion times. Further 

analysis of trial effects was performed on the individual obstacle completion times with an 

ANOVA with Sidak post hoc test. 

Table 2. Obstacle completion times (seconds). 

Footwear Condition Obstacle Baseline 1-inch Sole 2-inch Sole 

Log Balance 12.7 (3.0) 15.4 (3.4) 16.0 (4.4) 

Up and Down 5.4 (1.0) 6.0 (2.2) 6.4 (3.0) 

Tires 7.8 (0.9) 8.3 (1.3) 8.7 (1.4) 

House 9.3 (0.9) 9.5 (1.2) 9.9 (1.8) 

Zig-zag 5.9 (0.7) 5.9 (0.7) 6.3 (0.9) 

Note: values given as mean (SD), N=12 

A statistically significant effect of trial was identified for the log balance (p = 0.024), up and 

down (p = 0.013) and house (p = 0.002). Their mean values and post hoc analysis results are 

presented graphically in figure 6. The time to complete each of the three obstacles tended to 

decrease with each run through the course. For the log balance, a significant difference in mean 

times was identified between the first and third runs only. For the up and down and house, the 

mean times of the second and third runs were found to differ significantly from that of the first 

run but not from one another. 

*based on post hoc analyses, indicated mean differs significantly from first run mean. 

Figure 6. Mean values for obstacle times significantly affected by trial. 

Log Balance, p=0.024

0

5

10

15

20

123

Trial

Time (seconds)

Up & Down, p=0.013

0

2

4

6

8

123

Trial

Time (seconds)

House, p=0.002

0

2

4

6

8

10

12

123

Trial

Time (seconds)

* * * * * 
16 

4.3 Comfort, Stability, and Difficulty Questionnaire Responses 

In order to compute mean values and conduct statistical analysis of the questionnaire responses, 

each response level was assigned a numerical value: 1=very low, 2=low, 3=slightly low, 

4=slightly high, 5=high, 6=very high. A MANOVA with main effects for activity, footwear 

condition, trial and participant, and interaction effects for activity*footwear condition, 

activity*trial and footwear condition*trial, was performed on the responses. Statistically 

significant main effects were identified for footwear condition (p = 0.000), trial (p = 0.024), 

activity (p = 0.000), and participant (p = 0.000). Further analysis of footwear condition and trial 

effects was performed on the questionnaire responses by ANOVAs with Sidak post hoc tests. 

Mean values and post hoc analyses results for the effect of footwear condition on the comfort, 

stability and difficulty questionnaire responses are presented graphically in figure 7. Ratings of 

both comfort and stability tended to decrease, while ratings of difficulty tended to increase with 

increasing sole thickness. For all three, mean ratings for the 1- and 2-inch conditions were found 

to differ significantly from those for the baseline condition, as well as from one another. 

ANOVA results for the effect of trial were not significant. 

*based on post hoc analyses, indicated mean differs significantly from baseline mean. 

**based on post hoc analyses, indicated mean differs significantly from baseline and 1-inch means. 

Figure 7. Mean values for questionnaire responses across footwear conditions. 

5. Discussion 

According to the BAA issued by DARPA for the EHPA program, the developed exoskeletal 

system must take into account ergonomics and other human factors considerations and must 

maintain or enhance human agility. Therefore, the purpose of this study was to identify potential 

human factors issues related to the additional sole thickness of an exoskeleton boot interface. 

This was accomplished through the evaluation of biomechanical variables for five movements, 

time to negotiate five obstacles, and subjective ratings of comfort, stability, and difficulty, during 

three different footwear conditions. 

Comfort, p=0.000

1

2

3

4

5

6

Baseline

1-inch2-inch

Rating

* 

** 

Stability, p=0.000

1

2

3

4

5

6

Baseline

1-inch2-inch

Rating

* 

** 

Difficulty, p=0.000

1

2

3

4

5

6

Baseline

1-inch2-inch

Rating

* 

** 
17 

A statistically significant effect of footwear condition was identified only for the squatting/ 

kneeling biomechanical data and the questionnaire responses, and of the 61 biomechanical 

variables measured, only 12 were found to be significantly affected by footwear condition (see 

figure 5). The affected angular measures (hip flexion, knee flexion, ankle abduction and 

adduction, and ankle internal and external rotation) were still within the normal range of motion 

for their corresponding joint (Norkin & White, 1985). Additionally, ankle dorsiflexor, adductor 

and abductor moment values were within the same range as those normally seen during walking 

(Eng & Winter, 1995), while knee extensor moment values were within the same range as those 

normally seen during running (DeVita, Torry, Glover, & Speroni, 1996). The changes observed 

in maximum and minimum ankle angles in the frontal and transverse planes, along with 

increased hip and knee flexion and increased knee extensor and ankle dorsiflexor moments may 

indicate an adaptation in balancing strategy and stability control during squatting and kneeling 

because of the increasing sole thickness. The increased amount of time required to squat and 

kneel as sole thickness increased could possibly be attributed to the participant’s decreased sense 

of stability, as indicated by the questionnaire responses. 

As one might expect, with respect to the questionnaire, ratings of comfort and stability 

decreased, while ratings of difficulty increased with increasing sole thickness. The actual 

differences in baseline and 2-inch ratings, however, were quite small. Mean ratings of comfort 

and stability decreased from “high” to just above “slightly low,” while mean ratings of difficulty 

increased from between “very low” and “low” to between “low” and “slightly low”. 

Interestingly, with respect to the obstacle completion times, trial was found to have a statistically 

significant effect on the log balance, up and down, and house times, but no effect of footwear 

condition was identified. Participants tended to complete the log balance, up and down, and 

house more quickly with each successive run, regardless of footwear condition. This is most 

likely indicative of a practice or learning effect and may have been eliminated if the number of 

training trials were increased or by training to achieve an asymptote in completion time, rather 

than allowing each participant to individually determine his own readiness. Running multiple 

trials for each footwear condition and then averaging the results may have been another viable 

solution to this problem. 

From the values in table 2, it can be seen that completion times for each of the five obstacles 

showed an increasing trend with increased sole thickness. However, a statistically significant 

effect of footwear condition was not identified (p = 0.39), possibly because of the substantial 

effect of trial on obstacle completion time. 
18 

6. Conclusions 

Of the human factors issues examined in this study, the effect of additional sole thickness on 

users’ perceptions of comfort, stability, and difficulty is more important than its effect on the 

measured biomechanical variables. Mean ratings of comfort, stability, and difficulty for the 1- 

and 2-inch sole conditions are statistically different from mean ratings for the baseline condition, 

and although the differences are small, they point to areas that are important for user acceptance 

of a system. Therefore, it is important to design a comfortable and stable exoskeleton boot 

interface with an overall design goal to ensure that moving in the exoskeleton is as easy as 

moving in regular boots. 

Despite the impact that footwear condition was observed to have on the values of a few of the 

squatting and kneeling biomechanical variables, all 12 participants were still able to perform the 

movements correctly. In addition, the biomechanical variables found to be significantly different 

from the baseline for squatting and kneeling are still within human range of motion limits and 

comparable to values seen for normal walking and running. Thus, their impact on the usability 

of an exoskeleton would probably be small. Additionally, walking and running are likely to be 

the two most frequent movements performed by a Soldier wearing an exoskeleton, and footwear 

condition failed to have a significant effect on the biomechanical variables for walking and 

running or the obstacle completion times. 

Therefore, it appears that the exoskeleton boot interface, if designed to be comfortable and 

stable, could incorporate a sole as thick as 2 inches without substantial impact on any of the 

human factors issues investigated in this study. 
19 

7. References 

DeVita, P.; Torry, M.; Glover, K. L.; Speroni, D. L. A functional knee brace alters joint torque 

and power patterns during walking and running. Journal of Biomechanics 1996, 29 (5), 583-

588. 

Eng, J. J.; Winter, D. A. Kinetic analysis of the lower limbs during walking: What information 

can be gained from a three-dimensional model? Journal of Biomechanics 1995, 28 (6), 753-

758. 

Hamill, J.; Knutzen, K. M. Biomechanical basis of human movement, 2nd ed. Baltimore, MD: 

Lippincott Williams & Wilkins, 2003. 

Hanlon, W. E.; Brainerd, S. T.; Bruno, R. S.; Ellis, P. H.; Hickey, C. A. Jr.; Woodward, A. A. 

Portability test and human factors evaluation of ten antiarmor systems; Technical 

Memorandum 6-84; Aberdeen Proving Ground, MD: U.S. Army Human Engineering 

Laboratory, 1984. 

Hanlon, W. E.; Hickey, C. A. Jr.; Ortega, S. V. Human engineering laboratory mobilityportability and human factors evaluation of the advanced antitank weapons systems-medium 

(AAWS-M) candidates; Technical Memorandum 4-90; Aberdeen Proving Ground, MD: U.S. 

Army Human Engineering Laboratory, 1990. 

Headquarters, Department of the Army. Use of Volunteers as Subjects of Research; AR 70-25; 

Washington, DC, 1990. 

Norkin, C. C.; White, D.J. Measurement of Joint Motion: A guide to goniometry. Philadelphia, 

PA: F.A. Davis Company, 1985. 

Robbins, S.; Waked, E.; Allard, P.; McClaran, J.; Krouglicof, N. Foot position sense awareness 

in younger and older men: the influence of footwear sole properties. Journal of the 

American Geriatric Society 1997, 45 (1), 61-6. 

Robbins, S.; Waked, E.; Gouw, G. J.; McClaran, J. Athletic footwear affects balance in men. 

British Journal of Sports Medicine 1994, 28 (2), 117-122. 

Sekizawa, K.; Sandrey, M. A.; Ingersoll, C. D.; Cordova, M. L. Effects of shoe sole thickness on 

joint position sense. Gait & Posture 2001, 13, 211-228. 
20 

INTENTIONALLY LEFT BLANK
21 

Appendix A. Three-Dimensional Biomechanics Terminology (from Hamill & 

Knutzen, 2003) 

Figure A-1. Planes of motion and axes of rotation. 

Longitudinal axis 

Frontal plane 

Anterioposterior axis 

Mediolateral axis 

Sagittal plane 

Transverse plane 
22 

 Hip Knee Ankle Sagittal Plane Frontal Plane 

 

Transverse Plane 

Figure A-2. Joint motion terminology. 

Medial 

rotation 

Lateral 

rotation 

Medial 

rotation

Lateral 

rotation

Abduction 

Adduction 

Adduction Abduction 

Flexion 

Extension 

Flexion

Extension

Dorsiflexion 

Plantarflexion 
23 

Appendix B. Comfort, Stability, and Difficulty Questionnaire 

Participant #: Footwear Condition: 

Part A: For this footwear condition, rate each factor for each activity by placing an “X” in the 

box under the heading that best represents your feeling. 

Activity Factor Very Low Low Slightly 

Low 

Slightly 

High High Very High 

 Comfort 

Walking Stability 

 Difficulty 

 Comfort 

Running Stability 

 Difficulty 

 Comfort 

Squatting Stability 

 Difficulty 

 Comfort 

Kneeling Stability 

 Difficulty 

Comments: 

 
24 

Participant #: Footwear Condition: 

Part B: For this footwear condition, rate each factor for each obstacle by placing an “X” in the 

box under the heading that best represents your feeling. 

Obstacle Factor Very 

Low Low Slightly Low 

Slightly 

High High Very High 

Comfort 

Log Balance Stability 

Difficulty 

Comfort 

Stability Elevated 

Up & Down 

Difficulty 

 Comfort 

Tires Stability 

 Difficulty 

 Comfort 

House Stability 

 Difficulty 

 Comfort 

Zig Zag Stability 

 Difficulty 

Comments: 

 
25 

Appendix C. Biomechanical Variables Data Tables 

Table C-1a. Temporal-spatial variables, joint angles and ground reaction forces for walking. 

Sole Condition 

Variable 

Baseline 1-inch Sole 2-inch Sole 

 Stride Length (m) 1.625 (0.124) 1.636 (0.114) 1.634 (0.111) 

 Stride Time (s) 1.132 (0.050) 1.142 (0.078) 1.163 (0.070) 

 Velocity (m/s) 1.439 (0.142) 1.439 (0.143) 1.413 (0.166) 

 % Stance 60.2 (2.1) 62.9 (2.6) 61.4 (2.3) 

Maximum 30.7 (4.1) 30.9 (3.8) 29.2 (3.5) Hip Minimum -21.6 (2.1) -21.4 (3.3) -21.7 (2.4) 

Maximum 73.3 (5.0) 71.8 (4.5) 68.3 (6.1) Knee 

Minimum -6.2 (3.6) -3.7 (3.5) -6.0 (5.8) 

Sagittal Plane 

Maximum 10.6 (4.6) 12.1 (4.1) 12.1 (4.6) Ankle 

Minimum -13.0 (3.4) -12.2 (2.7) -12.6 (3.2) 

Maximum 2.9 (2.3) 2.7 (1.8) 3.0 (2.3) Hip Minimum -6.6 (2.9) -6.7 (2.1) -6.1 (2.8) 

Maximum 8.4 (3.6) 6.5 (3.1) 7.8 (5.0) Knee 

Minimum -2.6 (3.6) -3.3 (3.1) -2.7 (3.4) 

Frontal Plane 

Maximum 7.6 (3.6) 5.8 (3.5) 3.7 (3.8) Ankle 

Minimum -6.5 (3.3) -7.7 (2.8) -8.3 (3.6) 

Maximum -2.4 (5.4) -1.7 (5.9) -2.5 (7.5) Hip Minimum -12.2 (3.9) -11.3 (3.7) -11.0 (3.7) 

Maximum 12.2 (5.2) 12.3 (5.3) 11.9 (7.5) Knee 

Minimum -18.1 (6.8) -17.4 (6.4) -19.1 (7.0) 

Maximum 4.4 (3.3) 4.7 (3.6) 5.3 (2.5) 

Angle (degrees) 

Transverse Plane 

Ankle 

Minimum -7.2 (3.7) -6.3 (3.6) -5.6 (2.4) 

Maximum 1.25 (0.06) 1.27 (0.06) 1.23 (0.06) Vertical 

Minimum 0.06 (0.03) 0.05 (0.02) 0.07 (0.06) 

Anterior- Maximum 0.24 (0.03) 0.23 (0.03) 0.21 (0.03) 

Posterior Minimum -0.19 (0.03) -0.18 (0.04) -0.17 (0.04) 

Maximum 0.11 (0.05) 0.10 (0.02) 0.10 (0.01) 

Ground 

Reaction Force 

(N/BW) 

MedialLateral Minimum -0.02 (0.01) -0.02 (0.01) -0.04 (0.01) 

Note: Values given as mean (s.d.), N=12 

Positive values indicate flexion, adduction, and external rotation; upward, posterior and medial GRF 

Negative values indicate extension, abduction and internal rotation; downward, anterior and lateral GRF 
26 

Table C-1b. Joint moments and powers for walking. 

Sole Condition Variable 

Baseline 1-inch Sole 2-inch Sole 

Maximum 0.90 (0.20) 1.04 (0.25) 0.90 (0.32) Hip Minimum -0.99 (0.17) -1.00 (0.21) -1.00 (0.27) 

Maximum 0.62 (0.14) 0.58 (0.13) 0.60 (0.17) Knee 

Minimum -0.47 (0.14) -0.47 (0.14) -0.47 (0.12) 

Maximum 1.76 (0.15) 1.88 (0.19) 1.84 (0.16) 

Sagittal Plane 

Ankle 

Minimum -0.41 (0.08) -0.42 (0.08) -0.43 (0.07) 

Maximum 1.04 (0.45) 0.89 (0.11) 0.89 (0.15) Hip Minimum -0.17 (0.07) -0.18 (0.07) -0.17 (0.08) 

Maximum 0.46 (0.33) 0.37 (0.12) 0.33 (0.12) Knee 

Minimum -0.14 (0.06) -0.13 (0.06) -0.14 (0.08) 

Frontal Plane 

Maximum 0.20 (0.12) 0.23 (0.15) 0.24 (0.16) Ankle 

Minimum -0.10 (0.22) -0.03 (0.03) -0.02 (0.03) 

Maximum 0.21 (0.25) 0.12 (0.03) 0.11 (0.05) Hip Minimum -0.11 (0.03) -0.10 (0.05) -0.09 (0.04) 

Maximum 0.09 (0.02) 0.09 (0.03) 0.10 (0.02) Knee 

Minimum -0.08 (0.18) -0.03 (0.02) -0.04 (0.01) 

Maximum 0.04 (0.02) 0.04 (0.02) 0.05 (0.03) 

Moment (Nm/kg) 

Transverse Plane 

Ankle 

Minimum -0.22 (0.04) -0.23 (0.05) -0.25 (0.05) 

Maximum 1.41 (0.52) 1.36 (0.46) 1.25 (0.52) Hip Minimum -0.82 (0.22) -0.85 (0.28) -0.80 (0.25) 

Maximum 0.79 (0.26) 0.80 (0.21) 0.77 (0.18) Knee 

Minimum -1.48 (0.66) -1.21 (0.46) -1.00 (0.39) 

Maximum 2.34 (0.66) 2.33 (0.59) 2.36 (0.71) 

Sagittal Plane 

Ankle 

Minimum -1.16 (0.51) -1.37 (0.47) -1.31 (0.38) 

Maximum 0.73 (0.82) 0.47 (0.13) 0.42 (0.15) Hip Minimum -0.35 (0.20) -0.30 (0.18) -0.25 (0.11) 

Maximum 0.12 (0.08) 0.11 (0.07) 0.08 (0.04) Knee 

Minimum -0.37 (0.52) -0.17 (0.07) -0.14 (0.06) 

Frontal Plane 

Maximum 0.27 (0.25) 0.27 (0.28) 0.30 (0.26) Ankle 

Minimum -0.14 (0.08) -0.09 (0.05) -0.08 (0.07) 

Maximum 0.07 (0.05 0.07 (0.05 0.06 (0.03 Hip Minimum -0.13 (0.12) -0.10 (0.04) -0.08 (0.05) 

Maximum 0.05 (0.03) 0.05 (0.02) 0.06 (0.03) Knee 

Minimum -0.06 (0.07) -0.06 (0.02) -0.06 (0.03) 

Maximum 0.05 (0.04) 0.04 (0.03) 0.05 (0.05) 

Power (W/kg) 

Transverse Plane 

Ankle 

Minimum -0.07 (0.04) -0.07 (0.04) -0.09 (0.05) 

Note: Values given as mean (s.d.), N=12 

Positive values indicate extensor, abductor, and internal rotator moment; and power generation 

Negative values indicate flexor, adductor, and external rotator moment; and power absorption 
27 

Table C-2a. Temporal-spatial variables, joint angles and ground reaction forces for running. 

Sole Condition 

Variable 

Baseline 1-inch Sole 2-inch Sole 

 Stride Length (m) 2.450 (0.281) 2.361 (0.388) 2.436 (0.284) 

 Stride Time (s) 0.794 (0.035) 0.786 (0.063) 0.797 (0.047) 

 Velocity (m/s) 3.084 (0.317) 2.995 (0.355) 3.059 (0.347) 

 % Stance 34.3 (2.8) 37.6 (3.5) 36.8 (2.4) 

Maximum 35.6 (8.0) 36.3 (7.2) 36.1 (7.6) Hip Minimum -28.1 (5.9) -27.0 (4.3) -28.3 (5.7) 

Maximum 91.9 (10.9) 93.8 (11.6) 90.3 (12.1) Knee 

Minimum 6.3 (5.1) 8.4 (5.7) 5.9 (5.0) 

Sagittal Plane 

Maximum 20.9 (3.6) 22.9 (3.7) 22.8 (3.8) Ankle 

Minimum -15.1 (4.2) -11.3 (5.8) -12.9 (3.8) 

Maximum 4.6 (1.8) 4.1 (1.2) 4.6 (1.9) Hip Minimum -5.3 (2.5) -5.7 (2.6) -5.7 (3.1) 

Maximum 7.0 (4.5) 6.2 (3.2) 7.7 (5.7) Knee 

Minimum -2.4 (3.1) -3.8 (4.3) -4.4 (5.1) 

Frontal Plane 

Maximum 7.9 (3.8) 6.4 (3.6) 7.6 (7.6) Ankle 

Minimum -11.9 (3.7) -13.7 (3.4) -14.7 (5.0) 

Maximum 2.8 (5.9) 3.0 (6.9) 2.4 (7.1) Hip Minimum -16.1 (7.1) -15.2 (6.6) -16.1 (8.7) 

Maximum 11.9 (4.9) 10.0 (4.9) 11.0 (6.3) Knee 

Minimum -6.4 (4.1) -5.9 (4.9) -5.6 (5.6) 

Maximum 6.5 (4.2) 6.4 (4.9) 7.1 (2.9) 

Angle (degrees) 

Transverse Plane 

Ankle 

Minimum -4.0 (3.4) -3.1 (5.0) -2.7 (2.6) 

Maximum 2.42 (0.20) 2.42 (0.17) 2.40 (0.18) Vertical 

Minimum 0.04 (0.04) 0.04 (0.04) 0.02 (0.03) 

Anterior- Maximum 0.26 (0.03) 0.25 (0.04) 0.24 (0.04) 

Posterior Minimum -0.23 (0.07) -0.19 (0.07) -0.20 (0.07) 

Maximum 0.23 (0.05) 0.23 (0.04) 0.22 (0.04) 

Ground 

Reaction Force 

(N/BW) 

MedialLateral Minimum -0.00 (0.01) -0.00 (0.01) -0.01 (0.01) 

Note: Values given as mean (s.d.), N=12 

Positive values indicate flexion, adduction, and external rotation; upward, posterior and medial GRF 

Negative values indicate extension, abduction and internal rotation; downward, anterior and lateral GRF 
28 

Table C-2b. Joint moments and powers for running. 

Sole Condition Variable 

Baseline 1-inch Sole 2-inch Sole 

Maximum 1.08 (0.24) 1.30 (0.72) 1.22 (0.61) Hip Minimum -0.82 (0.17) -0.87 (0.18) -0.95 (0.15) 

Maximum 2.38 (0.50) 2.32 (0.63) 2.40 (0.49) Knee 

Minimum -0.39 (0.07) -0.39 (0.06) -0.37 (0.06) 

Maximum 2.67 (0.29) 2.83 (0.33) 2.74 (0.37) 

Sagittal Plane 

Ankle 

Minimum -0.29 (0.12) -0.31 (0.16) -0.34 (0.14) 

Maximum 1.51 (0.36) 1.42 (0.28) 1.44 (0.36) Hip Minimum -0.18 (0.08) -0.19 (0.09) -0.18 (0.11) 

Maximum 0.96 (0.48) 0.89 (0.49) 0.93 (0.40) Knee 

Minimum -0.11 (0.08) -0.11 (0.08) -0.11 (0.05) 

Frontal Plane 

Maximum 0.51 (0.31) 0.47 (0.28) 0.58 (0.38) Ankle 

Minimum -0.03 (0.02) -0.03 (0.03) -0.03 (0.03) 

Maximum 0.09 (0.05) 0.10 (0.05) 0.09 (0.05) Hip Minimum -0.13 (0.05) -0.15 (0.09) -0.13 (0.07) 

Maximum 0.06 (0.04) 0.06 (0.03) 0.06 (0.02) Knee 

Minimum -0.19 (0.07) -0.23 (0.04) -0.21 (0.06) 

Maximum 0.05 (0.04) 0.04 (0.04) 0.04 (0.03) 

Moment (Nm/kg) 

Transverse Plane 

Ankle 

Minimum -0.31 (0.05) -0.31 (0.09) -0.31 (0.06) 

Maximum 3.00 (0.91) 2.84 (1.13) 3.00 (1.21) Hip Minimum -1.71 (0.70) -1.65 (0.61) -2.31 (1.12) 

Maximum 3.80 (1.51) 4.31 (1.64) 4.22 (1.77) Knee 

Minimum -6.91 (1.54) -6.61 (2.74) -6.50 (2.13) 

Maximum 8.39 (1.12) 8.46 (0.97) 8.13 (1.41) 

Sagittal Plane 

Ankle 

Minimum -5.13 (0.71) -5.52 (0.73) -5.57 (1.31) 

Maximum 0.46 (0.38) 0.47 (0.39) 0.64 (0.62) Hip Minimum -1.06 (0.64) -0.89 (0.59) -0.99 (0.51) 

Maximum 1.00 (0.96) 0.97 (0.98) 0.93 (0.86) Knee 

Minimum -0.70 (0.63) -0.62 (0.62) -0.77 (0.60) 

Frontal Plane 

Maximum 0.71 (0.70) 0.63 (0.57) 0.98 (0.93) Ankle 

Minimum -0.46 (0.40) -0.38 (0.40) -0.69 (0.69) 

Maximum 0.16 (0.11) 0.20 (0.18) 0.16 (0.10) Hip Minimum -0.12 (0.09) -0.08 (0.05) -0.10 (0.07) 

Maximum 0.22 (0.16) 0.20 (0.13) 0.21 (0.21) Knee 

Minimum -0.05 (0.05) -0.08 (0.06) -0.07 (0.05) 

Maximum 0.05 (0.03) 0.06 (0.08) 0.07 (0.06) 

Power (W/kg) 

Transverse Plane 

Ankle 

Minimum -0.21 (0.10) -0.19 (0.08) -0.17 (0.09) 

Note: Values given as mean (s.d.), N=12 

Positive values indicate extensor, abductor, and internal rotator moment; and power generation 

Negative values indicate flexor, adductor, and external rotator moment; and power absorption 
29 

Table C-3a. Cycle time, joint angles, and ground reaction forces for squatting. 

Sole Condition 

Variable 

Baseline 1-inch Sole 2-inch Sole 

 Cycle Time (s) 3.079 (0.466) 3.143 (0.470) 3.056 (0.537) 

Maximum 93.9 (9.9) 95.4 (8.6) 93.9 (9.8) Hip Minimum -5.1 (2.2) -3.7 (2.4) -5.6 (3.2) 

Maximum 131.1 (9.2) 130.5 (9.7) 128.4 (10.0) Knee 

Minimum -5.0 (4.2) -3.0 (3.2) -4.1 (4.6) 

Sagittal Plane 

Maximum 29.2 (4.9) 29.1 (4.9) 28.2 (4.7) Ankle 

Minimum -2.7 (3.0) -2.4 (2.8) -2.4 (3.5) 

Maximum -2.3 (2.5) -2.3 (2.1) -2.1 (2.2) Hip Minimum -25.4 (7.2) -25.1 (8.7) -24.7 (9.2) 

Maximum 3.4 (2.8) 3.1 (3.2) 4.9 (6.4) Knee 

Minimum -14.3 (6.3) -16.8 (10.3) -15.8 (11.6) 

Frontal Plane 

Maximum 2.9 (2.6) 2.2 (1.9) 1.1 (2.6) Ankle 

Minimum -15.5 (4.9) -16.8 (5.8) -16.4 (5.7) 

Maximum -9.3 (5.2) -7.9 (3.8) -9.0 (6.0) Hip Minimum -18.0 (4.4) -17.1 (4.1) -17.6 (5.2) 

Maximum 6.3 (4.8) 6.2 (4.8) 7.0 (5.4) Knee 

Minimum -5.3 (5.1) -4.2 (5.9) -5.0 (4.8) 

Maximum 6.9 (3.4) 7.2 (4.8) 8.4 (3.4) 

Angle (degrees) 

Transverse Plane 

Ankle 

Minimum -3.1 (3.7) -3.3 (3.7) -1.3 (3.5) 

Maximum 0.63 (0.05) 0.63 (0.05) 0.63 (0.04) Vertical 

Minimum 0.40 (0.05) 0.40 (0.05) 0.42 (0.04) 

Anterior- Maximum 0.02 (0.01) 0.02 (0.01) 0.02 (0.01) 

Posterior Minimum -0.01 (0.01) -0.02 (0.01) -0.02 (0.01) 

Maximum 0.06 (0.03) 0.06 (0.01) 0.06 (0.02) 

Ground 

Reaction Force 

(N/BW) 

MedialLateral Minimum -0.01 (0.05) -0.02 (0.02) -0.02 (0.02) 

Note: Values given as mean (s.d.), N=12 

Positive values indicate flexion, adduction, and external rotation; upward, posterior and medial GRF 

Negative values indicate extension, abduction and internal rotation; downward, anterior and lateral GRF 
30 

Table C-3b. Joint moments and powers for squatting. 

Sole Condition Variable 

Baseline 1-inch Sole 2-inch Sole 

Maximum 0.73 (0.19) 0.76 (0.21) 0.76 (0.16) Hip Minimum -0.11 (0.08) -0.08 (0.06) -0.11 (0.12) 

Maximum 1.09 (0.17) 1.09 (0.18) 1.09 (0.14) Knee 

Minimum -0.11 (0.08) -0.09 (0.08) -0.10 (0.14) 

Maximum 0.34 (0.16) 0.36 (0.18) 0.34 (0.16) 

Sagittal Plane 

Ankle 

Minimum -0.02 (0.08) -0.05 (0.12) -0.03 (0.12) 

Maximum 0.25 (0.36) 0.21 (0.13) 0.21 (0.15) Hip Minimum -0.37 (0.37) -0.40 (0.16) -0.45 (0.18) 

Maximum 0.35 (0.31) 0.26 (0.09) 0.26 (0.08) Knee 

Minimum -0.00 (0.21) -0.04 (0.08) -0.06 (0.09) 

Frontal Plane 

Maximum 0.13 (0.15) 0.15 (0.12) 0.16 (0.09) Ankle 

Minimum -0.02 (0.09) 0.01 (0.07) 0.02 (0.05) 

Maximum 0.03 (0.09) 0.01 (0.06) 0.02 (0.03) Hip Minimum -0.07 (0.06) -0.08 (0.06) -0.07 (0.03) 

Maximum 0.08 (0.11) 0.09 (0.08) 0.08 (0.05) Knee 

Minimum -0.10 (0.18) -0.05 (0.05) -0.06 (0.04) 

Maximum 0.02 (0.11) 0.01 (0.06) 0.01 (0.03) 

Moment (Nm/kg) 

Transverse Plane 

Ankle 

Minimum -0.06 (0.07) -0.07 (0.07) -0.06 (0.03) 

Maximum 1.02 (0.28) 1.07 (0.31) 1.02 (0.23) Hip Minimum -0.79 (0.24) -0.86 (0.33) -0.85 (0.29) 

Maximum 1.91 (0.45) 1.90 (0.51) 1.80 (0.40) Knee 

Minimum -1.65 (0.44) -1.53 (0.35) -1.56 (0.40) 

Maximum 0.11 (0.10) 0.10 (0.08) 0.10 (0.07) 

Sagittal Plane 

Ankle 

Minimum -0.14 (0.08) -0.15 (0.13) -0.10 (0.05) 

Maximum 0.28 (0.13) 0.18 (0.08) 0.21 (0.13) Hip Minimum -0.28 (0.21) -0.20 (0.07) -0.21 (0.12) 

Maximum 0.28 (0.30) 0.21 (0.10) 0.19 (0.09) Knee 

Minimum -0.22 (0.19) -0.14 (0.10) -0.16 (0.07) 

Frontal Plane 

Maximum 0.03 (0.03) 0.04 (0.03) 0.03 (0.03) Ankle 

Minimum -0.04 (0.04) -0.04 (0.03) -0.03 (0.02) 

Maximum 0.03 (0.01) 0.02 (0.01) 0.02 (0.01) Hip Minimum -0.02 (0.01) -0.02 (0.01) -0.01 (0.01) 

Maximum 0.04 (0.06) 0.02 (0.02) 0.02 (0.01) Knee 

Minimum -0.03 (0.05) -0.02 (0.02) -0.02 (0.01) 

Maximum 0.01 (0.02) 0.01 (0.01) 0.01 (0.00) 

Power (W/kg) 

Transverse Plane 

Ankle 

Minimum -0.01 (0.02) -0.01 (0.01) -0.01 (0.01) 

Note: Values given as mean (s.d.), N=12 

Positive values indicate extensor, abductor, and internal rotator moment; and power generation 

Negative values indicate flexor, adductor, and external rotator moment; and power absorption 
31 

Table C-4a. Cycle time, joint angles, and ground reaction forces for right kneeling. 

Sole Condition 

Variable 

Baseline 1-inch Sole 2-inch Sole 

 Cycle Time (s) 3.522 (0.393) 3.761 (0.509) 3.956 (0.305) 

Maximum 12.0 (5.2) 19.3 (9.8) 19.4 (9.3) Hip Minimum -8.1 (4.6) -6.5 (3.1) -7.8 (3.3) 

Maximum 119.6 (9.7) 131.7 (14.9) 130.1 (14.7) Knee 

Minimum -0.1 (5.0) 1.3 (4.2) -0.3 (5.9) 

Sagittal Plane 

Maximum 33.3 (5.2) 35.1 (6.7) 35.8 (5.6) Ankle 

Minimum 2.9 (2.4) 1.5 (3.7) 1.3 (3.6) 

Maximum 2.8 (2.1) 2.0 (2.4) 2.8 (2.6) Hip Minimum -12.3 (4.1) -12.3 (3.9) -11.3 (2.9) 

Maximum 14.2 (9.8) 11.9 (6.7) 13.4 (8.0) Knee 

Minimum -0.7 (3.6) -3.2 (5.6) -2.6 (5.7) 

Frontal Plane 

Maximum 8.5 (4.6) 4.5 (5.8) 3.1 (4.6) Ankle 

Minimum -12.8 (4.1) -14.3 (5.4) -17.0 (6.9) 

Maximum -3.5 (5.0) 0.3 (6.5) 0.8 (4.7) Hip Minimum -17.7 (5.1) -19.0 (7.6) -20.4 (6.8) 

Maximum 4.9 (3.9) 5.7 (4.0) 5.6 (3.4) Knee 

Minimum -6.4 (3.8) -7.2 (6.6) -7.8 (7.3) 

Maximum 7.1 (2.7) 9.1 (5.5) 11.5 (5.4) 

Angle (degrees) 

Transverse Plane 

Ankle 

Minimum -13.7 (6.6) -9.1 (6.0) -8.6 (6.2) 

Maximum 1.01 (0.04) 1.02 (0.03) 1.04 (0.03) Vertical 

Minimum 0.24 (0.06) 0.22 (0.05) 0.20 (0.05) 

Anterior- Maximum 0.15 (0.02) 0.14 (0.02) 0.14 (0.02) 

Posterior Minimum -0.01 (0.01) 0.00 (0.01) -0.01 (0.02) 

Maximum 0.10 (0.02) 0.10 (0.01) 0.10 (0.02) 

Ground 

Reaction Force 

(N/BW) 

MedialLateral Minimum -0.00 (0.01) 0.00 (0.01) 0.00 (0.01) 

Note: Values given as mean (s.d.), N=12 

Positive values indicate flexion, adduction, and external rotation; upward, posterior and medial GRF 

Negative values indicate extension, abduction and internal rotation; downward, anterior and lateral GRF 
32 

Table C-4b. Joint moments and powers for right kneeling. 

Sole Condition Variable 

Baseline 1-inch Sole 2-inch Sole 

Maximum 0.17 (0.23) 0.22 (0.22) 0.14 (0.22) Hip Minimum -1.18 (0.16) -1.08 (0.26) -1.14 (0.23) 

Maximum 1.38 (0.18) 1.60 (0.27) 1.71 (0.24) Knee 

Minimum -0.12 (0.26) -0.09 (0.13) -0.04 (0.13) 

Maximum 1.20 (0.20) 1.24 (0.18) 1.18 (0.23) 

Sagittal Plane 

Ankle 

Minimum -0.15 (0.14) -0.25 (0.15) -0.34 (0.11) 

Maximum 0.91 (0.21) 0.89 (0.11) 0.92 (0.13) Hip Minimum -0.18 (0.08) -0.14 (0.13) -0.16 (0.12) 

Maximum 0.54 (0.14) 0.57 (0.10) 0.57 (0.14) Knee 

Minimum -0.08 (0.05) -0.13 (0.10) -0.17 (0.12) 

Frontal Plane 

Maximum 0.23 (0.13) 0.28 (0.18) 0.27 (0.11) Ankle 

Minimum -0.07 (0.09) -0.05 (0.08) -0.04 (0.05) 

Maximum 0.12 (0.07) 0.11 (0.06) 0.11 (0.03) Hip Minimum -0.06 (0.06) -0.04 (0.06) -0.04 (0.03) 

Maximum 0.06 (0.06) 0.03 (0.06) 0.03 (0.02) Knee 

Minimum -0.13 (0.08) -0.18 (0.08) -0.17 (0.05) 

Maximum 0.02 (0.06) 0.02 (0.05) 0.03 (0.02) 

Moment (Nm/kg) 

Transverse Plane 

Ankle 

Minimum -0.20 (0.04) -0.20 (0.09) -0.21 (0.04) 

Maximum 0.41 (0.15) 0.41 (0.16) 0.51 (0.15) Hip Minimum -0.34 (0.22) -0.37 (0.22) -0.48 (0.28) 

Maximum 2.73 (0.44) 2.46 (1.00) 2.45 (1.00) Knee 

Minimum -2.58 (0.93) -2.35 (0.83) -2.41 (0.63) 

Maximum 0.91 (0.14) 0.91 (0.17) 0.91 (0.17) 

Sagittal Plane 

Ankle 

Minimum -1.02 (0.17) -1.02 (0.21) -0.95 (0.14) 

Maximum 0.28 (0.15) 0.27 (0.10) 0.25 (0.09) Hip Minimum -0.39 (0.11) -0.36 (0.15) -0.33 (0.14) 

Maximum 0.36 (0.19) 0.40 (0.32) 0.30 (0.20) Knee 

Minimum -0.18 (0.13) -0.21 (0.13) -0.17 (0.09) 

Frontal Plane 

Maximum 0.08 (0.04) 0.12 (0.06) 0.10 (0.04) Ankle 

Minimum -0.12 (0.08) -0.09 (0.10) -0.12 (0.08) 

Maximum 0.04 (0.04) 0.05 (0.03) 0.05 (0.02) Hip Minimum -0.03 (0.03) -0.04 (0.02) -0.04 (0.02) 

Maximum 0.04 (0.06) 0.05 (0.03) 0.06 (0.05) Knee 

Minimum -0.04 (0.05) -0.06 (0.04) -0.06 (0.04) 

Maximum 0.06 (0.06) 0.07 (0.04) 0.05 (0.03) 

Power (W/kg) 

Transverse Plane 

Ankle 

Minimum -0.04 (0.04) -0.05 (0.02) -0.04 (0.02) 

Note: Values given as mean (s.d.), N=12 

Positive values indicate extensor, abductor, and internal rotator moment; and power generation 

Negative values indicate flexor, adductor, and external rotator moment; and power absorption 
33 

Table C-5a. Cycle time, joint angles, and ground reaction forces for left kneeling. 

Sole Condition 

Variable 

Baseline 1-inch Sole 2-inch Sole 

 Cycle Time (s) 3.292 (0.421) 3.462 (0.393) 3.522 (0.444) 

Maximum 95.2 (6.3) 98.4 (5.4) 102.4 (9.8) Hip Minimum -2.5 (4.9) -0.7 (2.0) -1.9 (4.7) 

Maximum 119.1 (8.3) 123.6 (5.9) 128.7 (7.7) Knee 

Minimum 3.6 (6.9) 4.5 (2.9) 3.1 (6.4) 

Sagittal Plane 

Maximum 21.2 (7.2) 22.8 (4.9) 24.2 (4.7) Ankle 

Minimum -0.3 (2.6) -0.1 (2.4) -0.9 (2.4) 

Maximum 2.2 (2.3) 1.5 (2.5) 2.4 (3.0) Hip Minimum -18.7 (6.0) -24.0 (5.8) -23.5 (5.5) 

Maximum 4.9 (3.9) 3.5 (1.9) 4.9 (5.2) Knee 

Minimum -10.2 (5.1) -15.3 (6.2) -15.5 (7.6) 

Frontal Plane 

Maximum -0.4 (3.3) -1.1 (2.5) -1.2 (2.5) Ankle 

Minimum -15.4 (4.8) -17.3 (4.2) -18.3 (4.1) 

Maximum -2.4 (4.5) -3.7 (5.8) -4.3 (7.3) Hip Minimum -15.6 (3.6) -17.0 (4.9) -18.4 (6.9) 

Maximum 4.6 (3.0) 7.5 (4.3) 7.1 (5.1) Knee 

Minimum -5.8 (3.4) -2.6 (3.7) -3.7 (5.8) 

Maximum 8.3 (3.9) 9.5 (3.0) 10.9 (3.7) 

Angle (degrees) 

Transverse Plane 

Ankle 

Minimum -2.2 (3.5) -1.9 (2.9) -1.5 (3.0) 

Maximum 1.02 (0.04) 1.02 (0.06) 1.03 (0.04) Vertical 

Minimum 0.27 (0.07) 0.27 (0.08) 0.24 (0.08) 

Anterior- Maximum 0.02 (0.01) 0.03 (0.02) 0.02 (0.03) 

Posterior Minimum -0.09 (0.04) -0.10 (0.03) -0.09 (0.04) 

Maximum 0.09 (0.02) 0.09 (0.01) 0.08 (0.01) 

Ground 

Reaction Force 

(N/BW) 

MedialLateral Minimum -0.00 (0.02) -0.00 (0.02) -0.01 (0.02) 

Note: Values given as mean (s.d.), N=12 

Positive values indicate flexion, adduction, and external rotation; upward, posterior and medial GRF 

Negative values indicate extension, abduction and internal rotation; downward, anterior and lateral GRF 
34 

Table C-5b. Joint moments and powers for left kneeling. 

Sole Condition Variable 

Baseline 1-inch Sole 2-inch Sole 

Maximum 1.34 (0.32) 1.46 (0.28) 1.42 (0.25) Hip Minimum -0.25 (0.17) -0.17 (0.14) -0.24 (0.18) 

Maximum 1.27 (0.13) 1.35 (0.16) 1.41 (0.09) Knee 

Minimum 0.01 (0.11) -0.01 (0.11) 0.02 (0.12) 

Maximum 0.59 (0.22) 0.61 (0.19) 0.57 (0.19) 

Sagittal Plane 

Ankle 

Minimum -0.07 (0.09) -0.04 (0.08) -0.10 (0.13) 

Maximum 0.82 (0.26) 0.73 (0.12) 0.73 (0.16) Hip Minimum -0.34 (0.19) -0.34 (0.18) -0.31 (0.22) 

Maximum 0.49 (0.16) 0.55 (0.18) 0.56 (0.15) Knee 

Minimum -0.07 (0.14) -0.09 (0.10) -0.06 (0.07) 

Frontal Plane 

Maximum 0.13 (0.08) 0.23 (0.07) 0.23 (0.10) Ankle 

Minimum -0.05 (0.11) -0.00 (0.06) -0.01 (0.05) 

Maximum 0.03 (0.10) 0.01 (0.02) 0.03 (0.02) Hip Minimum -0.15 (0.05) -0.18 (0.05) -0.16 (0.05) 

Maximum 0.09 (0.03) 0.10 (0.03) 0.10 (0.04) Knee 

Minimum -0.11 (0.06) -0.10 (0.02) -0.13 (0.03) 

Maximum 0.05 (0.06) 0.05 (0.03) 0.07 (0.03) 

Moment (Nm/kg) 

Transverse Plane 

Ankle 

Minimum -0.12 (0.03) -0.12 (0.03) -0.12 (0.03) 

Maximum 2.55 (0.78) 2.63 (0.76) 2.60 (0.81) Hip Minimum -1.84 (0.65) -2.20 (0.61) -2.02 (0.61) 

Maximum 2.74 (0.69) 2.70 (0.52) 3.14 (0.81) Knee 

Minimum -2.28 (0.96) -2.12 (0.69) -2.44 (0.74) 

Maximum 0.29 (0.20) 0.36 (0.21) 0.32 (0.20) 

Sagittal Plane 

Ankle 

Minimum -0.26 (0.18) -0.22 (0.05) -0.25 (0.17) 

Maximum 0.24 (0.13) 0.27 (0.09) 0.25 (0.13) Hip Minimum -0.21 (0.07) -0.22 (0.07) -0.26 (0.15) 

Maximum 0.23 (0.17) 0.35 (0.15) 0.42 (0.24) Knee 

Minimum -0.21 (0.15) -0.33 (0.23) -0.29 (0.15) 

Frontal Plane 

Maximum 0.05 (0.04) 0.06 (0.04) 0.06 (0.03) Ankle 

Minimum -0.04 (0.03) -0.05 (0.02) -0.06 (0.04) 

Maximum 0.04 (0.02) 0.06 (0.01) 0.05 (0.04) Hip Minimum -0.06 (0.05) -0.07 (0.03) -0.06 (0.02) 

Maximum 0.03 (0.01) 0.04 (0.02) 0.04 (0.01) Knee 

Minimum -0.03 (0.01) -0.03 (0.02) -0.04 (0.02) 

Maximum 0.02 (0.02) 0.02 (0.02) 0.03 (0.03) 

Power (W/kg) 

Transverse Plane 

Ankle 

Minimum -0.03 (0.02) -0.03 (0.01) -0.02 (0.01) 

Note: Values given as mean (s.d.), N=12 for Baseline and 2-inch conditions, N=10 for 1-inch condition 

Positive values indicate extensor, abductor, and internal rotator moment; and power generation 

Negative values indicate flexor, adductor, and external rotator moment; and power absorption 
-30

-20-10

0

10203040

0 20 40 60 80 100

-20

0

20406080

0 20 40 60 80 100

-15-10

-5

05

1015

0 20 

-8-6-4-2

024

0 20 40 60 80 100

-4-2

02468

0 20 40 60 80 100

-10

-8-6-4-2

02468

0 20 

-20-15-10

-5

0

0 20 40 60 80 100

-6-4-2

02468

1012

0 20 40 60 80 100

-8-6-4-2

0246

0 20 4

Hip Knee 

Sagittal Frontal Transverse 

Figure D-1. Joint angles (degrees) over one stride of walking: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12, 0%=Begi

lines=Begin Swing, 100%= End Swing. 

 Ext Flx 

 Flx 

 Pla Dor 

 Abd Add 

Abd Add 

 Abd Add 

 Int 

 Int Ext 

 Int Ext 

35 
-1.5

-1

-0.5

0

0.5

1

1.5

0 20 40 60 80 100

-0.6-0.4-0.2

0

0.20.40.60.8

0 20 40 60 80 100

-1

-0.5

0

0.5

1

1.5

2

0 20 

-0.2

0

0.20.40.60.8

1

0 20 40 60 80 100 -0.2

-0.1

0

0.10.20.30.4

0 20 40 60 80 100

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

0 20 

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0 20 40 60 80 100

-0.1

-0.08-0.06-0.04-0.02

0

0.020.04

0 20 40 60 80 100

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0 20 

Hip Knee 

Sagittal Frontal Transverse 

Figure D-2. Joint moments (Nm/kg) over one stride of walking: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12, 0%=Be

lines=Begin Swing, 100%= End Swing. 

 Flx Ext 

 Dor Pla 

 Abd 

 Add Abd 

Add Abd 

 Ext Int 

 Ext Int 

 Ext Int 

 Flx Ext 

36 
-1

-0.5

0

0.5

1

1.5

0 20 40 60 80 100

-1.5

-1

-0.5

0

0.5

1

0 20 40 60 80 100

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

0 20 

-0.4-0.2

0

0.20.40.6

0 20 40 60 80 100

-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0 20 40 60 80 100

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0 20 

-0.1

-0.08-0.06-0.04-0.02

0

0.020.040.06

0 20 40 60 80 100

-0.06-0.04-0.02

0

0.020.04

0 20 40 60 80 100

-0.05-0.04-0.03-0.02-0.01

0

0.01

0 20 

Hip Knee 

Sagittal Frontal Transverse 

Figure D-3. Joint powers (W/kg) over one stride of walking: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12, 0%=Begin 

lines=Begin Swing, 100%= End Swing. 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

37 
-40

-30-20-10

0

10203040

0 20 40 60 80 100

0

20406080

100

0 20 40 60 80 100 -20

-10

0

102030

0 20 

-6-4-2

024

0 20 40 60 80 100

-2

02468

0 20 40 60 80 100

-20-15-10

-5

05

10

0 20 

-16-14-12-10

-8-6-4-2

02

0 20 40 60 80 100

-10

-5

05

1015

0 20 40 60 80 100

-4-2

0246

0 20 4

Hip Knee 

Sagittal Frontal Transverse 

Figure D-4. Joint angles (degrees) over one stride of running: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12, 0%=Begi

lines=Begin Swing, 100%= End Swing. 

 Ext Flx 

 Flx 

 Pla Dor 

 Abd Add 

Abd Add 

 Abd Add 

 Int 

 Int Ext 

 Int Ext 

38 
-1

-0.5

0

0.5

1

1.5

0 20 40 60 80 100

-0.5

0

0.5

1

1.5

2

2.5

0 20 40 60 80 100 -0.5

0

0.5

1

1.5

2

2.5

3

0 20 

-0.5

0

0.5

1

1.5

2

0 20 40 60 80 100

-0.2

0

0.20.40.60.8

1

0 20 40 60 80 100 -0.1

0

0.10.20.30.40.50.6

0 20 

-0.15

-0.1

-0.05

0

0.05

0.1

0 20 40 60 80 100

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

0 20 40 60 80 100

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0 20 

Hip Knee 

Sagittal Frontal Transverse 

Figure D-5. Joint moments (Nm/kg) over one stride of running: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12, 0%=Be

lines=Begin Swing, 100%= End Swing. 

 Flx Ext 

 Pla 

 Abd 

 Abd 

 Ext Int 

 Ext Int 

 Ext Int 

 Flx Ext 

 Abd 

39 
-1

-0.5

0

0.5

1

1.5

2

2.5

3

0 20 40 60 80 100

-8-6-4-2

0246

0 20 40 60 80 100

-6-4-2

02468

10

0 20 

-1

-0.8-0.6-0.4-0.2

0

0.20.4

0 20 40 60 80 100

-1

-0.5

0

0.5

1

0 20 40 60 80 100

-1

-0.5

0

0.5

1

0 20 

-0.04-0.02

0

0.020.040.060.08

0.1

0.12

0 20 40 60 80 100

-0.05

0

0.05

0.1

0.15

0.2

0 20 40 60 80 100

-0.2

-0.15

-0.1

-0.05

0

0.05

0 20 

Hip Knee 

Sagittal Frontal Transverse 

Figure D-6. Joint powers (W/kg) over one stride of running: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12, 0%=Begin 

lines=Begin Swing, 100%= End Swing. 

Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

Abs Gen 

 Gen 

 Abs 

40 
-0.2

0

0.20.40.60.8

1

1.21.4

0 20 40 60 80 100 -0.2

-0.1

0

0.10.20.3

0 20 40 60 80 100

-0.02

0

0.020.040.060.08

0.1

0 20 

-0.5

0

0.5

1

1.5

2

2.5

3

0 20 40 60 80 100 -0.3

-0.2-0.1

0

0.10.20.3

0 20 40 60 80 100

-0.05

0

0.05

0.1

0.15

0.2

0.25

0 20 

Vertical Anterior/Posterior Late

Walking Running

Figure D-7. Ground reaction forces (N/BW) over one stride of walking and running: (Blue=Baseline, Green=1-inch Sole, Red=2-inch 

0%=Begin Stance, vertical lines=Begin Swing, 100%= End Swing. 

 Ant Post 

 Vert 

 Med 

Ant Post 

 Vert 

 Med 

41 
-20

0

20406080

100

0 20 40 60 80 100 -20

0

20406080

100120140

0 20 40 60 80 100 -5

05

1015202530

0 20 

-30-25-20-15-10

-5

0

0 20 40 60 80 100

-20-15-10

-5

05

0 20 40 60 80 100

-20-15-10

-5

05

0 20 

-20-15-10

-5

0

0 20 40 60 80 100

-6-4-2

0246

0 20 40 60 80 100

-4-2

02468

0 20 

Hip Knee 

Sagittal Frontal Transverse 

Figure D-8. Joint angles (degrees) over one cycle of squatting: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12.

 Flx 

 Flx 

 Dor 

 Abd 

 Abd 

 Abd 

 Int 

 Int Ext 

 Int Ext 

42 
-0.2

0

0.20.40.60.8

0 20 40 60 80 100

-0.2

0

0.20.40.60.8

1

1.2

0 20 40 60 80 100

0

0.05

0.1

0.15

0.2

0.25

0.3

0 20 

-0.5-0.4-0.3-0.2-0.1

0

0.10.20.3

0 20 40 60 80 100

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0 20 40 60 80 100

0

0.020.040.060.08

0.1

0.120.14

0 20 

-0.08-0.06-0.04-0.02

0

0.02

0 20 40 60 80 100

-0.08-0.06-0.04-0.02

0

0.020.040.06

0 20 40 60 80 100

-0.06-0.05-0.04-0.03-0.02-0.01

0

0 20 

Hip Knee 

Sagittal Frontal Transverse 

Figure D-9. Joint moments (Nm/kg) over one cycle of squatting: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12. 

 Flx Ext 

 Pla 

 Add Abd 

 Abd 

 Abd 

 Ext Int 

 Ext Int 

 Ext Int 

 Flx Ext 

43 
-1

-0.5

0

0.5

1

1.5

0 20 40 60 80 100

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

0 20 40 60 80 100

-0.15

-0.1

-0.05

0

0.05

0.1

0 20 

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0 20 40 60 80 100

-0.2-0.1

0

0.10.20.3

0 20 40 60 80 100

-0.02-0.01

0

0.010.020.03

0 20 

-0.04-0.03-0.02-0.01

0

0.010.020.03

0 20 40 60 80 100

-0.015

-0.01

-0.005

0

0.005

0.01

0.015

0.02

0 20 40 60 80 100

-0.006-0.004-0.002

0

0.0020.0040.006

0 20 

Hip Knee 

 Abd Frontal Transverse 

Figure D-10. Joint powers (W/kg) over one cycle of squatting: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12. 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

44 
-10

-5

05

101520

0 20 40 60 80 100 0

20406080

100120140

0 20 40 60 80 100

05

101520253035

0 20 

-14-12-10

-8-6-4-2

024

0 20 40 60 80 100

-2

02468

101214

0 20 40 60 80 100 -15

-10

-5

05

10

0 20 

-20-15-10

-5

0

0 20 40 60 80 100

-6-4-2

0246

0 20 40 60 80 100

-15-10

-5

05

10

0 20 

Hip Knee 

Sagittal Frontal Transverse 

Figure D-11. Joint angles (degrees) over one cycle of right kneeling: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12. 

 Flexion 

 Flexion 

 Dorsiflexion 

 Abduction 

 Adduction 

 Abd Add 

 Internal Rotation 

 Int. Rot. Ext. Rot. 

 Int. Rot. Ext. Rot. 

45 
-1.2

-1

-0.8-0.6-0.4-0.2

0

0.20.4

0 20 40 60 80 100

-0.5

0

0.5

1

1.5

2

0 20 40 60 80 100

-0.4-0.2

0

0.20.40.60.8

1

1.2

0 20 

-0.2

0

0.20.40.60.8

1

0 20 40 60 80 100 -0.2

-0.1

0

0.10.20.30.40.50.6

0 20 40 60 80 100

-0.05

0

0.05

0.1

0.15

0.2

0.25

0 20 

-0.04-0.02

0

0.020.040.060.08

0.1

0 20 40 60 80 100

-0.02

0

0.020.040.060.08

0.1

0.120.14

0 20 40 60 80 100 -0.2

-0.15

-0.1

-0.05

0

0.05

0 20 

Hip Knee 

Sagittal Frontal Transverse 

Figure D-12. Joint moments (Nm/kg) over one cycle of right kneeling: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12. 

 Flx Ext 

 Dor Pla 

 Abd 

 Add Abd 

Add Abd 

 Ext Int 

 Ext Int 

 Ext Int 

 Flx Ext 

46 
-0.3

-0.2-0.1

0

0.10.20.30.4

0 20 40 60 80 100

-3-2-1

0123

0 20 40 60 80 100

-1

-0.5

0

0.5

1

0 20 

-0.4-0.3-0.2-0.1

0

0.10.20.3

0 20 40 60 80 100

-0.2-0.1

0

0.10.20.30.4

0 20 40 60 80 100

-0.08-0.06-0.04-0.02

0

0.020.040.060.08

0 20 

-0.02-0.01

0

0.010.020.03

0 20 40 60 80 100

-0.03-0.02-0.01

0

0.010.020.030.04

0 20 40 60 80 100

-0.02-0.01

0

0.010.020.030.04

0 20 

Hip Knee 

Sagittal Frontal Transverse 

Figure D-13. Joint powers (W/kg) over one cycle of right kneeling: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12.

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

47 
-20

0

20406080

100120

0 20 40 60 80 100

0

20406080

100120140

0 20 40 60 80 100

05

10152025

0 20 

-25-20-15-10

-5

05

0 20 40 60 80 100

-20-15-10

-5

05

0 20 40 60 80 100

-20-15-10

-5

0

0 20 

-16-14-12-10

-8-6-4-2

0

0 20 40 60 80 100

-6-4-2

0246

0 20 40 60 80 100

-2

02468

10

0 20 

Hip Knee 

Sagittal Frontal Transverse 

Figure D-14. Joint angles (degrees) over one cycle of left kneeling: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12. 

 Flexion 

 Flexion 

 Dorsiflexion 

 Abduction 

 Abduction 

 Abduction 

 Internal Rotation 

 External Rotation 

 Int. Rot. Ext. Rot. 

48 
-0.5

0

0.5

1

1.5

0 20 40 60 80 100 0

0.20.40.60.8

1

1.21.4

0 20 40 60 80 100

0

0.10.20.30.40.50.6

0 20 

-0.4-0.2

0

0.20.40.60.8

0 20 40 60 80 100

-0.1

0

0.10.20.30.40.5

0 20 40 60 80 100

0

0.05

0.1

0.15

0.2

0.25

0 20 

-0.16-0.14-0.12

-0.1

-0.08-0.06-0.04-0.02

0

0.02

0 20 40 60 80 100

-0.1

-0.05

0

0.05

0.1

0 20 40 60 80 100

-0.1

-0.08-0.06-0.04-0.02

0

0.020.040.06

0 20 

Hip Knee 

Sagittal Frontal Transverse 

Figure D-15. Joint moments (Nm/kg) over one cycle of left kneeling: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12. 

 Flx Ext 

 Dor Pla 

 Abd 

 Abd 

 Abd 

 Ext 

 Ext Int 

 Ext Int 

 Flx Ext 

49 
-3

-2-1

0123

0 20 40 60 80 100

-3-2-1

01234

0 20 40 60 80 100

-0.3-0.2-0.1

0

0.10.20.30.4

0 20 

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0 20 40 60 80 100

-0.3-0.2-0.1

0

0.10.20.30.4

0 20 40 60 80 100

-0.04-0.02

0

0.020.040.06

0 20 

-0.04-0.03-0.02-0.01

0

0.010.020.03

0 20 40 60 80 100

-0.015

-0.01

-0.005

0

0.005

0.01

0.015

0.02

0 20 40 60 80 100

-0.02

-0.015

-0.01

-0.005

0

0.005

0.01

0.015

0 20 

Hip Knee 

Sagittal Frontal Transverse 

Figure D-16. Joint powers (W/kg) over one cycle of left kneeling: (Blue=Baseline, Green=1-inch Sole, Red=2-inch Sole), N=12. 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

 Abs Gen 

50 
0

0.10.20.30.40.50.60.7

0 20 40 60 80 100 -0.004

-0.002

0

0.0020.0040.0060.008

0.01

0 20 40 60 80 100

-0.02-0.01

0

0.010.020.030.040.050.060.07

0 20 

0

0.20.40.60.8

1

1.2

0 20 40 60 80 100

0

0.020.040.060.08

0.1

0.120.14

0 20 40 60 80 100

0

0.020.040.060.08

0.1

0 20 

0

0.20.40.60.8

1

1.2

0 20 40 60 80 100 -0.08

-0.06-0.04-0.02

0

0.02

0 20 40 60 80 100

0

0.020.040.060.08

0.1

0 20 

Vertical Anterior/Posterior Late

Squatting Right Kneeling Left Kneeling 

Figure D-17. Ground reaction forces (N/BW) over one cycle of squatting, right kneeling, and left kneeling: (Blue=Baseline, Green=1-i

N=12. 

 Anterior Post. 

 Vertical 

 Medial 

 Posterior 

 Vertical 

 Lateral Med. 

 Anterior 

 Vertical 

 Lateral Medial 

51 
52 

NO. OF 

COPIES ORGANIZATION

 1 DEFENSE TECHNICAL 

 (PDF INFORMATION CTR 

 ONLY) DTIC OCA 

 8725 JOHN J KINGMAN RD 

 STE 0944 

 FORT BELVOIR VA 22060-6218 

 1 US ARMY RSRCH DEV & ENGRG CMD 

 SYSTEMS OF SYSTEMS 

 INTEGRATION 

 AMSRD SS T 

 6000 6TH ST STE 100 

 FORT BELVOIR VA 22060-5608 

 1 INST FOR ADVNCD TCHNLGY 

 THE UNIV OF TEXAS AT AUSTIN 

 3925 W BRAKER LN STE 400 

 AUSTIN TX 78759-5316 

 1 DIRECTOR 

 US ARMY RESEARCH LAB 

 IMNE ALC IMS 

 2800 POWDER MILL RD 

 ADELPHI MD 20783-1197 

 1 DIRECTOR 

 US ARMY RESEARCH LAB 

 AMSRD ARL CI OK TL 

 2800 POWDER MILL RD 

 ADELPHI MD 20783-1197 

 2 DIRECTOR 

 US ARMY RESEARCH LAB 

 AMSRD ARL CS OK T 

 2800 POWDER MILL RD 

 ADELPHI MD 20783-1197 

 1 DIRECTOR 

 US ARMY RESEARCH LAB 

 AMSRD ARL CI ES M MUNGIOLE 

 2800 POWDER MILL RD 

 ADELPHI MD 20783-1197 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR M DR M STRUB 

 6359 WALKER LANE SUITE 100 

 ALEXANDRIA VA 22310 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MA J MARTIN 

 MYER CENTER RM 2D311 

 FT MONMOUTH NJ 07703-5630 

NO. OF 

COPIES ORGANIZATION

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MC A DAVISON 

 320 MANSCEN LOOP STE 166 

 FT LEONARD WOOD MO 65473-8929 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MD T COOK 

 BLDG 5400 RM C242 

 REDSTONE ARSENAL AL 35898-7290 

 1 COMMANDANT USAADASCH 

 ATTN ATSA CD 

 ATTN AMSRD ARL HR ME MS A MARES 

 5800 CARTER RD 

 FT BLISS TX 79916-3802 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MI J MINNINGER 

 BLDG 5400 RM C242 

 REDSTONE ARSENAL AL 35898-7290 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MM DR V RICE 

 BLDG 4011 RM 217 

 1750 GREELEY RD 

 FT SAM HOUSTON TX 78234-5094 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MG R SPINE 

 BUILDING 333 

 PICATINNY ARSENAL NJ 07806-5000 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MH C BURNS 

 BLDG 1002 ROOM 117 

 1ST CAVALRY REGIMENT RD 

 FT KNOX KY 40121 

 1 ARMY RSCH LABORATORY - HRED 

 AVNC FIELD ELEMENT 

 ATTN AMSRD ARL HR MJ D DURBIN 

 BLDG 4506 (DCD) RM 107 

 FT RUCKER AL 36362-5000 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MK MR J REINHART 

 10125 KINGMAN RD 

 FT BELVOIR VA 22060-5828 
53 

NO. OF 

COPIES ORGANIZATION

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MV HQ USAOTC 

 S MIDDLEBROOKS 

 91012 STATION AVE ROOM 111 

 FT HOOD TX 76544-5073 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MY M BARNES 

 2520 HEALY AVE STE 1172 BLDG 51005 

 FT HUACHUCA AZ 85613-7069 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MP D UNGVARSKY 

 BATTLE CMD BATTLE LAB 

 415 SHERMAN AVE UNIT 3 

 FT LEAVENWORTH KS 66027-2326 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR M DR B KNAPP 

 ARMY G1 MANPRINT DAPE MR 

 300 ARMY PENTAGON ROOM 2C489 

 WASHINGTON DC 20310-0300 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MJK MS D BARNETTE 

 JFCOM JOINT EXPERIMENTATION J9 

 JOINT FUTURES LAB 

 115 LAKEVIEW PARKWAY SUITE B 

 SUFFOLK VA 23435 

 2 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MQ M R FLETCHER 

 US ARMY SBCCOM NATICK SOLDIER CTR 

 AMSRD NSC SS E J OBUSEK 

 BLDG 3 RM 341 

 NATICK MA 01760-5020 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MT DR J CHEN 

 12350 RESEARCH PARKWAY 

 ORLANDO FL 32826-3276 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MS MR C MANASCO 

 SIGNAL TOWERS RM 303A 

 FORT GORDON GA 30905-5233 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MU M SINGAPORE 

 6501 E 11 MILE RD MAIL STOP 284 

 BLDG 200A 2ND FL RM 2104 

 WARREN MI 48397-5000 

NO. OF 

COPIES ORGANIZATION

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MF MR C HERNANDEZ 

 BLDG 3040 RM 220 

 FORT SILL OK 73503-5600 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MW E REDDEN 

 BLDG 4 ROOM 332 

 FT BENNING GA 31905-5400 

 1 ARMY RSCH LABORATORY - HRED 

 ATTN AMSRD ARL HR MN R SPENCER 

 DCSFDI HF 

 HQ USASOC BLDG E2929 

 FORT BRAGG NC 28310-5000 

 1 DARPA 

 DEFENSE SCIENCES OFC (J MAIN) 

 3701 NORTH FAIRFAX DR 

 ARLINGTON VA 22203-1714 

 1 OAK RIDGE NATL LABORATORY 

 ROBOTICS AND ENERGETIC SYSTEMS 

 ENG SCIENCE AND TECH DIV J JANSEN 

 PO BOX 2008 BETHAL VALLEY RD 

 BLDG 7601 MS 6305 

 OAK RIDGE TN 37831-6426 

 ABERDEEN PROVING GROUND

 1 DIRECTOR 

 US ARMY RSCH LABORATORY 

 ATTN AMSRD ARL CI OK TECH LIB 

 BLDG 4600 

 1 DIRECTOR 

 US ARMY RSCH LABORATORY 

 ATTN AMSRD ARL CI OK S FOPPIANO 

 BLDG 459 

 1 DIRECTOR 

 US ARMY RSCH LABORATORY 

 ATTN AMSRD ARL HR MR F PARAGALLO 

 BLDG 459 

 10 DIRECTOR 

 US ARMY RSCH LABORATORY 

 ATTN AMSRD ARL HR SB A BOYNTON (5) 

 P CROWELL (5 CYS) 

 BLDG 459