^\D
`
`BY RICHARD C. NELSON
`AND
`PHILIP E. MARTIN
`
`BIOMECHANICS LABORATORY
`THE PENNSYLVANIA STATE UNIVERSITY
`UNIVERSITY PARK, PENNSYLVANIA
`
`MARCH 1982
`
`UNITED STATES ARMY NATICK
`RESEARCH & DEVELOPMENT LABORATORIES
`NATICK, MASSACHUSETTS 01760
`
`APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED
`
`Petitioner Ex. 1083 Page 1
`
`

`
`Approved for public release; distribution unlimited.
`
`Citation of trade names in this report does not
`constitute an official indorsement or approval of the
`use of such items.
`
`Destroy this report when no longer needed. Do not
`return it to the originator.
`
`!
`
`Petitioner Ex. 1083 Page 2
`
`

`
`ITMrTT.A.qfiTFTEn
`SECURITY CLASSIFICATION OF THIS PAGE (*hm Dmtm Kntmrmd)
`READ INSTRUCTIONS
`REPORT DOCUMENTATION PAGE
`BEFORE COMPLETING FORM
`2. OOVT ACCESSION NO. 3. RECIPIENT'S CATALOO NUMBER
`I. REPORT NUMBER
`NATICK TR-82/016
`
`S. TYPE OF REPORT A PERIOD COVEREO
`«. TITLE (md Subtitl.)
`Final Report for Period Oct-
`VOLUME II, EFFECTS OF GENDER, LOAD, AND BACKPACK
`ober 1, 1979 to August 31, 1981
`ON EASY STANDING AND VERTICAL JUMP PERFORMANCE.
`
`7. AUTHORfA)
`Richard C. Nelson, Ph.D.
`Philip E. Martin, M.S.
`
`«. PERFORMING ORO. REPORT NUMBER
`IPL-240
`ft. CONTRACT OR GRANT NUMBERO)
`
`DAAK60-79-C-0131
`
`ft. PERFORMING ORGANIZATION NAME AND ADDRESS
`Biomechanics Laboratory
`The Pennsylvania State University
`University Park. Pennsylvania 16802
`II. CONTROLLING OFFICE NAME AND ADORESS
`US Army Natick Research and Development Laboratori
`e 3
`ATTN: DRDNA-ICCH
`Natick, Massachusetts 01760
`14. MONITORING AGENCY NAME A AOORESSf" dlttormntfrom Controlling OtUc»)
`
`10. PROGRAM ELEMENT. PROJECT. TASK
`AREA A WORK UNIT NUMBERS
`6.2,
`1L162723AH98AJ005
`
`12. REPORT DATE
`March 1982
`IS. NUMBER OF PAGES
`74
`IS. SECURITY CLASS, (of Oil a report)
`UNCLASSIFIED
`
`is«, DECLASSIFICATION/DOWNGRADING
`SCHEDULE
`
`16. DISTRIBUTION STATEMENT (of thlo Report)
`
`Approved for public release; distribution unlimited.
`
`17. DISTRIBUTION STATEMENT (of fh« mbattmct ontorod In Stock 20, If dlllmrmnt from Report)
`
`B
`
`19. KEY WORDS (Continue on rmeormm »14m If nocmacmwy mxd Identity by block number)
`loads
`load carrying
`military personnel
`males
`anthropometry
`exercise
`females
`combative movement
`field tests
`frame-pack systems
`performance
`field operations
`
`IB. ABSTRACT (VmtmaM em ntwmtmm etdm ft trmteeemry mod Identify by block numb*)
`This study was conducted to determine the effects of loads worn or carried
`and the type of backpack used on parameters of the easy standing and vertical
`jumping performance of men ajnd women. Fourteen men and eleven women participa-
`ted in the easy standing test and eleven men and ten women participated in the
`vertical jump under each of the following load conditions: Load 1 - baseline
`(shorts, t-shirt, sneakers); Load 2 - fighting gear (utility shirt and trousers,
`boots, ALICE fighting gear); Load 3 - combat gear (Load 2 plus PASGT helmet,
`PASGT armor vest, simulated M16 rifle); Load A - combat gear and 20-lb backpack
`oo,; JAM 7» 1473 COfTIO« OP » MOV BB I» OBSOLETE
`
`UNCLASSIFIED
`SECURITY CLASSIFICATION OF THIS PAGE (tmem Dmtm mntoreeQ
`
`Mhftaah
`
`^imnmi
`
`|r.-.,.^,.^...^ .|n1|M
`
`MM
`
`Petitioner Ex. 1083 Page 3
`
`

`
`SKCUMTV CLASSIFICATION OP THIS PM*(Wkm Dmlm Mmtmn*)
`load (Load 3 plus backpack with 20-lb load); Load 5 - combat gear and 35-lb back-
`pack load (Load 4 plus an additional 15 lb in pack). The men were also tested
`under a sixth load condition: Load 6 - combat gear and 50-lb backpack load
`(Load 4 plus an additional 30 lb in pack). The subjects carried Loads 4 through
`6 using four different backpack systems. Two of these consisted of Army frames
`equipped with the standard Army pack. The third was an experimental item, a
`packboard made of rigid aluminum, used with the Army pack. The fourth backpack
`was a commercially-available, internal frame system. Analyses of the easy
`standing data indicated that both men and women demonstrated greater stability
`with the medium than with the lighter or heavier loads. The internal frame
`backpack resulted in greater postural stability relative to the three, external-
`frame systems. Increasing loads produced a systematic, linear decrease in
`vertical jumping performance. Analyses of the effects of backpacks on the
`parameters of jumping performance revealed few differences among the packs.
`However, it was found that height of jump was somewhat better with the internal
`frame system than with the external-frame backpacks. Additional analyses were
`carried out on the trial-to-trial reliability of easy standing and on ground
`reaction force parameters of vertical jumping adjusted for body weight and
`system weight.
`
`li
`
`±^
`
`■■ .,.,.,,,•..,.■ r, ■**.*räl*jmtmmaä^mktLä^ä*m
`
`WClASSIftFP
`StCUftlTY CLASSIFICATION OP THIS PAOEfWhi« Dmtm Bnfr*)
`
`Petitioner Ex. 1083 Page 4
`
`

`
`PREFACE
`
`This is the second of four volumes comprising the final report of
`research performed under Contract Number DAAK60-79-C-0131 with the Individual
`Protection Laboratory, US Army Natick Research and Development Laboratories,
`Natick, Massachusetts. The work was formulated and directed by Drs. Carolyn
`K. Bensel and Richard F. Johnson, Human Factors Group, Individual Protection
`Laboratory. Dr. Bensel was the contract monitor and Dr. Johnson was the
`alternate.
`
`WH
`
`1tmm
`
`ÜÜ
`
`aAMjMl
`
`am
`
`Petitioner Ex. 1083 Page 5
`
`

`
`TABLE OF CONTENTS
`
`Page
`
`PREFACE 1
`
`LIST OF FIGURES 5
`
`LIST OF TABLES 6
`
`INTRODUCTION 9
`
`Backpack Sy9terns 9
`Load Conditions 12
`Load I 12
`Load 2 12
`Load 3 12
`Load 4 12
`Load 5 12
`Load 6 12
`
`EASY STANDING 14
`
`Subjects and Experimental Design 14
`
`Test Procedures 16
`
`Results 26
`Test Reliability 16
`Eff""ts of Gender and Load 18
`Effects of Gender, Load, and Backpack 19
`Effects of Load and Backpack 20
`Comparative Analysis of Load Effects 20
`Summary 22
`
`VERTICAL JUMP 22
`
`Subjects and Experimental Design 23
`
`Test Procedures 23
`
`Experimental Variables 24
`
`Results 24
`Effects of Gender and Load 24
`Effects of Gender, Load, and Backpack 29
`Effects of Load and Backpack 32
`Comparative Analysis of Load Effects 32
`Summary 37
`
`DISCUSSION 38
`
`rr
`
`-.•■''fr-irttirvn-iif.i •» ' r h'nim
`
`Petitioner Ex. 1083 Page 6
`
`

`
`■Hi
`
`TABLE OF CONTENTS (continued)
`
`REFERENCES
`
`APPENDICES
`
`A. Clothing and Equipment Used in This Study
`
`B. ANOVA Summary Tables for Easy Standing
`
`C. ANOVA Summary Tables for Vertical Jump
`
`Page
`
`40
`
`Al
`
`57
`
`63
`
`j u
`
`*
`
`±*
`
`wtmU^Mm^hiä^tmM
`
`Petitioner Ex. 1083 Page 7
`
`

`
`V
`
`mtmm
`
`*mm
`
`LIST OF FIGURES
`
`Figure 1. Four Backpack Systems: A - ALICE LC-2;
`B - ALICE LC-1; C - LOCO; D - PACKBOARD
`
`Figure 2. On-Line System for Force Platform Measurements.
`
`Figure 3. Subject Performing Easy Standing Test.
`
`Figure 4. Mean CPX, CPY, and CPT Values for Men under
`Six Load Conditions.
`
`Figure 5. Mean CPX, CPY, and CPT Values for Women under
`Five Load Conditions.
`
`Figure 6. Subject Performing Vertical Jump Test.
`
`Figure 7. Typical Ground Reaction Force-Time Curve during
`a Vertical Jump.
`
`Figure 8. Mean Time of Force Application for Men and
`Women under Experimental Load Conditions.
`
`Figure 9. Mean Peak Force for Men and Women under
`Experimental Load Conditions.
`
`Figure 10. Mean Peak Force/Body Weight Ratios for Men and
`Women under Experimental Load Conditions.
`
`Figure 11. Mean Peak Force/System Weight Ratios for Men and
`Women under Experimental Load Conditions.
`
`Figure 12. Mean Height of Jump for Men and Women under
`Experimental Load Conditions.
`
`Figure A-i. ALICE Fighting Gear.
`
`Figure A-2. ALICE Pack.
`
`Figure A-3. ALICE LC-2 Frame.
`
`Figure A-4. ALICE LC-1 Frame.
`
`Figure A-5. PACKBOARD.
`
`Figure A-6. LOCO.
`
`Page
`
`11
`
`15
`
`17
`
`21
`
`21
`
`25
`
`26
`
`34
`
`34
`
`35
`
`35
`
`36
`
`43
`
`45
`
`47
`
`49
`
`51
`
`53
`
`SKZJJUti
`
`naniü
`
`.
`
`Petitioner Ex. 1083 Page 8
`
`

`
`LIST OF TABLES
`
`Page
`
`t
`
`Table 1. Approximate Values for Selected Characteristics
`of the Four Backpacks
`
`Table 2. Mean Load Values (kg) for Men and Women for
`Easy Standing
`
`Table 3. Mean Load Values (kg) for Men and Women for
`Vertical Jump
`
`Table 4. Physical Characteristics of Subjects in Easy
`Standing Test
`
`Table 5. Frequencies of Trial-to-Trial Reliability
`Coefficients for Men and Women under All
`Test Conditions
`
`Table 6. Frequencies of Trial-to-Trial Reliability
`Coefficients for Men and Women under Four
`Backpack Conditions
`
`Table 7. Mean CPX, CPY, and CPT Values for Gender and Load
`
`Table 8. Mean CPX, CPY, and CPT Values for Gender, Load,
`and Backpack
`
`Table 9. Mean CPX, CPY, and CPT Values for Load and
`Backpack for Men
`
`Table 10. Mean Values of CPX, CPY, AND CPT for Men and
`Women
`
`Table 11. Physical Characteristics of Subjects in Vertical
`Jump Test
`
`Table 12. Mean Time (msec) of Force Application for Gender
`and Load
`
`Table 13. Mean Peak Force Values (Newtons) for Gender and
`Load
`
`Table 14. Mean Peak Force Relative to Body Weight for Gender
`and Load
`
`Table 15. Mean Peak Force Relative to System Weight for
`Gender and Load
`
`Table 16. Mean Values of Height of Jump (cm) for Gender
`and Load
`
`10
`
`13
`
`13
`
`14
`
`16
`
`18
`
`19
`
`-9
`
`20
`
`22
`
`23
`
`24
`
`27
`
`27
`
`28
`
`28
`
`'illif«II H-fll 111 I II IHM
`
`-
`
`Petitioner Ex. 1083 Page 9
`
`

`
`LIST OF TABLES (continued)
`
`Page
`
`Table 17. Mean Time (msec) of Force Application for 29
`Gender, Load, and Backpack
`
`Table 18. Mean Peak Force (Newtons) for Gender, Load, 30
`and Backpack
`
`Table 19. Mean Values of Peak Force/Body Weight for 30
`Gender, Load, and Backpack
`
`Table 20. Mean Values of Peak Force/System Weight for 31
`Gender, Load and Backpack
`
`Table 21. Mean Values of Height of Jump (cm) for Gender, 31
`Load, and Backpack
`
`Table 22. Mean Ground Reaction Force Parameters for 32
`Backpack and Load
`
`Table 23. Mean Vertical Jump Parameters for Men and.Women 33
`Under All Load Conditions
`
`Table 24. Differences in Peak Force (N) and Increased 36
`Load (N) for Adjacent Load Conditions
`
`Table B-l. ANOVA Summary of CPX for Gender and Load (1-3) 58
`
`Table B-2. ANOVA Summary of CPY for Gender and Load (1-3) 58
`
`Table B-3. ANOVA Summary of CPT for Gender and Load (1-3) 59
`
`Table B-4. ANOVA Summary of CPX Gender, Load (4-5), and 59
`Backpack
`
`Table B-5. ANOVA Summary of CPY for Gender, Load (4-5), and 60
`Backpack
`
`Table B-6. ANOVA Summary of CPT for Gender, Load (4-5), and 60
`Backpack
`
`Table B-7. ANOVA Summary of CPX for Load (4-6) and Backpack 61
`
`Table B-8. ANOVA Summary of CPY for Load (4-6) and Backpack 61
`
`Table B-9. ANOVA Summary for CPT for Load (4-6) and Backpack 62
`
`Table C-l. ANOVA Summary of Time and Force Application for 64
`Gender and Load (1-3)
`
`Table C-2 ANOVA Summary of Peak Force at Takeoff for Gender 64
`and Load (1-3)
`
`AM
`
`j
`
`Petitioner Ex. 1083 Page 10
`
`

`
`LIST OF TABLES (continued)
`
`i 1
`1 j
`\
`
`]
`
`Page '■■■ j
`
`Table C-3. ANOVA Summary of Peak Force/Body Weight
`for Gender and Load (1-3)
`
`65
`
`/!
`
`i
`
`Table C-4. ANOVA Summary of Peak Force/System Weight
`for Gender and Load (1-3)
`
`Table C-5.
`
`ANOVA Summary of Height of Jump for Gender
`and Load (1-3)
`
`Table C-6.
`
`ANOVA Summary of Time of Force Application for
`Gender, Load (4-5), and Backpack
`
`Table C-7.
`
`ANOVA Summary of Peak Force at Takeoff for Gender,
`Load (4-5), and Backpack
`
`Table C-8. ANOVA Summary of Peak Force/Body Weight for
`Gender, Load (4-5), and Backpack
`
`Table C-9.
`
`ANOVA Summary of Peak Force/System Weight for
`Gender, Load (4-5), and Backpack
`
`Table C-10. ANOVA Summary of Height of Jump for Gender, Load
`(4-5), and Backpack
`
`Table C-ll. ANOVA Summary of Height of Jump for Backpack
`and Load (4-6)
`
`Table C-12. ANOVA Summary of Time of Force Application
`for Backpack and Load (4-6)
`
`Table C-13. ANOVA Summary of Peak Force at Takeoff for
`Backback and Load (4-6)
`
`Table C-14. ANOVA Summary of Peak Force/Body Weight for
`Backpack and Load (4-6)
`
`Table C-15. ANOVA Summary of Peak Force/System Weight for
`Backpack and Load (4-6)
`
`65 i
`
`i
`
`66
`
`67
`
`68
`
`69
`
`70
`
`71
`
`72
`
`72
`
`73
`
`73
`
`74
`
`-•■=.-•>■
`
`r'f'lnÜ
`
`llnllliflM III
`
`Petitioner Ex. 1083 Page 11
`
`

`
`Effects of Gender, Load, and Backpack on Easy
`Standing and Vertical Jump Performance
`
`INTRODUCTION
`
`This is the second of four studies on the biomechanics of load carrying
`behavior being conducted in the Biomechanics Laboratory at The Pennsylvania
`State University under the direction and sponsorship of the Army Natick
`Laboratories. The first study in this series dealt with the effects of
`gender and load on combative movement performance. The subjects performed
`under five (women) or six (men) load conditions which included only one
`frame-pack system, the ALICE LC-2. This second study was designed to
`further compare male and female performance, evaluate the effects of load,
`and also to compare four frame-pack systems.
`
`Fundamental movements of easy standing and vertical jumping were
`selected for this purpose since both had been used successfully in previous
`load carrying experiments. * These tests used sophisticated laboratory
`force platform and on-line computer systems. The subjects, experimental
`design, test procedures, and results for these tests are described in separate
`sections later in this report.
`
`The four frame-pack systems and six load conditions were common to
`both easy standing and jumping experiments. Consequently, descriptions of
`the backpacks and loads are presented in this section.
`
`Backpack Systems
`
`The four backpacks used in this study included three with external frames
`and one with an internal frame. The same top-loading pack, a standard Army
`item, was used on each of the external frames. A brief description of each
`system is included here. Appendix A contains additional information on
`these items.
`
`a. ALICE LC-2 is the Army's standard frame. It is made of aluminum
`tubing and has foam-padded shoulder and lower back straps. The waist belt,
`made of wide nylon webbing, is attached to the padded back strap.
`
`Nelson, R.C. and P.E. Martin. Volume I. Effects of Gender and Load on
`Combative Movement Performance (Tech. Rep. NATICK/TR-82/011). Natick,
`Massachusetts: US Army Natick Research and Development Laboratories,
`February 1982.
`
`2
`Nelson, R.C, T.E. Clarke, and R.N. Hinrichs. An Investigation into the
`Biomechanics of Load Carrying: The Effects of Gender, Body Size, and
`Backpack on Load Carrying Behavior. Natick, Massachusetts: US Army Natick
`Research and Development Laboratories, in preparation.
`3
`Nelson, R.C, T.E. Clarke, and R.N. Hinrichs. An Investigation into the
`Biomechanics of Load Carrying: The Effects of Load and Backpack on Load
`Carrying Behavior. Natick, Massachusetts: US Army Natick Research and
`Development Laboratories, in preparation.
`
`,,^flü*iftjü?i—imifa« ., lttt„-1..-4>,».,..- J
`
`Petitioner Ex. 1083 Page 12
`
`

`
`mmm
`
`1
`
`b. ALICE LC-1 was the standard Army frame prior to the Introduction of
`the LC-2. The frame itself is of the same design as the LC-2. However,
`the shoulder and back straps are of different dimensions and are not foam-
`padded. In addition, the waist strap is made of narrow webbing and attaches
`to the frame.
`
`c. LOCO is a commercially-available, internal-frame system. The frame
`consists of two, vertical, aluminum stays which extend the length of the pack
`and are on the side of the pack closest to the wearer's body. The pack
`Itself is a top-loading bag to which foam-padded shoulder straps and a waist
`belt are attached.
`
`d. PACKBOARD is an experimental item which was fabricated for this
`study. It consists of a flat sheet of aluminum. The shoulder, back, and
`waist straps attached to it are identical to those used with the ALICE LC-2.
`
`These four backpack systems are pictured in Figure 1; their physical
`dimensions and component weights are listed in Table 1.
`
`Table 1
`
`Approximate Values f r Selected Characteristics
`of the Four Backpacks
`
`Length* Width* Depth* Frame and Bag Weight**
`Backpack (cm) (cm) (cm) (kg)
`
`ALICE LC-2
`
`ALICE LC-1
`
`LOCO
`
`PACKBOARD
`
`52
`
`51
`
`61
`
`54
`
`46
`
`46
`
`35
`
`46
`
`40
`
`39
`
`30
`
`32
`
`3.23
`
`2.84
`
`1.41
`
`3.57
`
`Dimensions were measured with the pack loaded with the
`basic 9.1 kg load (Load 4) which consisted of a sleeping
`bag, mattress, waterproof clothes bag, poncho, socks,
`and undershirt. The length and width dimensions were
`the greatest values for the frame-pack systems in their
`respective directions. The depth dimension was an
`estimate of the maximum distance the pack projected
`from the body.
`
`**
`
`Combined weight when empty.
`
`10
`
`I MJflBflJBU llllflt • 2i ^UMBSfcufr
`
`J
`
`Petitioner Ex. 1083 Page 13
`
`

`
`u o
`w q o <
`
`H PM
`
`I Q
`<J •-
`O
`U
`•• O
`CO iJ
`0
`0) I
`4J
`CO CJ
`
`C/l •«
`rH
`M I
`Ü u
`co a
`ft
`^ w
`o o
`cö H
`PQ HJ <!
`U
`=1 I o
`
`Pn PQ
`
`CD
`
`00
`•H
`
`11
`
`Petitioner Ex. 1083 Page 14
`
`

`
`"1
`
`Load Conditions
`
`A careful selection of loads was made to cover a wide range of
`typical military loads. In addition, a minimal load condition was
`added to provide baseline performance data for comparative purposes.
`The other loads represented systematic increases. In all, there were
`six different loads. The male subjects performed under all six load
`conditions while the female subjects were excluded from Load 6. The
`following is a general description of the six loads. Additional
`information on the clothir^ and equipment comprising the loads is
`presented in Appendix A and in Ref. 1.
`
`Load 1 served as the baseline condition. Subjects wore shorts,
`socks, t-shirt, and sneakers.
`
`Load 2 was considered the fighting gear condition. The subjects
`wore underwear, socks, utility shirt and trousers, boots, and the
`standard, ALICE fighting gear which included a water-filled canteen
`with cover, intrenching tool with carrier, and two small arms ammo
`cases containing 1.75 kg sandbags.
`
`Load 3 was designated the combat gear condition. The subjects
`wore a PASGT helmet and armor vest and carried a simulated M-16
`rifle in addition to those items included in Load 2.
`
`Load 4 included all items from Load 3 plus one of the four
`frame-pack combinations containing a 20-pound (9.1 kg) load. This
`load consisted of a sleeping bag, mattress, waterproof clothes bag,
`poncho, socks, and undershirt.
`
`Load 5 included all items from Load 4 plus an additional weight
`of 15 pounds (6.8 kg) placed in the pack. The extra load consisted
`of three, 5-pound (2.3 kg) barbell disks.
`
`Load 6 was carried by the men only and included all items from
`Load 4 plus 30 additional pounds (13.6 kg) in the form of three,
`10-pound (4.5 kg) disks placed in the pack.
`
`Because of the differences in the weights of the frames, the
`weight varied among the backpacks for Load Conditions 4 to 6.
`Furthermore, the number of subjects differed slightly for the
`standing and jumping tests. The mean values for all loads and
`backpacks for men and women for the two movements are presented
`in Tables 2 and 3.
`
`12
`
`MMMjiaÜiääi*LL£lL^*-.^ iifum-n,,,.
`
`Petitioner Ex. 1083 Page 15
`
`

`
`mmmmm
`
`Table 2
`Mean Load Values (kg) for Men and Women for Easy Standing
`
`LOAD
`
`BACKPACK
`MEN (N-14) .75 9.40
`ALICE LC-2
`ALICE LC-1
`LOCO
`PACKBOARD
`
`3 4
`.49
`
`5
`
`6
`
`29 83 36 63 43 44
`29 42 36 22 43 03
`27 97 34 77 41 58
`30 15 36 95 43 76
`
`LOAD MEAN 29.34 36.14 42.95
`
`WOMEN (N=ll) 756 9.04 16.92 "
`ALICE LC-2
`29.26 36.06
`
`ALICE LC-1
`
`LOCO
`
`28.85 35.65
`
`27.40 34.20
`
`29.58 36.38
`PACKBOARD
`
`LOAD MEAN 28.77 35.57
`
`Mean Load Values (kg) for Men and Women for Vertical Jump
`
`Table 3
`
`BACKPACK
`MEN (N-ll) .73 9.41
`ALICE LC-2
`
`ALICE LC-1
`
`LOCO
`
`PACKBOARD
`
`LOAD
`3
`.54
`
`4
`
`6
`
`29 88 36 68 43 49
`29 47 36 27 43 08
`28 02 34 82 41 63
`30 20 37 00
`43 81
`
`LOAD MEAN 29.39 36.19 43.00
`
`WOMEN (N-10) 758 9.04 16.95 ~~ " "
`ALICE LC-2
`29.29 36.09
`ALICE LC-1
`LOCO
`27.43 34.23
`PACKBOARD
`29.61 36.41
`
`28.88 35.68
`
`LOAD MEAN 28.80 35.60
`
`13
`
`L i' afla dl
`
`Petitioner Ex. 1083 Page 16
`
`

`
`~1
`
`i
`
`m*m
`
`EASY STANDING
`
`This test was used as a measure of postural stability under the
`influence of the different loads and backpacks. The subject stood
`on the force platform as motionless as possible during the test interval.
`The test utilized the sophistication of the laboratory force platform
`(Kistler, Model 9261A and on-line computer (PDP Model 11-34) systems shown
`in schematic form in Figure 2. The data acquisition program sampled Fz,
`Mx and My for ten seconds at 50 Hz. By dividing the moments by F2, the
`X» Y coordinates for the center of pressure location were obtained for
`each of the 500 samples. These data were then smoothed using a 5-point
`moving average technique. The experimental data were the accumulated
`absolute displacements in the X direction, denoted CPX, and representing
`anterior-posterior movement; the Y direction, CWT, reflecting medial-lateral
`motion; and the vectoral sum of these, referred to as the total excursion,
`CPT. These values were measured in units of meters, but are included here
`in centimeters for ease of presentation and compatibility with previous
`research (Ref. 2 and 3).
`
`Subjects and Experimental Design
`
`A total of 25 students, 14 men and 11 women, all undergraduates enrolled
`in the University Army R.O.T.C. program, served as subjects. They were a
`subset of the 30 subjects, representative of military personnel, who completed
`the first study in this series (Ref. 1). Descriptive data for these subjects
`are presented in Table 4.
`
`Table 4
`
`Physical Characteristics of Subjects
`in Easy Standing Test
`
`Characteristics
`
`Gender
`
`N Age (yrs) Height (cm) Weight (kg)
`
`X S.D. X S.D. X S.D.
`
`Men
`
`Women
`
`14 20.8 1.8
`
`175.0 7.6
`
`11 20.7 1.6
`
`166.4 4.8
`
`69.2 7.4
`
`60.8 10.9
`
`The data collection for easy standing was carried out in one test
`session. All subjects completed three trials under each condition. The
`first three load conditions were presented to the subjects in sequential
`fashion beginning with Load 1. Thereafter, the order of backpacks was
`randomly assigned and all load conditions (assigned at random) were completed
`once a specific backpack was placed on the subject.
`
`Because of the complexity in experimental design, it was necessary to
`conduct the data analysis in three parts. The first dealt with the comparison
`of male and female performance under the first three load conditions. Part
`two, based on performance under Loads 4 and 5, involved a comparison of men
`and women and evaluation of the four backpacks. In part three, the effects
`of load and backpack on male performance for Loads 4, 5, and 6 were investigated
`
`14
`
`•-«•■••-**■••■■
`
`^i^tfMHIMfeib
`
`.
`
`Petitioner Ex. 1083 Page 17
`
`

`
`mm
`
`To PDP
`Computer
`
`To Digital
`Input
`
`X V 2 ■*'x^f^2
`
`Remote Terminal
`
`Force Platform
`
`Figure 2. On-Line System for Force
`Platform Measurements.
`
`15
`
`mmmmm
`
`Petitioner Ex. 1083 Page 18
`
`

`
`i-
`
`Test Procedures
`
`The subject was instructed to step onto the force platform, assume a
`self-determined, comfortable stance, focus on an "X" marked on the curtain in
`front of him, and maintain a stable body position for a ten-second period.
`The subject placed his arms at his sides for Loads 1 and 2 and held the
`rifle in both hands in front of the body for Loads 3 to 6. The data were
`recorded on disc and the calculated values were displayed on a terminal
`and printed on a line printer. Trials were repeated at one-minute intervals
`until three were completed for a given experimental condition. The subject
`then changed the load according to the prescribed order and continued the
`test process. Figure 3 shows a subject on the force platform undergoing the
`easy standing test.
`
`Results
`
`Test Reliability. Trial-to-trial reliability coefficients were
`determined separately for the men and the women as a means of assessing the
`reproducibility of the experimental variables. Tables 5 and 6 contain a
`summary of the results of this analysis. Table 5 contains the frequencies
`of the reliability coefficients at 0.10 intervals across all six loads for
`all three variables. A total of 18 coefficients was calculated for Loads 1,
`2, and 3; 72 coefficients for Loads 4 and 5; and 36 coefficients for Load 6,
`resulting in a total of 234 coefficients. Of this number 80% were above
`0.70 and 58% were above 0.80.
`
`Table 5
`
`Frequencies of Trial-to-Trial Reliability Coefficients for
`Men and Women under All Test Conditions
`
`Load
`
`Number
`of Coefficients
`
`<0.50
`
`0.50
`
`0.60
`
`0.70
`
`0.80
`
`0.90
`
`RELIABILITY COEFFICIENTS
`
`1
`
`2
`
`3
`
`4
`
`5
`
`6
`
`18
`
`18
`
`18
`
`72
`
`72
`
`36
`
`1
`
`2
`
`3
`
`1
`
`1
`
`1
`
`1
`6
`
`3
`
`2
`
`4
`
`3
`
`1
`
`6
`
`7
`
`6
`
`5
`
`7
`
`1
`
`18
`
`15
`
`6
`
`6
`
`3
`
`6
`
`26
`
`34
`
`11
`
`1
`
`2
`
`6
`
`15
`
`13
`
`11
`
`TOTALS
`
`234
`
`% of Total
`
`7
`
`3%
`
`14
`
`6%
`
`27
`
`12%
`
`51
`
`22%
`
`86
`
`37%
`
`48
`
`21%
`
`16
`
`^liihYffcr ihAiJ
`
`fl M.WMM
`
`Petitioner Ex. 1083 Page 19
`
`

`
`Figure 3. Subject Performing Easy Standing Test.
`
`17
`
`Petitioner Ex. 1083 Page 20
`
`

`
`A further analysis was carried out based only on the trials in which
`a pack was worn. These results are shown in Table 6. A total of 180
`coefficients, 45 for each Backback condition, are presented. Since these
`coefficients represent a major portion of the total presented in Table 5,
`the overall results are the same. It is interesting to note the similarity
`in frequencies for the first three Backpacks, while the PACKBOARD demonstrated
`considerably higher reliability coefficients.
`
`Table 6
`
`Frequencies of Trial-to-Trial Reliability Coefficients
`for Men and Women under Four Backpack Conditions
`
`Backpack
`
`ALICE LC-2
`
`ALICE LC-1
`
`LOCO
`
`PACKBOARD
`
`dumber of
`Coefficients
`45
`45
`45
`45
`
`RELIABILITY COEFFICIENTS
`
`0.50
`
`0.60
`
`0.70
`
`0.80
`
`0.90
`
`11
`
`10
`
`10
`
`7
`
`20
`
`20
`
`18
`
`10
`
`6
`
`5
`
`5
`
`22
`
`TOTALS 180
`
`% of Total
`
`13
`
`7%
`
`22
`12%
`
`38
`
`21%
`
`68
`
`38%
`
`38
`
`21%
`
`Dependent t-tests were also calculated as a means of assessing any
`changes in mean performance which may have occurred from trial to trial.
`Of ».he 234 t-tests, only 28 were statistically significant at the .05 level,
`Considering the large number of ^-ratios calculated and the lack of indepen-
`dence in multiple comparisons of three trials, it was evident that the mean
`performance was relatively stable from trial to trial for all experimental
`variables. Overall, it was concluded that, under the variety of test
`conditions, the coefficients obtained and mean comparisons conducted
`indicated an acceptable level of test reliability.
`
`Effects of Gender and Load. A two-way ANOVA was used to evaluate the
`differences between men and women and among Loads 1, 2, and 3 for CPX, CPY,
`and CPT. The mean values are presented in Table 7, and ANOVA summaries are
`included in Appendix B.
`
`I
`
`18
`
`a• iu ini■ 1
`
`_*^iM
`
`riflfe
`
`Petitioner Ex. 1083 Page 21
`
`

`
`WMWIN»
`
`Table 7
`
`Mean CPX, CPY, and CPT Values for Gender and Load
`
`MAIN EFFECT
`
`GENDER
`MEN (N-14)
`WOMEN (N-ll)
`
`LOAD
`
`CPX(cm)
`
`CPY(cm)
`
`CPT(cm)
`
`5.89
`6.94
`
`6.62
`6.16
`6.29
`
`4.77
`4.93
`
`5.23
`4.70
`4.59
`
`8.66
`9.48
`
`9.53
`8.78
`8.76
`
`Means not connected by vertical lines are significantly different (P<.05)
`
`A tendency for greater stability (lower values) on the part of the men
`was present, but the differences were not significant. Load differences
`were present for CPY and CPT whereby Loads 2 and 3 were similar but both
`differed significantly from Load 1. No significant interactions between
`Gender and Load were present. Less body motion was observed for the
`heavier load conditions. Further, use of the armor vest, helmet and M-16
`rifle in Load 3 did not increase the CP values above those for Load 2. This
`is partly explained by the distribution of the added load close to the body
`of th~ subject. A consistent pattern of higher CPX than CPY values can be
`observed. This was due to the placement of the additional load primarily on
`the anterior and posterior surfaces of the body.
`
`Effects of Gender, Load, and Backpack. A three-way ANOVA was utilized
`to evaluate the influence of Gender, Load and Backpack on postural stability.
`The mean values are presented in Table 8.
`
`Mean CPX, CPY, and CPT Values for Gender, Load, and Backpack
`
`Table 8
`
`MAIN EFFECT
`
`GENDER
`MEN
`WOMEN
`
`LOAD
`
`4
`5
`
`BACKPACK
`ALICE LC-2
`ALICE LC-1
`LOCO
`PACKBOARD
`
`CPX(cm)
`
`CPY(cm)
`
`CPT(cm)
`
`4.55
`5.70
`
`4.79
`5.32
`
`5.12|
`5.19:
`4.761
`5.15
`
`5.37
`7.14
`
`5.92
`6.38
`
`6.31
`5.33
`5.79
`6.17
`
`19
`
`5.05
`10.32
`
`8.65
`9.45
`
`9,23
`9,30
`8.51:
`9.15
`
`m
`
`j
`
`Petitioner Ex. 1083 Page 22
`
`

`
`None of the interactions were significant. The male subjects showed
`greater stability for all three measurements, however, only the mean difference
`for CPT was significant. Differences between Load means for all three
`parameters were significant with the higher values associated with the greater
`load. The significant differences among the packs were due to the lower values
`for the LOCO pack. None of the differences among the other three packs were
`significant. For CPX and CPY the LOCO pack differed significantly from two
`of the other three backpacks while for CPT it differed from all three. The
`LOCO pack allows for the load to be positioned closer to the body which
`probably accounts for the greater postural stability.
`
`Effects of Load and Backpack. As a means of utilizing the Load 6 data
`for men, a two-way ANOVA involving Load and Backpack was carried out. These
`results appear in Table 9.
`
`Mean CPX, CPY, and CPT Values for Load and Backpack for Men
`
`Table 9
`
`MAIN EFFECT CPX(cm) CPY(cm) CPT(cm)
`
`LOAD
`
`4
`5
`6
`
`BACKPACK
`ALICE LC-2
`ALICE LC-1
`LOCO
`PACKBOARD
`
`5.27
`5.48
`5.76
`
`5.62
`5.70
`5.26
`5.44
`
`4.37
`4.74
`5.14
`
`7.82
`8.28
`8.81
`
`8.58
`4.96
`8.52
`4.79
`4.36! 7.77:
`4.881
`8.35
`
`The Load X Backpack interaction was not significant indicating similar
`performance across the load-pack combinations. Postural stability decreased
`as the load increased with significant differences noted between Loads 4 and
`6 for CPY and CPT. The backpack results tended to favor the LOCO pack for
`all three variables, but it differed significantly only from the ALICE LC-2
`for CPT. Previous studies have demonstrated less body movement for the LOCO
`pack in comparison with external frame systems (Ref. 3).
`
`Comparative Analysis of Load Effects. Because of the variety of load
`and backpack conditions, it was not possible to evaluate their effects in
`one statistical treatment. The three lower loads offer similar conditions,
`but Loads 4 and 5 were influenced by the variability among the four frame-pack
`systems, while the females were not tested under Load 6. In an attempt to
`assess the overall effect of load on postural stability, mean values were
`obtained for each condition. These are presented numerically in Table 10
`and graphically in Figures 4 and 5. In the case of Loads 4, 5, and 6, the
`data from all four backpacks have been used to calculate the Load mean.
`
`20
`
`tmm
`
`Mfc—Jüi
`
`Petitioner Ex. 1083 Page 23
`
`

`
`lO.O-i WEN
`
`E
`
`O
`
`O
`
`Q
`O
`CO
`
`8.0-
`
`6.0-
`
`4.0-
`
`ar 0J r
`
`CPT
`
`T r
`T
`10 20
`30 40 50
`LOAD (kg)
`
`Figure 4. Mean CPX, CPY, and CPT Values for Men under Six Load Conditions
`
`12.0-1 WOMEN
`
`10.0-
`
`E
`o
`
`^ 8.0-
`O
`2
`
`Q
`O
`03
`
`6.0-
`
`4.0-
`
`CPT
`
`CPX
`
`CPY
`
`-r
`10
`
`T-
`"T"
`20
`30
`LOAO (kg)
`
`40
`
`"I
`50
`
`Figure 5. Mean CPX, CPY, and CPT Values for Women under Five Load Conditions
`
`21
`
`Petitioner Ex. 1083 Page 24
`
`

`
`Table 10
`
`Mean Values of CPX, CPY, and CPT for Men and Women
`
`GENDER VARIABLE 12 3 4 5
`
`MEN
`
`(N-14)
`
`WOMEN
`(N=ll)
`
`CPX(cm)
`CPY(cm)
`CPT(cm)
`
`CPX(cm)
`CPY(cm)
`CPT(cm)
`
`6.05
`5.30
`9.18
`
`7.34
`5.15
`10.0
`
`5.75
`4.59
`8.45
`
`6.67
`4.84
`9.20
`
`5.88
`4.43
`8.36
`
`6.80
`4.80
`9.26
`
`5.27
`4.37
`7.82
`
`6.75
`5.32
`9.69
`
`5.48
`4.74
`8.28
`
`5.76
`5.14
`8.81
`
`7.53
`6.07
`10.94
`
`The data indicate a non-linear pattern across the load conditions with
`a tendency for greater stability to occur at the middle loads. This U-shaped
`pattern suggests that, when relatively light loads are added close to the body,
`they result in diminished body sway in comparison to the unloaded condition.
`As the lo