Pelvis and Trunk Motion Comparisons Between Male and Female Soldiers While Walking with Heavy Loads

With the recent decision permitting female soldiers to enter Combat Arms roles, knowledge of sex differences in military load carriage is more operationally relevant. Limited work comparing the effect of heavy carried loads (>30 kg) in men and women has attributed differences in gait mechanics to sex without matching for anthropometrics that may contribute to differences. PURPOSE: To examine the effect of carrying light to heavy loads on pelvis and trunk range of motion (ROM) between anthropometrically matched male and female soldiers. METHODS: Four male and 4 female Soldiers were matched on height and body weight (differences < 2.54 cm and 4.54 kg). All participants walked unloaded (BW), and with vest-borne loads of 15, 35 and 55 kg. Each load was carried for 10 min while walking on a level treadmill at 1.3 m∙s-1, with pelvis and trunk segmental angles collected after 5 min. Four mixed model ANOVAs (sex x load) compared trunk and pelvis frontal and transverse plane ROM. RESULTS: There were sex x load interactions for trunk transverse and frontal plane motion (Table 1). Specifically, as load increased: (A) trunk axial rotation decreased more in females than males (p=0.037), and (B) trunk frontal plane motion increased for males and remained relatively constant for females (p=0.034). Pelvis frontal plane ROM also increased at 55 kg in both sexes relative to carrying no additional load. CONCLUSIONS: Despite anthropometric matching, preliminary results suggest sex-related differences in trunk frontal plane motion while carrying loads ≥ 35 kg and no sex-related differences in pelvis motion. DISCLAIMER: The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.Table 1: Pelvis and Trunk Frontal (Y) and Transverse (Z) plane ranges of motion for different loads among male and female soldier