Males and Females Respond Similarly to Walking With a Standardized, Heavy Load

Abstract

Females in the military sustain a higher incidence of lower extremity injuries compared to males. Previous investigations of gender differences during load carriage used loads normalized to body mass; as a result of anthropometric and strength differences between genders, this may partially normalize to strength, masking gender or size differences in response to load. We compared gait kinetics and kinematics between genders based on a standardized load, instead of loads relative to body mass. 11 males and 11 females walked at 1.5 m/s over level ground with a 22 kg rucksack using three load conditions: unloaded, low-back placement, and mid-back placement. We found a gender by load interaction for average trunk position (p < 0.05). Stride length decreased 1.3% in loaded vs. unloaded walking. Loaded walking increased knee extensor (65%) and ankle plantarflexor torque (23%, all p < 0.0001), but not hip extensor torque (p > 0.05) compared to unloaded walking. The lack of gender differences may indicate that females do not adapt gait mechanics to account for smaller stature and lesser absolute strength compared to males, which may contribute to the high injury rate in female military recruits.

Effects of Stride Length on Lower Limb Stiffness when Running with Body Borne Load

“…Both males and females increased PS hip and knee flexion angle as load increased 38 . Furthermore, similar increases were seen in external knee flexion and ankle dorsiflexion moments with the addition of load 37,38 . This research is limited as only sagittal plane biomechanics were reported, however it does indicate at least some level of similarity between males and females with the addition of load during walking.…”

“…When serving in these infantry positions, military personnel can be required to run with very large loads which may contribute to the high rate of injury seen by females in the military 3 . To date, sex comparisons during loaded locomotion have been limited to analyzing sagittal plane biomechanics while walking with load, where no differences between males and females have been observed 37,38 . When running without load, differences in the frontal and transverse planes, but not the sagittal plane, have been observed between males and females 39,40 , yet little to no research exists directly comparing sex differences when running with military relevant loads.…”

Sex Differences in Lower Limb Biomechanics During a Single-Leg Cut with Body Borne Load

“…While examining a standardized load of 22 kg at a predetermined marching speed, there were no lower limb kinetic or kinematic variables were significantly different between the sexes 35 . Krupenevich et al speculated that the lack of biomechanical adaptation to the addition of load may lead to higher injury rates among female trainees and soldiers; If females fail to exhibit these sex-specific differences compared to males during load carriage, it may be that they are not making the adaptations necessary to safely carry standardized loads.…”

“…When males and females don body borne load relative to their weight and march at a self-determined speed, there is a lack of significant differences between the sexes in gait mechanics 35,36 . While examining a standardized load of 22 kg at a predetermined marching speed, there were no lower limb kinetic or kinematic variables were significantly different between the sexes 35 .…”

“…These elevated joint moments require greater force generation by the hip and knee musculature to prevent collapse of the limb, but increase the stresses placed on the musculoskeletal system and risk of injury 25 . Both large knee flexion, with an extended knee 26 , and abduction moments reportedly strain the soft-tissue structures of the joint 27 35 or Silder et al 36 reported a significant difference in lower limb biomechanics between male and female participants when walking with body borne load, despite the fact females reportedly exhibit a sex dimorphism in hip and knee biomechanics during unloaded walking [37][38][39] . However, it is unknown if female exhibit a sex dimorphism in lower limb biomechanics during performance of rapid change of direction tasks routinely required of military personnel during training 40 .…”