Effects of cues to walk softly and quietly on gait mechanics during load carriage

Walking with load carriage is a routine and necessary activity for many occupations and recreational athletes, however it induces significant physical strain, resulting in high rates of musculoskeletal injury. Gait alteration cues to run softly/quietly have been shown to reduce external forces related to injury in runners. However, the effects of these cues have yet to be explored for load carriage. 38 participants completed testing on an instrumented treadmill while kinematics were tracked via optical motion capture. Participants first completed a habitual load carriage trial (HAB) at a self-selected pace (1.23 ± 0.12 m/s) while carrying an 18 kg weighted vest. They were given a 5-min warm-up followed by data collection. Participants were then cued to modify their gait by walking "quietly and softly" (SOFT), using the same pace as for HAB. Outcome variables were averaged across 20 strides, including peak hip/knee/ankle joint internal sagittal and frontal plane moments, peaks/excursion in joint angles, double-stance time, stride length, and cadence. The SOFT condition resulted in decreased second peak hip abduction and peak knee flexion moments, and second peak vertical forces, but increased peak knee extension moments and first peak vertical forces (p < 0.05, Cohen's d≥0.5). Further, the SOFT condition resulted in increased peak flexion angles (hip/knee) and reduced extension/plantarflexion angles (hip/knee/ankle). Given the conflicting changes in external forces, the results do not support SOFT as a modification to reduce overall musculoskeletal injury risk during load carriage.