Effects Of A Powered Pneumatic Knee Exoskeleton On Gait Stability During A 2-mile Loaded Walk

Exoskeletons (EXOs) may assist with the demands of walking with load carriage, an activity leading to high rates of injury in the military. While studies have shown that decreased local dynamic stability (LDS), a measure of gait stability, may increase injury risk, few studies have considered the effects of EXOs on LDS. PURPOSE: : Determine the effects of a knee-actuated EXO on LDS, at the beginning and end of a 2-mile walk with load carriage. METHODS: 11 healthy Soldiers (9 m/2f) completed a familiarization session with the EXO. This was followed by two visits, with and without the EXO (order counterbalanced), where they performed a 2-mile walk at a self-selected pace (2.99 ± 0.23 mph), while carrying 30% of body weight. Inertial measurement units were placed on the pelvis and right shank (sampling rate = 2,000 Hz). LDS was calculated using 100 consecutive strides at the beginning (first 100 strides) and end (last 100 strides) of trials. The unfiltered 3D gyroscope signals were processed using custom python code. LDS was calculated as the maximum short-term divergence exponent from the reconstructed state-space, with higher divergence exponents indicating lower stability. A repeated measures two-way ANOVA was used to test for the interactive and main effects of time and EXO condition on LDS. RESULTS: There was a significant main effect of EXO on LDS at the right shank, with lower mean stability while wearing the EXO vs. No EXO (Table). All other effects were non-significant. CONCLUSIONS: The results indicate that wearing a lower extremity EXO may reduce gait stability, at least in the short-term, possibly requiring more familiarization with the EXO for adequate adaptation. With reduced LDS at the shank with wearing the EXO, but not at the pelvis, it may be that distal stability, compared to center of mass, is more sensitive to subtle changes in supported gait. Opinions in this manuscript are the authors private views, not official policy or views of the US Army. Supported by: MO21500/MO210170