Powered Pneumatic Knee Exoskeleton Affects Gait Parameters And Kinematics During 2-mile March

Soldiers are at a high risk of knee injury, with a large proportion of these due to the excessive weights they carry, with marching loads reaching up to 80% of body weight (BW). Exoskeletons are wearable assistive devices that reduce the biological work performed by a joint. Military research has investigated the use of exoskeletons to reduce loads and increase performance. However, the effects of knee exoskeletons on gait parameters and lower extremality (LE) kinematics during loaded marching are unknown. PURPOSE: Determine the effects of a pneumatic knee exoskeleton on Soldiers’ gait parameters and LE kinematics during a 2-mile loaded march. METHODS: 9 healthy Soldiers (8 m/1f) performed a 2-mile march at a self-selected speed, wearing 30% BW, with and without the knee exoskeleton. Participants completed a familiarization day with the exoskeleton to determine march speed. Visits were randomized and counter balanced (i.e., with (Exo) and without (NoExo) the exoskeleton). Inertial measurement units were placed on the feet, shanks, thighs, and pelvis to measure gait parameters; this included spatiotemporal variables, range of motion (ROM) and peak angles for hip/knee/ankle during stance (ST) and swing (SW) phases. Paired t-tests were used to compare Exo and NoExo conditions. RESULTS: Stride length increased with the exoskeleton (Exo: 149.8 ± 4.3 cm, NoExo: 144.6 ± 4.1 cm, p = .02), along with the percent of time spent in double stance (Exo: 27.5 ± .8%, NoExo: 26.1 ± 0.9%, p = 0.01). The Exo showed a higher percent of time spent in stance vs. swing for the left (ST Exo: 63.8 ± .5%, ST NoExo: 62.9 ± .5%, p = .02) and right (ST Exo: 63.9 ± .4%, ST NoExo: 63.1 ± .4%, p = .01) legs. Finally, the Exo showed higher left ST hip ROM in the sagittal plane (Exo: 51.2 ± 2.5, NoExo: 46.9 ± 2.4, p = .02) and average right knee flexion during swing (Exo: 38.4 ± 2.0, NoExo: 44.3 ± 2.5, p = .04). All remaining comparisons were nonsignificant. CONCLUSION: Use of the Exo showed changes on Soldiers gait parameters, indicating there may be an effect on energy expenditure and performance. However, a direct effect can not be concluded at this time. LE kinematics were largely unaffected using the Exo. Supported by MO21500/MO210170. The opinions expressed are the authors' and are not to be construed as official or as reflecting the views of the Army or Department of Defense.