A biomechanical comparison of powered robotic exoskeleton gait with normal and slow walking: An investigation with able-bodied individuals

Background: Overground lower-limb robotic exoskeletons are assistive devices used to facilitate ambulation and gait rehabilitation. Our understanding of how closely they resemble comfortable and slow walking is limited. This information is important to maximise the effects of gait rehabilitation. The aim was to compare the 3D gait parameters of able-bodied individuals walking with and without an exoskeleton at two speeds (self-selected comfortable vs. slow, speed-matched to the exoskeleton) to understand how the user's body moved within the device.

Methods: Eight healthy, able-bodied individuals walked along a 12-m walkway with and without the exoskeleton. Three-dimensional whole-body kinematics inside the device were captured. Temporal-spatial parameters and sagittal joint kinematics were determined for normal and exoskeleton walking. One-way repeated measures ANOVAs and statistical parametric mapping were used to compare the three walking conditions (P < .05).

Findings: The walking speeds of the slow (0.44[0.03] m/s) and exoskeleton (0.41[0.03] m/s) conditions were significantly slower than the comfortable walking speed (1.54[0.07] m/s). However, time in swing was significantly greater (P < .001, d = -3.64) and double support was correspondingly lower (P < .001, d = 3.72) during exoskeleton gait than slow walking, more closely resembling comfortable speed walking. Ankle and knee angles were significantly reduced in the slow and exoskeleton conditions. Angles were also significantly different for the upper body.

Interpretation: Although the slow condition was speed-matched to exoskeleton gait, the stance:swing ratio of exoskeleton stepping more closely resembled comfortable gait than slow gait. The altered upper body kinematics suggested that overground exoskeletons may provide a training environment that would also benefit balance training.