Kinematic and myoelectric response to ankle exoskeletons during non-steady state locomotion in healthy adults

Ankle exoskeleton (exo) optimization typically focusses on steady-state (SS) walking conditions, even though non-steady-state (nSS) walking comprises a large portion of daily locomotion. An improved understanding of how exos impact nSS and SS gait differently may further inform optimal exo design. We investigated the impacts of ankle exo stiffness on kinematics and muscle activity in healthy adults during SS walking and acceleration from quiet standing. Peak ankle dorsiflexion and ankle plantarflexor activity on the first stride of nSS showed the largest deviations from SS walking. Sensitivity to exo stiffness was greatest early in gait initiation, but generally approached SS values within three strides. Differences between strides emphasize that SS models for exo optimization may be suboptimal for gait initiation.