Motor Adaptation Effect of Active Joint Movement During Cycling Generated by Ankle Assist Ergometer: A Proof-of-Concept Study in Healthy Participants

To promote multi-joint movement considering limb coordination, we introduce a portable ankle assist ergometer (AAE) to deliver passive ankle joint motion at a specific crank angle per cycle during cycling. This study aimed to verify the motor adaptation effect using the developed AAE in healthy young participants. We converted the pedals of a commercial ergometer into an ankle-assisting tool driven by a motor and brake. The AAE delivered ankle dorsiflexion assistance to young adult participants from 90° after the top dead center until the bottom dead center of the crank angle during cycling. We obtained 1) a significant difference between the ankle dorsiflexion angular velocity at the bottom dead center before and immediately after assistance ( p < 0.05 ) and 2) an increase in dorsiflexion muscle activation (p < 0.05). These effects persisted after the removal of the assistance. Our results suggest that the AAE activates the central pattern generator and induces motor adaptation of ankle movement by limb coordination during a motion cycle. We believe that the proposed AAE contributes to eliminating barriers to the clinical implementation of the rehabilitation tools delivering cyclic motion.