Acute effects of ankle exosuit on biomechanics, muscle activity, and energy cost of walking in adolescents with unilateral cerebral palsy

Background: This study aimed to investigate the potential of an assistive ankle exosuit to acutely augment clinically relevant walking parameters in adolescents with Cerebral Palsy (CP). Methods: Ten exosuit-naïve adolescents with unilateral CP (11–16 years old) walked on a treadmill without the exosuit (baseline), and with the exosuit (ReWalk ReStore®) providing unilateral dorsiflexion and plantarflexion assistance to their more-affected ankle. Five participants also walked with their regular orthosis. Energy cost of transport, kinematics and kinetics, and electromyography of Tibialis Anterior and Gastrocnemius Medialis muscles were assessed. Findings: The exosuit increased ankle dorsiflexion during swing-phase, alleviating drop-foot on the more-affected side observed during baseline walking. Peak ankle moment was increased with the exosuit. While participants' orthoses restricted plantarflexion during push-off, the exosuit enabled more-typical push-off plantarflexion motion. There were no significant changes in energy cost or muscle activity with the exosuit. Interpretation: The exosuit facilitated heel-toe ankle kinematics of the more-affected leg during gait, preventing drop-foot, while preserving plantarflexion during push-off. The exosuit slightly increased plantarflexor torque, however this did not translate to increased positive power from the more-affected ankle during gait. Lack of changes in muscle activity or energy cost indicate an inability of exosuit assistance to acutely alter these parameters on initial use of the device. These results display potential of an assistive exosuit to immediately augment ankle kinematics, but also underline limitations of the exosuit to acutely alter other clinical outcomes important for lasting gait changes, namely muscle activity and energy consumption.