Design and Validation of a Wearable Ankle Push-Off Device in Cerebral Palsy: Is Spring Resistance as Effective as Motorized Resistance?

Abstract

Powered ankle exoskeletons with biofeedback systems have proven effective at improving ankle plantar flexor muscle recruitment and push-off power in individuals with cerebral palsy (CP). However, their clinical translation and feasibility for at-home training remain limited. This study sought to design an unpowered wearable ankle device with spring resistance combined with a gamified ankle power biofeedback system. Our primary goal was to validate the device's ability to increase plantar flexor muscle recruitment and push-off power relative to baseline, and ensure that these improvements were comparable to those achieved with motorized resistance. Seven ambulatory individuals with CP completed walking sessions with (1) a powered ankle exoskeleton with motorized resistance, (2) our novel ankle device with spring resistance, and (3) shoes only (baseline); Both devices utilized the same biofeedback system. Relative to baseline, both the motorized and spring resistance increased peak (48%, p < 0.05) and mean (43-45%, p < 0.05) soleus activation and mean (37-39%, p < 0.05) medial gastrocnemius activation. No differences in muscle recruitment between spring and motorized devices were observed. Walking with spring resistance increased average ankle push-off positive power by 22% (p = 0.003) compared to motorized resistance and by 23% (p = 0.013) compared to baseline. An ankle device providing targeted spring resistance with ankle power biofeedback can effectively improve push-off muscle recruitment and power in individuals with CP. This supports future research studying outcomes following training with spring-based ankle resistance devices that lower barriers for clinical translation.