Adaptation of Gait Energetics to Ankle Exoskeleton Assistance Within and Across Visits: A Clinical Case Series

Wearable assistive devices have begun to show potential for improving walking economy in individuals with neuromuscular impairment. However, no studies have investigated how quickly individuals with neuromuscular disabilities adapt to assistance across different time scales, which makes experimental design challenging. The goal of this case series was to evaluate how individuals with cerebral palsy (CP) adapt to untethered powered plantar-flexor assistance within and across exoskeleton practice sessions. To assess inter-visit adaptation, one participant with mild CP (Gross Motor Function Classification System level (GMFCS) I) completed 112 minutes of exoskeleton walking practice across four visits. This participant's preferred level of assistance increased across practice sessions, and metabolic assessment indicated reduced acclimation time and improved walking economy; across visits, metabolic cost decreased by 18% during walking with exoskeleton assistance and by 13% while wearing the exoskeleton in an unassisted condition. To assess intra-visit adaptation, another participant with mild CP (GMFCS I) completed three 8-10 minute exoskeleton-assisted walking trials with the same level of assistance on a single visit. This participant exhibited a 16% reduction in the average metabolic cost relative to baseline during the final minute of walking on the third trial. Despite walking with assistance for 30 minutes, the participant did not appear to reach a fully acclimated state at the end of the third trial, suggesting that further improvements may have been observed with additional practice. These preliminary findings may prove useful for designing novel intervention studies and experimental protocols testing the potential benefit of wearable assistance in clinical populations.