Hip exoskeletons may hold potential to augment walking performance and mobility in individuals with disabilities. The purpose of this study was to design and validate a novel autonomous hip exoskeleton with a user-adaptive control strategy capable of reducing the energy cost of level and incline walking in individuals with and without walking impairment. First, in a small cohort of three unimpaired individuals, we validated the ability of our control strategy to provide hip flexion-extension torque that was proportional to the biological hip moment and reduce the energy cost of level and incline walking (24 ± 5% and 13 ± 5% reductions, respectively). Next, in a clinical feasibility experiment with an individual with significant walking impairment from cerebral palsy, we demonstrated that our untethered device and adaptive control scheme improved hip extension by 14° across the gait cycle, reduced average rectus femoris and semitendinosus muscle activity by 23% and 46%, respectively, and resulted in a 15% improvement in metabolic cost relative to walking without wearing the device.

Walking ability is critically important for pediatric health, well-being, and independence. Children with cerebral palsy (CP), the most prevalent cause of pediatric physical disability, often present pathological gait patterns that negatively impact walking capacity. Reduced function of the muscles surrounding the ankle joint in those with CP also greatly increases the energy cost of transport leading to reduce mobility. Ankle-foot-orthoses show limited effectiveness for clinically relevant improvement in gait mechanics, while orthopedic surgery, muscle injections and physical therapy are unable to completely restore gait function. While wearable exoskeletons hold promise for gait rehabilitation, appropriately controlling the timing and magnitude of powered assistance across individuals and conditions remains a considerable challenge. This work seeks to address this challenge through the design and initial clinical verification of a simple ankle exoskeleton control scheme designed to reduce the metabolic cost of transport during walking in an individual with CP. Preliminary experimental results from instrumented gait analysis following 5 training visits demonstrated a 45% increase in positive ankle power and a 16% reduction in net metabolic rate during walking with the exoskeleton providing powered plantar-flexion assistance compared to walking without the exoskeleton. Future work will expand this investigation to a larger cohort of individuals with CP and across additional modes of locomotion.