With MIT: primary research objective is to apply principles of biomechanics and neural control to guide designs of wearable robotic systems for human rehabilitation and physical augmentation; has employed cross bridge models of skeletal muscle to design and optimization of new class of human-powered mechanisms that amplify endurance for cyclic anaerobic activities; also built elastic shoes that increase metabolic economy for running, and leg exoskeletons for walking load-carrying augmentation; in assistive technology, group has developed powered orthotic and prosthetic mechanisms for use as assistive interventions in treatment of leg disabilities caused by amputation, stroke, cerebral palsy and multiple sclerosis.