Estimated changes in muscle-level dynamics and energetics under different levels of exoskeleton-applied work and torque

Assisting human locomotion with ankle exoskeletons is a complicated task, requiring consideration of both biological and device contributions to assisted joint mechanics. Assistance techniques have typically involved some combination of work input and torque support. The complex interaction that arises between the exoskeleton and human neuromuscular system, however, makes it difficult to understand why certain techniques are more effective than others and comparisons have often been confounded by differences other than device behavior. We previously conducted an experiment to study the independent effects of a specific mode of exoskeleton-applied net work and average torque on human mechanics and energetics [1]. We systematically varied net work independently from average torque while subjects walked with a unilateral ankle exoskeleton. We measured metabolic energy consumption, ground reaction forces, joint positions, and muscle activity.