Generally, I am interested in the mechanics, energetics, and control of terrestrial locomotion. For my doctoral dissertation studies I used powered exoskeletons as a tool to understand the contribution of ankle joint mechanical power to the metabolic cost of walking. Current research in my laboratory seeks to discover physiological principles underpinning locomotion performance and apply them to develop lower-limb robotic devices capable of improving both healthy and impaired human locomotion (e.g., for elite athletes, aging baby-boomers, post-stroke community ambulators). By focusing on the human side of the human-machine interface, we have begun to create a roadmap for the design of lower-limb robotic exoskeletons that are truly symbiotic—that is, wearable devices that work seamlessly in concert with the underlying physiological systems to facilitate the emergence of augmented human locomotion performance. We are particularly interested in the mechanics and control of compliant muscle-tendon units (e.g., ankle plantarflexors). We use simple mathematical models to explore how elastic mechanisms can be exploited to allow for economical force production and optimal mechanical energy transfer during both steady and unsteady cyclic movements, particularly in the context of mechanical assistance from wearable robots (e.g., exoskeletons). We test model predictions experimentally in (1) human Achilles’ tendon-triceps surae in vivo during walking, running and hopping using B-mode ultrasound imaging and (2) biological muscle-tendons in vitro (bullfrog) and in situ (rat) during simulated locomotion using sonomicrometry and real-time emulation of dynamical systems through ‘smart’ ergometer interfaces.