Effects of Passive Ankle Exoskeleton on Human Energy Expenditure: Pilot Evaluation

Exoskeletons can be utilized for rehabilitation purposes as well as for assistance and augmentation of motion of patients with disabilities, workers, the elderly and even healthy people. Compared to powered solutions, unpowered passive exoskeletons have been shown to have significantly higher chances of end user acceptance, because of simpler design, no complex electronics and potentially lower cost. In this paper we present the results of a flat walking test using an unpowered passive ankle exoskeleton. Important exoskeleton aspects such as ergonomics, comfort, and robust design are outlined and areas for improvement are highlighted. The paper also presents the results of the evaluation of the exoskeleton device in a pilot study, where its physiological effects are assessed for four participants via measurements of oxygen consumption and EMG muscle activity during five 10-min walking sessions under different conditions. Results show that significant metabolic cost reduction can only be achieved with a proper mechanism spring selection.