Removing energy with an exoskeleton reduces the metabolic cost of walking

Evolutionary pressures have led humans to walk in a highly efficient manner that conserves energy, making it difficult for exoskeletons to reduce the metabolic cost of walking. Despite the challenge, some exoskeletons have managed to lessen the metabolic expenditure of walking, either by adding or storing and returning energy. We show that the use of an exoskeleton that strategically removes kinetic energy during the swing period of the gait cycle reduces the metabolic cost of walking by 2.5 +/- 0.8% for healthy male users while converting the removed energy into 0.25 +/- 0.02 watts of electrical power. By comparing two loading profiles, we demonstrate that the timing and magnitude of energy removal are vital for successful metabolic cost reduction.

Automated summary

Evolutionary pressures have shaped human walking patterns to be highly energy-efficient, posing challenges for exoskeletons to reduce metabolic costs. However, some exoskeletons have successfully reduced metabolic expenditure by strategically removing kinetic energy during the gait cycle and converting it into electrical power. Timing and magnitude of energy removal are critical factors for effective metabolic cost reduction, as demonstrated through comparison of different loading profiles.