Preliminary investigation of effects of a quasi-passive knee exoskeleton on gait energetics

In this paper, we explain that the human knee behavior in the weight acceptance phase of gait (first -40% of gait cycle) resembles that of a linear torsional spring. This led us to study the effects of the assistance provided by a pair of quasi-passive knee exoskeletons, which implement springs in parallel with the knee joints in the weight acceptance phase. Using the exoskeletons in a series of experiments on seven participants, we found that the exoskeleton mildly but non-significantly reduces the metabolic power of walking. We also found that the metabolic power of walking is significantly correlated with both the positive rate of moment generation and positive mechanical power of the lower extremity joints. This suggests that augmenting exoskeletons can aim to reduce both the muscle force and work generation to reduce the metabolic cost of walking.