Effects of Joint Assistance on the Muscle Metabolism and Strength in Different States Based on Simulation

Abstract

A powered exoskeleton on reasonable design can effectively reduce the metabolic cost during walking. In order to explore the metabolism and muscle strength with powered exoskeleton assisted on joints under different states, we involved seven healthy subjects to walk on level and slope of 5° with different loads (0, 10, 20 and 30 kg), based on which we simulated the states of walking with different assistant torque on joints to analyze the metabolic cost and muscle force. The results demonstrated that the metabolism decreased more with the increase of hip extension assistance on flat and it had a more significant reduction under greater driving moment of hip flexion, hip extension, knee extension and ankle plantarflexion on slope. Both ankle plantarflexion and hip extension devices reduced more energy consumption than other powered devices, between which hip extension assistance increased the metabolic reduction rate significantly, especially on slope. Each kind of powered exoskeleton reduced the strengths of agonistic muscles assisted. In addition, hip extension device greatly reduced the strength of vastus intermedius and ankle plantarflexion device reduced the strengths of rectus femoris and vastus intermedius concurrently. The results predicted metabolism and muscle strength under different assistances in various states, providing advisement for drive design theoretically.