Effect of Changing the Position of Resistance Bands of Hip Exosuit on Walking Economy for Healthy Adults

In this thesis, we discuss the effect of changing the positions of resistance bands of passive hip exosuit on the metabolic energy consumption of subjects for overground walking. A passive hip exosuit is a rehabilitation device that is used for gait assistance. It is comprised of elastic resistance bands that absorb and release energy in a periodic manner during the gait cycle. The orientation and configuration of these resistance bands around the hip of the subject determine the timing of the assistance and the overall effectiveness of the device. Based on the evidence analyzed during the literature survey, we hypothesize that we can use passive hip exosuit to personalize the assistance for overground walking, wherein we will see the distinct band positions optimized for achieving maximum reduction in metabolic cost of walking. To test this hypothesis, we set up a two-day protocol for human subject trials, with day one dedicated to subject adaptation and day two for the human-in-the-loop (HIL) optimization using Bayesian Optimization. The passive hip exosuit device was set up to accommodate subjects of varying body types. During the course of the trials, we collected metabolic, EMG, and kinematics data for 8 subjects (7 male and 1 female). After analyzing the results, we noticed the personalized outcome for all subjects, indicating an optimal band position that resulted in a maximum reduction in metabolic cost compared to no device condition. Out of the total number, we observed that five subjects preferred posterior bands, two preferred anterior bands, and one preferred lateral bands as the optimal position. After analyzing the metabolic data, we observed that optimal band position offered a significant reduction in the metabolic cost of walking (6.64%, p=0.002). Similarly, EMG activity for the Soleus muscle showed significant changes (7.35%, p=0.021) when we compared optimal bands and no band conditions. We also observed trends in gait kinematics data that indicated possible biomechanical pathways responsible for this reduction. Based on the trends observed in EMG and gait kinematics, we see that optimal band positioning offered assistance to the push-off phase of the gait cycle, helping the subject in forward propulsion.