The Effects of a Wearable Hip Exoskeleton on Trunk and Lower Limb Muscle Activity during Walking

Background: Wearable hip exoskeletons have been developed to enhance walking ability and reduce muscle effort, particularly in older adults and individuals with walking impairments. They assist with daily activities, rehabilitation, and social interactions. Although considerable research has focused on their assistive capabilities, few studies have examined their effect on muscle activation. Purpose: This study aimed to compare muscle activation in the trunk and lower limbs of young adults walking under three different conditions: general walking, assistive mode, and resistance mode using a wearable hip exoskeleton. Study design: Cross-sectional study Methods: Twenty-nine healthy adults participated in this study. Surface electromyography was used to measure muscle activation during maximal voluntary contraction. Participants walked on a treadmill at 4 km/h under three conditions: general walking, resistance, and assistive modes. Each condition was measured for 2 min and repeated three times in a random order. Results: Muscle activation values for the external oblique, internal oblique, rectus femoris, and gluteus maximus muscles were statistically significant across all modes (p<0.05). External oblique activation was significantly increased in the resistance mode compared with that in the general walking and assistive modes. Internal oblique activation was significantly higher in resistance mode than in assistive mode. Gluteus maximus activation was also significantly elevated in the resistance mode compared to that in the other two modes. No significant differences were observed in the erector spinae, rectus femoris, or hamstring muscles. Conclusions: This study demonstrated that training with the resistance mode of a wearable hip exoskeleton not only increases the activation of the hip flexors but also enhances the activation of the trunk muscles. This suggests that the device has a broader impact on muscle engagement during walking, potentially offering more comprehensive benefits for strength and stability training in healthy adults.