Evaluation of the Effects of Passive Lower-Limb Exoskeletons on Muscle Activities According to Working Heights

Introduction: Research and development efforts regarding passive lower-limb exoskeletons are actively ongoing to reduce work-related musculoskeletal disorders (WMDSs) from improper and prolonged posture. The aims of this study were to evaluate the effects of passive lower-limb exoskeletons and working heights on muscle activity and subjective comfort ratings. Methods: In this study, 20 males performed a 10-min drilling task for three levels of working height (60, 85, and 110 cm), and three levels of intervention (WO: without exoskeleton, WCEX, and WCC) were used as independent variables. The EMG data of eight muscles and subjective discomfort ratings in each of the six body parts were analyzed in this study. Results: The results of this study confirm that the effect of wearing a lower-limb exoskeleton device may vary depending on the muscle type and working height. Overall, the positive effects of wearing were generally observed in the lower-limb muscles, whereas the muscle activity of the upper limbs showed an increasing trend when wearing the device at a height of 85 cm or more. Conclusions: Therefore, to obtain positive effects in both the upper- and lower-limb muscles, using the lower-limb exoskeletons at a working height of 85 cm or less is recommended.