In highly mobile workplaces, wearable walking assistant robots can reduce muscle fatigue in the lower extremities of workers and increase energy efficiency. In this study, walking efficiency according to the development of an ultralight wearable hip-assist robot for industrial workers was verified. Five healthy adult males participated in this study. Their muscle fatigue and energy consumption were compared with and without the robot while walking on a flat treadmill and stairs. When walking on the treadmill while wearing the robot, muscle fatigue in the rectus femoris and gastrocnemius decreased by 90.2% and 37.7%, respectively. Oxygen uptake and energy expenditure per minute also decreased by 8.9% and 13.1%, respectively. When climbing stairs while wearing the robot, fatigue of the tibialis anterior, semitendinosus, and gastrocnemius muscles decreased by 18.2%, 33.3%, and 63.6%, respectively. Oxygen uptake and energy expenditure per minute also decreased by 3.6% and 3.7%, respectively. Although wearing a hip-assist robot could reduce muscle fatigue and use metabolic energy more efficiently, it is necessary to further increase the energy efficiency while climbing stairs. This study is intended to provide basic data to improve the performance of robots.

[Purpose]The purpose of this study was to examine changes in muscle fatigue of the erector spinae, rectus abdominis, quadratus lumborum, and gluteus maximus muscles during repetitive lifting using the squat-to-lift and stoop-to-lift techniques. [Method] Participants were 17 healthy young students in their 20 s. The change in the median frequency of the surface electromyography signal was calculated between baseline and the fatigue trial, where fatigue was self-reported. [Results] A significant decrease in median frequency was identified for the quadratus lumborum and gluteus maximus muscles using the squat-to-lift technique (p < 0.05). [Conclusion] The squat-to-lift technique is associated with fatigue of the quadratus lumborum and gluteus maximus muscles and may not be preferable to the stoop-to-lift technique in all cases.