Analysis of Active Back-Support Exoskeleton During Manual Load-Lifting Tasks

Purpose: Manual material handling (MMH) tasks are the main causes of injuries and work-related musculoskeletal disorders in the industry. For preventing such disorders, several exoskeletons have been introduced to assist workers in performing MMH tasks. This study investigates the effect of an active back-support exoskeleton on muscle activity and analyzes its ergonomic effects. Methods: A custom-made active back-support exoskeleton consisting of two joints (lumber and hip) and three links (trunk, pelvis, and thigh) was used in this study. The ergonomic effect of this exoskeleton on manual load-lifting tasks was investigated by (1) analyzing the muscle activities of the lumbar erector spinae (LES) and upper trapezius using electromyography; (2) conducting the timed up and go (TUG) test; and (3) evaluating the subjective aspect (perceived discomfort). Eighteen healthy subjects participated in the experiment by performing load-lifting tasks and undergoing the TUG test. Thereafter, their perceived discomfort was assessed using the Borg scale. Results: Significant differences were observed with and without the exoskeleton in the (1) root mean squares of the right LES (p = 0.006) and left LES (p < 0.001), (2) time spent in the TUG test (p < 0.001), and (3) perceived exertion level (p < 0.001). The active back-support exoskeleton used in this study was effective in reducing muscle activity and risk related to the LES during manual load-lifting; however, problems regarding its usability arose because of its weight. Conclusion: The exoskeleton evaluated in this study can aid in reducing the load on the lumbar spine of workers by decreasing the muscle activity of the LES. From the usability perspective,users spent more time performing the tasks and perceived higher exertion levels while wearing the exoskeleton.