Influence of a passive exoskeleton on muscle activation, perceived discomfort, and mental workload in performing a precision overhead task

BackgroundUpper limb pain, dysfunction, musculoskeletal disorders, and worker absenteeism result from working over-shoulder, making precision tasks, and other occupational control tasks. Researchers have shown that the physical demand is reduced when an exoskeleton is used, but the precision task's productivity and quality depend on the speed of execution.ObjectiveHere, the study determined how an over-shoulder precision task and height change affect the upper extremity muscle activation behavior.MethodsA convenience sample of sixteen participants was employed. A mix of factors intervention (without vs. exoskeleton), wrist load (with (0.5 Kg) vs. without load), and task height (three height levels) were simulated. Surface electromyography, repeated-measures analysis of variance (ANOVA) tests.ResultsUsing an exoskeleton of our design for the experiment, we reduced muscle activation between 16% and 31.8% in shoulder muscles. However, the task height and wrist load factors increased muscle activation when they increased. Also, the wrist load factor significantly affected perceived discomfort in the shoulders.ConclusionsA correlation was found between the right shoulder's RPD, and the right upper trapezius’ mean amplitude affected by increased wrist load. The mental load produced by the precision task was classified as medium, and the performance factor was the most representative.