Investigation on Time to Fatigue for Upper Limb Muscle during a Repetitive Light Assembly Task

摘要

Repetitive tasks are known as one of the prevalent root causes of muscle fatigue. Light assembly tasks, which are common in electronic and electrical industries, are a class of repetitive tasks with involving light weight (<1 kg). The upper limb region was reported as most complained of strain by the workers doing this type of job. This study aims to investigate the time to fatigue for upper limb muscles in a light assembly task. Twenty subjects (10 males and 10 females) with mean (SD) age of 24.05 (1.76) years performed a light assembly task continuously for two hours. The time to fatigue was defined by significant changes in RMS of electromyography as well as grip strength. Results from RMS EMG show that upper trapezius muscle (right and left) was the muscle fastest being fatigued the fasted (90 minute), followed the right and the left anterior deltoid (95 minutes), the right and the left brachioradialis (100 minutes) and right and the left bicep brachii muscle (110 minutes). On the other hand, a significant change in grip and pinch strength occurred after 100 minutes and 120 minutes work, respectively.