Quantitative Estimation of Forearm Strength and Associated Muscle Fatigue on the Screw Driving Task

Abstract

Background: Upper extremity musculoskeletal disorders are highly prevalent work-related injuries. The problem is commonly related to tasks that involve forceful exertion and repetitive motion. This study investigated forearm muscular strength and fatigue when performing a screw driving task using the screw driving model.Methods: Ten male and two female adults participated in this study. The pre- and post-fatigue maximum handgrip, driving torque, push force, insertion rate of the screws and corresponding electromyographic responses were measured to assess the muscle strength loss and fatigue of the forearm when driving screws. Results: After screwing, the maximal grip force, maximal driving torque, and maximal push force losses were approximately 32%, 24% and 27%, respectively. The percentage force loss of grip force and driving torque in the brachioradialis and extensor carpi ulnaris was greater than those of the biceps brachii. The percentage of maximum driving torque and push force decreased significantly on the eighth screw compared with the first screw. The insertion rate decreased linearly with the number of inserted screws; however, a significant decrease in the insertion rate of the fourth screw was observed. Conclusion: Muscle fatigue may occur in subjects who are inserting more than four screws. More muscle force loss and a higher risk of fatigue occurred in the brachioradialis and extensor carpi ulnaris. The results of this study can be used to assess the risk of forearm injury and potential for muscle fatigue due to exposure to repetitive driving tasks. Keywords: muscle fatigue, maximum isometric forces, driving torque