Abstract
In a factory, problems such as static muscle load occur when workers elevate their arm while assembling goods by hand or by using hand tools. This study quantitatively assesses the influence of the work-plane height during screw-tightening work using a manual screwdriver on musculoskeletal load. Ten healthy male subjects were asked to carry out screw-tightening work using a manual screwdriver for four work-plane heights in an experimental apparatus. An analysis of the results from the viewpoint of an electromyogram, maximum joint torque ratio, pushing force, degree of subjective fatigue, and subjective difficulty of manipulation suggests that for a work-plane at eye height, the musculoskeletal load and degree of subjective fatigue are the worst. Therefore, the work-plane height strongly influences the elevation of workers' arms, and in turn, the musculoskeletal load. Moreover, the cervical division of the spinal chord is subjected to considerable fatigue when workers have to bend their head back in cases where the work-plane is above their head.
