Exploring muscle fatigue related to repetitive work in an industrial setting – preliminary results of a single-case study

Abstract

Work-related musculoskeletal disorders, a major public health problem, are mainly caused by the task nature and the work environment. One of the most important risk factors for the development of work-related musculoskeletal disorders is muscle fatigue. Therefore, its assessment can contribute to the application of preventive measures. Many studies have evaluated muscle fatigue associated with work tasks in laboratory settings, but they do not mimic industrial environments, with their constant noise, air pollution, and stress. A repetitive task of vertical screw-tightening performed by an experienced worker in a manufacturing and assembling industry was selected. Four assessment moments took place during the shift on 3 non-consecutive days. Outcomes included electromyography data from the upper trapezius and biceps brachii to assess muscle fatigue, painful symptoms in the upper limbs’ joints and trunk, and perceived exertion. An increase in painful symptoms and perceived exertion was reported by the worker throughout each of the analyzed shifts. A trend toward increased electromyography values was also observed. Muscle tension in the upper trapezius seems to have an inverse association with tension in the biceps brachii in this activity. Although it is possible to verify a trend towards an increase in electromyography, this trend is timid, with variability between the different cycles.