Determining the fatigue associated with different task complexity during maintenance operations in males using electromyography features

Purpose: Maintenance workers often perform tasks with high levels of complexity. The association between maintenance task complexity and muscle fatigue needs further investigation. In this study, the effect of maintenance task complexity on muscle fatigue and perceived workload was evaluated. Methods: Fifteen male participants performed two maintenance tasks with two levels of complexity: repairing a gearbox of piston pump (complex task) and repairing a faulty pump housing (simple task). The electromyographic (EMG) activity data from six muscle sites of the neck and the dominant side of the shoulder and arm were recorded. Muscle fatigue was assessed using normalized root-mean-square (RMS) of EMG data and the slopes of median frequency (MF) and mean power frequency (MPF). The NASA Task Load Index (TLX) was utilized as a secondary subjective measure for perceived workload. Findings: Compared to the simple task, performance of the complex task was associated with significantly higher values of RMS EMG (29.92% in average) for all sampled muscles. The slopes of MF and MPF for the flexor carpi radialis muscle during the complex task were significantly lower than that of the simple task. Also, TLX scores for the complex task were significantly higher than those for the simple task. Conclusions: Findings of this study indicate that, within the sampled muscles, the complexity of the maintenance task could cause more muscle fatigue, especially for the forearm muscle. The results of the TLX scores suggest that task complexity could contribute to a significant increase in mental, physical, and temporal demands, effort, and frustration. Relevance to industry: The findings of this study could be utilized to improve the designs of industrial maintenance tasks with respect to human ability and performance.