Forearm extensor and flexor muscle exertion during simulated gripping work -- an electromyographic study

OBJECTIVE: To study forearm muscular exertion during intermittent gripping work at three different regimes resembling vocational work. DESIGN: An electromyographic laboratory study of forearm fatigue during intermittent gripping work at 25% MVC with 10/10, 20/10 and 30/10 s of work/rest was performed. BACKGROUND: Data from the literature indicate that forearm flexors as well as extensors are activated during gripping. However, no systematic quantitative assessment of the muscular exertion has been made hitherto. METHODS: Nine female subjects participated. EMG was detected from five forearm muscles, three extensors and two flexors. Zero crossing rate alterations were used as an index of fatigue. RESULTS: The results show significant (P < 0.05) fatigue signs in at least two of the extensor muscles at all regimes while significant signs of fatigue was seen only at the 30/10 regime for the flexor muscles. CONCLUSIONS: Fatigue effects are generally larger on the extensor side. None of the studied regimes is acceptable from EMG fatigue point of view. RELEVANCE: The muscular fatigue of the forearm extensors in relation to the flexors during gripping work has not been systematically assessed before. Forearm fatigue distribution is probably of great importance for the understanding of forearm disorders related to muscular exertion.