Archives of oral biology
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Archives of oral biology · Aug 2001
Fatigue and pain in human jaw muscles during a sustained, low-intensity clenching task.
Fatigue, pain and changes in the electromyographic (EMG) activity of the jaw-closing muscles are well documented during short, high-intensity tooth-clenching tasks but less so during sustained, low-intensity tasks. In this study, 11 healthy men clenched on a bite-force meter for 60 min at 10% of the maximal voluntary contraction (MVC) and scored the intensity of fatigue and pain on separate 10 cm visual analogue scales (VAS). Surface EMG activity from the masseter and anterior temporalis muscles was recorded in 10 s epochs every 5 min throughout the task. ⋯ The mean frequency of the EMG activity decreased in all muscles during the task (95.7 vs. 46.6 Hz;P<0.001), and the root mean squares increased (53.2 vs. 154 microV, P<0.001). The changes in EMG activity were more strongly correlated with the sensation of fatigue than pain. These findings demonstrate that a sustained, low-intensity clenching task can induce subjective and electrophysiological indications of fatigue.