Effect of a fatigue test and chewing training on masticatory muscles.

The effects of fatigue induced by 30 min of intense chewing before and after 4 weeks of 1 h daily chewing training on masticatory muscles were studied in 15 healthy subjects while eight subjects served as controls. EMG measurements in the postural position and during maximal clenching in the intercuspal position and clinical examination of the stomatognathic system were performed. Marked clinical signs of dysfunction were recorded after the first fatigue test. The severity of dysfunction diminished during the 4-week training period and was back at the baseline level at the end of it. In the second fatigue test, after the training period, the subjects developed less dysfunction. In the control group, a mainly stable pattern was found during the observation period. There was a great variation in EMG activity during the experimental period and there were no statistically significant changes observed between any of the recordings in any of the groups.