Electromyographic Studies on Continuous Gum Chewing and Periodic Clenching

Eight healthy male subjects were asked to unilateral gum chewing continuously for 30min and other five subjects were asked to periodic clenching to the signals monitored on theoscilloscope for the same time. The signals were consisted of the three kinds of durations (500ms, 1s, 2s) and interval of 500ms. The force of clenching was as same as chewing. Surface EMG was picked up from a masseter muscle on the side of chewing. No significant changes were shown in EMG activity and mean frequency during gum chewingthrough the experiments. On periodic clenching, EMG activity strikingly decreaced in 5minand mean frequency was down significantly in 30min, of which tendency was clearer in long timedurations. These findings suggested that the fatigue was not appeared in gum chewing for 30min and it was appeared for a long time in periodic clenching as compared with gum chewing.