Home-Based Resistance Exercise Alters Electromygraphic Activity in the Jaw Muscles

Objectives: To determine whether resistance exercise alters the patterns of electromyographic (EMG) activity of the jaw muscles during standardised jaw movements. Methods: Electromyographic activity was acquired from the masseter, temporalis and digastric muscles in 12 healthy adults during a standardised lateral jaw movement task. Subjects were randomly allocated into an exercise or control group. The exercise group performed isotonic resistance exercises, 3 times a day for 4 weeks, by applying finger pressure to the mandible against right lateral (ipsilateral) jaw movement. The standardised movements were repeated after this and again 4 weeks later. Raw EMG signals were rectified, Butterworth filtered and normalised to maximum voluntary contraction. Statistical analyses of total EMG activity, maximum EMG activity, rate of EMG activity increase and timing of EMG activity onset and offset of this processed EMG signal were undertaken, between the control and exercise groups, and before and after exercise sessions (ANOVA, Mann-Whitney test). Results: All subjects performed the same standardised right lateral movements during and between testing sessions. The total EMG activity of all the tested muscles showed no statistically significant (p>0.05) changes between the exercise or control groups over the testing period. The left (contralateral) anterior temporalis, left (contralateral) masseter and right (ipsilateral) anterior digastric, showed significant (p<0.05) changes in 3 out of the 4 remaining tested variables. Furthermore, initial exercise training resulted in a significant (p<0.05) reduction in the duration of EMG activity in the ipsilateral anterior temporalis, with a concomitant significant (p<0.05) increase in the duration of EMG activity in the ipsilateral anterior digastric. Conclusion: Resistance exercise can alter the patterns of EMG activity of the jaw muscles during standardised jaw movements. Changes in the duration of EMG activity may imply that other jaw muscles altered their activity in order to complete the standardised jaw movement task.

Support: ADRF Grant-73/2006.