Abstract
The purpose of this study was to analyze the evoked EMG in masseter muscles in response to electrical and magnetic stimulation during fatigue.
In the electrical stimulation experiment, six healthy male subjects were asked to maximally clench their teeth for 15 sec 9 times. A single rectangular wave of 0.5 msec duration was applied to the skin over the mandibular notch during rest periods of maximum clenching. The evoked EMG was delivered by surface electrodes from ipsilateral masseter muscles. In the magnetic stimulation experiment, eight healthy malesubjects received magnetic stimulation via a figure 8-shaped coil to the optimum region of the scalp during rest periods.
With electrical stimulation, the latency of the evoked EMG was not changed during the sessions but the duration was extended and the amplitude was decreased.
With magnetic stimulation, the latency was longer and the amplitude was smaller than with electrical stimulations. When the periodic clenching passed, the amplitude decreased, while the latency and duration remained unchanged.
In conclusion, periodic clenching fatigue influenced the evoked EMG in masseter muscles induced by electrical and magnetic stimulation.
