Effects of electrode movements on masseteric electromyograms of teeth clenching in humans

In six healthy subjects, the integrated electromyographic (IEMG) activity of the right masseter muscle was recorded during 10 s of maximum voluntary teeth clenching, without and with manual movements (at a rate of 1.6 Hz, with a force of approximately 3N) of the bipolar surface electrodes affixed to the cheek. All IEMG recordings were undertaken at discrimination thresholds of 1 microV and 30 microV. Electrode movements were the likely source of some distortion (artefact) of the IEMG readings. An increase in the discrimination threshold (30 microV vs. 1 microV) seemed to decrease the artefactual effects of electrode movements, possibly because the movements exerted their major distorting effects on the smaller (low voltages) masseteric motor units.