Regression analysis of electromyographic activity of masticatory muscles versus bite force

Electromyographic (EMG) activity of the superficial masseter and the anterior temporal muscles versus the bite force was studied in 10 young women. They were fully dentate and had no dysfunction of the stomatognathic system. The descending part of the trapezius muscle was also chosen for EMG registration. The average bite force between the first molars was 396 N (Newton). Steeper slopes for the EMG versus force regression curve at high contraction levels than at low contraction levels for the superficial masseter muscle may indicate that this muscle has a recruitment pattern that differs from that of the anterior temporal muscle. In the case of the anterior temporal muscle there was no difference between the slopes for the EMG-force regression at low and high contraction levels. There was significantly increased activity in the descending part of the trapezius muscle mainly during high bite force levels in half the subjects.