The electrical activity resulting from the activity of the massester and anterior temporal muscles will be determined using the six-channel BTS TMJOINT electromyograph (BTS Engineering), with a bioelectric signal amplifier, wireless data transmission and disposable bipolar surface electrodes (Ag/AgCl - Medical Trace®) measuring 10 mm in diameter. The electromyographic (EMG) signal will be amplified with a gain of 2000 times and filtered within a frequency of 20 to 450 Hz. The impedance will be >1015 Ω//0.2 pF and the common rejection mode will be 60/10Hz 92 dB. The data will be digitized at 1000 frames per second using the BTS MYOLA® program.52 Surface EMG signals will be recorded in the right and left masseter and anterior temporal bundles with disposable surface electrodes (Ag/AgCl - Medical Trace®) measuring 10 mm in diameter attached over the belly of the muscle in the region of the greatest tonus (determined during maximum voluntary clenching). The positioning of each electrode will follow the recommendations of the Surface EMG for the Non-Invasive Assessment of Muscles.52 Bandage tape will used to secure the electrodes further, with care taken to avoid micro-movements. The inter-electrode distance will be 20 mm from center to center.Prior to attachment, the sites for the electrodes will be cleaned with a cotton ball soaked in alcohol to diminish impedance. A reference electrode (3 x 2 cm) coated with Lectron II conductive gel (Pharmaceutical Innovations®) will be attached to the left wrist of the volunteer to allow the recording of differential signals.