Definition reprinted with permission from Culebras, Antonio Butterworth-Heinemann:[amazon 0750696443 inline]
A recording of electrical activity from the muscular system; in sleep recording, synonymous with resting muscle activity or potential. The chin EMG, along with EEG and EOG, is one of the three basic variables used to score sleep stages and waking. Sleep recording in humans typically uses surface electrodes to measure activity from the submental muscles. These reflect maximally the changes in resting activity of axial body muscles. The submental muscle EMG is tonically inhibited during REM sleep.