Measurement of the electrical activity in skeletal muscle. This term is typically abbreviated to EMG. Often used to diagnose Neuromuscular disorders or to localize nerve damage, it is also used in biofeedback training.

In sleep research, EMG (a direct measurement of muscle tone) is used in sleep scoring to determine if the subject is asleep or awake. The longitudinal muscles of the neck are commonly used in that application, but other groups are used depending on the exact nature of the research, including the ocular muscles for rapid eye movement (REM) detection.