1. A graphic record of the contraction of a muscle as a result of electrical stimulation or the electric activity of a muscle either spontaneous or in response to artificial electric stimulation.
2. A record of the spiking electrical discharge of a muscle, motor unit, or muscle fiber generated in response to neutral impulses or arising spontaneously.
3. A record of eye movements when reading, obtained by measuring the potential difference between an electrode placed at the center of the forehead and one placed at the temple.
4. A record of the intrinsic electric activity in a skeletal muscle.

Such data aid the diagnosis of neuromuscular problems and are obtained by applying surface electrodes or by inserting a needle electrode into the muscle and observing electric activity with an oscilloscope and a loudspeaker.

Some electromyograms show abnormalities; such as, spontaneous electric potentials within the muscle under study, and help pinpoint lesions of motor nerves.

Electromyograms also measure electric potentials induced by voluntary muscular contraction.