What is Electromyography?

Electromyography (EMG) is a technique for measuring muscle responsiveness or electrical activity in response to nerve stimulation. The test is used to detect anomalies in the neuromuscular system. One or more tiny needles (also known as electrodes) are introduced through the skin into the muscle during the test. An oscilloscope is used to display the electrical activity picked up by the electrodes (a monitor that displays electrical activity in the form of waves). To make the activity audible, an audio amplifier is utilized. The electrical activity of muscle is measured using EMG during rest, minor contraction, and intense contraction. During rest, muscle tissue does not ordinarily produce electrical signals. A brief period of activity can be visible on the oscilloscope when an electrode is introduced, but no signal should be present after that.

Following the insertion of an electrode, you may be asked to contract the muscle by lifting or bending your leg. The action potential (the size and shape of the wave) that this produces on the oscilloscope shows the muscle’s ability to respond when the nerves are stimulated. More muscle fibers are stimulated as the muscle is contracted more forcefully, resulting in action potentials.