Definition of Electromyography:

Electromyography (EMG) is a test that checks the health of the muscles and the nerves that control the muscles.

See also: Nerve conduction velocity test

How the test is performed:

The health care provider will insert a very thin needle electrode through the skin into the muscle. The electrode on the needle picks up the electrical activity given off by your muscles. This activity appears on a nearby monitor, and may be heard through a speaker.

After placement of the electrodes, you may be asked to contract the muscle. For example, bending your arm. The electrical activity seen on the monitor provides information about your muscle's ability to respond when the nerves to your muscles are stimulated.

A nerve conduction velocity test is usually performed along with an EMG.

How to prepare for the test:

No special preparation is usually necessary. Avoid using any creams or lotions on the day of the test.

Body temperature can affect the results of this test. If it is extremely cold outside, wait in a warm room for a while before the test is performed.

How the test will feel:

You may feel some pain or discomfort when the needles are inserted, but most people are able to complete the test without significant difficulty.

Afterward, the muscle may feel tender or bruised for a few days.

Why the test is performed:

EMG is most often used when people have symptoms of weakness, and examination shows impaired muscle strength. It can help to tell the difference between muscle weakness caused by injury of a nerve attached to a muscle and weakness due to neurologic disorders.