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What is an EMG, and How Does it Work?

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Updated June 26, 2014

What is an EMG, and How Does it Work?
Photo © A.D.A.M.

What EMG is:

EMG, or electromyography, is a test that measures muscle strength. When you have an EMG, a thin needle-like electrode is inserted through your skin into the muscle. This electrode picks up detailed readings from your muscle, detecting the strength of its contraction.

Why You Might Have an EMG:

Some chronic pain disorders can cause or be caused by muscular weakness. Readings from an EMG can help your doctor determine if you have generalized muscle weakness, or muscle weakness that is caused by a neurological problem. EMGs are often performed in conjunction with a nerve conduction velocity test (NCV) to diagnose certain neurological disorders like carpal tunnel syndrome or sciatica.

What EMG Feels Like:

While you may have some discomfort during your EMG, most tests are not painful. The needle electrode is thin, though it may feel unpleasant as it is inserted. During the test you should feel little, if any, discomfort. Some people experience muscle tenderness for a day or two after the test, and some have minimal bleeding from the EMG needle sites. Most people, however, find EMGs to be painless.

Preparing For Your EMG:

Fortunately, you won’t need to do much to prepare for your EMG, other than arriving to your appointment on time. Most providers ask that you not apply anything topical to the test areas. In other words, don’t use any lotion or pain creams on until the test is over. Before you arrive at your appointment, ask your doctor if he plans on performing any other tests that may require preparations.

Source:

Medline Plus. Medical Encyclopedia: Electromyography. Accessed 6/9/09. http://www.nlm.nih.gov/MEDLINEPLUS/ency/article/003929.htm

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