Carl R. Darnall Army Medical Center - Health Library

Electromyography

(EMG)

Definition

Electromyography (EMG) measures and records the electrical activity of a muscle. It can record it at rest and when a muscle contracts.

An EMG is sometimes done studies that look at the electrical activity in your nerves.

EMG of the Shoulder
EMG shoulder 2

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Reasons for Test  ^

An EMG can be done to:

  • Find out the source of pain, cramping, or weakness
  • Tell muscle weakness and limitations apart from pain
  • Find out if muscles and nerves are working the right way
  • Tell muscle disorders apart from nerve disorders

Possible Complications  ^

Problems are rare, but all procedures have some risk. Your doctor will go over some of these problems, like:

  • Bleeding
  • Pain or bruising at the needle site
  • Infection at the needle site

What to Expect  ^

Prior to Test

Talk to your doctor about the medicines you are taking. You may be asked to make changes to them up to 1 week before the test.

On the day before and day of the test:

  • If your doctor tells you to, stop cigarettes, coffee, tea, and soft drinks for 2-3 hours before the test.
  • Take a bath or shower before the test.
  • On the day before, do not use lotion or oil.
  • Tell your doctor if you have a pacemaker or other implanted device.
  • Remove any clothing, jewelry, hairpins, eyeglasses, hearing aids, or other metal objects. They may cause problems with the EMG.

Description of the Test

A small needle electrode will be placed into a muscle that is at rest. You will be asked to rest or tense the muscle. The activity picked up by the needle will make a waveform. It will be recorded and studied. The test will be done on other muscles and limbs.

After Test

You will be able to leave after the test is done. When you are home:

  • Take any medications you stopped before the test
  • Do normal activities as you are able

How Long Will It Take?

30-90 minutes

Will It Hurt?

You may have some pain when the needle electrodes are placed. It feels like an injection into the muscle.

After the test, you may have muscle aches and discomfort for several days. Warm packs and pain medicine may help.

Results

The doctor doing the EMG may talk about the results with you. A report will also be sent to your primary doctor. Your doctor will talk to you about options based on the tests and other factors.

Call Your Doctor  ^

After the test, call your doctor if you have:

  • Signs of infection, such as fever and chills
  • Redness, swelling, pain, bleeding, or fluid leaking from around the needle sites
RESOURCES:

Family Doctor—American Academy of Family Physicians
http://www.familydoctor.org

National Institute of Neurological Disorders and Stroke
http://www.ninds.nih.gov

CANADIAN RESOURCES:

Health Canada
https://www.canada.ca

Muscular Dystrophy Canada
http://www.muscle.ca

REFERENCES:

Electromyography (EMG). Johns Hopkins Medicine website. Available at: http://www.hopkinsmedicine.org/healthlibrary/test_procedures/neurological/electromyography_emg_92,P07656. Accessed June 12, 2018.

FAQs before EDX testing. American Association of Neuromuscular & Electrodiagnostic Medicine website. Available at: http://www.aanem.org/Patients/FAQs-before-EDX-Testing. Accessed June 12, 2018.

Last reviewed June 2018 by EBSCO Medical Review Board Rimas Lukas, MD  Last Updated: 6/12/2018