Electromyography

(EMG)

by Cynthia M. Johnson, MA

Definition

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

It may also be done to look at the electrical activity in the nerves.

EMG of the Shoulder

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. The doctor will go over some problems that could happen, such as:

Excess bleeding
Infection at the needle site

What to Expect

Prior to Test

The care team may meet with you to talk about:

Any allergies you may have
Current medicines, herbs, and supplements that you take and whether you need to stop taking them before the test
Avoiding tobacco, coffee, tea, and soft drinks for 2 to 3 hours before the test
Avoiding skin lotion or oil before the test
Whether you have a pacemaker or other implanted device
Removing any objects that may interfere with the test, such as jewelry, hearing aids, or eyeglasses

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.

How Long Will It Take?

30 to 90 minutes

Will It Hurt?

Muscle aches and discomfort are common in the first few days. Medicine and home care can 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

If you think you have an emergency, call for medical help right away.

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:

Carpal tunnel syndrome. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/carpal-tunnel-syndrome. Accessed October 14, 2020.

Electromyography (EMG). Johns Hopkins Medicine website. Available at:
...(Click grey area to select URL)
Accessed October 14, 2020.

FAQs before EDX testing. American Association of Neuromuscular & Electrodiagnostic Medicine website. Available at:
...(Click grey area to select URL)
Accessed October 14, 2020.

Last reviewed September 2020 by EBSCO Medical Review Board Teresa Briedwell, PT, DPT
Last Updated: 6/4/2021

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