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  • Cynthia M. Johnson, MA
Publication Type:





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.

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

  • Excess bleeding
  • Infection at the needle site

What to Expect

Problems to Look Out For

Call the 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.

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.


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.





  • Carpal tunnel syndrome. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/carpal-tunnel-syndrome.
  • Electromyography (EMG). Johns Hopkins Medicine website. Available at: http://www.hopkinsmedicine.org/healthlibrary/test_procedures/neurological/electromyography_emg_92,P07656.
  • FAQs before EDX testing. American Association of Neuromuscular & Electrodiagnostic Medicine website. Available at: http://www.aanem.org/Patients/FAQs-before-EDX-Testing.


  • Teresa Briedwell, PT, DPT
Last Updated:

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.