Step-by-Step Explanation of What to Expect During the Electromyography Portion of Your Test
If you're scheduled for EMG, understanding exactly what happens during the electromyography portion of your test can help reduce anxiety and prepare you for what to expect. This article walks you through the procedure step-by-step.
[1] EMG (electromyography) measures the electrical activity of muscles. A thin needle electrode is inserted into a muscle, and the electrical signals produced by muscle fibers are recorded and displayed on a screen with sound. The technician evaluates both the electrical patterns and the sounds the muscle produces.
EMG typically follows nerve conduction studies (NCS) in a combined EMG/NCS testing session. Most testing sessions include both EMG and NCS to get complete information about nerve and muscle function.
[2] The needle used for EMG is extremely thin—much thinner than a needle used for blood tests or injections. It's specially designed for recording electrical activity from muscles. The needle has:
Yes, absolutely. The needle is sterile and single-use. A new needle is used for each muscle tested to prevent infection.
The technician chooses which muscles to test based on your symptoms and medical history. Typical muscles tested depend on your suspected diagnosis but might include muscles in the:
You'll be positioned comfortably so the technician has easy access to the muscles being tested. You might be sitting, lying down, or in various positions depending on which muscles are being evaluated.
[1] The technician gently inserts the needle into the muscle. You'll feel:
The sharp sensation is very brief. Once the needle is in the muscle, the sensation usually becomes dull pressure or slight ache rather than sharp pain.
[3] With the needle in the muscle and your muscle relaxed, the technician records and listens to electrical activity. In a normal, relaxed muscle, there should be no electrical activity—the muscle should be electrically "quiet."
If there IS electrical activity when the muscle should be quiet, this indicates a problem. Examples include:
This part of the test is very simple—you just relax your muscle while the needle is in it. The technician will tell you to "relax" and will listen to the sound coming from the speaker. You don't need to do anything; just stay as still and relaxed as possible.
[2] After recording resting activity, the technician asks you to gently contract the muscle. This produces characteristic electrical patterns called motor unit action potentials (MUAPs).
The technician evaluates:
The technician will ask you to gently contract the muscle, usually with instructions like:
You'll be asked to contract the muscle gently at first, then with increasing force. The technician will tell you when to relax between contractions. This part of the test is painless; you're simply contracting your muscle while the needle records the electrical activity.
[1] Depending on your symptoms, multiple muscles may need to be tested. Here's how this works:
The number of muscles tested varies depending on your condition and what the technician is evaluating. Typical testing might include 4-8 muscles, but this varies. Your doctor will determine how many muscles need testing.
[3] Most patients describe EMG as uncomfortable but tolerable:
Once all muscles have been tested:
Your muscles may feel mildly sore (like after exercise) for a day or two. This is normal. Ice packs and over-the-counter pain relievers help.
Minor bruising at needle insertion sites is possible but uncommon. If it occurs, it typically resolves within a few days.
This article is educational information only and does not constitute medical advice. The information here is based on current medical literature and professional standards but is not a substitute for professional medical evaluation, diagnosis, or treatment. Always consult with your healthcare provider regarding your specific medical situation, symptoms, and questions about sleep studies or any medical procedure.