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Electromyography
Electromyography (EMG) measures the electrical activity of muscles to help diagnose problems with muscles and the nerves that control them.
Quick answer
Electromyography: what it is and what the results mean
EMG records the electrical signals produced by muscles at rest and when they contract, using a fine needle electrode placed into the muscle. It is often done alongside nerve conduction studies.
- Why it is done: It is used to investigate muscle weakness, cramps, twitching or wasting, and to help diagnose conditions affecting the muscles themselves or the nerves supplying them, such as nerve damage, motor neurone disease and muscle disorders.
- Understanding results: The pattern of electrical activity shows whether a problem lies in the muscle, the nerve or the connection between them.
What it is
EMG records the electrical signals produced by muscles at rest and when they contract, using a fine needle electrode placed into the muscle. It is often done alongside nerve conduction studies.
Why it is done
It is used to investigate muscle weakness, cramps, twitching or wasting, and to help diagnose conditions affecting the muscles themselves or the nerves supplying them, such as nerve damage, motor neurone disease and muscle disorders.
What to expect
A fine needle electrode is inserted into selected muscles; you may feel brief discomfort as it goes in and are asked to relax and then gently tense the muscle. There are no electric shocks in the needle part. It takes 30–60 minutes.
Understanding the results
The pattern of electrical activity shows whether a problem lies in the muscle, the nerve or the connection between them. A specialist interprets the results alongside your symptoms and nerve conduction findings.
Good to know
Risks and limitations
It is generally safe, with mild soreness or minor bruising at the needle sites. It can be uncomfortable, and results depend on skilled interpretation. Blood-thinning medicines should be mentioned beforehand.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
Electromyography: frequently asked questions
Does an EMG involve electric shocks?
The EMG needle part does not. If nerve conduction studies are done at the same time, those involve small electrical pulses on the skin, which feel like brief tingles or taps rather than painful shocks.
How is EMG different from a nerve conduction study?
A nerve conduction study measures how well nerves carry signals using surface electrodes, while EMG uses a fine needle to record muscle activity directly. They are often done together to give a fuller picture.
Related tests
Other other investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- Relevant royal college / professional body
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