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By Mayo Clinic staffElectromyography (EMG) is a diagnostic test used to evaluate the electrical activity in your nerves as they transmit messages to your muscles when the muscles are contracting and when they're at rest. The purpose of an EMG is to assess the health of your muscles and the nerves that control them.
During an EMG, a thin needle with an electrode is inserted through your skin into a muscle. The electrode records the electrical activity in your nerve and muscle and transmits it to a receiver that displays the EMG results on a printout or on a computer screen. The electrical activity recorded during an EMG may also be broadcast over a speaker for your physician to hear.
An EMG can help diagnose disorders that affect muscle and nerve function, such as muscular dystrophies, and nerve disorders, such as neuropathies.