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There are two types of electrodiagnostic testing that are commonly used: electromyography, or EMG, and nerve conduction studies. These tests analyze the electrical activity taking place in the nerves and muscles.

EMG tests muscle activity; it involves inserting a needle through the skin and into the muscle. The needle records electrical activity in the muscle as the patient relaxes then contracts the muscle. When a normal muscle is at rest, there is no electrical activity. When the muscle contracts, electrical activity is recorded.