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An electromyogram, or EMG, measures the electrical activity produced by muscles. This technique is used to assess the health of muscles and their motor neurons, which are the nerve cells that control them. An EMG is done using a medical instrument called an electromyography, which detects the electrical signals generated by muscles when they are stimulated. These signals are translated into graphs, sounds, or numerical values, which are interpreted by your doctor.
During an EMG, a needle electrode is put to a muscle and also attached to a recording machine. Once the electrodes are in place, the electrical activity in that muscle is recorded while the muscle is at rest. Your doctor will ask you to contract the muscle slowly, and that electrical activity is recorded as well. Throughout the test, the electrode may be moved a number of times to assess the activity in different parts of the muscle or in different muscles altogether.
EMGs are helpful in diagnosing a number of neurological disorders. Your doctor may order an EMG if you have signs or symptoms of a nerve or muscle disorder, which may include tingling, numbness, muscle weakness, muscle pain, or cramping.