Electromyography (EMG) is a recording of the electrical activity associated with muscle contraction. A tiny electrode, size of a pin, is inserted through the skin into several muscles. This may be associated with minor discomfort. A nerve conduction test is also often done at the same time as an EMG in order to diagnose neurological diseases. This requires a small electrical stimulus on a nerve in the arm or leg. It shows how fast an impulse travels along a nerve.