A test that assesses the electrical activity of the muscles and the nerves controlling the muscles. It is used to help diagnose neuromuscular disorders. There are two kinds of EMG in widespread use: intramuscular (needle) and surface EMG. To perform intramuscular EMG, a needle electrode or a needle containing two fine-wire electrodes is inserted through the skin into the muscle tissue. Intramuscular EMG may be considered too invasive or unnecessary in some cases and an electrode placed on the surface of the skin is used.