Electromyography (EMG) is a procedure to test the electrical activity of muscles. Generally, EMG is performed with another test that measures the conducting function of nerves. This is called a nerve conduction velocity test. Both tests are often performed at the same office visit and by the same personnel. The classical symptoms for the EMG and NCV test is weakness, pain or tingling in the fingers of hands and legs.
An EMG is often performed when patients have unexplained muscle weakness. The EMG helps to distinguish between muscle conditions in which the problem begins in the muscle and muscle weakness due to nerve disorders. The EMG can also be used to detect true weakness, as opposed to weakness from reduced use because of pain or lack of motivation. EMGs can also be used to isolate the level of nerve irritation or injury.
The technical specialist will insert a very thin needle electrode through the skin into the muscle. The electrode on the needle picks up the electrical activity given by your muscles. This activity appears on a nearby monitor, and may be heard through a speaker. After placement of the electrodes, you will be asked to contract the muscle. For example, bending your arm. The electrical activity seen on the monitor provides information about your muscle's ability to respond when the nerves to your muscles are stimulated.