An electromyography (EMG) measures the electrical activity in muscles during movement. This testing, also called needle EMG, involves placing a needle electrode into the muscle being tested and having the patient move or contract the muscle from time to time. An electromyograph machine records the electrical signals from the muscle’s movements as sound waves. An abnormality detected in these electrical signals could indicate dysfunction within the muscle and/or the nerve that supplies it.

EMG is typically performed with a NCS (nerve conduction studies) as part of an electrodiagnostic study of chronic neck or back pain, tingling, numbness, and/or weakness.