Electromyography, or EMG, involves testing the electrical activity of muscles.Often, EMG testing is performed with another test that measures the conducting function of nerves. This is called a nerve conduction study.Because both tests are often performed at the same office visit and by the same personnel, the risks and procedures generally apply to both tests.Muscular movement involves the action of muscles and nerves and needs an electrical current. This electrical current is much weaker than the one in household wiring.In some medical conditions the electrical activity of the muscles or nerves is not normal. Finding and describing these electrical properties in the muscle or nerve may help the doctor diagnose the patient's condition.EMG may aid with the diagnosis of nerve compression or injury (such as carpal tunnel syndrome), nerve root injury (such as sciatica), and with other problems of the muscles or nerves. Less common medical conditions include amyotrophic lateral sclerosis, myasthenia gravis, and muscular dystrophy.