An electromyogram (EMG) is a recording of the electrical activity (nerve response) of muscle tissue at rest and during activity. During an EMG, a technician or physician will clean the skin over the muscle to be tested, then insert one or more needle electrodes into the muscle. The electrode is attached to a recording machine by wires and measures your muscle's electrical activity.

A healthy muscle at rest should have no electrical activity. Your physician or technician will ask you to contract your muscle during the test to create electrical activity. The tester may also move the electrode several times to test other parts of the muscle or body. EMGs typically take 30 minutes to an hour, though your exam may take more or less time.

An electromyogram may be used to distinguish between a muscle disorder and a nerve disorder, helping your healthcare team to diagnose or rule out certain neurological conditions, such as:

• Amyotrophic lateral sclerosis (ALS) or Lou Gehrig's disease
• Dystonia
• Essential tremor
• Facial nerve disorders
• Muscular dystrophy
• Neuromuscular disorders
• Neuropathy
• Tic disorders