An EMG (electromyography) of one limb measures electrical activity in muscles and the nerves that supply them to diagnose nerve or muscle disorders. A specialist inserts small needle electrodes into selected muscles (often with nerve conduction studies) to detect denervation, neuropathy, radiculopathy or myopathy. It may cause brief discomfort; bleeding, infection or rare nerve injury are uncommon risks.

Electromyography (EMG) uses a needle to record electrical activity from motor units in a muscle, detecting denervation, myopathy, and nerve disorders by assessing motor unit potentials and spontaneous activity. Single‑fiber EMG is a specialized technique that records action potentials from individual muscle fibers to measure jitter and blocking, providing high sensitivity for neuromuscular junction disorders like myasthenia gravis.

Single-fiber EMG uses a very thin needle and typically causes brief, sharp stinging on insertion and mild aching or muscle twitching during testing. Most people find it uncomfortable rather than severely painful; soreness may last a day. It’s usually well tolerated, though anxiety or testing sensitive muscles can increase discomfort. Serious complications are uncommon.

There are two main types of EMG: surface (or skin) EMG and intramuscular (needle) EMG. Surface EMG uses adhesive electrodes on the skin to record overall muscle activity noninvasively, useful for movement analysis and biofeedback. Needle EMG inserts a fine wire or needle into the muscle to record single‑motor‑unit activity, providing detailed information for diagnosing nerve or muscle disorders.

Most people recover from an EMG quickly and can resume normal activities immediately. You may have mild soreness, bruising or twitching at needle sites lasting hours to a few days. If muscles were tested, avoid heavy lifting or strenuous exercise for 24 to 48 hours. Serious complications are rare; contact your clinician for increasing pain, swelling, fever or prolonged numbness.

An EMG test typically costs about $200–$1,500 in the United States (private); insurance and facility affect out‑of‑pocket share. In the UK it’s free on the NHS or about £200–£700 privately. In countries like India prices often range roughly ₹800–₹6,000. Final cost depends on location, clinic type, whether nerve conduction studies are done, and specialist fees.