Electromyography (EMG) is an electrodiagnostic method for evaluating and recording electrical activity produced by skeletal muscles. 

Electromyograph is an instrument for performing EMG, producing a record called an electromyogram.

Electromyographs detect electric potentials generated by muscles when muscular cells are electrically or neurologically activated.

EMG signals are analyzed for detecting medical abnormalities, activation level, or recruitment order, or for physiological research, for example, biomechanics of movement.

Clinical and biomedical applications

EMG is used as a diagnostics tool for identifying neuromuscular diseases, or as a research tool for studying kinesiology, disorders of motor control, as well as a control signal for prosthetic devices such as prosthetic hands, arms and lower limbs.

EMG is usually performed with nerve conduction studies (NCS). 

Needle EMG and NCSs are typically indicated when there is pain in the limbs, weakness from spinal nerve compression, or concern about some other neurologic injury or disorder.

Needle EMG may aid with the diagnosis of nerve compression or injury, nerve root injury, and with other problems of the muscles or nerves, amyotrophic lateral sclerosis, myasthenia gravis, and muscular dystrophy.

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