Electromyograph (EMG)

Electromyography (EMG) evaluates the electrical activity produced by skeletal muscles. An electromyogram is a record of the electric potential or voltage produced by skeletal muscles when they are activated by nerve signals or stimulated by electrical signals. The signals can be analyzed to detect neuromuscular abnormalities, activation level, or recruitment order, or to analyze the biomechanics of human or animal movement.

Usually, one or more small needles (also called electrodes) are inserted through the skin into the muscle. The electrical activity picked up by the electrodes is then displayed visually on a screen and can be monitored by audio so the activity can be heard. EMG measures the electrical activity of muscle during rest, slight contraction and forceful contraction. Muscle tissue does not normally produce electrical signals during rest. As the muscle is contracted more forcefully, more and more muscle fibers are activated, producing action potentials. The display of the action potentials provides information about the ability of the muscle to respond when the nerves are stimulated. Nerve conduction studies can provide additional information about possible nerve damage. (Johns Hopkins).

Example of use for analysis of tremor in Parkinson's disease.