ELECTROMYOGRAPHY. ELECTROMYOGRAPHY An electromyogram (EMG) is a diagnostic test that records the electric activity of a nerve or muscle, permitting the detection of muscular or neuromuscular conditions. The physician can, for example, follow a myopathy´s development or localize nerves affected by an accident or inflammation. Needle-shaped electrodes are placed in the muscle and the patterns of electrical activity are projected on a screen or paper. Here, electromyograph showing low activity.