Electrodes are electrical devices that translate voltage changes into electrical signals for analysis. The active electrode is the electrode that records the voltages at the point of interest. Since voltage is a measurement of the electrical potential difference between two points, a second electrode is needed for measurements. This second electrode is the reference electrode. A ground electrode is placed on the patient for electrical safety.
Electromyography (EMG) is the neurodiagnostic test which samples the electrical activity of a muscle. The electromyographer places a needle intramuscularly for recording for evaluation of its insertional activity at rest and its voluntary motor units during contraction.
Insertional activityis the electrical signal generated when the recording needle is moved within the muscle. Normal muscle will show a short period of electrical changes....