Electromyography (EMG) records the muscle activity at rest and during contraction by inserting a small needle electrode into the muscle. The test typically takes approximately 15-30 minutes to complete. The procedure is entirely safe, even in patients who have pacemakers. There is a mild degree of discomfort with penetration of the skin by the needle but is usually well tolerated without the need for medication beforehand. Side effects may include minor bleeding and muscle soreness, which rarely lasts more than an hour or two after the exam. The test allows to distinguish between acute and chronic nerve damage in disc diseases or to detect muscle diseases as myositis or myasthenia gravis.