A, Diagram of electromyography (EMG) tracing showing positive sharp wave consistent with denervation 10 to 14 days after injury. Rhythm is regular, amplitude is 100 to 400 μV, duration is 5 to 150 ms, and rate is 2 to 40 Hz. B, Diagram of EMG tracing showing spontaneous denervation fibrillation potentials present within 14 to 18 days after injury. Rhythm is regular, amplitude is 50 to 1000 μV, duration is 0.5 to 2 ms, and rate is 2 to 30 Hz.