Fig. 2

Spontaneous EMG activity in muscle disease. Activity, termed pseudomyotonic bursts, that begins and ends abruptly, in the hypertrophied calf muscle of a DMD patient (a, b), contrasts with waxing and waning myotonic activity from a forearm extensor of a myotonic dystrophy patient (c, d). The activity in a was recorded from two fibers discharging at 22 and 11/s over a 45-s period with the three bursts (a–c) separated by 20 s. Bursts in b had a frequency of 15/s. Increasing and decreasing activity in c (maximum 50/s) and d (maximum 35/s) were induced by movement of the concentric recording electrode and direct stimuli, respectively. From reference [12]