Dynamic properties of partially denervated muscle

The mechanical and electrical properties of the partially denervated first dorsal interosseous muscle were measured in 14 patients and 14 normal control subjects. The following variables were studied during isometric contraction: maximum voluntary contraction; maximum rate of rise of tension in a rapid voluntary contraction; amplitude, rate of rise, time to peak, and duration of peak of the compound muscle action potential; twitch force, maximum rate of rise, contraction time, and half-relaxation time; and tetanic (50 Hz) force, rate of rise, and tetanus/twitch ratio. The force produced during repetitive stimulation of the ulnar nerve at 10, 20, 50, and 100 impulses per second was also analyzed. The major findings were: (1) decreased load bearing (voluntary contraction, twitch, and tetanus), (2) prolonged twitch contraction times and half-relaxation times, (3) decreased tetanus/twitch ratio, and (4) preserved rate of rise of tension.