Effects of Electrically Stimulated Exercise Training on Muscle Function in Multiple Sclerosis

Abstract

To investigate whether electrically stimulated exercise training might reduce muscle fatigue in persons with multiple sclerosis (MS), the dorsiflexor muscles of six patients were trained (60 min/d, 6d/wk, 8 wks) with electrically stimulated endurance exercise (50 Hz tetanic contractions, 25% duty cycle). There was evidence of transient mus cle injury at the onset of training (reduced tetanic force, elevated ratio of inorganic phosphate/phosphocreatine in the resting muscle). There was no significant effect of the training on mean muscle fatigability. After training, four of six patients had reduced fatigue (i.e., fall in tetanic force) during nine minutes of intermittent tetanic contractions. Two subjects had increased fatigue following training. Training-induced changes in fatigability were linearly associated with changes in (1) pre-exercise twitch con traction time (r2 = 0.70), and (2) the decrease in intracellular pH during exercise (r2 = 0.88), suggesting that altered fatigability after training may ...