High-repetitive submaximal treadmill exercise training: effect on normal and dystrophic mice.

Exercise as a treatment for muscular dystrophy is controversial. Whereas vigorous high-resistive exercise increases skeletal muscle degeneration in animals with neuromuscular disorders, the effect of low-intensity, high-repetitive exercise has been conflicting. The purpose of this study was to determine if low-intensity, high-repetitive exercise has a beneficial effect on dystrophic mice. Dystrophy mice and unaffected littermates were exercised daily starting at age three weeks on a treadmill (4 m/min, 18 degrees incline, 100 meters, three weeks' duration). Exercise increased the dystrophic soleus twitch tension, the rate of twitch tension development, and the rate of twitch tension relaxation by 55%, 58%, and 48%, respectively (p less than .05). The twitch:tetanus ratio increased by 57% (p less than .05). Both the soleus and the extensor digitorum longus from the exercised dystrophic mice had significantly less degeneration (as shown by reduced internal nuclei, necrosis, fiber splitting, and moth-eaten fibers) than the nonexercised dystrophic mice (p less than .05). This study suggests that exercise training programs can be beneficial or at least not result in further muscle fiber degeneration if (1) the exercise program is started early in the course of the disease; (2) submaximal high-repetitive or even high-resistive exercise is used; and (3) the histopathologic degeneration is slowly progressive or in an arrested state.