Beneficial effects of training on developing dystrophic muscle.

The objective of this study was to determine whether increased contractile activity is beneficial or detrimental to developing dystrophic muscle. Hamsters (20-days-old) were gradually introduced to running at a speed of 14 m/min at 10% grade for 2 (T2) or 4 (T4) h/d for 4 weeks, 5 d/wk. Histological and fiber type properties were determined in the soleus (SOL), plantaris (PL), and extensor digitorum longus and contractile properties in SOL and PL from 5 animals/group, including 5 controls. Experimental animals had normal body and muscle mass. Training for 2 h/d had little effect on SOL contractile properties, whereas 4 h/d resulted in significant increases in force, percentage of type I fibers, and type I hypertrophy. Force also increased in PL. Muscle necrosis was reduced in SOL (T2 and T4) and unchanged in PL. In conclusion, endurance training generally had a beneficial or, at least, no detrimental effect on developing dystrophic muscles.