Effect of Physical Exercise on Experimental Steroid-Induced Myopathy

ABSTRACT

BACKGROUND: Steroid myopathy is an unexpected side effect to the prolonged therapeutic use of steroids. To treat steroid myopathy, the followings are recommended; reduction of the steroid dose, usage of a nonfluorinated steroid, and conversion to an alternate day regimen. As muscle loading is encouraged in maintaining normal muscle properties, it is also apparent that physical exercise may be useful in the prevention and treatment of steroid myopathy. METHOD: The experiment was designed to investigate the effects of exercise on steroid myopathy. Rats being treated with triamcinolone acetonide (TA) (5 mg/kg/day) for 7 days exercised on a treadmill (speed 20m/min, 30 min/day, 3 days/week) for 2 weeks. The extensor digitorum longus (EDL) and soleus were then examined histochemically and ultrastructurally. RESULTS: Rats treated with TA showed significant loss of body and muscle weight. In the TA treated group, cross-sectional areas of type II fibers of both EDL and soleus were decreased in comparison with the controls. Necrotic changes were found only in type II fibers of the soleus. Recovery from the weight loss with type II fiber atrophy was more pronounced in the exercise group than that of the sedentary group, but was not significant statistically. Ultrastructural abnormalities, that consisted of subsarcolemmal mitochondrial accumulation, mitochondrial vacuolation, increased number of mitochondria in autophagic vacuoles, and dilatation of sarcoplasmic reticulum, were seen in TA treated muscles. These injuries were significantly reduced by the exercise, however, complete recovery could not be seen. CONCLUSIONS: These results suggest that treadmill exercise for 2 weeks partially ameliorate steroid myopathy in.