EFFECTS OF ANABOLIC-STEROIDS AND HIGH-INTENSITY EXERCISE ON RAT SKELETAL-MUSCLE FIBERS AND CAPILLARIZATION - A MORPHOMETRIC STUDY

The effects were investigated of high intensity short duration exercise and anabolic steroid treatment on the medial gastrocnemius muscle of female rats. Twelve rats were divided equally into four groups, exercise with and without steroid administration and sedentary with and without steroid administration. Animals were made to swim for 5 weeks, 6 days.week-1. Muscle fibres were classified as slow-twitch (ST), fast-twitch oxidative glycolytic (FOG) and fast-twitch glycolytic (FG). Muscle fibre size was measured as the equivalent circle diameter. Exercise (P < 0.001) and steroid (P < 0.05) treatments alone, significantly elevated FOG and decreased FG fibre proportions. Overall proportions of fast-twitch and ST muscle fibres did not vary with any of the treatments. Significant differences in the proportion of muscle fibres were found to exist between different areas within the gastrocnemius muscle (P < 0.05). Exercise and steroid treatments alone did not alter muscle fibre diameters. Combined exercise and steroid treatments did significantly increase ST fibre diameters (P < 0.05). Exercise only treatment resulted in significant increases in the number of capillaries surrounding ST fibre (P < 0.05) and FOG fibre (P < 0.01) types. In conclusion the main finding of this study indicated that anabolic steroids in conjunction with high intensity swimming instigated ST fibre hypertrophy. Exercise and steroid only treatments significantly elevated FOG fibre proportions while FG fibre proportions diminished. Exercise only treatment resulted in significant increases in the number of capillaries surrounding both ST and FOG fibre types.