An electron microscopic investigation of the skeletal muscle bioptates has been performed in 80 volunteer-sportsmen of different qualification specializing in race rowing and in skating. Common for all the sportsmen examined are those peculiarities in ultrastructural organization of the skeletal muscle fibers that demonstrate their adaptation to an increased muscle activity. Specificity of ultrastructural organization of the skeletal muscle fibers is revealed in connection with sportive specialization. Speed-force trainings in skater-sprinters produce hypertrophy of myofibrils; more often than other sportsmen they demonstrate dilatation of cisterns in the sarcoplasmic reticulum, appearance of granular inclusions in mitochondrial matrix. In skater-statyers sarcoplasm of muscle fibers sharply increases in volume. Sometimes, loading for endurance in skater-stayers produces rather essential disturbances in structure of muscle fibers up to their necrosis. In muscles of these sportsmen processes of "intracellular" regeneration are most distinctly observed.