RUNNING TRAINING PRODUCES THE METABOLIC AND STRUCTURAL CHANGES IN RAT SINGLE SKELETAL MUSCLE FIBER OF DIFFERENT TYPES

Abstract

The effects of different types of running trainings (sprint or endurance) on the glycolytic (lactate dehydrogenase : LDH, phosphofructokinase : PFK and pyruvate kinase : PK) and oxidative (succinate dehydrogenase : SDH and malate dehydrogenase : MDH) enzymes activities and on the mitochondrial contents in single muscle fiber of different types (slow-twitch oxidative : SO, fast-twitch oxidative glycolytic : FOG and fast-twitch glycolytic : FG) were studied employing biochemical and electron microscopic techniques. Male Wistar strain rats were trained by treadmill 5 days/week beginning the age of 3 weeks old for 16 weeks. Single muscle fibers were dissected from soleus and extensor digitorum longus muscles, and typed histochemically into SO, FOG and FG fibers. The remaining parts of the single muscle fiber were used for biochemical and electron microscopic analyses. Glycolytic enzymes activities were increased in FG and FOG fibers following sprint training. Oxidative enzymes activities were increased in all types of fiber following both trainings. Mitochondrial contents in single muscle fiber were increased in FOG fiber following sprint training and in SO fiber following endurance training. These results suggest that the increase of glycolytic enzymes activity following sprint training were depended on the the fast-type fiber specifically and that of oxidative enzymes activity were depended on all types of fiber in whole muscle. It seems that the increase of oxidative enzymes activity following exercise training alone was not only depended on the increase of mitochondrial contents in skeletal muscle fiber.