Effect of training on enzyme activity and fiber composition of human skeletal muscle.

GOLLNICK, P. D., R. B. ARMSTRONG, B. SALTIN, C. W. SAUBERT IV, W. L. SEMBROWICH, AND R. E. SHEPHERD. Eject of training on enzyme activity andjber composition of human skeletal muscle. J. Appl. Physiol. 34(l): 107-l 11. 1973.-The effect of a 5month training program on the oxidative and anaerobic capacity, fiber composition, fiber area, and glycogen concentration of multiple biopsy samples from the vastus lateralis muscle of six subjects was studied. The training program consisted of pedalling a bicycle ergometer 1 hr/day 4 days a week at a load requiring from 75 to 90% of the subjects maximal aerobic power. Mean maximal oxygen uptake increased 13 y0 (range 3.6~25%), and mean succinate dehydrogenase and phosphofructokinase activities increased 95 and 117 y0 (P < 0.01 ), respectively, after training. Oxidative potential (DPNH-diaphorase activity) increased in both fiber types whereas glycolytic capacity (alphaglycerophosphate dehydrogenase activity) appeared to have increased only in the fast twitch fibers. No change occurred in the percentages of slow or fast twitch fibers as identified from myosin ATPase activity. Slow twitch fibers were larger after training as compared to before training. The relative area the slow twitch fibers occupied in the muscle was also higher after training. Muscle glycogen was 2.5-fold higher after as compared to before training.