Enzyme activity and fiber composition in skeletal muscle of untrained and trained men.

GOLLNICK, P. D., R. B. ARMSTRONG, C. W. SAUBERT IV, K. PIEHL, AND B. SALTIN. Enzyme activity and Jiber composition in skeletal muscle of untrained and trained men. J. Appl. Physiol. 33(3): 3 12-3 19, 1972.-Succinate dehydrogenase (SDH) and phosphofructokinase (PFK) activities and the histochemical identification of fiber types and localization of oxidative activity were determined on biopsy samples from the vastus lateralis and deltoid muscles of 74 untrained and trained men. SDH activities were highest in the muscles of the groups participating in endurance training. Highest activities existed in the muscles that were extensively engaged in the endurance work. Only minor differences existed for PFK activities. Only slow twitch (ST) and fast twitch (FT) fibers were identified in the muscle samples. ST fibers predominated in the muscles of the endurance athletes. A wide variety of fiber populations existed in all groups. The percent distribution of a fiber was found to be indicative of the relative area that the fiber occupied in the muscle. Oxidative capacity of both fiber types was greater in the endurance athletes than in the other groups. Muscle glycogen was highest in the trained subjects. No consistent pattern for glycogen storage in the two fiber types existed.