Abstract

Tissue samples were obtained from the vastus lateralis muscle of elite Olympic weight and power lifters (OL/PL, n = 6), bodybuilders (BB, n = 7), and sedentary men (n = 7). Enzyme activities of citrate synthase (CS), lactate dehydrogenase (LD), 3-OH -acyl-CoA-dehydrogenase (HAD), and myokinase (MK) were assayed on freeze-dried dissected pools of slow-twitch (ST) and fast-twitch (FT) fiber fragments by fluorometric means. Histochemical analyses were carried out to assess fiber type composition and fiber area. CS and HAD activities were lower, and LD and MK were higher in FT than ST fibers in the entire subject pool (n = 20). CS of FT fibers and HAD of ST fibers were lower in athletes compared with nonathletes, whereas LD of both fiber types was higher in athletes. CS activity of ST fibers and MK activity of FT fibers were higher in BB compared with OL/PL. FT and ST fiber area was greater in athletes than in nonathletes. BB displayed greater fiber size than OL/PL. FT/ST area was greater in OL/PL than BB. It is suggested that long-term heavy-resistance training results in specific metabolic adaptations of FT and ST fiber types. These changes appear to be influenced by the type of resistance training. Verf.-Referat