Characteristics of skeletal muscle in competitive cyclists

Muscle samples from the vastus lateralis and maximal oxygen uptakes were obtained from 22 male and 7 female competitive cyclists, 19 untrained males, and 10 untrained females. Eleven of the 22 mule cyclists were designated elite cyclists (Group A) on the basis of their success in national and/or international competition. The remaining 11 male cyclists (Group B) were also trained but had not achieved the same level of competitive success. Significant mean differences (P <. 0.05) between Groups A and B were found for V02 max (67 and 57 inl/kg/min), mainte dehydrogenase (MDH) and phosphorylate (PH), in biopsied muscle. No differences were evident between Groups A and I) for % slow twitch (ST) and % fast twitch (FT) fibers, or in area FT or ST. Nor was there any difference in the mean activities of succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) between the groups. Significant correlations were found between Vo ₂ max and SDH, V02 max and MDH, and between SDH and MDH. These data also indicate that an extremely high percentage of FT or ST fibers may not be a requirement for success in competitive cycling as has been found in earlier studies 011 sprint or endurance running.