Abstract des Autors

Muscles biopsy samples were obtained from the gastrocnemius of 26 well-trained runners of widely varying ability. Portions of the sample were analyzed for succinate dehydrogenase (SDH) activity and for muscle fiber composition. VO2 max was determined during uphill treadmill running. Mean values for muscle SDH activity (14,6 U/g), fiber composition (55 slow twitch) and VO2max (60,9 ml/ kg x min/10) were lower than reported previously for groups of elite and subelite runners. The physiological data were consistent with the performance ability of the sample (5:12, 11:20 and 36:40 (min:s) for 1,2 and 6 miles, respectively). Within the sample, performance was most strongly related to VO2max (r=-0,84, -0,84, -0,87 and -0,88 for 1,2 and 6 miles). There was littlerelationship between muscle SDH actitivy and either performance (r=-0,11, -0,14, -0,20 for 1,2 and 6 miles) or VO2max (r=0,23). The relationship between muscle fiber composition and performance was only modestly (r=-0.52, -0.54, -0.55 for 1,2 and 6 miles). The results indicate that the primary determinant of cross-sectional differences in running performance is VO2max. Skeletal muscle metabolism apparently contributes little to these cross-sectional differences and may be of much greater importance to variations in performance within an individual.