Abstract des Autors

This study examined the contribution of phosphocreatine (PCr) and aerobic metabolism during repeated bouts of sprint exercise. Eight male subjects performed two cycle ergometer sprints separated by 4 min of recovery during two separate main trials. Sprint 1 lasted 30 s during both main trials, whereas sprint 2 lasted either 10 or 30 s. Muscle biopsies were obtained at rest, immediately after the fist 30-s sprint, after 3.8 min of recovery, and after the second 10-and 30-s sprints. At the end of sprint 1, PCr was 16.9+/-1.4% of the resting value, and muscle pH dropped to 6.69+/-0.02. After 3.8 min of revovery, muscle pH remained unchanged (6.80+/-0.03), but PCr was resynthesized to 78.7+/-3.3% of the resting value. PCr during sprint 2 was almost completely utilized in the first10 s and remained unchanged thereafter. High correlations were found between the percentage of PCr resynthesis and the percentage recovery of power output and pedaling speed during the initial 10 s of sprint 2. The anaerobic ATP turnover, as calculated from changes in ATP, PCr, and lactate, was 235+/-9 mmol/kg dry muscle during the first sprint but was decreased to 139+/-7 mmol/kg dry muscle during the scond 30-s sprint, mainly as a result of a ca. 454% decrease in glycolysis. Despite this ca. 41% reduction in anaerobic energy, the total work done during the second 30-s sprint was reduced by only ca. 18%. This mismatch between anaerobic energy release and power output during sprint 2 was partly compensated for by an increased contribution of aerobic metabolism, as calculated from the increase in oxygen uptake during sprint 2 (2.68+/-0.10 vs. 3.17+/-0.13 l/min; sprint 1 vs. sprint 2; P<0.01). These data suggest that aerobic metabolism provides a significant part (ca. 49%) of the energy during the second sprint, whereas PCr availability is important for high power output during the initial 10 s. Verf.-Referat