title: Contribution of phosphocreatine and aerobic metabolism to energy supply during repeated sprint exercise.
abstract: 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 first 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 recovery, 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 first 10 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 (r = 0.84, P < 0.05 and r = 0.91, P < 0.01). 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 second 30-s sprint, mainly as a result of a approximately 45% decrease in glycolysis. Despite this approximately 41% reduction in anaerobic energy, the total work done during the second 30-s sprint was reduced by only approximately 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 (approximately 49%) of the energy during the second sprint, whereas PCr availability is important for high power output during the initial 10 s.
authors.affiliation: Department of Physical Education, Loughborough University, United Kingdom.
authors.forename: G C
authors.initials: GC
authors.lastname: Bogdanis
authors.forename: M E
authors.initials: ME
authors.lastname: Nevill
authors.forename: L H
authors.initials: LH
authors.lastname: Boobis
authors.forename: H K
authors.initials: HK
authors.lastname: Lakomy
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000328:Adult; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism*; D013997:Time Factors
chemical_list: D010725:Phosphocreatine; D000255:Adenosine Triphosphate