The influence of recovery duration in high-intensity exercise performance after oral creatine supplementation

Abstract

Acceleration of the rate of phosphocreatine resynthesis during recovery from exercise may underlie increases in work output reported for creatine-supplemented subjects during repeated exercise bouts. The purpose of this study was to determine the effects of creatine supplementation on the ability to reproduce and maintain a high percentage of peak power output during the 2nd of 2 bouts of high-intensity cycle sprinting following 4 different recovery intervals. Eighty healthy, active male subjects were randomly assigned to I of 2 Groups; creatine or placebo, and 1 of 4 recovery Intervals-. (30, 60, 90 or 120 s). Power output was calculated on-line by computer as subjects pedaled as fast as possible against a fixed resistance (I I kg). A cut-off criterion of 30% decline from peak power was used to signal the end of each trial. Two maximal cycle ergometer sprints, separated by the assigned recover), interval were performed before and after a 5-d supplementation protocol in which 20 g/d of creatine or 20 g/d glucose placebo were ingested by creatine and placebo Groups, respectively. Maximal peak power output (PP) and the absolute time to fatigue (TTF) were compared pre- vs post-supplementation. Trial 2 PP means for subjects combined across Group and Time points (pre- vs post-supplementation) were significantly decreased with respect to Trial 1 following 30, 60, and 90 s recovery (p<.025). Non-significant differences between Trials I and 2 were noted for PP following 120 s recovery (p>.025). Significant differences between Trials 1 and 2 were found for TTF following all 4 recovery Intervals (p<.025). No significant Group interactions were noted in this study. Specifically, creatine supplementation had no effect on subjects' ability to reproduce or maintain a high percentage of PP during the 2nd bout of exercise following supplementation. it was concluded that creatine supplementation does not enhance the restoration and maintenance of power output following a fatiguing bout of high-intensity cycle exercise when a 2nd bout is performed following recovery durations thought to be most likely affected by a creatine-stimulatory effect on the rate of phosphocreatine resynthesis.