Effects of oral creatine supplementation on performance and muscle metabolism during maximal exercise
The purpose of this study was to determine the effects of oral creatine supplementation on performance and muscle metabolism during maximal exercise. Nine subjects (5 female, 4 male) performed two 30 s maximal exercise bouts on a cycle ergometer separated by a period of two weeks to allow for adequate washout. Each exercise bout was preceded by 4 days of supplementation with a placebo (PL) or creatine (CR). The subjects consumed 5g of PL or CR four times a day prior to the trial. Treatments were administered in a double-blind, crossover design. Power output was measured in watts every second for 30 s. There were no significant differences in average power output, peak power, or percent decline from peak power. There were no significant differences in muscle or plasma lactate concentrations. Total muscle Cr concentration was significantly higher in CR (20.0 + 0.9 vs .. 15.8 + 2.0 mmol/kg; p<0.05) prior to exercise and immediately following exercise (20.7 + 0.9 vs. 14.8 + 1.7 mmol/kg; p<0.05). There was no significant difference in muscle creatine phosphate concentration; however, the change in muscle PCr concentration tended to be greater during CR (6.4 + 1.3 vs. 2.5 + 1.6 mmol/kg; p = 0.07). The results indicate that four days of oral creatine supplementation does not improve power output on a single maximal cycle ergometer exercise, but may affect energy use in muscle metabolism.