Creatine supplementation and the total work performed during 15-s and 1-min bouts of maximal cycling

Nine untrained male subjects participated in a placebo (Pl)/creatine (Cr), single-blind study conducted over a 5-wk period. Placebo and Cr treatments were presented in a sequential manner because muscle Cr washout time after supplementation is unknown. The mean ( +/- SE) age, height, and initial body mass for the subjects was 25.7+/- 1.2 yr, 177 +/- 2 cm, and 78.5 +/- 3.8 kg, respectively. Each subject performed five 15-s bouts of maximal cycling (1-min rest periods) after 7 d of Pl (6 g glucose X 5 doses daily) and again after ingesting Cr for 7 d (5 g creatine plus 1 g glucose X 5 doses) with a 2-wk intervention period. Only 6 of 9 subjects were able to complete five 1-min bouts of maximal cycling (5-min rest periods) after an additional 2 d of Pl and Cr treatment. Cr ingestion resulted in a significant increase in the work performed during each 15-s bout of maximal cycling compared to Pl trials. Moreover, the total work completed during five 15-s bouts of cycling increased significantly from 47.5 +/- 2.3 kJ with Pl treatment to 50.6 +/- 2.3 kJ after Cr supplementation (P < 0.05). Peak blood lactate concentrations determined 4 min after the fifth 15-s work bout were 14.4 +/- 0.5 mmol.L-1 and 14.3 +/- mmol.L-1 for Pl and Cr trials, respectively (P < 0.05). Total work completed during five 1-min bouts of maximal cycling was not significantly increased after Cr supplementation (P > 0.05). Additionally, Cr supplementation did not slow the rate of decline in the work accomplished during repeated bouts of maximal cycling. These findings suggest that Cr ingestion may augment the rate of ATP resynthesis from phosphocreatine during exercise in untrained subjects.