Leenders et al (1) examined the effects of oral creatine monohydrate supplementation on performance during interval sets in elite collegiate male and female swimmers. 14 female and 18 male swimmers consumed a placebo during a 2-week baseline period. During a 2-week treatment period, the swimmers were randomly assigned to either 20 g of creatine or a placebo during the first 6 days and 10 g thereafter. The study was done in a double-blind fashion. Interval swimming performance was measured 6 times during the baseline period and 6 times during the treatment period. Twice weekly, an interval test of 6 x 50 m with each 50-m swim starting at a 3-min interval was performed. Once weekly, an interval test of 10 x 25 yd with every 25-yd swim starting at a 60-sec interval was performed. Body composition was measured using hydrostatic weighing. FINDINGS: There was no treatment effect of creatine on body mass, fat-free mass, or percent body fat. During the baseline period, there were no significant differences in swimming velocity for the interval sets for either males or females; the coefficients of variation were less than 2% for all sets, indicating that performances were repeated consistently and reliably. During the treatment period, creatine supplementation had no effect on average velocity in the 10 25-yd sprints in either males or females. Creatine also had no effect on the performance during 6 x 50 m interval set in women. However, creatine supplementation did have a significant effect on performance in the 6 x 50 m interval set in the men. Mean swimming velocity over the entire interval set improved by 2% in the creatine supplemented male swimmers (1.63 m/sec to 1.67 m/sec)as compared to the swimmers receiving a placebo.
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