Oral creatine supplementation and athletic performance: A critical review

Objective: To review and summarize the current data on oral creatine supple mentation regarding its potential efficacy in athletic performance, mechani sm of action, and metabolism. Data sources and study selection: Medline was searched using terms relating creatine supplementation to athletic performance. Studies that evaluated t he effects of oral creatine supplementation on exercise performance in huma ns were selected for inclusion. Selected studies on muscle metabolism and e xercise physiology were included if they provided useful information relati ve to creatine. Additional references were reviewed from the bibliographies of selected studies. Data extraction and synthesis: To summarize efficacy, extracted data were l isted in table format, grouping studies together by type of activity and ef ficacy on performance. Whenever possible, the effect of creatine supplement ation was quantified. Proposed explanations for creatine's efficacy or lack thereof in a particular type of activity were formulated. Conclusions: In laboratory settings, creatine supplementation is ergogenic in repeated 6-30-second bouts of maximal stationary cycling sprints. The da ta on a single sprint or first-bout sprint of any kind are inconsistent. Th e data regarding creatine's ergogenic effects on mass-dependent activities, such as running and swimming, are not convincing, perhaps because of the s ide effect of weight gain from water retention. Studies on weight lifting s uggest that creatine improves strength, possibly by increasing myofibrillar protein synthesis; however, more study is needed to prove this. No ergogen ic effects on submaximal or endurance exercise are evident. Individual resp onse to creatine supplementation can vary greatly.