Objectives: Oral creatine is the most widely used nutritional supplement among athletes. Our purpose was to investigate whether creatine supplementation increases maximal strength and power in healthy adults.
Study design: Meta-analysis of existing literature.
Data sources: We searched MEDLINE (1966-2000) and the Cochrane Controlled Trials Register (through June 2001) to locate relevant articles. We reviewed conference proceedings and bibliographies of identified studies. An expert in the field was contacted for sources of unpublished data. Randomized or matched placebo controlled trials comparing creatine supplementation with placebo in healthy adults were considered.
Outcomes measured: Presupplementation and postsupplementation change in maximal weight lifted, cycle ergometry sprint peak power, and isokinetic dynamometer peak torque were measured.
Results: Sixteen studies were identified for inclusion. The summary difference in maximum weight lifted was 6.85 kg (95% confidence interval [CI], 5.24-8.47) greater after creatine than placebo for bench press and 9.76 kg (95% CI, 3.37-16.15) greater for squats; there was no difference for arm curls. In 7 of 10 studies evaluating maximal weight lifted, subjects were young men (younger than 36 years) engaged in resistance training. There was no difference in cycle ergometer or isokinetic dynamometer performance.
Conclusions: Oral creatine supplementation combined with resistance training increases maximal weight lifted in young men. There is no evidence for improved performance in older individuals or women or for other types of strength and power exercises. Also, the safety of creatine remains unproven. Therefore, until these issues are addressed, its use cannot be universally recommended.