Positive and negative placebo effects resulting from the deceptive administration of an ergogenic aid.

摘要

The article describes a study examining placebo effects associated with the administration of a hypothetical ergogenic aid in sport. Forty-two team-sport athletes were randomly assigned to 2 groups. All subjects completed 3 x 30-m baseline sprint trials after which they were administered what was described to them as an ergogenic aid but was in fact 200 mg of cornstarch in a gelatin capsule. Group 1 was provided with positive information about the likely effects on performance of the substance, whereas Group 2 was provided with negative information about the same substance. The sprint protocol was repeated 20 min later. Although for Group 1 mean speed did not differ significantly between baseline and experimental trials, a significant linear trend of greater speed with successive experimental trials suggested that positive belief exerted a positive effect on performance (P < 0.01). Group 2 ran 1.57% slower than at baseline (P < 0.01, 95% confidence intervals 0.32-2.82%), suggesting that negative beliefexerted a negative effect on performance. Collectively, data suggest that subjects' belief in the efficacy or otherwise of a placebo treatment might significantly influence findings in experimental research.