The purpose of this study was to use the meta-analytic approach to examine the effects of caffeine ingestion on ratings of perceived exertion (RPE). Twenty-one studies with 109 effect sizes (ESs) met the inclusion criteria. Coding incorporated RPE scores obtained both during constant load exercise (n=89) and upon termination of exhausting exercise (n=20). In addition, when reported, the exercise performance ES was also computed (n=16). In comparison to placebo, caffeine reduced RPE during exercise by 5.6% (95% CI (confidence interval), 4.5% to 6.7%), with an equivalent RPE ES of 0.47 (95% CI, 0.35 to 0.59). These values were significantly greater (P<0.05) than RPE obtained at the end of exercise (RPE % change, 0.01%; 95% CI, 1.9 to 2.0%; RPE ES, 0.00, 95% CI, 0.17 to 0.17). In addition, caffeine improved exercise performance by 11.2% (95% CI; 4.617.8%). Regression analysis revealed that RPE obtained during exercise could account for 29% of the variance in the improvement in exercise performance. The results demonstrate that caffeine reduces RPE during exercise and this may partly explain the subsequent ergogenic effects of caffeine on performance.
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