This study used the meta-analytic approach to examine the effects of caffeine ingestion on exercise testing. Forty double-blind studies with 76 effect sizes (ES) met the inclusion criteria. The type of exercise test was classified as endurance, graded, or short-term. In comparison with placebo, caffeine improved test outcome by 12.3% (95% CI, 9.1 to 15.4), which was equivalent to an overall ES of 0.41 (95% CI, 0.31 to 0.51). Endurance exercise significantly improved test outcome (P < 0.05) more than either graded or short-term exercise. When exercise protocol was examined, time-to-exhaustion (Tlim) protocols had a significantly greater (P < 0.05) ES than either the graded or the non-Tlim protocol(s). The results from this meta-analysis confirm the ergogenic effects of caffeine, particularly for endurance testing that use Tlim protocols.
The authors are with the Dept of Sport, Exercise and Biomedical Sciences, University of Luton, Beds LU1 3JU, UK.