Objectives: Caffeine ingestion has well-established ergogenic effects for resistance exercise performance. However, the concept of a minimum effective caffeine dose has not yet been thoroughly examined in the literature. Therefore, this review aimed to explore the minimum ergogenic dose of caffeine on resistance exercise outcomes, such as muscular strength, endurance, and velocity, using a meta-analytic approach.
Methods: The search for eligible studies was performed through six databases. The methodological quality of the included studies was assessed using the PEDro checklist. A random-effects meta-analysis was performed for data analysis. Twelve studies that provided caffeine supplementation in doses from 0.9 to 2 mg/kg were included. The studies were classified as being of good or excellent methodological quality.
Results: The results revealed an ergogenic effect of caffeine for muscular strength (Cohen d: 0.17; 95% confidence interval [CI], 0.03-0.31; P = 0.02), muscular endurance (Cohen d: 0.21; 95% CI, 0.07-0.35; P = 0.003), and mean velocity (Cohen d: 0.56; 95% CI, 0.12-1.01; P = 0.01).
Conclusions: This review demonstrated an ergogenic effect of very low doses of caffeine on resistance exercise performance. The magnitude of these effects was similar to that previously reported with higher caffeine doses. These findings highlight that the minimal ergogenic doses of caffeine are even lower than previously suggested. Such doses of caffeine can be consumed through a regular diet, because for most individuals, a dose of approximately 1 to 2 mg/kg is equivalent to a dose of caffeine in one to two cups of coffee.
Keywords: Data synthesis; Exercise performance; Resistance training; Supplements.
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