Dose-Response Effect of Oral Caffeine Use on Aerobic Exercise Performance: A Systematic Review and Meta-Analysis

Background/Objective: Caffeine is one of the most extensively investigated supple-ments worldwide, with evidence showing improvements in physical performance across ingestion doses commonly used in sports nutrition (2–9 mg·kg⁻¹). However, studies report substantial variability in aerobic performance outcomes following caf-feine intake, indicating that acute consumption may produce meaningful ergogenic effects but can also impair performance, with time-trial variation ranging from ap-proximately –3% to +16%. Since higher doses may increase the risk of adverse side ef-fects without offering clear added benefits, this review examined the effects of low (≤3 mg·kg⁻¹), moderate (4–6 mg·kg⁻¹), and high (>6 mg·kg⁻¹) caffeine doses on time-trial performance. Methods: A systematic review and meta-analysis of randomized, place-bo-controlled clinical trials evaluating the effects of anhydrous caffeine on aerobic time-trial outcomes was conducted. Random-effects models were applied due to nota-ble heterogeneity across studies, and risk of bias was assessed using the Cochrane Risk of Bias tool. Results: Forty-eight studies (716 participants) met the inclusion crite-ria. Both low and moderate caffeine doses significantly reduced time-trial completion time relative to placebo. Low doses produced a standardized mean difference of –0.27 (95% CI: –0.44 to –0.11; p = 0.001), whereas moderate doses resulted in an SMD of –0.52 (95% CI: –0.77 to –0.28; p < 0.0001). Conclusion: This is the first meta-analysis to demonstrate that pre-exercise ingestion of low caffeine doses (1.3–3 mg·kg⁻¹) can en-hance generalized aerobic performance. Notably, the use of moderate caffeine doses (4–6 mg·kg⁻¹) appears to produce a more consistent ergogenic effect.