Does acute caffeine ingestion improve high-intensity interval exercise performance? A systematic review and meta-analysis

Objective This systematic review and meta-analysis evaluated the effects of caffeine (CAF) on high−intensity interval exercise (HIIE) performance and examined potential moderators. Methods Several databases were searched for studies of CAF on HIIE performance. Pooled effects were calculated using Hedge’s g ( g ) via a three-level random-effects meta-analysis. Subgroup analyses were performed based on sex, training status, CAF dose, CAF form, and interval type. A meta-regression analysis was conducted to investigate the potential moderating effect of the rest/work ratio on HIIE performance. Results Twenty studies were included (n = 320; 57 females). CAF significantly improved HIIE performance ( g = 0.28, 95% CI = 0.14 to 0.43), concurrently elevating blood lactate ( g = 0.50, 95% CI = 0.22 to 0.79) and glucose ( g = 0.56, 95% CI = 0.17 to 0.96). Subgroup analyses demonstrated significant improvements across all sexes ( g = 0.30–0.34), trained athletes ( g = 0.44), CAF dose (low and moderate) ( g = 0.28–0.33), CAF form (capsule and beverage) ( g = 0.32–0.33), and HIIE protocol (repeated short sprints and short intervals) ( g = 0.16–0.36), with no subgroup differences (all p > 0.05). The rest/work ratio was a significant moderator of HIIE performance ( β 2 = 0.003, p = 0.017). Conclusion CAF ingestion significantly enhances HIIE performance, with ergogenic benefits observed across both sexes and trained athletes. Effective ergogenic benefits can be achieved with a low dose (~3 mg/kg), administered as a capsule or beverage. Notably, meta-regression indicates that the rest/work ratio is a critical moderator of HIIE performance, with evidence of a nonlinear association.