Abstract
BACKGROUND: Caffeine, widely recognized as an ergogenic aid, has undergone extensive research, demonstrating its effectiveness to enhance endurance performance. However, there remains a significant gap in systematically evaluating its effects on time trial (TT) performance in cyclists. PURPOSE: This meta-analysis aimed to determine the efficacy of caffeine ingestion to increase cycling TT performance in cyclists and to evaluate the optimal dosage range for maximum effect. METHODS: A search of four databases was completed on 1 December 2023. The selected studies comprised crossover, placebo-controlled investigations into the effects of caffeine ingestion on cycling TT performance. Completion time (Time) and mean power output (MPO) were used as performance measures for TT. Meta-analyses were performed using a random-effects model to assess the standardized mean differences (SMD) in individual studies. RESULTS: Fifteen studies met the inclusion criteria for the meta-analyses. Subgroup analysis showed that moderate doses of caffeine intake (4-6 mg/kg) significantly improved cycling performance (SMD (Time) = -0.55, 95% confidence interval (CI) = -0.84 ~ -0.26, p < 0.01, I(2) = 35%; SMD (MPO) = 0.44, 95% CI = 0.09 ~ 0.79, p < 0.05, I(2) = 39%), while the effects of low doses (1-3 mg/kg) of caffeine were not significant (SMD (Time) = -0.34, 95% CI = -0.84 ~ 0.17, p = 0.19, I(2) = 0%; SMD (MPO) = 0.31, 95% CI = -0.02 ~ 0.65, p = 0.07, I(2) = 0%). CONCLUSION: A moderate dosage (4-6 mg/kg) of caffeine, identified as the optimal dose range, can significantly improve the time trial performance of cyclists, while a low dose (1-3 mg/kg) does not yield improvement. In addition, the improvements in completion time and mean power output resulting from a moderate dose of caffeine are essentially the same in cycling time trails.