Effect of caffeine ingestion on time trial performance in cyclists: a systematic review and meta-analysis

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, I² = 35%; SMD _MPO = 0.44, 95% CI = 0.09 ~ 0.79, p < 0.05, I² = 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, I² = 0%; SMD _MPO = 0.31, 95% CI = -0.02 ~ 0.65, p = 0.07, I² = 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.

Keywords: Ergogenic aid; cycling; power output; self-paced exercise; supplements; time trial.

Figure 1.

Flow diagram of study selection.

Figure 2.

Risk of bias summary of included studies.

Figure 3.

Funnel plot of standard mean difference against standard error for completion time. SE (SMD) Standard error of the mean difference, SMD Standard mean difference.

Figure 4.

Funnel plot of standard mean difference against standard error for mean power output. SE (SMD) Standard error of the mean difference, SMD Standard mean difference.

Figure 5.

Subgroup analysis of the effects of different caffeine doses intake on time trial performance (completion time) of cyclists. “a”, “b,” “c” represents the number of trials of the same study. Filled green square represents study-specific estimates, and filled diamond represents pooled estimates of random-effects. Std Mean Difference Standard mean difference, CI confidence interval, SD standard deviation.

Figure 6.

Subgroup analysis of the effects of different caffeine doses intake on time trial performance (mean power output) of cyclists. “a”, “b,” “c” represents the number of trials of the same study. Filled green square represents study-specific estimates, and filled diamond represents pooled estimates of random-effects. Std Mean Difference Standard mean difference, CI confidence interval, SD standard deviation.