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Caffeine expectancy does not improve interval running performance in trained runners

In a randomized controlled crossover trial, trained runners who believed they had consumed caffeine (placebo) showed no significant improvement in total session time for 5 x 1000-m interval running compared to a control condition (1021.50 ± 114.01 vs. 1017.23 ± 109.08 s, p = 0.270, ES = 0.31). No differences were found in pacing, heart rate, perceived exertion, or running kinematics, but participants reported increased feelings of activeness and some caffeine-related side effects (e.g., increased urine production, sleep disturbances) under the placebo condition.

Last updated: Aug 15, 2026•1 RCTs•📖 Read as article →

Evidence Score

Evidence Score44/100
Human RCT★★☆☆☆
Meta-analysis☆☆☆☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. Caffeine Expectancy Does Not Affect Interval Running Performance, Physiological Responses, or Running Kinematics in Trained Runners: A Randomized Controlled Crossover Trial.

observational

Valero F, González-Mohíno F, Alda-Blanco A, Rodríguez-Barbero S, Muñoz de la Cruz V, Juárez Santos-García D, Salinero JJ · Nutrients (2026)

Participants: N/A
Duration: Two sessions (crossover)
Intervention: Placebo capsule described as containing caffeine (3 mg·kg-1) vs. no ingestion (control)
Outcome: Interval running performance (total session time), pacing strategy, heart rate, running kinematics, perceived exertion (RPE), side effects
Effect Size: ES = 0.31
Population: Moderately trained runners (14 participants)

Result:

PubMed: 42588115DOI: 10.3390/nu18152492

Mechanism Graph

Participants ingested a placebo capsule believed to contain caffeine
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Expectancy of caffeine intake was created
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Physiological and performance measures were recorded during interval running
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No significant ergogenic effect was observed, but subjective side effects were reported

Limitations

  • ⚠Small sample size (n=14) may limit statistical power
  • ⚠Only moderately trained runners, not elite athletes
  • ⚠Single dose of placebo (3 mg·kg-1) may not reflect typical caffeine doses
  • ⚠Outdoor track conditions may introduce variability

Frequently Asked Questions

Does caffeine expectancy improve running performance?▼

No, this study found no significant improvement in interval running performance when runners believed they had consumed caffeine.

What was the effect size for the difference in performance?▼

The effect size was 0.31, which is small, and the difference was not statistically significant (p = 0.270).

Did caffeine expectancy affect any outcomes?▼

Yes, participants reported greater feelings of activeness and higher ratings of some caffeine-related side effects, such as increased urine production and sleep disturbances.

Who were the participants in this study?▼

The study included 14 moderately trained runners who completed two 5 x 1000-m interval training sessions.

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References

  1. 1.Valero F, González-Mohíno F, Alda-Blanco A, Rodríguez-Barbero S, Muñoz de la Cruz V, Juárez Santos-García D, Salinero JJ. "Caffeine Expectancy Does Not Affect Interval Running Performance, Physiological Responses, or Running Kinematics in Trained Runners: A Randomized Controlled Crossover Trial.." Nutrients, 2026. PMID: 42588115 DOI: 10.3390/nu18152492
Disclaimer: This content is for educational purposes only and is not medical advice. Evidence scores reflect the quality and quantity of available research, not clinical recommendations. Always consult a healthcare professional before starting any supplement or intervention.