The Study
Differential Time-of-Day Effects of Caffeine Capsule and Mouth Rinse on Cognitive Performance in Adolescent Male Volleyball Athletes: A Randomized Crossover Investigation
This study tested if caffeine helps teens think faster during volleyball practice, and it found that it does — but only for this specific group of boys who don’t usually drink caffeine. It doesn’t prove caffeine helps everyone, just these guys under these specific conditions.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
This study tested if drinking caffeine or swishing it in your mouth helps teen volleyball players think and react faster at different times of day.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 564 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1These small speed improvements are like gaining a year of training — they could help athletes react faster during fast-paced volleyball rallies.
- 2Caffeine capsules made players react 9–11 milliseconds faster and cut thinking errors by 20–22% in the morning and midday.
- 3Mouth rinse helped only with thinking errors at midday (16–22% better), but not with reaction speed.
- 4No benefits were seen at night.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Life
Year
2025
Authors
Salma Belhaj Amor, Wissem Dhahbi, Houda Bougrine, Manel Bessifi, Vlad Adrian Geantă, Vasile Emil Ursu, Khaled Trabelsi, Nizar Souissi
Related Content
Claims (5)
In adolescent male volleyball players with low caffeine consumption, a 3 mg/kg caffeine capsule taken in the morning or midday improves reaction speed by 9–11 milliseconds and reduces cognitive interference by 20–22% during attention tasks.
Rinsing the mouth with a caffeine solution at 3 mg/kg improves performance on a cognitive task measuring mental interference during midday in adolescent male volleyball players, but does not improve reaction time on simpler tasks.
Caffeine given as capsules or mouth rinses at 3 mg/kg does not consistently improve thinking performance in adolescent male volleyball players during evening training, even though their baseline performance is already high due to natural daily rhythms in alertness.
Giving adolescent male volleyball players 3 mg of caffeine per kilogram of body weight does not change their oral temperature, and any cognitive effects from caffeine occur through direct brain mechanisms, not through changes in body heat.
In adolescent male volleyball players, taking caffeine in capsule form leads to larger and more consistent improvements in reaction time and executive function during morning and midday sessions than using a caffeine mouth rinse, because absorption into the bloodstream produces stronger cognitive effects than stimulation in the mouth.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.