The Study
Differential Time-of-Day Effects of Caffeine Capsule and Mouth Rinse on Physical Performance and Volleyball-Specific Skills in Adolescent Male Volleyball Players
This study showed that when teen volleyball players took caffeine either as a pill or by swishing it in their mouth, they jumped higher and moved faster — especially in the morning. But it doesn’t prove caffeine caused this in every single person, just that it probably helped in this group under these conditions.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Teen volleyball players tried caffeine in two ways: swallowing a pill or just rinsing their mouth with a caffeinated solution. Both helped them jump higher and spike better, especially in the morning when they usually feel slower.
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 570 / 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.
- 1Yes — improving jump height by 2 cm or being half a second faster can make a big difference in competitive volleyball, especially early in the day when natural performance is lower.
- 2At 8 AM and 12 PM, both methods improved jump height by about 2 cm and made players 0.4–0.5 seconds faster in agility tests.
- 3Mouth rinse worked just as well as pills for spike and serve accuracy.
- 4Pills gave a tiny extra boost (0.5 cm) in some jumps at noon.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Nutrients
Year
2026
Authors
Salma Belhaj Amor, Wissem Dhahbi, Marouen Souaifi, H. Ceylan, Johnny Padulo, S. Vando, Nagihan Burçak Ceylan, R. Muntean, N. Souissi
Related Content
Claims (6)
Rinsing the mouth with a caffeine solution at 3 mg/kg improves volleyball spike and serve accuracy in adolescent male players just as much as swallowing a caffeine capsule, and this improvement occurs without caffeine entering the bloodstream.
Volleyball performance is better in the evening than in the morning, and this pattern occurs whether or not caffeine is consumed, showing that the body's daily rhythm affects skill execution.
In adolescent male volleyball players tested at midday, taking caffeine in capsule form leads to a small but measurable increase in explosive leg power during squat jumps and countermovement jumps compared to rinsing the mouth with caffeine solution.
In trained adolescent male volleyball players, taking 3 mg/kg of caffeine before exercise increases vertical jump height and change-of-direction speed more in the morning and midday than in the evening, due to reduced circadian-related declines in explosive power and agility.
Caffeine improves physical performance more in the morning than in the afternoon because core body temperature starts lower in the morning and rises more after caffeine intake.
Human physical performance is highest in the late afternoon or early evening, and this peak timing can be changed by regularly training at other times of day.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.