The effect of mouth rinsing with different concentrations of caffeine solutions on reaction time.

Virdinli SG, Kutlay E, Yuzbasioglu Y, Vollaard NBJ, Rudarli Nalcakan G. J Sports Sci. 2022 Apr;40(8):928-933. doi: 10.1080/02640414.2022.2038893. Epub 2022 Feb 23. PMID: 35193478.

Take-Home Message

Mouth rinsing with increasing concentrations of caffeine improves reaction time.


Caffeine is a common ergogenic aid that improves reaction time, alertness, and pain and delays fatigue. Mouth rinsing with 300 mg of caffeine (1.2% concentration) is a way to benefit from caffeine without unwanted side effects from an energy drink, sports gel, or other sources. However, no one has tested if various caffeine concentrations with mouth rinsing affect reaction times.

Study Goal

The authors completed a double-blind, randomized controlled crossover trial to investigate the effects of mouth rinsing of 3 different concentrations of caffeine on reaction times among trained athletes.


The researchers recruited 45 healthy, trained male athletes (volleyball and soccer at a national or international competitive level). The participants completed 6 sessions with at least 3 days between each session. First, they attended a session to determine if they could participate and become familiar with the testing protocol. During the subsequent five sessions, participants randomly received either no rinse (control) or a 25 mL solution with no caffeine or 1.2%, 1.8%, or 2.4% caffeine. They rinsed for 10 seconds and then spat the solution into a graduate cylinder to ensure that they minimized what they swallowed. After rinsing, participants completed 2 reaction time tests (hand and foot).


Overall, all caffeine concentrations improved reaction times for both the hand and foot test compared to the water rinse or control (no rinse). While 2.4% caffeine led to faster reaction times than 1.2% and 1.8%, the authors found no difference between 1.2% and 1.8% caffeine. The participants reported no side effects but could distinguish the caffeine rinses from the water rinse. However, they could not differentiate between the 3 caffeine concentrations.


Overall, mouth rinsing with a caffeine solution improved reaction time performance. Furthermore, 2.4% concentrations may offer faster reaction times than lower concentrations. It would be interesting to learn if these findings apply to high school, college, or recreational athletes. Additionally, all participants had no prior experience with caffeine mouth rinses. It would be interesting to learn if repeated exposure to caffeine mouth rinses influences outcomes. Finally, more research should identify the optimal amount of caffeine and the best delivery method to improve performance without side effects. It’s possible that higher doses could be beneficial but are there risks?

Clinical Implications

Clinicians should be honest that caffeine mouth rinses could improve reaction time, but there is very little research exploring the best/safest concentration.

Questions for Discussion

To what extent do you encourage or discourage the use of caffeine as an ergogenic aid? What are your concerns with encouraging caffeine supplementation?

Written by Kyle Harris
Reviewed by Jeffrey Driban

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