The Effects of Caffeine Mouth Rinsing During the Battery of Soccer-Specific Tests in the Trained Male Soccer Players: Fasted Versus Fed State

Caffeine (CAF) mouth rinsing has been considered a practical nutritional strategy among athletes. Recent studies indicate that this nutritional strategy's efficacy may depend on the athlete's prandial state. Therefore, the main aim of the current study is to determine the effect of CAF mouth rinsing on a battery of soccer-specific tests of soccer players in fasted (FST) or fed states (FED). Thirteen male soccer players (age: 18.1 ± 0.9 years, body mass: 60.1 ± 8.4 kg, height: 174.2 ± 7.3 cm, and body mass index: 20.14 ± 2.7 kg/m2) randomly participated in a randomized, double-blind, Latin square study design. Participants completed four experimental trials while performing eight serial mouth rinses of 750-mg CAF or a taste-matched placebo (PLA) for 15 s and then immediately expectorated. Two trials commenced 2 hr after a high-carbohydrate breakfast (FED), and two trials were performed after an overnight fast (FST). Following the final mouth rinse, sprint test, countermovement jump, Yo-Yo Intermittent Recovery Test Level 1, and rating of perceived exertion were measured, respectively. There was a main effect of condition for Yo-Yo Intermittent Recovery Test Level 1 performance (p = .021), while interaction between Condition × Prandial (p = .671) and the main effect of prandial state (p = .437) was not significant for Yo-Yo Intermittent Recovery Test Level 1 (CAF-FST = 2,155 ± 484 m, PLA-FST = 1,933 ± 549 m, CAF-FED = 2,098 ± 679 m, and PLA-FED = 1,864 ± 535 m). In addition, there was no significant main effect of condition, prandial, and interaction between Condition × Prandial for the sprint test and countermovement jump and the rating of perceived exertion (all p > .5). These data suggest that CAF mouth rinsing increases intermittent running performance in soccer players. This improvement is likely to be similar in the FST and FED states.