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.
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