The effect of a single high dose of caffeine on the visual reaction time of young elite soccer players at rest and during varying intensities of physical activity

Aim: To examine the effect of a single high dose of caffeine on visual reaction time (VRT) in young elite soccer players at rest and under different intensity physical exercise conditions. Materials and methods: In a double-blind, placebo-controlled randomized study with a balanced design, 54 soccer players from one of the leading Russian soccer academies, aged 15 to 17 years ( n = 54, age — 15.9 ± 0.8 years, height — 180 ± 8.3 cm, weight — 69.5 ± 8.8 kg, BMI — 21.4 ± 1.4 kg/m²), participated. After a standardized warm-up, all participants completed a battery of tests, including a 30-meter sprint, countermovement jump, change-of-direction running, T -test, dribbling, and repeated sprint ability test. Sixty minutes before VRT measurement, all participants received either 400 mg of caffeine, presented as caffeine or placebo, or placebo, presented as placebo or caffeine. VRT was measured four times: before caffeine intake, 60 minutes after intake (before warm-up), after the warm-up, and after completing the last test. Results: No significant effect of caffeine on VRT was found after its administration in any of the groups ( p > 0.05). When analyzing the changes in VRT throughout the testing process, from measurements taken before the warm-up to those taken after its completion, no significant differences were observed in any of the groups ( p > 0.01). Conclusion: A single oral intake of 400 mg of caffeine, and the belief that it was consumed, does not affect visual reaction time in young elite soccer players either at rest or after maximal intensity physical exercise.