Acute Effects of a Low Dose of Caffeine on Physiological and Performance Factors in Young Male Soccer Players: A Randomized Crossover Study.

OBJECTIVES

This research aimed to study the acute consumption of caffeine on the performance of young male soccer players in the Loughborough soccer passing test (LSPT) and Yo-Yo intermittent recovery test level 1 (YYIR1), and also on the heart rate (HR), blood pressure (BP), and rate pressure product (RPP), immediately after the YYIR1.

METHODS

In a randomized, counterbalanced, crossover design, 12 young male soccer players (16.5 ± 0.52 y; 63 ± 8.06 kg; training background: 4-5 sessions/wk) voluntarily completed 2 distinct experimental sessions: 1) caffeine and 2) placebo. In each test session, 1 h after taking a caffeine or placebo (flour) capsule (3 mg·kg-1), the participants first completed the LSPT and then the YYIR1. HR, systolic BP (SBP), and diastolic BP (DBP) were measured before the start, 1 h after the start, and immediately after the end of the YYIR1. Because the Shapiro-Wilk test confirmed the normality of the data, parametric tests [repeated-measures analysis of variance (ANOVA) and dependent t-test] were used to analyze the research questions.

RESULTS

Two-way repeated-measures ANOVA revealed significant main effects of condition (P = 0.006) and time (P < 0.001) for HR, without a significant condition × time interaction (P = 0.144); however, post hoc analysis showed significantly higher HR after caffeine ingestion compared with placebo immediately after the YYIR1 (P = 0.025). A significant condition × time interaction was observed for DBP (P = 0.014), although pairwise comparisons showed no significant post hoc differences (all P ≥ 0.101). No significant main or interaction effects were found for SBP or RPP (all P ≥ 0.066).

CONCLUSIONS

Within the limits of the current sample size, acute ingestion of 3 mg·kg-1 caffeine elicited modest physiological responses in adolescent soccer players, significantly augmenting postexercise HR without substantially altering BP, RPP, or soccer-specific performance factors. However, given the observed numerical improvements in functional test results, these findings should be interpreted cautiously, as low-dose caffeine may offer subtle practical benefits that warrant further investigation with greater statistical power.