Effect of Acute Caffeine Intake on Maximal Aerobic Speed in University Soccer Players Assessed by the 30–15 Intermittent Fitness Test

The aim of this study was to analyze the effect of acute caffeine intake on maximal aerobic speed (MAS) assessed using the 30-15 Intermittent Fitness Test (IFT) in university soccer players. An experimental, randomized, double-blind, crossover design was employed, involving 26 male university team players (<i>n</i> = 26). Each participant completed the test under two conditions: caffeine supplementation (220 mg; 2.85 ± 0.27 mg/kg, range 2.60-3.16 mg/kg) and placebo, separated by a 72 h washout period. The final running speed achieved (VIFT) was used as an estimator of MAS. Statistical analysis included descriptive statistics, normality testing, and paired Student's <i>t</i>-test, with a significance level set at <i>p</i> < 0.05. The results revealed a significant improvement in VIFT under the caffeine condition (19.94 ± 1.67 km/h) compared with placebo (18.72 ± 1.50 km/h), with a mean difference of 1.22 km/h (6.5%) and a large effect size (dz = 1.24; <i>p</i> < 0.001). It is concluded that acute caffeine intake was associated with a significant improvement in intermittent aerobic performance in university soccer players under the conditions of the present study, suggesting that caffeine may represent a potentially useful strategy in similar applied contexts.