Introduction:

The objective of this study was to analyze the effect of caffeine ingestion in soccer performance, particularly in the countermovement jump test (CMJ).

Material and Methods:

A total of 17 players from a U-19 amateur Spanish team participated in this pilot study. A double-blind placebo-controlled randomized experimental design was used in 2 different sessions (1.5 hour per session) separated by 1 week. CMJ was collected at the beginning and at the end of sessions; Rating of Perceived Exertion (RPE) was recorded. Players ingested caffeine or placebo at the beginning of session (minute 0 of session), providing a total of 4mg of caffeine or a placebo per kg of body mass. Side effects from caffeine and placebo ingestions were analyzed. The effect sizes (ES) were calculated using values for Cohen’s and Quantitative differences were assessed qualitatively (QA).

Results:

The jump height with caffeine supplementation at the beginning of training was 37.03 (±3.87) cm and at the end was 39.35 (±4.05) cm, obtaining significant improvements (p<0.05; ES:0.56; QA:99/1/0). Significant differences on CMJ at the end of the training session between caffeine and placebo groups were observed (39.35 [±4.05] cm vs. 36.85 [±3.15] cm; p<0.05; ES:0.65; QA:0/1/99). Significant differences on RPE between groups were observed. A non-significant tendency to suffer more side effects with caffeine ingestion was obtained.

Conclusions:

This study shows how the ingestion of 4mg of caffeine per kg of body mass could be an ergogenic aid to improve soccer performance. However, further studies with bigger soccer players sample would be necessary to refute the present results.

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