-
Study aim
-
To compare caffeine capsule, chewing gum, and mouth rinse with placebo on fatigue, anaerobic power, passing accuracy, jump performance, and psychophysiological responses after small-sided games in young professional male football players.
-
Design
-
Randomized, double-blind, placebo-controlled crossover trial. Sixteen players are assigned to four random sequences; each completes all four conditions with a 7-day washout.
-
Settings and conduct
-
Sessions will be held at the Faculty of Sport Sciences and Health, University of Tehran, with practical tests on the standard grass field. Before testing, a familiarization session and a habitual caffeine questionnaire will be completed. Experimental sessions include five 4-min 4v4 sets with 2-min recovery. Five minutes later, RPE, EES, and MF are assessed first, followed by CMJ, SJ, McDonald test, and RAST.
-
Participants/Inclusion and exclusion criteria
-
Inclusion: male football players aged 15–18 years with ≥3 years of national league experience; no injury in the past 6 months; no caffeine/supplements for 48 h or tobacco/psychotropic drugs for 72 h before testing; similar 24-h pre-test diet. Exclusion: new injury, caffeine adverse reaction, protocol non-compliance, absence, or withdrawal.
-
Intervention groups
-
Four crossover conditions: (1) 400 mg caffeine capsule, consumed 30 min before warm-up; (2) 400 mg caffeinated gum (2×200 mg), chewed for 5 min starting 5 min before warm-up; (3) 750 mg caffeine mouth rinse used before the first set and between sets; and (4) placebo consisting of a cellulose capsule, caffeine-free gum, and caffeine-free mouth rinse with similar taste. Sessions are 7 days apart.
-
Main outcome variables
-
Fatigue index, peak and mean power by RAST; passing accuracy by McDonald test; jump performance by CMJ and SJ; rating of perceived exertion (RPE), exercise enjoyment (EES), and mental fatigue (MF).