Effects of Caffeinated Chewing Gum on Psychophysiological Responses and Kinematic Profiles During Intermittent and...

Background/Objectives: Caffeinated chewing gum is a practical, rapidly absorbed ergogenic aid increasingly used in team sports, yet its interaction with different small-sided soccer game (SSG) formats in young male players remains unclear. This study evaluated the effects of acute caffeinated (CAF) chewing gum on psychophysiological responses and kinematic profiles during intermittent (INT) and continuous (CON) 3-a-side SSGs. Methods: Twenty-four young male soccer players (18.4 ± 0.5 years) completed four 3-a-side SSG sessions separated by 48 h in a randomized, double-blind, placebo (PLA)-controlled, crossover design (CAF-INT, PLA-INT, CAF-CON, PLA-CON). Participants chewed 300 mg of CAF or PLA gum for 5 min, with mastication completed 5 min before warm-up session. The heart rates and kinematic profiles were recorded during the SSGs, and the ratings of perceived exertion (RPE), exercise enjoyment scale (EES), and visual analogue scale (VAS) to perceived mental fatigue (MF) were assessed post-game. Results: Compared with the PLA, the CAF increased the heart rate responses (HR), EES, total distance (TD), player load (PL), acceleration (ACC), and distances covered in selected speed zones (from Z0 to Z5), while reducing the RPE and MF. Significant format × supplementation interactions indicated that CAF-induced changes in high-intensity kinematic outcomes (TD, PL, ACC, Z2-Z5) and HR responses (HR_mean, HR_max) were generally greater in INT, whereas CAF-induced increases in low-intensity running distances (Z0 and Z1) and %HR_max were more pronounced in the CON format (all p < 0.05 for the reported effects; ηp2 = 0.16-0.93 for CAF main effects [large effects]). The EES improvements were more pronounced in the CON format, whereas the MF and RPE reductions were more pronounced in the INT format. Conclusions: CAF chewing gum may be a practical acute strategy for modulating psychophysiological responses and kinematic profiles during SSGs, with the effects depending partly on the game format.