Acute caffeine and theanine supplementation alleviate the negative effect of mental fatigue on coordination and aerobic performance in soccer players
Objective To explore the effect of acute caffeine and theanine supplementation on coordi-nation and aerobic performance in mentally fatigued soccer players.Methods A randomized crossover de-sign was employed with 15 male amateur soccer players.Participants underwent three different interven-tions—caffeine(caffeine group),theanine(theanine group),and placebo(placebo group)—with a one-week washout period between each intervention.After each supplementation,participants performed a 45-minute Stroop task to induce mental fatigue,followed by a speed dribbling test(SDT)and the 30-15 intermittent fitness test(30-15IFT)to assess coordination and aerobic performance,respectively.Mea-surements included visual analog scale for mental fatigue(VAS-MF),motivation(VAS-MO),Brunel mood scale for fatigue(BRUMS-F)and vigor(BRUMS-V)pre-and post-Stroop task,response time(RT),response accuracy(ACC),average heart rate(HRave)during Stroop,mental exertion(VAS-ME)post-Stroop,rating of perceived exertion(RPE),HRave,and peak heart rate(HRpeak)during SDT and 30-15IFT.All data were analyzed using repeated measures ANOVA.Results The change in VAS-MF(ΔVAS-MF)before and after the Stroop task was lower in the caffeine group compared to the placebo group(P=0.064),while the theanine group showed similar ΔVAS-MF to the latter group(P=0.999).Both the caffeine and theanine groups had significantly faster RT(P=0.003 and 0.033,respectively)and higher ACC(P=0.006 and 0.033,respectively)during the Stroop task compared to the placebo group.Moreover,coordination performance in both the caffeine and theanine groups was better than the placebo group(P=0.096 and 0.078,respectively).Meanwhile,aerobic performance in the caffeine group was significantly better than the placebo group[time to exhaustion(TTE):P=0.012;last stage ve-locity of 30-15IFT(VIFT):P=0.007;maximal oxygen uptake(VO2max):P=0.008],whereas no significant differences were found between the theanine group and the placebo group in the aerobic performance(TTE:P=0.999;VIFT:P=0.999;VO2max:P=0.999).Conclusion Both acute caffeine and theanine supple-mentation can mitigate the negative effect of mental fatigue on coordination performance in soccer play-ers.Additionally,acute caffeine supplementation can also alleviate the negative impact of mental fa-tigue on aerobic performance.