The current study examined the relationships between the effects of consuming a caffeine-containing “energy drink” upon (i) short-term maximal performance, (ii) reaction times, and (iii) psychological factors (i.e., mood state, ratings of perceived exertion (RPE), and affective load) and on physiological parameters (i.e., blood pressure and blood glucose). A randomized, double-blind, placebo-controlled, counterbalanced crossover design was implemented in this study. Nineteen male physical-education students (age: 21.2 ± 1.2 years; height: 1.76 ± 0.08 m; body-mass: 76.6 ± 12.6 kg) performed two test sessions: after drinking the “Red Bull’ beverage (RB) and after drinking a placebo (PL). One hour after ingestion of each drink, resting blood glucose and blood pressure were measured and the participants completed the Profile of Mood States questionnaire. Then, after a 5-min warm-up, simple visual reaction time and handgrip force were measured, and the 30-s Wingate test was performed. Immediately after these tests, the RPE, blood glucose, and blood pressure were measured, and the affective load was calculated. Differences between treatments were assessed using two-way repeated measures analyses of variance and paired t-tests, as appropriate. Relationships between the test variables were assessed using Bland–Altman correlations. Significant (i) improvements in peak and mean power output, handgrip force, pre- and post-exercise blood glucose, blood pressure, and vigor and (ii) reductions in reaction times, depression, confusion, fatigue, anger, anxiety, RPE, and affective load scores were observed after RB compared to PL. There were significant correlations of (i) physical performances and reaction times with (ii) RPE, affective load, and pre- and post-exercise blood glucose levels. Gains in peak and mean power were significantly correlated with reductions in fatigue, anxiety (peak power only), and anger (mean power only). The reduction of reaction times was significantly correlated with decreases in confusion and anger and with increases in vigor. Handgrip force and reaction times were significantly correlated with pre- and post-exercise blood pressures. We conclude that RB ingestion has a positive effect on physical performance and reaction times. This effect is related to ergogenic responses in both psychological (i.e., RPE, affective load, and mood state) and physiological (i.e., blood glucose and blood pressure) domains.
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