Chen, S. C., Davis, J. M., Matthews, E., Crowley, P., Greene, N., Quig, M., Wilson, A., Payn, T., & Lyerly, W. (2006). Effects of caffeine and carbohydrate ingestion on physical/mental functions during sports exercise. Medicine and Science in Sports and Exercise, 38(5), Supplement abstract 731.

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This study determined the effects of caffeine ingestion combined with a carbohydrate-electrolyte sports drink on mental and physical functions during intermittent high-intensity exercise that mimicked the demands of competitive team sports. Active mild to moderate caffeine users (M = 6; F = 5) completed three practice sessions followed by four experimental trials. Experimental trials consisted of four ~15-minute quarters of shuttle running at various intensities including walking, running, maximal sprinting, and jumping. Various physical and mental function tests (20-m maximal sprint, 15-repetition maximal vertical jumping, gross motor skill test, target-jumping accuracy test, force sensation, rating of perceived exertion, profile of mood states and Stroop Color-Word Test) were administered throughout the experimental trial. Heart rate, blood pressure, core body temperature, plasma volume change and body fluid loss were also measured. Ss drank a 6% CHO-electrolyte solution (3 ml/kg) before exercise, and immediately before the simulation and after each quarter and halftime. Ss ingested capsules containing a placebo, 80, 120, or 400 mg caffeine in a repeated measures, double-blind, counterbalanced design.

When compared with CHO alone, the three caffeine doses produced similar benefits in the second half on some of the physical and mental function tests including faster 20-m sprint, higher average jump heights, and improved self-reported perception of fatigue, vigor, and overall mood state. In the 400 mg caffeine condition, force sensation was reduced post-exercise, but when compared to all other treatments there was a higher tension score, and small increases in heart rate, systolic blood pressure, and core body temp.

Implication. Low doses of caffeine (80 or 120 mg) prior to exercise adds to the previously reported benefits of CHO feedings on some physical and mental functions during the latter stages of team sport exercise without negative side effects.

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