JGGG contributed to data collection and manuscript preparation, L

JGGG contributed to data collection and manuscript preparation, LGMA participated in statistical analysis and manuscript preparation. BSG, JZVP contributed to the coordination and helped draft the manuscript. All authors

read and approved the final manuscript.”
“Introduction Caffeine (1,3,7- trimethylxanthine) is a natural alkaloid present in the leaves, fruits and seeds of various plants (coffee, kola, tea, mate, etc); yet it can also be artificially synthesized in the laboratory. This dual origin of caffeine has Selleckchem CDK inhibitor turned this substance into the most frequently ingested drug in the world [1] since it is present in foods and drinks (chocolate, coffee, and soft drinks), dietary supplements, and over-the-counter medications. In the sports setting, caffeine is consumed prior to competing by 74% of elite national and international athletes, based on the caffeine concentration GS-7977 found in the urine samples obtained for doping analysis [2]. The current popularity of caffeine in sports is associated with the physical benefits derived from its ingestion Fosbretabulin supplier in

a wide variety of sports activities [3] and the removal of caffeine from the list of prohibited substances published by the World Anti-doping Agency in 2004 [4]. The ingestion of pure anhydrous caffeine in capsules or powder has been the most typical experimental setting to investigate the effects of caffeine on sports performance [5]. The ingestion of 3 to 9 mg of caffeine per kg of body mass has been repeatedly shown as ergogenic in several exercise activities [6–12]. Doses of caffeine as high as 13 mg/kg [13] or as low as 2 mg/kg [14] have been reported to have an ergogenic effect of

a similar magnitude to the one observed with the typical 3-to-9 mg/kg doses. However, the ingestion of 1 mg/kg of caffeine has failed to improve endurance performance Carbachol [14]. As opposed to caffeine capsules, the newly created caffeine-containing energy drinks have become the most used means for caffeine intake in the sports population [15–17]. These energy drinks typically contain moderate amounts of caffeine (32 mg per 100 mL of product) in addition to carbohydrates, taurine, glucoronolactone and B-group vitamins [18]. The effects of these energy drinks on physical performance are diverse and the scientific literature scarce. The intake of one serving of an energy drink (250 mL, equivalent to ~1 mg of caffeine per body weight) did not enhance maximal oxygen uptake during a maximal effort test [19], peak power during three repetitions of the Wingate test [20, 21] or running velocity during 24 “all-out” sprints [22]. However, one serving of an energy drink improved reaction time, alertness and aerobic and anaerobic performance tests [23].

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