Conversely to what was initially thought, CAF intake does not seem to be able to accelerate fat metabolism and to spare muscle glycogen during exercise, which would explain the increased performance observed in endurance tasks [4,7]. Currently, this potential effect of CAF is credited to its affinity to ACP-196 supplier adenosine receptors (A1 and A2a). When CAF molecules bind with these pre and post synaptic receptors, it inhibits adenosine action, promoting the release of excitatory neurotransmitters, increasing corticomotor

excitability [8,9]. This stimulatory effect of CAF on the central learn more nervous system may be responsible for modifying the motivation parameters that cause sustain discomfort during physical exercise, reducing the rating of perceived exertion (RPE) during 4EGI-1 cell line exercise [10]. Although the ergogenic effect of CAF on the neuromuscular system has been discussed in detail in a previous review study [11], it is noteworthy that the majority of studies have so far adopted open-loop protocols. Despite being a sensitive test that quantifies changes in performance [12], it does not represent the reality of sports competitions. Although closed-loop protocols have been less frequently used in investigations on the effect of CAF on physical performance [13–16], they have greater ecological validity than open-loop protocols

due to its similarity with actual competitive situations, as well as having the ability to evaluate athletes’ pacing strategy [17]. Moreover, few studies have investigated the effect of CAF on RPE on time trials, where the subject can choose and plan his pacing strategy during the effort. As a result, it has been difficult to extrapolate information on the use of CAF to competitive situations. Therefore, the objective of the

present study was to analyze the effect of CAF ingestion on the performance and physiological variables associated with fatigue in 20-km cycling time trials using a closed-loop protocol. Methods Experimental design Glycogen branching enzyme A double-blind, randomized, placebo-controlled crossover study with previous familiarization was approved by the Londrina State University Ethics Committee. Thirteen male cyclists (71 ± 9 kg; 176 ± 5 cm; 253 ± 142 km.week−1) with at least two years of competitive experience were recruited for the study. All participants had been free of injuries for at least six months before the tests. Prior to tests, the subjects visited the laboratory to become aware of the purpose of the study and sign an informed consent. Schedules were set, and subjects returned to the laboratory to perform anthropometric measurements and a pre-experimental trial to become familiarized with the equipment and the experimental protocol. Participants were randomized into 2 groups and received caffeine (CAF) capsules (6 mg.