Discussion
The key novel findings of this study demonstrate that guarana supplementation decreased both SRT (after exercise) and CRT (before exercise) in comparison with placebo, supporting previous literature that guarana increases speed of attentionThe improvement in SRT following guarana supplementation is consistent with previous research and further supports the notion that guarana may possess cognitive stimulant-like effects which therefore enhances information processing speedIt is important to note that true comparisons to previous literature are difficult as key differences exist in exercise intensity and duration, as well as when cognitive tests commenced. For example, during the Pomportes In the current study, guarana elicited a greater magnitude of effects than the equivalent caffeine dose of 5 mg/kg, suggesting that the combination of caffeine and guarana provides superior simulant-like effects. Despite this, the pharmacokinetics and central nervous system stimulant contributions of caffeine in the current study cannot be ignored. It is well known that caffeine supplementation results in heightened alertness, vigilance, attention and reaction timeThe interaction caffeine has with the other components found within guarana are not yet clear. Evidence suggests that synergistic relationships when co-consumed with other bioactive compounds may result in greater stimulant-like effects. For example, guarana contains traces of several other purine alkaloids (methylxanthines), such as theobromine and theophyllineThe study acknowledges several key limitations. First, the 5-min period between exercise and cognitive tests may not necessarily be translatable and applicable in the field, where athletes or professionals (police/military) are required to make crucial decisions while under physical exertion. Further research should therefore try to eliminate or reduce the time between exertion and testing. Applying relevant cognitive tests to real-world sporting or professional situations would also be pertinent, such tests could place further emphasis on problem solving and higher executive functioning rather than only SRT and CRT. Second, the sample size in the current study was small; therefore, caution must be taken when interpreting the results, particularly when considering the wider applicability of the outcomes. The authors also acknowledge that the study population was specifically young active individuals, some of which came from a cycling club; this therefore impacts the generalisability of the results. It is also plausible to suggest that variations in the erogenicity of caffeine supplementation, and by extension guarana supplementation, may be as a result of inter-individual subtle differences in CYP1A2 and ADORA2A genes