Caffeine, genetic variation and anaerobic performance in male athletes: a randomized controlled trial

Effect of caffeine on muscle oxygen saturation during short-term all-out exercise: a double-blind randomized crossover study

“…Investigations on the two main polymorphisms linked to the interindividual differences in response to caffeine intake ( i.e., − 163C > A in the CYP1A2 gene [ 40 ] and 1976C > T in the ADORA2A gene [ 41 ]) revealed that individuals with different genotypes in these polymorphisms obtained similar benefits of caffeine on the Wingate test. Additionally, a recent investigation tested the effect of 14 genetic polymorphisms on the response to caffeine intake during the Wingate test and the authors concluded that variations in these candidate genes did not modify the effect of caffeine on the Wingate test [ 33 ]. However, these results of this latter investigation may have been influenced by the lack of ergogenic effect of caffeine on Wingate performance [ 33 ].…”

“…Additionally, a recent investigation tested the effect of 14 genetic polymorphisms on the response to caffeine intake during the Wingate test and the authors concluded that variations in these candidate genes did not modify the effect of caffeine on the Wingate test [ 33 ]. However, these results of this latter investigation may have been influenced by the lack of ergogenic effect of caffeine on Wingate performance [ 33 ]. To date, most of the current evidence indicates that genetic variability in genes associated to caffeine metabolism does not modify caffeine's benefits on short-duration maximal-intensity exercise [ 33 , 40 ].…”

“…However, these results of this latter investigation may have been influenced by the lack of ergogenic effect of caffeine on Wingate performance [ 33 ]. To date, most of the current evidence indicates that genetic variability in genes associated to caffeine metabolism does not modify caffeine's benefits on short-duration maximal-intensity exercise [ 33 , 40 ]. Still, some studies indicate the contrary for endurance exercise [ 42 ].…”

“…The conflicting results of the first experiments investigating the effect of oral administration of caffeine on the Wingate test [18,32] are still present in more recent investigations [33,34]. The lack of an ergogenic effect of caffeine on the Wingate test in some investigations is unclear as in these investigations the participants' fitness level and the dose of caffeine administered were not different from those investigations with confirmed caffeine's ergogenicity in the Wingate test [18,[32][33][34][35] It is possible that habituation to caffeine -due to chronic intake of this substance [36]-, and the identification of caffeine intake -to obtain psychological advantages produced by this stimulant [37], -, may explain some of the differences between investigations. Still, the cause of lack of caffeine's ergogenicity in some investigations remains uncertain.…”

Caffeine, CYP1A2 Genotype, and Exercise Performance: A Systematic Review and Meta-analysis

“…For the overall SMD of each genotype, adjusted effects were calculated using the fitted model using the emmprep and the emmeans functions. To avoid pseudoreplication, three studies (19)(20)(21) were considered as the same study within the three-level structure (i.e., were given the same study ID code), as they reported results from a single experiment using data collected among the same participants. The same approach was applied when individual studies presented more than one exercise test, meaning different outcomes from the same study were coded similarly to account for the between-outcome and between-study variance.…”