Caffeine Is Ergogenic for Adenosine A_2A Receptor Gene (<i>ADORA2A</i>) T Allele Homozygotes: A Pilot Study

Abstract

Background: Caffeine improves exercise performance for some people, but not all. The reason for this variability is unknown. Differences in caffeine sensitivity have been explained by variation in a single nucleotide polymorphism in ADORA2A (rs5751876), a gene that codes for the adenosine A2A receptor. Carriers of the C allele (CT/CC) consume more caffeine and are less sensitive to caffeine than T allele homozygotes (TT). The study aim was to determine if the polymorphism in ADORA2A influences the effect of the adenosine antagonist caffeine on total work performed during a cycling time trial. Methods: Women with high self-reported caffeine sensitivity and low daily caffeine consumption participated in a randomized, double-blinded, crossover experiment. On visit 1, participants performed a cycling test and gave saliva samples that were genotyped using competitive allele-specific polymerase chain reaction analysis. On visits 2 and 3, cycle ergometry began 60 min after consuming capsules containing 5 mg/kg body weight caffeine or flour (placebo). Cycling consisted of a 5 min warm-up, 20 min at a work rate eliciting 60% of , and a 10 min all-out time trial. Results: Total work during the time trial increased after caffeine consumption for the TT (n=6, age=21.3 years, mL/kg/min) but not the CT/CC (n=6, age=20.5 years, mL/kg/min) group when compared to placebo, F(1, 8)=6.93, p=0.03, η2p=0.46. Conclusions: Caffeine is ergogenic for adenosine A2A receptor gene (ADORA2A) T allele homozygotes.