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
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$$\dot{{ \rm V}}{ \rm O}_{2 { \rm peak}}$$
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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
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$$\dot{{ \rm V}}{ \rm O}_{2 { \rm peak}}$$
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, 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,
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$$\dot{{ \rm V}}{ \rm O}_{2 { \rm peak}} = 31.6$$
\end{document}
mL/kg/min) but not the CT/CC (n=6, age=20.5 years,
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$$\dot{{ \rm V}}{ \rm O}_{2 { \rm peak}} = 33.8$$
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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.
