Ergogenic Effects Of Caffeine Are Associated With Variation In The Adenosine A2a Receptor Gene (ADORA2A)
Bryan D. Loy MSSE May 2014 - Volume 46 - Supplement 1 5S p77
There are individual differences in the ergogenic effects of caffeine. Caffeine is an adenosine receptor antagonist. Variations in caffeine sensitivity have been linked to variations at
nucleotide position 1083 (rs5751876) in the ADORA2A gene which codes for the adenosine A2A receptor. Prior studies show that T allele homozygotes (TT) for the ADORA2A gene
consume less caffeine and show greater sensitivity to caffeine than C allele carriers (CC, CT).
PURPOSE: To determine if total work performed during a 10-min cycling time-trial differs as a function of ADORA2A genotype. TT carriers were hypothesized to show larger
increases in total work after consuming caffeine compared to CC/CT carriers.
METHODS: College students with high self-reported caffeine sensitivity and typical daily caffeine consumption (
<250 mg.day-1) were recruited. On Day 1, eligible volunteers
performed a cycling VO2peak test and gave saliva samples that were genotyped using competitive allele specific polymerase chain reaction analysis. On Day 2 and 3, cycle ergometry
was started 60-mins after consuming capsules containing 5 mg.kg-1 body weight caffeine or flour (placebo). Capsules were given double-blind, and the capsule order was
counterbalanced and randomized. Cycling consisted of a 5-min warm-up at 50 watts, 20-mins at the work rate eliciting 60% of VO2peak (~50% Wpeak) and a 10-min all-out time trial.
At the end of each minute during the trial participants made a choice to cycle during the next minute at either the same power, 10 W higher or 10 W lower. Complete data were obtained
from 7 TT and 19 CC/CT carriers. An independent samples t-test on difference scores tested the hypothesis.
RESULTS: The CC/CT and TT groups did not differ significantly on the Day 1 exercise test (Wpeak = 175±37 vs. 159±24; VO2peak = 34.3±8.2 vs. 31.1±4.2 ml.kg.min-1). The change
in total work was significantly different between genotypes, t(24) = -2.31, p = .03. Total work increased after caffeine consumption for the TT group (6.1 ± 4.5 kJ) but did not change for
the CC/CT group (-0.05 ± 6.5 kJ). The TT group had insignificantly larger decreases in perceived exertion (-1.0 vs. -0.6) and quadriceps pain (-1.2 vs. -0.5) in the caffeine trial.
Caffeine increases total work in a 10-min cycling time trial among those with the ADORA2A TT genotype but not for C allele carriers.
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