The effects of caffeine consumption on performance enhancement in resistance exercise outcomes have been debated due to inconsistent results from previous studies.
The effect of caffeine on hormonal responses has been shown to vary greatly among individuals. The genetic differences that cause this variation are thought to be due to genetic variations (DNA polymorphisms), particularly in genes responsible for caffeine metabolism, such as CYP1A2 or ADORA2A.
The ADORA2A genes encode the adenosine A2A receptor (A2AR), which plays an important role in many body functions, such as caffeine sensitivity.
A double-blind, crossover trial in 30 men, who had undergone at least one year of resistance training, was conducted to determine the effect of ADORA2A and its polymorphism rs5751876 on testosterone (TS) or growth hormone (GH) levels, following caffeine consumption.
Participants were classified as light caffeine consumers and a genotyping study was conducted to determine the participants' genetic profiles.
They received either maltodextrin or 6 mg of caffeine per kilogram of body weight one hour before resistance training. TS, GH, and TG levels were determined before, after, and for 15 minutes after resistance exercise.
The same protocol was followed after a seven-day wash.
The TT genotype group in the intervention showed significantly higher GH levels than those of the TC/CC type—before the test (p=0.012), after the test (p=0.007), and 15 minutes after exercise (p=0.001).
Post-exercise GH levels in participants with the TT genotype were also higher than those in the placebo group (p = 0.05).
Similarly, TS concentrations in the intervention group were significantly higher for those with the TT genotype compared to TC/CC gene carriers, both immediately after exercise (p = 0.001) and 15 minutes after training (p = 0.026).
In this study, it appears that athletes carrying the TT gene are more likely to experience anabolic responses after resistance training with caffeine consumption.
Evidence suggests that higher TS levels may provide an advantage to athletes. Carrying the ADORA2A-rs5751876-TT genotype may be advantageous for energy performance. The researchers wrote.
The researchers also conducted a cross-sectional study to determine resting TS, GH, and testosterone (Gh) levels in the sera of 94 elite athletes who were moderate caffeine consumers.
The RCT validated the results of this study. In the group of athletes with the ADORA2A TT genotype, TS and GH levels were significantly higher (p=0.0125) than those with the TC/CC genotype.
There is increasing evidence that genetic polymorphisms can influence individual responses to supplements such as caffeine or whey protein. We found that the ADORA2A rs5751876 gene polymorphism can alter the hormonal response to resistance training when caffeine is consumed.
We believe that the cross-sectional study may reflect the effect of chronic caffeine consumption on TS and GH levels in athletes, who are light consumers. This is partly a replication of the results of the resistance exercise study.
It is possible to develop personalized active and sports nutrition products, adapted to individual genetic profiles.
It is important to note that this study has some limitations. For example, the study was conducted on a small number of participants. This study needs to be extended and replicated in groups of different geographical origins, if it is to translate the results into broader terms.
ADORA2A gene and hormonal response to exercise after caffeine supplementation require functional studies. Added researchers.
Source: Nutrients
https://doi.org/10.3390/nu16121803
The effect of ADORA2A genetic polymorphism on hormonal response to resistance training: a double-blind, placebo-controlled crossover study
Authors: Mohammad Rahman Rahimi, et al
English 
French