Irish Journal of Medical Science (1971 -)

, Volume 188, Issue 1, pp 337–345 | Cite as

The effect of CYP1A2 genotype on the ergogenic properties of caffeine during resistance exercise: a randomized, double-blind, placebo-controlled, crossover study

  • Rahman RahimiEmail author
Original Article



The purpose of this study was to examine the effect of CYP1A2 -163C>A polymorphism on the ergogenic effects of caffeine supplementation during a resistance exercise (RE) session.


In a randomized, double-blind, placebo (PL)-controlled, crossover study, 30 resistance-trained men took part in two RE sessions (three sets to failure at 85% of one repetition maximum, 2-min rest between sets), including bench press (BP), leg press (LP), seated cable row, and shoulder press (SP) following caffeine (CAF) (6 mg kg−1) or PL (6 mg kg−1 of maltodextrin) ingestion 1 h prior to the trial. The number of repetitions was recorded after each set, along with calculation of total number of repetitions for each exercise. Genomic DNA was isolated from the whole blood samples for analyzing the CYP1A2 -163C>A polymorphism through amplification refractory mutation system–polymerase chain reaction (ARMS–PCR). Subjects were classified as either AA (n = 14) or AC/CC genotypes (n = 16).


The two-way ANOVA with repeated measures revealed differences between AAs and AC/CCs under CAF conditions for repetitions performed in sets 1, 2, and 3 of BP (F(1, 28) = 14.84, P = 0.001, ƞ2 = 0.34), LP (F(1, 28) = 8.92, P = 0.006, ƞ2 = 0.24), SR (F(1, 28) = 17.38, P = 0.0001, ƞ2 = 0.38), and SP (F(1, 28) = 3.76, P = 0.063, ƞ2 = 0.11). CAF also increased the total number of repetitions performed for all three sets in AAs versus AC/CCs for BP (F(1, 28) = 8.72, P = 0.006, ƞ2 = 0.23), LP (F(1, 28) = 4.67, P = 0.03, ƞ2 = 0.14), SR (F(1, 28) = 5.54, P = 0.02, ƞ2 = 0.16), and SP (F(1, 28) = 3.89, P = 0.058, ƞ2 = 0.12) in athletes who were homozygous carriers of the A allele, compared to the C allele carriers. Therefore, AA homozygotes were able to carry out a greater total volume of RE work under CAF but not PL conditions, compared to the C allele carriers.


In conclusion, acute ingestion of CAF significantly enhanced RE performance in resistance-trained men who were homozygous for the A allele, but not for C allele carriers. Further studies are needed to replicate the potential role of the CYP1A2 -163C>A polymorphism on the ergogenic effects of CAF in other modes of exercise and in other populations.


Caffeine CYP1A2 -163C>A polymorphism Resistance exercise 



The author wishes to thank the subjects who volunteered for the study.

Funding information

This research project was funded by the University of Kurdistan (grant number 14/20137; Monday, 13 July 2015).

Compliance with ethical standards

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Conflict of interest

The author declares that there is no conflict of interest.

Informed consent

Informed consent was obtained from all individual participants included in the study.


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Copyright information

© Royal Academy of Medicine in Ireland 2018

Authors and Affiliations

  1. 1.Department of Exercise PhysiologyUniversity of KurdistanSanandajIslamic Republic of Iran

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