Abstract Aim 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. Methods 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 )orPL(6mgkg −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 DNAwas 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). Results The two-way ANOVAwith 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,ƞ 2 =0.34),LP(F (1, 28) =8.92,P =0.006,ƞ =0.24),SR (F (1, 28) =17.38, P =0.0001, ƞ 2 = 0.38), and SP (F (1, 28) =3.76, P =0.063, ƞ 2 = 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,ƞ 2 =0.23),LP(F =4.67, P =0.03,ƞ 2 =0.14),SR(F (1, 28) =5.54,P =0.02,ƞ 2 =0.16),andSP(F (1, 28) =3.89,P =0.058,ƞ 2 = 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. Conclusion 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.
