The influence of the CYP1A2 polymorphism on the effect of caffeine ingestion and mouth rinsing on 3km cycling performance

PURPOSE: The objectives were to determine the effects of caffeine ingestion and mouth rinsing on cycling performance, and to assess whether the CYP1A2 gene is related to the size of the performance effects. METHODS: Thirty-eight recreational cyclists completed four simulated 3-kilometer time trials (TT). Subjects ingested either 6mg/kgBW of caffeine or placebo one hour prior to each TT. Additionally, 25 ml of 1.14% caffeine, or placebo solution was mouth rinsed before each TT. Treatments were: placebo ingestion+placebo rinse (Placebo), placebo ingestion+caffeine rinse (Rinse), caffeine ingestion+caffeine rinse (Ingestion+Rinse), caffeine ingestion+placebo rinse (Ingestion). Subjects were genotyped and classified as AA homozygotes or C allele carriers for the rs762551 polymorphism in CYP1A2. Magnitude based inferences were used to evaluate treatment differences. RESULTS: Both Ingestion+Rinse (‘likely’) and Ingestion (‘possibly’) improved performance compared to Placebo. Performance differences between Ingestion+Rinse and Ingestion and between Rinse and Placebo were ‘likely trivial.’ C allele carriers experienced greater gains (‘likely’) with Ingestion compared to AA homozygotes. Additional analyses revealed that caffeine intake conferred larger benefits for subjects that performed trials prior to 10am. CONCLUSIONS: Caffeine ingestion, but not mouth rinse, improved cycling performance. C allele carriers experienced the largest improvement in performance with caffeine ingestion, especially prior to 10am.