Influence of CYP1A2 genotype on neuromuscular function following acute caffeine administration

Abstract

The purpose of this study is to examine whether genetic variation in CYP1A2 (-163A>C, rs762551) influences the effects of acute caffeine supplementation on neuromuscular function of the lower body at rest and in response to a fatiguing work bout. Forty-two young, healthy males completed the entire study protocol and were genotyped for CYP1A2 enzyme. Subjects were then classified as AA (FAST: n = 26) or AC/CC (SLOW; n =16). This study consisted of 3 separate visits to the laboratory, a familiarization session and 2 experimental sessions: caffeine (CAF; 6 mg/kg/bw) or placebo (PLA). During each session, neuromuscular function, including motor unit behavior, muscle activation, spinal and supraspinal excitability, and muscle contractile properties were assessed. Additionally, each experimental visit ended with repeated, intermittent submaximal contractions at 50% of the subject's maximum effort to fatigue. The main findings from this investigation were the overall lack of ergogenic effects of caffeine on neuromuscular function of the lower body musculature. Specifically, no significant alterations in motor unit behavior, muscle activation, or spinal or supraspinal excitability were found from pre- to post-testing in either condition. However, the present data suggest that caffeine may augment the decline seen in muscle contractile properties in the placebo condition. The present data also suggests a limited role, if any, for the CYP1A2 genotype in mediating the effects of caffeine on neuromuscular function.