Heart Rate Recovery after Maximal Exercise Is Associated with Acetylcholine Receptor M2 (CHRM2) Gene Polymorphism

Determinants of heart rate (HR) recovery after exercise are not well known, although attenuated HR recovery is associated with an increased risk of cardiovascular mortality. PURPOSe: Since acetylcholine receptor subtype M2 (CHRM2) plays a key role in cardiac chronotropic response, we tested the hypothesis that in healthy individuals the CHRM2 gene polymorphisms are associated with HR recovery one minute after the termination of maximal exercise test, both before and after endurance training. METHODS: The study population consisted of sedentary males and females (n=95, 42±5 yr) assigned either to a training (n=80) or a control group (n=15). A 2-week laboratory-controlled endurance training program included five 40-min sessions a week at 70–80% of the maximum HR. RESULTS: The HR recovery differed between the Intron 5 rs324640 genotypes at baseline (C/C −33±10, C/T −33±7 and T/T −40±1 1 beats per minute (bpm), P=0.008). Endurance training further strengthened the association: the less common C/C homozygotes showed 6 and 12 bpm lower HR recovery than the C/T heterozygotes, and the T/T homozygotes (P=0.001), respectively. A similar association was found between an A/T transversion at the 3' UTR of the CHRM2 gene and HR recovery at baseline (P=0.025) and after endurance training (P=0.005). CONCLUSIONS: These data suggest that DNA sequence variation in the CHRM2 locus is a potential modifier of HR recovery in the sedentary state, and after short-term endurance training program in healthy individuals. Supported by the Medical Council of the Finnish Academy of Science, Helsinki, Finland and the Ministry of Education, Helsinki, Finland.