Evidence of major genes for exercise heart rate and blood pressure at baseline and in response to 20 weeks of endurance training: The HERITAGE Family Study

Major gene effects on exercise heart rate (HR) and blood pressure (BP) measured at 50 W and 80% maximal oxygen uptake (V̇O₂max) were assessed in 99 White families in the HERITAGE Family Study. Exercise HR and BP were measured both before and after 20 weeks of endurance training. The baseline phenotypes were adjusted for the effects of age and BMI, whereas the training responses (post-training minus baseline) were adjusted for the effects of age, BMI and the corresponding baseline values, within four sex-by-generation groups. Baseline exercise HR at 50 W was under the influence of a major recessive gene and a multifactorial component, which accounted for 30% and 27% of the variance, respectively. The training response was found to be under the influence of a major dominant gene, which accounted for 27% of the variance. These significant major gene effects were independent of the effects of cigarette smoking, baseline V̇O₂max, and the resting HR levels. No significant interactions were found between genotype and age, sex, or BMI. No major gene effect was found for exercise BP. Instead, we found the baseline exercise BP at 50 W and 80% V̇O₂max and the training response at 50 W were solely influenced by multifactorial effects, which accounted for about 50%, 40% and 20% of the variance, respectively. No familial resemblance was found for training responses in exercise HR or BP at 80% V̇O₂max. Segregation analysis also was carried out for exercise HR in Whites pooled with a small sample of Blacks in HERITAGE. Similar major effects were found, but the transmission from parents to offspring did not follow Mendelian expectations, suggesting sample heterogeneity. In conclusion, submaximal exercise HR at baseline and in response to endurance training was influenced by putative major genes, with no evidence of interactions with sex, age or BMI, in contrast to a multifactorial etiology for exercise BP.