Multivariate genetic analysis of Lifetime exercise and environmental factors

We investigated whether the association between exercise and individual-specific factors that correlate with exercise may be explained by genetic or common environmental factors. Lifetime exercise data were available from 147 MZ and 153 DZ adult male twin pairs with a mean age of 50 yr (SD = 8 yr). The best-fitting quantitative genetic model for adulthood exercise level consisted of additive genetic effects, genetic effects due to dominance and unique environment effects, with genetic effects explaining 51% (95% CI = 29-63%) of the variance. Factors associated with adulthood exercise level were adolescent exercise, participation in competitive sports, perceived health, smoking status, and percent body fat. In bivariate models, approximately half of the covariation between those factors and adulthood exercise level was accounted for by unique environmental effects (i.e., factors not shared by the co-twins). Additive genetic effects explained less (3-20%) than dominance genetic effects (23-53%) of the covariation between those factors and adulthood exercise. Shared environmental effects were present only in the bivariate model of adulthood and adolescent exercise, explaining 11% of the covariance. : The genetic component shared in common by exercise and factors associated with exercise suggests that there may be a complex pathway of genetic selection and predisposition for a physically active lifestyle.