Maximum oxygen uptake and cardiac size and function in twins

Abstract

The contribution of heredity to the interindividual variability of maximum oxygen uptake and of cardiac size and function of healthy male twins, age 18 to 31 years, was studied to evaluate the role of the heart in the inheritance of aerobic power. Twelve pairs of monozygotic and 12 pairs of dizygotic twins were examined. Weight (p < 0.05), relative weight (Quetelet index) (p < 0.01) and skinfold thickness (p < 0.01) were found to be genetically determined, as well as heart rate at rest (p < 0.05) and systolic blood pressure (p < 0.05). Genetic variation was significant (p < 0.05) both for absolute and for weight-adjusted oxygen uptake, measured at peak exercise on the bicycle ergometer. However, the influence of inheritance on aerobic power was not associated with a significant genetic effect on the end-diastolic left ventricular internal diameter or on its fractional shortening as assessed by echocardiography. Genetic variation had a significant (p < 0.05) effect on left ventricular mass, but this could be attributed to the inheritance of body size. These data indicate that cardiac factors are not significantly involved in the inheritance of aerobic power and suggest that cardiac hypertrophy in athletes is secondary to training.