Purpose: This study examines the contribution of genetic factors to submaximal aerobic performance phenotypes measured before and after 20 wk of endurance training.
Methods: Submaximal oxygen consumption (VO(2)) at three power outputs, 50 W (VO(2)50W), 60% (VO(2)60%) and 80% (VO(2)80%) of VO(2max) and power outputs at 60% (PO60%) and 80% (PO80%) of VO(2max) were measured during cycle ergometer exercise tests in 483 subjects from 99 white families participating in the HERITAGE Family study. The baseline phenotypes were adjusted for the effects of age, sex, and body mass using stepwise multiple regression procedures. The response phenotypes, computed as the difference (Delta) between the posttraining and baseline measures, were adjusted for age, sex, and the baseline value.
Results: All submaximal exercise phenotypes measured at baseline and in response to training were characterized by a significant familial resemblance. Maximal heritabilities of the baseline phenotypes range from 48% to 74% with significant spouse, sibling, and parent-offspring correlations. The hypothesis of maternal inheritance where mother-offspring and sibling correlations were forced to be equal was found to fit the data for VO(2)60%, VO(2)80% and PO80%. For the response phenotypes, the maximal heritabilities tended to be lower (23--57%) with a significant maternal inheritance for Delta VO(2)60%, Delta PO60%, and Delta PO80%.
Conclusion: These results suggest that the submaximal working capacities of sedentary subjects and their responses to endurance training are influenced by familial/genetic factors with a significant contribution of maternal inheritance.