Females have a blunted cardiovascular response to one year of intensive supervised endurance training

Cross-sectional studies in athletes suggest that endurance training augments cardiovascular structure and function with apparently different phenotypes in athletic males and females. It is unclear whether the longitudinal response to endurance training leads to similar cardiovascular adaptations between sexes. We sought to determine whether males and females demonstrate similar cardiovascular adaptations to 1 yr of endurance training, matched for training volume and intensity. Twelve previously sedentary males (26 ± 7, n = 7) and females (31 ± 6, n = 5) completed 1 yr of progressive endurance training. All participants underwent a battery of tests every 3 mo to determine maximal oxygen uptake (Vo_2max) and left ventricle (LV) function and morphology (cardiac magnetic resonance imaging). Pulmonary artery catheterization was performed before and after 1 yr of training, and pressurevolume and Starling curves were constructed during decreases (lower-body negative pressure) and increases (saline infusion) in cardiac volume. Males progressively increased Vo_2max, LV mass, and mean wall thickness, before reaching a plateau from month 9 to 12 of training. In contrast, despite exactly the same training, the response in females was markedly blunted, with Vo_2max, LV mass, and mean wall thickness plateauing after only 3 mo of training. The response of LV end-diastolic volume was not influenced by sex (males +20% and females +18%). After training Starling curves were shifted upward and left, but the effect was greatest in males (interaction P = 0.06). We demonstrate for the first time clear sex differences in response to 1 yr of matched endurance training, such that the development of ventricular hypertrophy and increase in Vo_2max in females is markedly blunted compared with males.