Influence of Heart Size and Sex on Cardiovascular Adaptations to Two Years of Endurance Exercise Training in Sedentary Middle-Aged Adults

Sedentary aging is linked to low cardiorespiratory fitness and the development of a small, stiff heart, which are important risk factors for developing heart failure with preserved ejection fraction (HFpEF). Endurance exercise training throughout life can maintain fitness and prevent myocardial stiffening from occurring; however, starting exercise training later in life is less effective. Reasons underlying the increased risk for HFpEF in females with low fitness remain unclear. Because older females with smaller, stiffer hearts appear to be more likely to develop HFpEF, we were interested in investigating whether sex or pretraining heart size affects how a heart responds to chronic aerobic exercise.

At #AHA25, we presented our results showing the changes in fitness and exercise-induced cardiac remodeling of 28 late-middle-aged adults (15 females, age: 54±5 yr) who were previously sedentary in response to two years of endurance exercise training. Male participants had a greater increase in cardiorespiratory fitness than female participants with training. However, both sexes experienced similar degrees of cardiac remodeling, as males and females had similar increases in left ventricular end-diastolic volume indexed to body surface area (LV EDVi) with the exercise intervention. Notably, participants of each sex with the smallest pretraining LV EDVi at rest experienced the greatest increase in EDVi with training.

Our results demonstrate that the improvement in cardiorespiratory fitness with endurance exercise training is influenced by sex but that the degree of cardiac remodeling associated with training in previously sedentary adults is not different between sexes nor impaired by having a smaller pretraining LV EDVi. Accordingly, a smaller baseline LV EDVi does not appear to limit the trainability of a sedentary person’s heart. These findings can help in exercise prescriptions and interventions to prevent HFpEF for both males and females, a key focus of our lab.