Date of Award

December 2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Exercise Science

Advisor(s)

Kevin S. Heffernan

Subject Categories

Medicine and Health Sciences

Abstract

Endurance exercise typically leads to beneficial cardiac adaptations manifested as increased cardiac mass, higher cardiac function and lower central hemodynamic load (blood pressure, aortic stiffness and wave reflections). However, studies in male marathoners suggest detrimental cardiac remodeling, such that larger cardiac mass is associated with reduced cardiac function and higher central hemodynamic load. There are well-established sex differences in cardiac adaptations to endurance exercise and central hemodynamics across the lifespan. Whether there are sex differences in cardiovascular adaptations in marathoners requires further scrutiny. We examined sex differences in 1) Left ventricle (LV) structure, 2) LV function 3) 24-hour central hemodynamic load and 4) ventricular-vascular coupling in marathon runners and recreationally active adults. LV structure and function were measured using 3-dimensional echocardiography (3DE). LV mass index (LVMI) was used as an index of LV structure. LV longitudinal (LS) circumferential (CS), area (AS), and radial strain (RS) were used as indices of LV function. An ambulatory oscillometric blood pressure (BP) cuff was used to measure 24-hour hemodynamic load after a non-exercise control day and following a 30-minute run/walk. 24-hour hemodynamic load was comprised of brachial and aortic BP, aortic stiffness measured as pulse-wave velocity (PWV) and pressure from wave reflections. Measures from central hemodynamics and 3DE were combined to derive the ratio of arterial elastance (Ea) to ventricular elastance (Elv) as a global measure of ventricular-vascular coupling. Our findings suggest that although female marathoners had larger LVMI they did not have LV dysfunction or increased central hemodynamic load and had better overall ventricular-vascular coupling. Furthermore, chronic marathon training and racing does not appear to be associated with LV dysfunction, or increased central hemodynamic load in otherwise healthy middle-aged men and women.

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Open Access

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