Impact of lifelong exercise "dose" on left ventricular compliance and distensibility

Abstract

Background: Sedentary aging has deleterious effects on the cardiovascular system, including decreased left ventricular compliance and distensibility (LVCD). Conversely, Masters level athletes, who train intensively throughout adulthood, retain youthful LVCD.

Objectives: The purpose of this study was to test the hypothesis that preservation of LVCD may be possible with moderate lifelong exercise training.

Methods: Healthy seniors (n = 102) were recruited from predefined populations, screened for lifelong patterns of exercise training, and stratified into 4 groups: "sedentary" (<2 sessions/week); "casual" (2 to 3 sessions/week); "committed" (4 to 5 sessions/week); and "competitive" Masters level athletes (6 to 7 sessions/week). Right heart catheterization and echocardiography were performed while preload was manipulated using lower body negative pressure and rapid saline infusion to define LV pressure-volume relationships and Frank-Starling curves.

Results: Peak oxygen uptake and LV mass increased with escalating doses of lifelong exercise, with little change in systolic function. At baseline, LV distensibility was greater in committed (21%) and competitive (36%) exercisers than in sedentary subjects. Group LV stiffness constants (sedentary: 0.062 ± 0.039; casual: 0.079 ± 0.052; committed: 0.055 ± 0.033; and competitive: 0.035 ± 0.033) revealed: 1) increased stiffness in sedentary subjects compared to competitive athletes, whereas lifelong casual exercise had no effect; and 2) greater compliance in committed exercisers than in sedentary or casual exercisers.

Conclusions: Low doses of casual, lifelong exercise do not prevent the decreased compliance and distensibility observed with healthy, sedentary aging. In contrast, 4 to 5 exercise sessions/week throughout adulthood prevent most of these age-related changes. As LV stiffening has been implicated in the pathophysiology of many cardiovascular conditions affecting the elderly, this "dose" of exercise training may have important implications for prevention of cardiovascular disease.

Keywords: aging; diastolic function; distensibility; exercise training; hemodynamics; ventricular compliance.

Figure 1. Normalized Peak VO₂ by Group

Peak VO₂ increased with increasing doses of lifelong exercise.

Figure 2. Group-averaged Frank-Starling Relationships

Competitive exercisers showed a statistically significant increase in stroke volume index at baseline compared to sedentary subjects and casual exercisers. Solid circles = sedentary subjects; open circles = casual exercisers; solid triangles = committed exercisers; open triangles = competitive exercisers.

Figure 3. Group-Averaged Preload Recruitable Stroke Work

This index of Left ventricular systolic function was similar between groups. Solid circles = sedentary subjects; open circles = casual exercisers; solid triangles = committed exercisers; open triangles = competitive exercisers.

Figure 4. Group-Averaged Transmural Pressure–Volume Relationships

Transmural end-diastolic pressure–volume relationships as determined by right heart catheterization (pulmonary capillary wedge pressure-right atrial pressure) and echocardiography (left ventricular volume) for sedentary subjects (open circles), casual exercisers (solid circles), committed exercisers (open triangles), and competitive exercisers (solid triangles). Data are mean group ± SEM (horizontal bars = volume; vertical bars = pressure) with best curve fit as described in the text. The disparities between groups persisted with the use of transmural pressures, confirming that differences in compliance and distensibility noted in the group-averaged left ventricular pressure volume relationships were attributable to myocardial properties rather than extracardiac factors such as pericardial constraint.

Central Illustration. Group-Averaged Left Ventricular Pressure–volume Relationships

Left ventricular end-diastolic pressure–volume relationships are shown as determined by right heart catheterization (pulmonary capillary wedge pressure) and echocardiography (left ventricular volume) for sedentary subjects (open circles), casual exercisers (solid circles), committed exercisers (open triangles), and competitive exercisers (solid triangles). Data are mean group ± SEM (horizontal bars = volume; vertical bars = pressure), with best curve fit through these data points as described in the text. Data points correspond to 2 levels of lower body negative pressure (LBNP, i.e., lowest pressure and volume), 2 baseline data points (third and fourth data points from below), and 2 saline infusions (2 highest pressures and volumes). Note the leftward shift and steeper slope of curve for the sedentary and casual exercisers, reflecting a stiffer, less distensible ventricle in comparison to the rightward shift and flatter slope of curve for the committed and competitive exercisers, reflecting a more distensible and compliant ventricle. Committed exercisers demonstrated improved ventricular compliance and distensibility compared to that in casual exercisers and sedentary subjects, almost matching those achieved by competitive exercisers.