Abstract Body (Do not enter title and authors here): Background: Very high level, lifelong aerobic exercise results in lower ventricular stiffness and left ventricular wall stress (LVWS) LVWS is an important predictor of future heart failure risk. To what degree LVWS changes with various doses of lifelong aerobic exercise is unknown.

Objective: The purpose of this study was to determine the impact of lifelong exercise on LVWS.

Methods: Seniors (n = 58) who consistently participated in lifelong patterns of exercise training were recruited and categorized into 3 groups: “sedentary” (<1 exercise sessions/week); “moderate” (2 to 3 sessions/week); and “active” (4 to 7 sessions/week). Right heart catheterization and echocardiography were performed at baseline (x 2; once before lower body negative pressure (LBNP) and again before saline infusion) and while manipulating preload using LBNP (-15 mmHg suction) and rapid normal saline (NS) infusion (15 mL NS/kg). LVWS was calculated from pulmonary capillary wedge pressure (PCWP) and LV wall thickness and radius using Law of Laplace and expressed in Pascals (Pa). Strain was calculated using (V−Vmin)/Vmin, where Vmin was the smallest end-diastolic volume measured (during LBNP) and V was the volume during each condition.

Results: LVWS increased as preload increased. As shown in the figure, peak LVWS during saline load (top panel: sedentary 3.1 +/- 1.1 Pa, moderate 2.5 +/- 0.7 Pa, active 2.3 +/- 0.5 Pa) and stress-strain slopes (sedentary 12.3 +/- 10.3, moderate 6.5 +/-4.1, active 5.7 +/- 2.7 Pa) were highest in sedentary seniors compared to seniors in the moderate (p=0.008) and active groups (p=0.006).

Conclusions: In healthy, older individuals, lower LVWS was apparent even with lifelong, moderate levels of physical activity (2 to 3 sessions/week) and similar to those who exercised at more frequent levels (4-7 times per week). Exercising 2 to 3 times a week may provide a sufficient “dose” to reduce LVWS, highlighting the benefits of even casual training on ventricular structure and potential to mitigate the lifetime risk of heart failure with exercise.