Well ,at least one recent research paper answered that question in the affirmative.
Dr. Nole and colleagues (see below for reference) did a detailed study on the effects of endurance and resistance exercise on a small group of patients, some of who only had diastolic dysfunction (DD) and others who in addition had heart failure (HF) with preserved ejection fraction.
For purposes of the study normal diastolic function was defined as having: the following echocardiographic findings 1) E/A greater than one,2)E/e prime less than 10 and 3) preserved E/A greater than one during the valsalva maneuver.The E/A ratio is the ratio of early diastolic filling of the ventricle to the late filling (aka atrial kick).The E/e prime ratio is the ratio of velocity of early diastolic filling to the movement of the mitral value annulus as determined by tissue Doppler and is thought to be a reasonable estimate of the pulmonary capillary pressure,but not under all conditions including Left bundle branch block.
See here for the full text article.
Basically the exercise program which was mainly endurance training with some resistance exercise added later in the program lead to improvement in symptoms in those who were symptomatic and in indices of diastolic function as determined by cardiac echos.
Other studies have also demonstrated that exercise training can improve diastolic function.I have commented before about the effects of long time endurance exercise and the possible mitigation of age related diastolic dysfunction.
The other site of improvement in exercise capacity resulting from an exercise program is improvement in the A-V 02 difference and several studies have indicated that it is that aspect of physiology that improves in HF patients who benefit from endurance exercise.This is the first paper I have seen that suggests that the heart benefits as well.
.W , , , , , , , , , , , and (2014) Effects
of long-term endurance and resistance training on diastolic function,
exercise capacity, and quality of life in asymptomatic diastolic
dysfunction vs. heart failure with preserved ejection fraction, ESC Heart Failure, 1, pages 59–74, doi: 10.1002/ehf2.12007