RecruitingPrecision Rehabilitation for Veterans With (HFpEF)This study is being completed because there is conflicting information regarding the value of monitored exercise in patients with heart failure with preserved ejection fraction (HFpEF). The purpose of this study is to collect baseline information necessary for researchers to pursue a larger study evaluating how monitored exercise performed during cardiac rehabilitation may improve heart health and the amount of oxygen delivered to the tissues during exercise. Researchers must first examine whether the facility is capable of supporting such a study and whether in a modest number of patients, there is no clear detrimental effect to exercise. Rather, there may be an important improvement that has been underestimated to date. Participation will require a time commitment for performing exercise 3 times per week for 12 weeks in addition to having a small amount of blood drawn twice. There will also be a specialized form of a stress test (cardiopulmonary exercise test; "CPET") with ultrasound imaging of the heart (echocardiography) completed twice.