Physical Activity, Cardiac and Skeletal Muscle Energetics in Healthy Subjects and HFpEF Patients

Inclusion Criteria: All Participants: * Women and men between the ages of 40 and 85 years, inclusive, at the Screening visit. * Women of childbearing potential require a negative pregnancy test. * Participants who are willing and able to comply with all scheduled visits, laboratory tests, lifestyle considerations, and other study procedures. * Capable of giving signed informed consent, which includes willingness to be compliant with the requirements and restrictions listed in the informed consent document and in this protocol. Healthy Participants Only : * Healthy participants with no history of diabetes mellitus, or significant heart or vascular disease, including a history of heart failure, myocardial infarction, revascularization or positive exercise tolerance test for ischemia (if previously performed). * BMI of 30.0 - 50.0 kg/m2, inclusive Heart Failure Participants Only: * Previous clinical diagnosis of heart failure with New York Heart Association (NYHA) Class II-IV symptoms at screening visit and present for at least 1 month. * Symptom(s) of HF requiring treatment with diuretic(s) for at least 30 days prior to screening * Left ventricular ejection fraction (EF) \>=50% by echocardiography, MRI, CT or x-ray or nuclear ventriculography at screening visit or within prior 12 months. * Patients with at least 1 of the following: * HF hospitalization (defined as HF listed as the major reason for hospitalization and treatment with diuretics) or outpatient diuresis visit …