Half of heart failure patients have preserved ejection fraction (HFpEF). Like patients with reduced ejection fraction (HFrEF), HFpEF patients suffer from exercise intolerance (low VO2max), which reduces physical function, quality of life, and survival. Strikingly, there is no medication proven to increase survival for HFpEF patients. Whereas exercise intolerance in HFrEF patients is the result of cardiovascular limitations, physical dysfunction in HFpEF patients is largely the result of peripheral abnormalities in skeletal muscle. Indeed, research in HFpEF patients identified that physical function and VO2peak are directly related to leg lean mass, and drugs focused on improving cardiovascular function have failed to improve VO2peak. Unfortunately, no therapy has been identified for this population that can concurrently improve cardiovascular and muscle health. The need for improved muscle therapies is reinforced by the fact that HFpEF patients are commonly older adults who are predisposed to muscle wasting. Strategic essential amino acid (EAA) ingestion has been shown to improve the adaptive response of muscle to exercise. Therefore, the investigators will determine, in HFpEF patients, the extent to which ingesting a strategic mixture of EAAs during an acute aerobic exercise training program enhances the response to this exercise strategy.