**8. Patients with heart failure**

Chronic HF consists of exertional dyspnea and fatigue in the setting of HFrEF (*i.e.*, systolic dysfunction), a preserved left ventricular ejection fraction (HFpEF, *i.e.*, diastolic dysfunction), or a combination of the two. The prevalence of HF is increasing such that decompensated HF is the single most common admitting diagnosis and results in more than 1 million hospitalizations annually [35]. 25% of patients are readmitted within a month and 66% within one year of their initial HF hospital admission [36]. The merits of exercise training in patients with HFrEF include improved clinical outcomes (*e.g.*, hospitalizations) and health-related quality of life [37]. Exercise also helps to augment capacity of exercise (10–30%, as measured by O2peak), central hemodynamic function, autonomic nervous system function, and peripheral vascular and skeletal muscle function in patients with HFrEF. These adaptations help patients to exercise to an increased peak work rates or exercise at a suboptimal level with a lower HR, less perceived effort, and less dyspnea and fatigue. Emerging data indicates that patients with HFpEF also benefit from exercise training, as evidenced by improved skeletal muscle function, quality of life, and exercise capacity [38].
