• Adult patients with NYHA class II or III HF admitted to an MGH inpatient unit or outpatients at the MGH Heart Center. Investigators will enroll subjects who develop mild to moderate HF symptoms during activity but not at rest. NYHA class II/III HF patients comprise the majority of subjects in studies that identify links between physical activity and improved exercise capacity, QoL, and survival making them an ideal study population. HF diagnosis, clinical stability, and NYHA class will be clarified with the inpatient or outpatient cardiology team.