Inclusion Criteria:  NYHA functional class I-IIIb. LVEF < 40%. Clinically-stable for > 3 months [no change in disease status or medication]. Willing and able to provide written informed consent and perform cycle-ergometer or treadmill based exercise.  Exclusion Criteria:  NYHA class IV HF. Diagnosis of diastolic HF. Comorbidities such as obesity (BMI >36), uncontrolled systemic hypertension, type 2 diabetes, and COPD (FEV1 <50%). Musculoskeletal or other conditions that would limit exercise participation. Pregnant or nursing women