PI relocated, unable to complete the study. No replacement PI identified.

The investigators will assess the efficacy and safety of utilizing high-intensity interval training in stable heart failure patients on functional outcomes. Specifically, an assessment of baseline peak oxygen uptake and peak cardiac output will be assessed before and 8 weeks after intense interval training. Measurements of quality of life will be assessed before and after training as well as the number of arrhythmic events before and after training. The control group will be a group that will follow a moderate exercise training protocol over a similar period.

Aerobic exercise training of moderate intensity is recommended as safe and effective for all stable outpatients with chronic heart failure who are able to participate in improving physical conditioning. Emerging data suggest that high-intensity exercise training in select heart failure patients may achieve even greater improvement in functional capacity than moderate intensity training leading to a better quality of life. In the few studies to date, aerobic capacity, heart function is increased to a better extent in heart failure patients that undergo an eight-week high-intensity exercise program (32 exercise sessions) compared to the standard of care. The goal of this pilot study is to collect data on safety and efficacy of high-intensity interval training in stable heart failure patients to demonstrate better physiological and clinical outcomes with fewer long-term health care costs compared to the standard of care. Twenty participants with stable heart failure (age range = 40 to 65 years of age) will be randomized into two different groups: the standard of care group, in which subjects will exercise for 40 minutes at 40 to 60 % of heart rate reserve (HRR) for eight weeks (32 sessions); and the high-intensity interval training group, in which subjects will perform four sets of 4-minutes at > 85% of HRR, with three minutes of active rest between intervals, for six weeks (32 sessions). The functional outcomes measured will be cardiac function (i.e. stroke volume, cardiac output, ejection fraction), pulmonary function (diffusing capacity, lung volumes, spirometry), exercise capacity (peak oxygen uptake) at rest and during exercise before and after eight weeks of exercise training (32 sessions). Adverse events related to each exercise training session (i.e. cardiac arrest, myocardial infarction during exercise, or within the first hour afterward) as well as arrhythmias will be recorded via Holter monitoring 24-hrs post-exercise. Quality of life will also be measured. The exercise training will be supervised at Grady Hospital. This novel approach has the chance to become impactful to these patients and will challenge the current negative perception of high-intensity exercise training in this patient population. The investigators anticipate this study will help reform the current exercise guidelines in these participants.

Inclusion Criteria:

1. Stable, chronic heart failure with a left ventricular ejection fraction of 20 to 40%.
2. New York Heart Association (NYHA) class I to III symptoms with treatment that includes beta-blocker and angiotensin-converting enzyme (ACE) inhibitor and angiotensin receptor blocker (ARB) Therapy for at least eight weeks prior to exercise training if ejection fraction is < 35%.
3. No recent major cardiovascular hospitalizations or procedures within the previous three months.
4. Age 40-65 years
5. Aerobic capacity ≥ 12 mL/kg/min.
6. Subjects with an implantable cardioverter defibrillator (ICD) are also included.
7. Subjects with right ventricular systolic pressure ≤ 60 mmHg at rest.

Exclusion Criteria:

1. Inability to exercise (orthopedic or neurological problems).
2. History of seizure disorders.
3. History of atrial fibrillation or ventricular tachycardia in the past 3 months.
4. Implantable cardioverter defibrillator shocks due to atrial fibrillation or ventricular fibrillation within the past 3 months.
5. Presence of pacemaker.
6. Uncontrolled diabetes mellitus.
7. Diabetic insulin pump.
8. Uncontrolled hypertension.
9. Renal insufficiency (creatinine: > 2.5 mg/dl).
10. Severe left ventricular hypertrophy (> 1.8 cm wall thickness) or dynamic left ventricular outflow tract obstruction.
11. Greater than mild degree of valve stenosis or presence of an artificial heart valve.
12. Drug addiction.
13. Not being able to read and understand the consent form.
14. Signs of unreliableness.