Effectiveness of Low -Versus High -Volume High -Intensity Interval Training in Patients With Chronic Heart Failure

Inclusion Criteria: 1. Chronic stable heart failure patient with reduced ejection fraction (EF \<40) 2. Age Above 18 years old 3. Both males and females 4. The ability to provide informed consent Exclusion Criteria: 1. Based on the Scientific Statement from the American Heart Association: contraindications for exercise Testing and Training. (Fletcher et al., 2013) 1. Acute myocardial infarction (MI), within 2 days 2. Ongoing unstable angina 3. Uncontrolled cardiac tachy or brady arrhythmia with hemodynamic compromise 4. Active endocarditis 5. Symptomatic severe aortic stenosis 6. Decompensated heart failure 7. Acute pulmonary embolism, pulmonary infarction, or deep vein thrombosis 8. Acute myocarditis or pericarditis 9. Acute aortic dissection 10. Physical disability that precludes safe and adequate testing or training 11. Known obstructive left main coronary artery stenosis 12. Hypertrophic obstructive cardiomyopathy with severe resting gradient 13. Recent stroke or transient ischemic attack 14. Mental impairment with limited ability to cooperate 15. Resting hypertension with systolic or diastolic blood pressures \>200/110 mmHg 16. Uncorrected medical conditions, such as significant anemia, important electrolyte imbalance, and hyperthyroidism 2. Acute decompensated heart failure NYHA class IV