High-Intensity Interval Training vs Moderate-Intensity Continuous Training in Phase II Cardiac Rehabilitation

This randomized controlled trial will compare the effects of High-Intensity Interval Training (HIIT) and Moderate-Intensity Continuous Training (MICT) in patients undergoing Phase II cardiac rehabilitation after stable coronary artery disease or post-angioplasty. A total of 66 participants will be randomly assigned into two groups.

The HIIT group will perform treadmill-based interval exercise 3 times per week at 85-95% heart rate reserve with active recovery periods, while the MICT group will perform continuous treadmill exercise at 65-75% heart rate reserve for 30-45 minutes.

Primary outcomes include left ventricular ejection fraction (echocardiography), functional capacity (6-minute walk test), and lipid profile (LDL, HDL, triglycerides, total cholesterol) measured before and after intervention. Health-related quality of life (HRQoL) will also be assessed. The study aims to determine which exercise protocol produces greater improvement in cardiac and functional outcomes.

Inclusion criteria

• Adults aged 18-60 years.
• Diagnosed with stable coronary artery disease confirmed by angiography, stress testing, or echocardiography.
• Left ventricular ejection fraction ≥45%.
• Functional NYHA Class I or II.
• Medically cleared by a cardiologist to participate in exercise (including recent ECG or stress test if necessary).
• Lightly active lifestyle prior to study (not involved in structured exercise programs).

Exclusion criteria

• Unstable angina or recent myocardial infarction (within the past 6 weeks).
• Uncontrolled hypertension (systolic BP >180 mmHg or diastolic BP >110 mmHg).
• Severe valvular heart disease, arrhythmias, or left ventricular dysfunction (EF <35%).
• Musculoskeletal disorders (e.g., severe osteoarthritis, recent fractures, or surgeries) preventing safe participation in exercise.
• Neurological disorders affecting mobility or safe exercise (e.g., stroke, Parkinson's disease).
• Uncontrolled diabetes mellitus (HbA1c >9% or recent hypoglycemia).
• Any other condition judged by the investigator to make participation unsafe.