Cardiovascular Risk of High- Versus Moderate-Intensity Aerobic Exercise in Coronary Heart Disease Patients

Study Questions:

What is the relative risk and benefit of exercise intensity on cardiovascular events in persons undergoing cardiac rehabilitation?


The authors examined the risk of cardiovascular events occurring during organized high-intensity interval exercise training and moderate-intensity training among 4,846 coronary heart disease (CHD) patients in four Norwegian cardiac rehabilitation centers. High-intensity exercise training sessions were performed as interval training with 4-minute intervals with the aim to reach an intensity of 85-95% of heart rate (HR) peak with lower level at 50-70% HR peak. Moderate-intensity exercise sessions were performed at approximately 60-70% of HR peak. All sessions included a warm up and cool down. An adverse event related to exercise training was defined as cardiac arrest or acute myocardial infarction during exercise, or within the first hour afterwards.


Of the 4,846 participants, 70% were men and mean age was 57.8 years. Reason for referral included myocardial infarction (MI) (7%), angioplasty (40%), coronary surgery (35%), valve surgery (11%), and heart failure (7%). The average number of sessions was 37 per participant. Of a total of 175,820 exercise training hours where all patient performed both types of training, there was one fatal cardiac arrest during moderate-intensity exercise (129,456 exercise hours), and two nonfatal cardiac arrests during high-intensity interval exercise (46,364 exercise hours). There were no myocardial infarctions in the data material. As the number of high-intensity training hours was 36% of the number of moderate-intensity hours, the rates of complications to the number of patient-exercise hours were 1 per 129,456 of moderate-intensity exercise, and 1 per 23,182 of high-intensity exercise.


The risk of a cardiovascular event is low after both high-intensity exercise and moderate-intensity exercise in a cardiovascular rehabilitation setting. Considering the significant cardiovascular adaptations associated with high-intensity exercise, such exercise should be considered among CHD patients.


Exercise performed at higher relative intensities elicits greater increase in aerobic capacity and greater cardioprotective effects (e.g., blood pressure, lipids, glycemic) than exercise at moderate intensities. Current guidelines for cardiac rehabilitation or secondary prevention programs are to perform moderate exercise between 60-70% of peak HR. Vigorous exertion increases the likelihood of acute MI and sudden cardiac death, especially in sedentary persons with occult or manifested CHD performing irregular vigorous physical activity. While this study suggests the risk of death and MI during high level interval cardiac rehab training is low, it should be noted that only 7% of the patients had an MI, the fitness of the Norwegian patient may be better than most, patients self-selected the exercise protocol, and the safety of interval training in CHD and other cardiovascular disease over the long-term is not established.

Clinical Topics: Arrhythmias and Clinical EP, Diabetes and Cardiometabolic Disease, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Prevention, Atherosclerotic Disease (CAD/PAD), Implantable Devices, SCD/Ventricular Arrhythmias, Acute Heart Failure, Interventions and Coronary Artery Disease, Exercise

Keywords: Exercise Tolerance, Coronary Artery Disease, Myocardial Infarction, Referral and Consultation, Exercise, Rehabilitation Centers, Blood Pressure, Risk Factors, Heart Arrest, Angioplasty, Heart Rate, Death, Secondary Prevention, Blood Glucose, Heart Failure, Cardiovascular Diseases

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