Researchers tracked 4,846 patients with coronary heart disease at 4 Norwegian cardiac rehabilitation centers. The cardiac rehab involves follow-up medical and lifestyle care to help people recover from a heart attack, heart failure or a heart surgery. All patients in the study participated in moderate-intensity training and organized high-intensity interval exercise training.
The moderate-intensity workout included one hour of walking or other exercise that resulted in exertion at about 60-70 percent of people's maximum heart rate.
For intense workout, people trained with repeated 4-minute intervals: 4 minutes of high impact exercise, such as cycling, jogging or cross country skiing, to get the heart rate up to 85-95 percent of maximum exertion, followed by 4 minutes of a more relaxed activity, such as walking.
It was found that a total of 129,456 hours were spent on working out at moderate intensity with one person died from cardiac arrest and 46,364 hours at high intensity with 2 cardiac arrests but survived.
Apparently, the findings indicated that the risk of a cardiovascular event is low after both high-intensity exercise and moderate-intensity exercise in a cardiovascular rehabilitation setting.
Nevertheless, the differences in the number of cardiac arrests during moderate and intense exercise were too small to conclude that the intense workout is as safe as the moderate workout.
As such, it is not recommended for cardiologists to broadly prescribe intense workout for heart disease patients. People should still stick to their prevailing guidelines by doing moderate workout until more data showing that intense workout are safe.