Intervals Better Than Aerobics For Heart?

Jade Teta ND, CSCS

A January 2009 article in the Journal of the American College of Cardiology adds to the growing evidence that high-intensity interval training may be more beneficial to the heart than continuous moderate intensity exercise. In this study they looked at the response of a high fat meal (HFM) on blood vessel function. It is a well established fact that a meal high in fat, like the cheese pizza used in this study (we could argue it is the fat & starch not just the fat), produces unfavorable changes in what is called endothelial (pronounced EN-DOE-THEE-LEE-AL) function. This is a fancy term that relates to the tiny cells lining our blood vessels that react to chemical signals and changes in blood pressure to help the blood vessel respond appropriately. Decreased endothelial function is a major contributing factor to atherosclerosis and heart disease. Eating a high fat meal/high carb meal creates unfavorable changes in this system for several hours.

In this study researchers looked at the effect of doing different types of exercise 16 to 18 hours prior to the meal. In past studies, continuous aerobic exercise prior to a high fat meal decreased some of the negative effects. This study compared a continuous aerobic exercise protocol of running at 60-70% of maximum heart rate (MHR) for 47 minutes to an interval training workout involving four 4-minute bouts of exercise at 85-95% of MHR with each bout separated by 3 minutes of rest at 50-60% MHR. The two exercise sessions were equal in terms of the number of calories burned. There was also a group that did no exercise.

This study also looked at antioxidant release generated by exercise as well as artery diameter studies. By studying whether an artery dilates (gets bigger) with exercise, we can see how well blood flow is maintained. In other words, it is a good thing if the arteries stay open and reactive. The study also measured shear rate which is basically how much pressure the moving blood is exerting on the artery walls which can cause damage.

In this study the no exercise group and the continuous exercise group saw decreases in artery diameter and increased shear rates. The high-intensity interval training was able to protect the body from these effects causing the arteries to remain open and suffer very low shear rates. In regard to endothelial dependent vascular function, the continuous exercise protocol decreased the negative impact of the high fat meal but was not able to completely protect the blood vessel wall. The high intensity interval training on the other had was not only able to completely protect the artery wall from the effects of the high fat meal, but it actually increased the activity of the endothelial cells not only reversing, but improving function.

This study hints that high intensity interval training may be superior to continuous aerobic exercise in addressing one of the key underlying factors involved in the induction and progression of cardiovascular disease. Another novel finding in this article is that high intensity interval training was shown to greatly enhance, to a significant degree, the the production of antioxidants by the body. Again it outperformed continuous aerobic exercise in this regard. This study and others like it are beginning to show that high-intensity interval exercise is not only great for changing body composition but may also excel at protecting the heart.

Tyldum, Et. Al. Endothelial dysfunction induced by post prandial lipemia: complete protection afforded by high-intensity aerobic interval exercise. Journal of the American College of Cardiology. January 2009;53(2): 200-206.