(Second of two parts)
In my last column, I presented a case in favor of moderate exercise as an effective means to improving your health. Moderate exercise burns calories, which helps with weight management, and it especially helps reduce fat around the midsection – a prime site for health-destroying activities in the body. Moderate exercise also promotes insulin sensitivity. This counteracts insulin resistance, which leads to type 2 diabetes.
Moderate exercise is more comfortable and convenient than vigorous exercise, but it takes longer to achieve similar outcomes as far as burning calories is concerned. Let’s do the math. A brisk walk will burn about 100 calories per mile for an adult male and about 80 calories for an adult female (20 percent less because females are smaller and have less muscle mass). Jogging will burn more calories per minute, because you will jog the mile more quickly and will burn about 120 calories per mile.
So the question becomes am I better off to walk three miles in one hour and burn 300 calories, or jog 2.5 miles in less than half the time and burn the same number of calories? When it comes to weight management and insulin sensitivity, it doesn’t matter, so the choice is up to you. But additional health benefits can be yours from jogging and other fitness-producing exercises.
If you are willing to bite the bullet and engage in fitness-producing exercise, you will achieve all of the benefits associated with moderate exercise, plus a few more. Take blood pressure, for example. Moderate exercise can help lower blood pressure indirectly by reducing body fatness and increasing insulin sensitivity. Vigorous exercise does the same, but it also has a direct effect on the vessels that control blood pressure.
This means a much greater overall impact to lower blood pressure. The same is true for raising HDL, the good cholesterol. Vigorous exercise exerts a direct effect on HDL, which is more powerful than the indirect effect of moderate exercise.
Vigorous exercise stresses the heart muscle much more and causes adaptations that do not occur with moderate exercise. There is the proliferation of stress proteins in heart muscle cells, which can lessen the severity of a heart attack. Stress proteins help protect heart cells when an artery is blocked, because they can keep heart cells alive longer even though oxygen is denied. Stress proteins also help heart and muscle cells cope with excessively high body temperatures that can occur during exercise on a hot day or as a result of an excessively high fever.
Another unique benefit of vigorous exercise is nitric oxide production in the arterial wall. Nitric oxide is a powerful vasodilator (it expands the diameter of vessels), which lets more blood flow through vessels and reach hungry tissues.
Moderate and vigorous exercise relieve stress. But vigorous exercise may be more effective in creating a physiological effect as well as a psychological effect (change of scenery, getting your mind off what’s bothering you, etc.). After a demanding workout, the muscles are more relaxed, and chemicals released into the bloodstream help promote a sense of well-being.
Research is clear about how much vigorous exercise is needed to increase fitness. Assuming the exercise involves major muscle groups in the body (principally the legs and trunk), the heart rate must be elevated into the target zone. Minimally, this is 70 percent of the maximum heart rate (220 minus your age equals your maximum heart rate). For a 20-year-old, the target zone is 140 beats per minute. Once elevated, the heart rate must be sustained at the high level for at least 20 minutes continuously, and exercise must be performed at least three times a week, and preferably four.
The bottom line
Exercise does not follow a one-size-fits-all model. On the contrary, there is an exercise strategy for everyone.
If a comfortable and convenient brisk walk fits nicely into your lifestyle, that’s fine. If you find the additional health benefits associated with vigorous exercise attractive and are willing to pay the price required by exercises like jogging, go for it.
You also could opt for something in between, like interspersing jogging intervals into your walks. This may bestow at least some of the additional health benefits associated with vigorous exercise.
Bryant Stamford is professor and chairman of the department of exercise science at Hanover College in Hanover, Ind. Address questions or suggestions to “The Body Shop,” The Courier-Journal, P.O. Box 740031, Louisville, Ky. 40201-7431.