Tuesday, January 6, 2009

How Much Do I Have to Work Out?

That depends on what you plan to accomplish by working out. If your goal is to complete the Ironman Triathlon or compete in the Mr. Universe contest, then you know that you had better workout intensely and often. If, however, the goal of the exercise program is to raise your level of health somewhat, then the answer gets a little tricky.

The Standard
Most fitness professionals are still proponents of the standard recommendation: "exercise three or more times per week at a heart rate of 60-90 percent of maximum for at least twenty minutes." This certainly isn’t a bad recommendation, especially since it’s been well known for years that habitual inactivity is associated with increased death rates, but there is some very good data that suggests that surprisingly modest levels of physical activity will provide ample stimulus to improve overall health, lower chronic disease risk factors and increase longevity. In recent years, sedentary lifestyle has been elevated to the disease risk status comparable to other risk factors such as high blood cholesterol, blood pressure and cigarette smoking.

Modest Levels of Activity
In 1995, two very interesting articles were published on this topic in the Journal of the American Medical Association. The first sent shock waves through the fitness community when it announced that intense exercise wasn’t needed for health benefits. The article, which was co-authored by some of the most prominent researchers in health and fitness, suggested that if people could incorporate 30 minutes of total physical activity throughout the course of the day, the result would be a 12% decrease in mortality in the United States. The activity, the panel indicated, need not be structured, intense or even resemble "exercise" in any way. Such everyday activities as walking, gardening, taking the stairs, etc... are excellent candidates to get the total minutes of activity up to the recommended 30 per day.

The twenty member panel that came up with the recommendation was convened by the Centers for Disease Control and pointed to the growing body of research indicating that the health benefits of physical activity are linked principally to the total amount of activity performed. The panel’s recommendations were endorsed by the American College of Sports Medicine, but in no way should suggest that individuals who are currently performing more intense exercise should back off. What it does mean, however, is that even modest levels of physical activity, even if it isn’t intense enough to result in optimal fitness, has a strong positive influence in lowering the risk of many chronic diseases such as heart disease, high blood pressure, osteoporosis, certain cancers, diabetes, stress/anxiety and depression.

The Second Article
The second JAMA article seemed to contradict the first when it reported that health benefits and lifespan were advanced by vigorous, but not by moderate exercise. This study used data from the study of over 17,000 Harvard Alumni which just ten years previously had caused a stir when it reported significant health benefits of moderate physical activity. This particular study, however, classified participant’s exercise intensity by self-reports. Subjects categorized as vigorous exercisers were compared with a group that included both moderate and low intensity exercisers.

The well-known "law of diminishing returns" my have been at work here, resulting in the appearance of health benefits only in the vigorous exercise group. Previous research has shown convincingly that the health benefits of exercise are not as dramatic in intense exercisers when compared to the large gains that are possible in beginning exercisers. For example, in subjects who improve their fitness level from unfit to moderately fit, the decline in premature death is as much as 40 percent. In those exercisers who progress from moderate to high fitness, however, the decline in premature death rates is only about 15 percent.

And the Moral of the Story Is...
It is certainly a confusing issue, but the moral of the story is that small amounts of physical activity are better than nothing at all and that more intense exercise is even better than that. The distinction between optimal fitness and optimal health must be kept in mind. Health benefits can certainly be attained via modest intensity physical activity accumulated throughout the day (burning 2,000 calories per week is recommended), but fitness benefits must be obtained via higher intensity exercise more along the lines of the good old ACSM recommendations (20 minutes, 3x per week, at 60-90% of maximum heart rate).

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