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THE EXERCISE INTENSITY DEBATE:
MAJOR SUPPORT FOR THE HEALTHFUL LIFE VIEWS AND RECOMMENDATIONS

(July 2003)

The goal of the Healthful Life Program - and this website in regard to health promotion and disease prevention - is to tell the public:

In the United States, there has been a concerted effort to demonstrate that casual or leisurely pace walking will provide the same health benefits, the same reduction in coronary heart disease and heart attack occurrence as more vigorous activities. Multiple studies have made that claim.

In reviewing those studies, we have pointed out inconsistences in the data presented, as well as differences in the exercisers as contrasted with the non-exercisers in other respects that could have accounted for the results no matter how hard the authors tried to "adjust" for those differences. We have also pointed out that there are many good studies that find that heart disease and heart attack rates are only lowered by doing at least moderately vigorous physical activity regularly.

The physical activity intensity is measured in METs. A MET is the energy burned or the oxygen consumed at rest. Two METs is double that energy usage - slow walking is a 2 MET intensity; so walking for an hour at that pace provides 2 MET-hours of physical activity. Moderately vigorous activity requires greater than 3 MET intensity - walking one mile every twenty minutes is a 3.5 METs pace. Jogging at a moderate pace is about a 6 MET intensity.

CLICK HERE for tables of METs values indicating intensity for physical activities at work, in the home, and recreationally.

We have urged a goal of at least 12 MET-hours per week (the sum of all activities, multiplying the intensity by the hours of each activity per week) of moderately vigorous or vigorous activity in order to achieve health benefits; those benefits include not only reduced risk of heart attacks, but also some reduced risk of bowel and breast cancer. Physical activities at work, at home, and recreationally all count.

We have said that, if you cannot for any reason achieve the goals of moderately vigorous activities, do less, but do what you can, and try not to be sedentary. And, we have said that less than 10 to 12 MET-hours a week of at least moderately vigorous activity might or might not have health benefits.

(See the Human Tune-Up or the Archives under "exercise and health" for our physical activity recommendations).

The bandwagon for doing mild to moderate physical activities (less than moderately vigorous) has been on a roll; Healthful Life has not felt the evidence for less than moderately vigorous exercise was persuasive. Now, a study from Wales gives strong support to our views. Almost 2,000 men ages 40 to 64 were followed for ten years, during which time 252 of the men died, most from heart disease. There was no evidence that either light or moderate physical activity (walking at leisurely or normal pace, bowling, playing golf, etc) reduced the risk of dying from heart attacks. More vigorous activity - jogging, swimming, walking at a brisk pace for one hour at a time, hiking, etc did reduce heart disease death rates.

This study (which we will review in detail subsequently) is by no means the last word. There are still plenty of experts who will insist less strenuous physical activity has similar health benefits. But, this study, as well as others, is a clear warning - we should not be glib about assuring people of the health benefits of mild to moderate physical activity. Moderately vigorous and vigorous physical activities clearly have health benefits (reduced risk of heart attack, reduced risk of some cancers), but the health benefits of less strenuous activity are not clear - there may or may not be some. Still, less strenuous physical activity could have health benefits (particularly for older persons), and may also help with weight control, and is surely better than being sedentary.

There are lots of benefits, both physical and mental, from exercise. But, it is critical to emphasize that the most important disease prevention actions in regard to coronary heart disease, heart attacks, and bowel and breast cancer are the following:

For coronary heart disease and heart attacks:

  Not smoking
  Keeping cholesterol levels in desirable range
  Keeping blood pressure in lower part of the normal range
  Keeping high-density lipoprotein cholesterol (HDL - good cholesterol) in a desirable range
  Avoiding overweight - at the very least not allowing yourself to become more than 20 percent over ideal   weight

For bowel cancer: Starting at age 45 (our recommendation) or age 50 (the recommendation of others)

  Regular bowel examinations - either full colonoscopy every ten years or alternatively left-sided bowel   examination (sigmoidoscopy) every five years plus annual examination of stools for blood (hemoccult   test)

For breast cancer: Annual mammogram starting at age 40.

Those are the bedrock recommendations. For each of the diseases, there are other actions that can be added (see Archives under each category), including physical activity, but those listed above are the basic prevention actions for those three diseases and are what every adult should be doing to help them increase their chances of leading longer, healthier lives.

(One possibility Healthful Life will be exploring is that, for older persons, over ages 60 or 65, less strenuous activities may have health benefits, whereas, for younger persons, at least moderately vigorous activities are required.)