We’ve heard it all before. Moderate exercise for at least 30 minutes a day, most days of the week, will lower our risk of coronary heart disease and improve our overall health. But for those of us who heeded the call, nagging questions remained: What type of exercise should I be doing? Am I doing enough? Is it possible that the 65-year-old man who walks a brisk three miles every day is exercising at the same intensity (and therefore getting the same healthful benefits) as I am, jogging along at a steady 10 minutes per mile? A recent study set out to examine the relationship between relative intensity of physical activity and the risk of developing coronary heart disease.

In a study published in the March 4, 2003 issue of the journal Circulation, theresearchers report that it isn’t what you do that matters—it’s the intensity (or effort) with which you do it.

About the Study

The study followed 7,337 men with an average age of 66 years from 1988 to 1993. In questionnaires sent to the men periodically, the researchers asked the men to report the activities they undertook and to rate their perceived level of exertion (nothing at all to maximal) and the frequency and duration of each activity. The men were also asked about any factors that might affect the relationship between their level of activity and coronary heart disease (e.g., height, weight, cigarette smoking, diet, high blood pressure , high cholesterol , diabetes, and any family history of premature death).

The study defined relative intensity as the energy required by a particular individual to complete an activity compared to his fitness level.

The men were also asked to report whether they had been diagnosed with myocardial infarction or angina pectoris, or had undergone coronary artery bypass grafting (CABG) surgery or coronary angioplasty .

The Findings

Eight percent of the men in the study rated their usual level of exertion during exercise as weak or less intense; 39% as moderate; 27% as somewhat strong; and 27% as strong or more intense.

The main finding from this study is that among older men, the higher a person’s perceived level of intensity, the lower their risk of developing coronary heart disease. This finding applied equally among men who exercised at high levels of intensity as well as men whose activity level was very low.

The relative risk of coronary heart disease among men who perceived their exercise exertion as moderate was 14% lower than those who rated their exercise level as weak or less intense. Men who perceived their exercise level as somewhat strong had a 31% lower risk compared to men who perceived their exercise level as weak or less intense, while men who perceived their workout as strong or more intense had a 28% lower rate.

Men who exercised at a higher perceived level of intensity had a lower risk of coronary heart disease than those who exercised at a lower relative perceived level of intensity even after the authors adjusted for age, body mass index (BMI), cigarette smoking, prevalence of hypertension , diabetes mellitus, early parental mortality, alcohol intake, and diet.

How Does This Affect You?

The findings of this study support the current recommendation to exercise moderately for at least 30 minutes a day, most days of the week as a means of lowering your risk of coronary heart disease. It also suggests that you are the best judge of what constitutes a moderate level of exercise for you. Therefore, for those approximately 30 minutes a day, you should choose an activity and an intensity level appropriate for your current age and health status. It also means the briskly walking 65-year-old man I jog past every morning may very well be exercising at the same intensity (or even higher) than I am.

As always, you should be sure to consult your physician before embarking on an exercise program of any kind.

Because the participants of this study were all men, it is unclear whether the results of this study apply to women.