Benefits of Exercise - Cardiovascular Disease

In this section, we deal with the impact of exercise on cardiovascular disease (disease of the heart and blood vessels that is caused by a blocking of the blood vessels, usually due to the buildup of plaque. It includes coronary heart disease and stroke). Reference 3 presents results of a study involving 180 post-menopausal women, aged 45 to 64, and 197 men aged 30 to 64. All of them have low HDL - less than 60 mg per deciliter in women and 45 mg per deciliter in men. Likewise, they have moderately elevated (per 1998 criteria) LDL - between 125 and 210 mg per deciliter in women and between 125 and 190 in men. The subjects were randomly assigned to 1) aerobic exercise, 2) the NCEP step 2 diet, 3) exercise + this diet, and 4) no intervention.

Perhaps the most interesting conclusion from this study is that the diet alone is ineffective! It resulted in no significant reduction in LDL or increase in HDL. The aerobic exercise involved an initial phase that involved one hour sessions three times a week. A 7-8 month maintenance phase followed, during which the participants performed aerobic activity equivalent to 10 miles a week of brisk walking or jogging. The results show that only a combination of exercise and diet make a real difference: men lowered their LDL by 20 points, and women lowered it by 14. HDL increased just very slightly (1-2 units). In order to translate this into actual risk reduction, we use the Framingham Risk Calculator Spreadsheet, and assume that the individuals are 55 years old, non smoking, blood pressure 130 mm Hg, unmedicated. Based on these assumptions, we calculate that the risk reduction is around 15% in the exercise + NCEP Step II diet.

Reference 4 presents results of a similar study. Like the previous study, exercise (this time - alone!) does improve cholesterol levels, raising HDL by 10% for high-intensity and high-amount of aerobic exercise (roughly jogging 20 miles / 32 kilometers per week), and dropping LDL by 1.5%. Hardly a dramatic improvement, and as a result of strenuous exercise that would be difficult for most people.

The direct relationship between cholesterol and heart disease risk has been questioned, as we have noted elsewhere on this site. Consequently, a more direct measurement of the effect of exercise on risk would be more meaningful. We present the results of such studies next.

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