Answer to Question 1
Reviews of the evidence of physical activity and cancer prevention from epidemiological studies reveal that exercise is associated with an average 20 to 30 reduction in risk of cancers of the breast and a 30 to 40 of the colon; each hour of weekly physical activity is associated with a 6 lower risk of breast cancer. There is some evidence that ongoing physical activity may reduce breast cancer risk through promoting an increase in apoptosis (cellular death) of tumor cells and through reducing circulating estrogen levels; changes in estrogen metabolism can result in a decrease in breast epithelial cell proliferation. However, more research is needed to determine the exact mechanisms responsible for exercise-related breast cancer prevention.
Answer to Question 2
Aerobic exercise is the type of exercise with the largest body of supportive evidence for reducing cardiovascular disease risk. However, some studies also document CHD prevention benefits for resistance exercise as well. For example, one study found that men who lifted weights for a minimum of 30 minutes each week in the study later exhibited a 23 reduced risk of developing CHD than those who did not weight train. The exercise-related risk reduction benefit for cardiovascular disease is similar in magnitude for men and women and appears to be the same across ethnicities.
Possible mechanisms for reducing CHD through exercise are the reduction of body fat (especially in the mid-region where it is most dangerous), blood pressure, and inflammation, along with the control of insulin sensitivity, blood sugar levels, and blood lipid levels. A single 30-minute bout of moderate intensity aerobic exercise can reduce blood pressure. Physical activity also raises high-density lipoproteins (HDL) (the good cholesterol). As a result, the ratio of good cholesterol to total cholesterol becomes more favorable, a risk reduction result that may not be evident by just examining the total cholesterol. The ratio of HDL to total cholesterol is a far more important health risk indicator than total cholesterol by itself.
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These older adults are participating in an exercise class at their assisted-living facility
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