Vigorous activity can reduce the risk of breast cancer by about 30 percent, according to an 11-year study of more than 32,000 postmenopausal women.
Vigorous activity was defined as heavy housework -- such as scrubbing floors, washing windows, and chopping wood -- and strenuous sports or exercise.
However, while the exercise reduced breast cancer risk in normal-weight women, it had no effect in women who were overweight or obese. Non-vigorous activity, such as light housework and light sports or exercise also offered no protection against breast cancer.
U.S. News & World Report October 31, 2008