According to a study published in Breast Cancer Research, regular activity such as running, heavy housework, demanding yard work, aerobics, was found to reduce a woman’s breast cancer risk by about 30 percent. The study was conducted over an 11-year period and included 32,000 women who were post-menopausal. But the activity only protected women if they were neither overweight nor obese.

The participants were given questionnaires about their exercise habits that consisted of a variety of things, ranging from light housework, vacuuming, washing clothes, painting, home repairs, general gardening, light sports or exercise, to walking, recreational tennis, bowling, golf, for “non-vigorous” category of exercises and heavy housework, heavy yard work, digging in the garden to running, fast jogging, aerobics, bicycling on hills, to strenuous sports, for activity classified as “vigorous.”

Contrary to other studies, that have shown that light activity had an impact on the risk of breast cancer in the long run, this study shows that light exercise had no effect against breast-cancer.

“In this cohort of postmenopausal women, breast cancer risk reduction appeared to be limited to vigorous forms of activity,” said lead author of the study Michael Leitzmann from the National Cancer Institute at the US National Institutes of Health.

According to the American Cancer Society’s statistics, breast cancer accounts for nearly one in three cancers diagnosed in American women. The incidence of breast cancer increases dramatically after age fifty, with fifty percent of breast cancers diagnosed in women over the age of forty-five. Obese women, especially those who are post-menopausal, women who consume excessive amounts of alcohol (greater than two ounces per day) and those who smoke are at increased risk.