While previous studies have shown that exercise may protect against breast cancer, a new study by the National Cancer Institute of the U.S. National Institutes of Health points out that not all exercise qualifies. In following 32,269 women for 11 years, the researchers discovered that those engaging in vigorous exercise on a regular basis were the ones less likely to develop the disease, regardless of their weight. Their reduced risk amounted to a stunning 30 percent.

Activities that qualify as vigorous include heavy housework, like scrubbing floors and washing windows, or heavy yard work, such as digging or chopping wood. Healthful, fun activities included fast jogging, competitive tennis, bicycling on hills and fast dancing.

The study suggests two possible mechanisms responsible for the benefit measured: enhanced immune function and decreased inflammation in the body. It’s important to note that excess weight is believed to increase the risk of cancer. Source: Breast Cancer Research, 2008