Washington, Oct 2 : Post-menopausal women can cut down their risk of breast cancer by engaging in a moderate to vigorous workout, says a new study.

"With an estimated 182,460 new cases diagnosed in the United States in 2008, breast cancer is recognised as the most common cancer affecting US women," says Tricia M Peters, of US National Cancer Institute (USNCI) in Maryland, who led the study.

Vigorous exercise has been thought to reduce cancer risk for some time. However, this new study is one of the first investigations to look at the importance of various intensities of exercise at different stages in an individual's life.

Over 110,000 post menopausal women were asked to rate their level of physical activity at ages 15-18, 19-29, 35-39, and in the past 10 years.

It was found, over 6.6 years of follow up, that women who engaged in more than seven hours per week of moderate-to-vigorous exercise for the last 10 years were 16 percent less likely to develop breast cancer than those who were inactive.

However, no link was observed between breast cancer risk and physical activity in women who were active at a younger age, says an USNCI release.

Peters concludes: "With breast cancer still claiming so many lives, all the information on potential preventive measures we can get is vital".

These findings were published in the open access journal BMC Cancer.(IANS)