At least for post-menopausal women, keeping moving may reduce their risk of kidney stones, U.S. researchers found. Mathew Sorensen of the University of Washington saw the benefit of physical activity after analyzing eight years of data on about 93,700 women in the Women\'s Health Initiative database -- a study begun in 1991, which consisted of a set of clinical trials and an observational study involving 161,808 generally healthy postmenopausal women. \"Even with small amounts of exercise, there appeared to be a reduction in the risk of kidney stone formation. And it didn\'t appear that the intensity of exercise mattered. It was more the amount of activity,\" Sorensen said in a statement. Walking regularly was enough to lower the risk, compared with women who were inactive, Sorensen said. However, being overweight or obese raised the risk of kidney stones, The study was presented at a meeting of the American Urological Society.