My yoga teacher told me that if I stand on one leg for six seconds, it will increase its bone density. Is that true?

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Probably not - although no scientific study has addressed the question directly. There is evidence, however, that related activities could build bone strength.

For instance, sedentary women age 25 to 45 can increase their bone density if they do about two minutes a day of jumping, says exercise physiologist Miriam Nelson, director of the John Hancock Center for Physical Activity and Nutrition at Tufts University. While there may be no direct evidence for the benefits of one-legged standing per se, she says, "yoga poses are great for improving balance and stability, which may reduce the risk of falling."

There are data showing that women who stand up on their toes and then drop down onto their heels (barefooted on a hard floor) 50 times a day for six months can increase bone density by 3 percent to 4 percent, says exercise physiologist William Evans, chairman of Nutritional Longevity at the University of Arkansas for Medical Sciences. In fact, he says, there's a move afoot (as it were) to get schoolchildren to jump up and down to improve their bone health.

But just standing on one leg for a few seconds, he says, is unlikely to put enough stress on bones to have any effect on bone density.

JUDY FOREMAN

E-mail health questions to foreman@globe.com.