Weighing impact on bone loss

By LISA LIDDANE
KNIGHT RIDDER NEWSPAPERS
We've heard for years that exercise can help keep our bones strong and may reduce our risk of osteoporosis. But just how much exercise do we need to achieve this?
Researchers at the Johns Hopkins School of Medicine in Baltimore found that low-intensity activities such as light housework and walking may not be enough to prevent aging-related bone loss.
The finding, which appears in this month's Journal of Internal Medicine, is interesting because government health experts have been suggesting that daily tasks can count toward the amount of time devoted every day to physical activity, said Kerry Stewart, the study's lead author and associate professor of medicine in cardiology.
"Just routine activities do not seem to preserve bone," Stewart said.
Although the study was conducted on 84 healthy women and men ages 55 to 75, it's a good idea -- from a prevention standpoint -- not to wait until you're 54 to consider the relationship between exercise and bone health. And if you're young, remember that bone loss also might affect the health and well-being of your loved ones.
So does this mean that people who have been participating only in light activity should switch to more moderate-intensity activity?
Stewart isn't ready to recommend that. He and his colleagues will be conducting studies to find out whether moderate exercise might help preserve bone.
What can help
Yet the National Osteoporosis Foundation, or NOF, touts the importance of weight-bearing and resistance exercises for building and maintaining bone mass and density.
Weight-bearing exercises are those in which your bones and muscles work against gravity. This is any exercise in which your feet and legs are bearing your weight. Soccer, basketball, jogging, walking, stair climbing, dancing and soccer are examples. Swimming and cycling on flat roads are not weight-bearing.
According to the NOF, specific exercises to twist, bend, stretch and compress bones are needed to strengthen the common sites at risk: the upper arm at the shoulder, the forearm at the wrist, the thigh bone at the hip, and the spine.
Resistance training improves muscle mass and strengthens bone. This includes weight lifting, such as using free weights and weight machines or working with your own body weight.
Some exceptions that require a physician's clearance first:
UYou have been sedentary
UYou are frail
UYou have had a fracture
UYou fall frequently
UYou already have osteoporosis
Stewart said some people may be capable of only light-intensity daily activities, so the findings do not necessarily apply to them.
If you're healthy and have been counting on light-intensity daily tasks for physical activity but want to improve bone health by switching to a weight-training or moderate weight-bearing fitness program, remember to do it gradually.
XLisa Liddane is a health and fitness writer for The Orange County Register and an American Council on Exercise-certified group fitness instructor. Write to her at the Register, P.O. Box 11626, Santa Ana, Calif. 92711 or send e-mail to lliddane@ocregister.com.