Rated
Nov 12
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3 reviews
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fitness, exercise, bone density
• nytimes.com
There was a time, not so long ago," when most researchers assumed "that any and all activity would be beneficial for bone health," says Dr. Daniel W. Barry, an assistant professor of medicine at the University of Colorado, at Denver, and a researcher who has studied the bones of the elderly and of athletes. Then came a raft of unexpected findings, some showing that competitive swimmers had lower-than-anticipated bone density, others that, as an earlier Phys Ed column pointed out, competitive cyclists sometimes had fragile bones and, finally, some studies suggesting, to the surprise of many researchers, that weight lifting did not necessarily strengthen bones much. In one representative study from a few years ago, researchers found no significant differences in the spine or neck-bone densities of young women who did resistance-style exercise training (not heavy weight lifting) and a similar group who did not.
the current state-of-the-science message about exercise and bone building may be that, silly as it sounds, the best exercise is to simply jump up and down, for as long as the downstairs neighbor will tolerate. "Jumping is great, if your bones are strong enough to begin with," Dr. Barry says. "You probably don't need to do a lot either." (If you have any history of fractures or a family history of osteoporosis, check with a physician before jumping.) In studies in Japan, having mice jump up and land 40 times during a week increased their bone density significantly after 24 weeks, a gain they maintained by hopping up and down only about 20 or 30 times each week after that.
If hopping seems an undignified exercise regimen, bear in mind that it has one additional benefit: It tends to aid in balance, which may be as important as bone strength in keeping fractures at bay. Most of the time, Dr. Barry says, "fragile bones don't matter, from a clinical standpoint, if you don't fall down."
Then came a raft of unexpected findings, some showing that competitive swimmers had lower-than-anticipated bone density, others that, as an earlier Phys Ed column pointed out, competitive cyclists sometimes had fragile bones and, finally, some studies suggesting, to the surprise of many researchers, that weight lifting did not necessarily strengthen bones much.
An emerging scientific consensus seems to be, he says, that "large forces released in a relatively big burst" are probably crucial. The bone, he says, "needs a loud signal, coming fast." For most of us, weight lifting isn't explosive enough to stimulate such bone bending. Neither is swimming. Running can be, although for unknown reasons, it doesn't seem to stimulate bone building in some people.