For the past decade the fitocracy has been telling us that, as our bodies age, we should be kind to our joints by doing more low-impact exercise.
Once again, it appears that a bit of well-intentioned advice hasn't been entirely good.
Even occasional high-impact aerobic exercise can reduce the risk of hip fractures by 33 percent in men and 12 percent in women, according to a group of British researchers.
Yes, scientists have shown previously that weight-bearing exercise helps reduce the risk of fractures from osteoporosis in old age.
What has been unclear is what kind of exercise might be most protective, since weight-bearing exercise includes everything from walking to doing power squats. Because hip fractures are a common and disabling problem for older people, researchers have been looking for better ways to help boost bone.
They seem to have found it in high-impact exercise. Led by Nicholas Wareham of the University of Cambridge Institute of Public Health, the British researchers showed that high-impact exercise resulted in greater ankle-bone density than other forms of exercise or none at all. (Ankle-bone thickness is a well-regarded marker for hip-bone density.)
Among high-impact activities that reduced risk of hip fracture were step aerobics, competitive running, jogging, tennis, squash, football, hockey, volleyball and basketball. Just two hours a week of these activities cut the risk of hip fractures by 33 percent in men aged 45 to 74 years, Wareham said. In women, also aged 45 to 74, the same amount of activity decreased the risk of hip fracture by 12 percent.
What Wareham and his colleagues didn't expect was finding that many popular activities had no effect on reducing future hip-fracture risk. Among them: walking, mowing the lawn, golf, skiing, bowling, dancing and even backpacking and mountain climbing. Neither did bicycling, rowing, wind surfing, sailing or even conditioning exercises.
"Clearly, anybody contemplating physical activity to achieve a health benefit has to consider the potential benefits across the board, not just bone health," said Wareham, whose findings were published in the British Medical Journal.
That means, he said, engaging in both high- and low-impact exercise from middle age on.
Wareham and his colleagues are careful to note that high-impact exercise remains a preventive measure as opposed to a treatment, and its benefits decline with age. Also, because of the dangers of falling, "it could be very risky for elderly people," he said. "But earlier in life, if you have preserved muscle strength and are thinking about the future and how to preserve your bones, it would be good to do something more vigorous than walking."
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