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Good Vibrations Strengthen Legs in Sheep

Fast, passive massage increases bone density

WEDNESDAY, Aug. 8, 2001 (HealthDayNews) -- Sheep that get a gentle, daily bone "massage" show remarkable increases in bone density, new research says.

The stimulation, delivered by a rapidly vibrating pad about the size of a bathroom scale, boosted bone mass in the animals' rear legs by more than a third over untreated sheep, the researchers say. The approach, which the scientists say already has been tested in people with "encouraging" results, could help prevent osteoporosis and possibly even treat brittle bones in people with already weakened skeletons.

The work, which appears in the Aug. 9 issue of the journal Nature, was led by Clinton Rubin, a biomechanical engineer at the State University of New York in Stony Brook.

It's well known that load-bearing workouts, like walking or running, increase bone mass, but the latest work suggests that even far more passive exercise can strengthen the skeleton. What's more, unlike most drug treatments for osteoporosis, the vibrations build bones rather than merely prevent their erosion.

Using a device to deliver extremely high-frequency but low-intensity vibrations, Rubin and his colleagues stimulated the hind legs of ewes for 20 minutes a day, five days a week, then let them romp around the pasture with the rest of the flock. "The signals are so low they're barely perceptible," says Rubin, who bribed the sheep with bags of oats to get them to stand on a platform.

After a year, the mechanically stimulated animals had a 34.2 percent higher average femur density than the untreated sheep, as well as several other positive bone changes. Their rate of new bone formation was twice that of their paddock mates, and they had about 2.5 times more mineralizing surface, another measure of bone gain.

"It demonstrates that this stimulus is anabolic, or bone producing," says Rubin. The improvement was confined to the spongy interior, or trabecular component, of the femurs, he says.

The vibrations are far weaker than the maximum bones can tolerate without damage, perhaps 1,000 times less stressful than running. Safe enough, in other words, for patients with established osteoporosis. Indeed, Boston scientists are starting a study to see if the treatment can improve the skeletons of the frail elderly, Rubin says.

The device in Rubin's study comes from Exogen, Inc., a division of the English medical products firm Smith & Newphew. Jack Ryaby, Exogen's vice president for research and new technology, says, "There's definitely a big market [for the stimulator] because osteoporosis is a large market."

Exogen is negotiating with the U.S. Food and Drug Administration to design a clinical trial to test its device, a study that should begin next year, Ryaby says.

In theory, patients could use the machine to improve their bone health while watching television, reading or performing other stationary tasks.

What To Do

The National Osteoporosis Foundation estimates that 10 million Americans, 80 percent of whom are women, suffer from the disease. Another 18 million have thinning skeletons that put them at risk of developing the condition, which can lead to fractures of the spine, hip and other bones.

To learn more, try the National Osteoporosis Foundation or the National Institutes of Health.

For a (somewhat technical) look at the biomechanics of bone, check this University of Western Australia site.

SOURCES: Interviews with Clinton Rubin, Ph.D., professor and chair, department of biomedical engineering, State University of New York, Stony Brook, and Jack Ryaby, vice president of research and new product development, Exogen, Piscataway, N.J.; Aug. 9, 2001 Nature
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