Research in motion
FOR 10 minutes most days, 10-year-old Sonya Gomez stands on what looks like a gently vibrating bathroom scale. Leaning on a walker because her body has been weakened by cerebral palsy, she stands in hopes that an experimental treatment will fortify her bones and invigorate her muscles, even though she can barely tell anything’s happening.
“Every morning she eats breakfast while I’m getting ready. She brushes her teeth. Then she gets on the machine,” says her mother, Anna Gomez, of Whittier.
Sonya is participating in a pilot study examining whether super-high frequency, low-force stimulation can help kids with her disorder, who because of their limited mobility don’t build bones or muscle as robustly as their peers. “A lot of kids with cerebral palsy can’t do vigorous exercise therapy,” says Tishya Wren, a biomechanical engineer who leads the study out of Childrens Hospital Los Angeles.
The hope is that vibration therapy can help Sonya grow her skeleton past adolescence by gentle vibration instead of playground rough and tumble -- a technique that has been shown to increase bone density in turkeys, sheep and mice by as much as 35%.
Known as vibration or “dynamic motion” therapy, the technique goes beyond helping children such as Gomez. It has been tested in older women who are losing bone mass after menopause and younger women who have bone density at the low end of healthy. It’s even being studied as a way to keep astronauts’ bones and muscles strong in space.
So far, results in people have shown gains in bone density as high as 6%. But researchers also count as successful the ability of the technique to simply slow bone loss. A recent study suggests the technique can also improve muscle mass -- a property that could be important for elderly people, helping to prevent dangerous falls.
An ‘active, alive tissue’
The therapy works because bone responds to force. “Most people think of bone as the Georgia O’Keefe skeleton drying in the sun -- but it is an active, alive tissue,” says bone bioengineer Clinton Rubin of State University of New York at Stony Brook, who pioneered the vibration technique, originally working with turkeys.
Bone is continuously being pulled on by muscles, says Rubin -- a rapid, gentle shaking that puts low-level stress on the bones all day. Since muscles vibrate between 20 and 50 cycles per second (or hertz), Rubin developed a machine to vibrate at 30 hertz. (The plate also vibrates up and down to generate force, moving less than 50 micrometers in either direction.)
Propping ewes on this gadget for 20 minutes a day for a year improved both the quality and bulk of their back legs, Rubin found. Not only were the sheep bones about one-third denser, they were 12% stiffer and 27% stronger.
Rubin’s device has been deemed safe by the Food and Drug Administration -- and now he and others are conducting studies to prove the machine is medically useful. In one experiment, Rubin and colleagues followed 70 post-menopausal women for a year. Half of them were instructed to stand on the vibrating plate for 10 minutes twice each day, while the other half stood in place on similar devices that didn’t vibrate.
Although the scientists didn’t see an effect over the entire group, they did find that women with the thinnest bones benefited from the treatment. Instead of losing about 2% of their spine density, the women either lost less than one-tenth of a percent or gained just a tad -- with the women who stood closest to the 20-minute goal improving the most.
Another study in children with cerebral palsy showed that bones of children who used the technology grew in density by about 6%, while bones in those who didn’t thinned by almost 12%.
Muscles seem to benefit too. Bone researcher Dr. Vicente Gilsanz at Childrens Hospital Los Angeles just completed a study of 140 young women age 15 to 20 who had low bone density. He found a modest benefit for bone, with density improving by about 2% to 4%. But the girls’ thigh muscles increased in mass by about 5%.
NASA is planning to try the device on the space station where, freed from the tug of gravity, astronauts lose bone mass 10 times faster than adults on Earth. NASA physician Dr. Victor Schneider at NASA headquarters in Washington, D.C., says the vibration plates are scheduled to go to the International Space Station in 2007 or 2008, along with bungee cords to strap the astronauts to the vibrating plates.
But first they are being tested on Earth. Volunteers are staying in bed for a few days to months -- a standard way to simulate the lack of gravity of space -- and the plates are strapped to their feet and turned on every day.
Anna Gomez’s hopes for her daughter Sonya are more down-to-earth. “If it’s going to help her, I want her on it,” she says. “I’m not going to be around forever, so I’ve got to do what I can now that she’s small.”
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Vibration hits the gym
Making its way into U.S. gyms and houses is another kind of vibrating technology, from Europe. Developed by the Dutch Olympic trainer Guus van der Meer, the Power Plate promises to bulk up muscle as part of a personal training regime.
This device and similar teeth-rattling knockoffs shake much harder than Clinton Rubin’s machine. Athletes and celebrities such as Madonna are rumored to use them in their workout routines.
The machines are set to a similar vibration frequency as Rubin’s plate but shake up and down at four to 15 times the force of gravity (as opposed to one-third the force of gravity).They have been shown to help build muscle and pump out hormones but their effects on bone density are unknown.
Because these plates can shimmy an object off their surface, Rubin says he worries that people with weak bones might put their skeletons in danger.
