To improve balance, a vibrating insole

By Gareth Cook, Globe Staff, 10/3/2003

It might sound like utter quackery, akin to cure-all magnetic bracelets, but scientists say they have made a dramatic medical advance by developing a vibrating shoe insole.

The insole, designed by medical researcher Jim Collins at Boston University, improves balance in elderly people and can give a tippy 73-year-old the steady equilibrium of a 23-year-old with the flip of a switch, according to a study to be published in tomorrow's edition of the British journal Lancet.

Though the insoles are currently 1-inch-thick laboratory prototypes, a refined version could help reduce the number of falls among the elderly, say Collins and other scientists, reducing a costly and frightening health problem. Every year, about one-third of people over 65 suffer a fall, causing injuries and threatening their independence. The total bill, from fractured hips and other serious ailments, comes to at least $20 billion every year, according to one study.

"I think this is terribly important," said Dr. Jonathan Bean, director of geriatric physical medicine and rehabilitation at the Spaulding Rehabilitation Hospital. "It is using high-tech research to come up with a very low-tech solution to a complex problem."

Using clear gel insoles, Collins and a team that includes researchers from BU and Harvard Medical School have shown that vibrations too small to be felt can counteract the effects of age-related nerve degradation that makes people wobbly on their feet.

The vibrations work by increasing the tiny pressure signals that tell the body how it is leaning. A young, healthy body uses a variety of clues, including pressure felt on the bottom of the feet, to sense when it is tipping and make adjustments to remain upright. As a person gets older, though, the nerves in the soles of the feet become less sensitive, depriving the body of some of the information needed to make the balancing process work.

With the insole turned on, the random vibrations add to the pressure signals, boosting them so the nerves can sense weak pressures that they otherwise would have missed, said Collins.

Collins and his colleagues have been working on adding random noise to make systems more sensitive, a concept called "stochastic resonance," for a decade. In 2000, an engineer heard about the work and licensed the patents from BU, starting a Rhode Island-based medical device company, Afferent, with the aim of turning the insoles into a consumer product.

Afferent already has received several government grants, including a two-year, $750,000 award this year, as well as a $1 million investment from Pharos LLC, a business development company based in Waltham.

But Collins, who holds a stake in Afferent, warned that the technology was years from being ready for public use. It will take engineering to make the insoles small enough to fit in any shoe, but the most significant hurdle will be finding a way to supply electricity to the insoles, which are now powered by a battery several inches thick.

"You can't have 80-year-old Mrs. McGillicuddy walking around with a car battery strapped to her back," said Collins.

The research published in Lancet shows the idea works surprisingly well in the lab.

To measure a person's balance, volunteers are blindfolded and asked to stand as still as they can. The better their balance, the less they sway -- and the sway can be measured very precisely using video cameras and a reflector on a person's back, according to the paper, whose lead author is BU scientist Attila A. Priplata.

To test the vibration concept, the team recruited two groups of volunteers, one with an average age of 23, the other 73. Each subject was asked to stand on a pair of gel insoles with vibrating devices inserted in them.

Subjects then were asked to increase the vibration until they could barely feel it. The researchers then turned down the power slightly so the subject could not feel it.

The team then ran trials, switching the insoles off and on without telling the subjects and comparing the results. By every geometric measure they used, the elderly subjects swayed significantly less with the vibrations than without, Collins said.

By one measure, for example, the elderly group had a natural sway of 5.5, compared to a natural sway of 5.1 for the young group. When the device was switched on, though, the measure for the elderly dropped from 5.5 to 5.0.

Other research has shown that these types of sway measurements can be used to predict the likelihood that a person will suffer accidental falls, Collins said.

But before the idea can make its way into a device for the public, Collins and his team will have to test it on a larger population and include volunteers who have serious balance problems, said Bean.

Collins said he plans to do broader trials now, and said he also has a personal motivation: His grandmother recently fell and broke her hip.

"She had to go for rehabilitation for months," Collins said. "This is clearly a big problem that is not being addressed."

Gareth Cook can be reached at cook@globe.com.