Shoes giving off good vibrations

Friday, October 3, 2003

A buzz in the soles may keep elderly people on their toes and reduce the risk of debilitating falls, preliminary research suggests.

The experiment, outlined this week in The Lancet medical journal in Great Britian, found that elderly people showed signs of better balance when they stood on a pair of battery-operated randomly vibrating insoles.

Although users aren't conscious of the subtle buzz, the idea is that the vibrations amplify balance-related signals between the feet and the brain that become dulled with age or illness.

Experts said the research shows promise but scientists need to see if the technique improves balance when people walk, turn or reach, which is when they are most vulnerable to a fall.

When a person leans or sways to one side, the pressure on the sole of that side increases. Normally, the nervous system senses the change in pressure and sends a message to the brain so the posture can be adjusted.

Those messages can be blunted by age, stroke or conditions such as diabetes.

"I think the vibrating insole holds promise and is definitely worth studying," said Dr. Mary Tinetti, chief of geriatrics at Yale University School of Medicine, who was not connected with the study.

The research, funded by the U.S. National Institutes of Health, was conducted by scientists at Boston University and Harvard Medical School.

They recruited 27 healthy volunteers -- 15 people in their 20s and 12 elderly people -- to stand on the gel-based insoles, which were placed on the floor for the experiment. The volunteers were told to keep their eyes closed and their arms by their sides. The insoles were connected to a large battery pack and each was implanted with three small vibrating discs.

The intensity of vibration was set individually so that it was just below the threshold that could be felt. The scientists conducted before and after tests on various tasks involved in balance control.

The young volunteers showed some improvement with the vibrating insoles, but the elderly people showed more improvement, said James Collins, a professor of biomedical engineering at Boston University who directed the project.

"The improvements we are seeing in the elderly -- that is, we move them down to, or close to, the level in the young -- we view as being very positive and suggestive that this technology may in fact be able to improve elderly balance to the point where we could significantly reduce the risk of falls," Collins said.

The fact that the young people also improved indicates there may be potential for such insoles for young people who need extra help with balance, such as construction workers, gymnasts, acrobats or other athletes, Collins said.

The idea behind the insoles is "stochastic resonance," an effect where a weak signal is easier to detect when it is surrounded by a background of random noise -- the vibrations.

"It's a counterintuitive notion because engineers and the public tend to think of noise as being a nuisance for detection and information transfer. We tune static out of our radios, we buy cell phones that have low interference. In general, we want to get rid of noise," Collins said. "But noise, under certain circumstances, can be good."

"Our neurons are threshold based, which means the signals need to exceed some amplitude before they can be detected. Noise boosts the strength of the signal above the threshold," he said.

Collins plans to test the insoles with more frail elderly people and in studies that involve walking and turning.

Providing those work out, the biggest challenge will be to design a practical pair of shoes, or insoles that can be worn inside any pair of shoes, Collins said. No such insoles are currently commercially available.

"I think this is a terrific first effort to show a benefit from this technology," said Jack Guralnik, chief of epidemiology and demography at the U.S. National Institute on Aging, who was not connected with the study. But more tests are needed to determine whether it would help people with neurologic disease or other impairments to their balance, he said.

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