Sole Vibrations: Another Approach to Fall Prevention
Falls pose a serious health risk to seniors. They are the leading cause of fractures and accidental deaths in people older than age 65 and a major contributor to nursing home admissions for those 75 and older. Falls are also costly in dollar terms. In 2000, direct medical costs in the U.S. totaled $179 million dollars for fatal and $19 billion dollars for nonfatal fall injuries.
Researchers in the Institute for Aging Research (IFAR) at Hebrew SeniorLife have worked hard to understand what causes and find ways to prevent falls among older adults. They have looked at musculoskeletal conditions such as osteoporosis and arthritis, which affect mobility, and cardiovascular conditions that affect gait and cause syncope (fainting). Another team of investigators is taking yet another tack. They are giving a whole new meaning to the expression "quaking in your boots," discovering that this can actually be a good thing.
Biomedical engineer Attila A. Priplata, Ph.D., is a young scientist who recently joined the IFAR faculty and has worked with Lewis A. Lipsitz, M.D., co-director of IFAR, and other Boston researchers to postulate the theory that stimulating the sensory system might help prevent falls. To understand his research we have to first understand the meaning of "postural sway."
We generally think of standing in place as a static situation; however, this is not actually the case. A subtle but constant displacement and correction of the center of gravity occurs in the human body as it works to maintain balance in a standing position. This phenomenon is referred to as postural sway. The ability to make these adjustments is reduced in old age, causing postural sway to become more dramatic. The further a person's upper body moves off center, the harder it becomes to recover and remain standing.
The human balance control system that influences postural sway relies on feedback from somatic sensation, or sense of touch, along with visual input and neural information provided by the vestibular system located in the inner ear. Somatic sensation also diminishes with age and as the result of certain conditions, including diabetes and stroke.
Dr. Priplata and his colleagues stimulate the sensory system with what is referred to in the scientific lexicon as "noise input." An imperceptible vibration is fed to strategic locations on the soles of the feet. In their most recent studies, volunteers stood on molded gel insoles that were wired with vibrating elements called tractors. Although the vibration they received was at a subsensory level, it seemed to do the trick. The stimulation had an immediate effect by reducing postural sway.
Dr. Priplata explains that as the sensory system is dulled by age or disease, an individual may not adequately feel the contour of walking or standing surfaces. The pressure from the vibrating insoles acts to "jump start" the central nervous system. Rejuvenated, it sends out neural impulses reminding the body to make the biomechanical adjustments needed to maintain balance. Described another way, the pressure exerted by the vibrating insoles serves to fine tune the sensory ability of the soles of the feet so that they can better play their part in the balancing act.
This discovery has potential for commercial application. Perhaps one day vibrating gel insoles could be inserted into the shoes of those in need of a somatic sensory boost. The challenge will be coming up with a power source strong enough to deliver the necessary impulse to be effective, yet portable enough to be practical. Only time will tell if the footwear of the future will make a real difference in reducing the risk of falls for aging adults.