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Falls are the leading cause of accidental deaths among people over the age of 75 and the second leading cause for those aged 45 to 75, according to the National Safety Council. Although the consequences of falling are well known, the relationship between aging and falling is still a mystery.

Working in his Locomotion Research Laboratory at Virginia Tech, Thurmon Lockhart is determined to solve this mystery. "Fifty percent of people over 75 will either die or be forced to enter institutional care because of falls," he said. "What I want to find out is why these falls happen."

Lockhart, an assistant professor of industrial and systems engineering with a research background in biomechanics and human motor control, also wants to learn how to help prevent falls.

"About one-third of the elderly living at home fall each year and one in forty of them are hospitalized," he noted. "Of those admitted to the hospital, only about 50 percent will be alive one year later. And the economic projections are that $20 to $50 billion will be spent in the U.S. by 2020 on the medical costs resulting from hip fractures alone."

Funded by a grant from the Centers for Disease Control and Prevention (CDC) and the National Institutes of Health (NIH), Lockhart is suiting up young and old volunteers in a harness and a network of sensors that test musculoskeletal and neuromuscular changes and biomechanical responses during slips and recoveries.

As a test subject walks back and forth along an experimental platform in Lockhart's lab, the sensors monitor muscle and joint activities in the feet, ankles, legs, hips and arms. At a randomly chosen moment in the test, a student assistant stealthily pours a slippery solution of liquid detergent and water behind the subject. On the way back, the subject slips and goes through the motions of recovery (an actual fall is prevented by the harness).

All the data from the monitoring sensors is fed into a computer model, providing information to the researchers about the subject's gait while walking and the body motions involved during slipping and recovery. Lockhart and his students are running tests on a group of 60 volunteers divided into three age groups -- 18 to 35, 40 to 55 and over 65.

There's more to Lockhart's study than investigating the mechanics of walking, slipping and recovering, however.

"Another important factor is understanding the intrinsic changes to gait and balance brought about by aging," he said. For example, as people age their walking gait tends to change. "We may take slower and shorter steps, making a higher velocity contact impact with our heels -- which in turn seems to make slipping more likely. Why does this happen?"

Also as we age, Lockhart noted, sensory factors such as vision, inner ear and touch sensitivity decline. "These changes make us less able to detect that we're slipping until it's too late."

Lockhart's tests also include strength measurements taken while subjects are recovering from slips. Understanding the mechanics of recovery could help the researchers learn how to prevent slips from becoming falls.

In addition to the first three phases of this CDC/NIH-sponsored project -- learning the mechanics of slipping and falling; determining the gait, visual and sensory, environmental, strength and perceptual factors behind the mechanics; and modeling the muscle, joint and bone involvement -- Lockhart plans a fourth phase.

"I want to develop intervention strategies," said Lockhart, who also is affiliated with Virginia Tech's Center for Gerontology. "For example, after our modeling helps us understand the mechanics of falling, we might be able to develop special shoes, strength training routines or environmental and flooring designs that will help prevent falls among the elderly."

Lockhart and Stefan Duma, an assistant professor of mechanical engineering, already have a provisional patent on a hip pad they created that can reduce impact injuries from falls. Based on air bag technology, a sensor device triggers deployment of the "HIP-bag" when the wearer takes a fall.

Lockhart and a student researcher are conducting another study of falling among the elderly who live in nursing homes. By investigating data collected at Warm Hearth Village, an assisted living facility in Blacksburg, the researchers hope to devise a model for predicting the risks of falling for individual residents.

"We need to understand more about the mechanics involved in being older," said Lockhart, who became especially interested in the subject a few years ago when his elderly father fell and broke his ankle. "It's important that we not simply accept the folklore about aging and injuries if we can learn how to prevent those injuries."

For more information about this research, contact Thurmon Lockhart at 540-231-9088 or lockhart@vt.edu.