Richard Grove, 73 years old and a robust 6 feet tall, set out with confident strides across a laboratory floor the other day. His first five steps went great, then his left foot hit a slippery patch and skidded. His arms windmilled over his head as if he were throwing a baseball with each hand, and his right foot shot forward to come even with his left. But he quickly regained his balance and kept on walking. This was no accident: Grove had just slipped for science. Millions of years after our ancestors started walking upright, researchers are looking for better ways to keep us from falling down. And at this University of Pittsburgh lab, hundreds of volunteers like Grove - who was protected from falling by a special harness - have skidded their way into that effort. The stakes for such research, experts say, are enormous. Last month's death of novelist Kurt Vonnegut, 84, who had fallen in his home, underlines the dangers of taking a spill. In fact, about a third of Americans 65 and older fall each year, the federal government says. In 2003, for example, some 1.8 million people over 65 were treated in emergency rooms after falling, and about 13,700 died. But falling is not just a problem of the elderly. In the workplace, about a quarter-million workers each year suffer injuries from falls that are bad enough to make them take time off, according to the US Department of Labor. That costs billions of dollars. Even without hitting the ground, some 30,000 employees suffered sprains or strains from the wrenching experience that made them lose workdays in 2005. And as the workforce gets older, the age-related problems of falling are starting to gain prominence on the job, says Mark Redfern, co-director of the University of Pittsburgh's Human Movement and Balance Laboratory. That's where Grove was tested. There are many ways to fall, of course, but slipping is a prominent cause of workplace injury. And by some estimates, half to two-thirds of falls in the elderly come from slipping or tripping. It was a spill on an icy sidewalk in 2003 that led to the death of diet guru Dr. Robert Atkins, 72, for example. At the Pittsburgh lab and maybe a dozen others of similar scale worldwide, scientists are still scrutinizing some basic questions about that distressingly common experience:
Exactly how do some people save themselves from falling?
How does aging affect that response?
Can older people be trained to recover from a slip without falling?
Slipping research focuses on a very brief moment. Rakie Cham, co-director of the Pittsburgh lab, says a severe slip leaves only about a quarter-second to save oneself from falling.
How do you do that?
One-tenth to two-tenths of a second after your foot hits a slippery spot, she said, your knee and hip joints react to try to bring the skidding foot back. And you try to push your hip forward to regain your balance.
If that doesn't work, you whip your other foot forward, just as Grove did in the lab. That happens between about one-fifth and one-quarter of a second after the skid starts.
"If you're a little late," Redfern said, "you're way late."
And if it doesn't work, you're going down.
It sounds simple, but scientists are still unraveling the details.
Mark Grabiner of the University of Illinois in Chicago and a colleague recently sent 52 old and young adults for a stroll over artificial ice, to see what reactions make a difference between falling and just wobbling.
Two things stood out. People who were able to slow down the slipping foot were more likely to recover, Grabiner said. More surprising was a finding about the other foot. The most crucial thing about its placement is how far to the left or right from the center it is.
Study analysis implies that "if I can improve the location of that foot in the sideways direction by only four centimeters (about 1.5 inches), I increase the likelihood of this person recovering by 50 percent," Grabiner said.
But can people be trained to react differently to an event that happens so quickly and unexpectedly? Grabiner said he's had success in training older women to keep from falling after tripping. So he believes the new data will help his efforts to train older men to recover from slips.
In fact, studies do suggest people who've practiced recovery moves can improve their reactions to slipping, Cham said. "You retain a library of what to do in these types of challenging situations," she said. "Your reactions become more appropriate and perhaps faster."
The big question, she said, is how long that effect persists after the training is over.
Some research is focusing on subtleties of walking that people don't even notice. Angela DiDomenico of the Liberty Mutual Research Institute for Safety in Hopkinton, Mass., is studying "microslips." These are routine, tiny skids forward of the heel.
Researchers want to find out if large unnoticed microslips indicate a person at risk of falling, or a floor that's especially dangerous, she said.
Other studies at that lab and other researchers also focus on environmental factors like floors and the things that make them slippery. Such research has helped Liberty Mutual Insurance Co. advise commercial policyholders on workplace safety, said Karl Jacobson, senior vice president for loss prevention.
The company prescribes things like how to effectively remove animal fats from restaurant kitchen floors.
Grove, the volunteer who slipped in the Pittsburgh lab, was closely monitored during his experiment. He wore sensors on his legs to record muscle activity. And tiny balls stuck to various parts of his body served as landmarks so a computer could analyze his movements with great precision, and in three dimensions.
Grove had signed a consent form that told him the floor would be slippery at some point, and of course he wore the harness to prevent falling. But as he strode across the floor again and again without incident, his guard was lowered.
At one point, when his back was turned, lab manager April Chambers smeared a mix of water and glycerol on the vinyl tile floor. On his next stroll, Grove's heel found the slick.
"It was a little shocking," he said later.
The lab will soon start having subjects trip as well as slip, with a study of how people adjust their gait if they expect trouble.
On the Net:
Information on falls in elderly: http://www.cdc.gov/ncipc/duip/preventadultfalls.htm
University of Pittsburgh laboratory: http://hmbl.bioe.pitt.edu/home.htm
Tripping experiments at the Cleveland Clinic: http://www.uic.edu/ahp/knad/grabiner/