"It's definitely a weird feeling at first," says freshman softball player Madison Hanten, probably speaking for anyone who ever stepped on an antigravity treadmill.
But that initial reaction usually is followed by deep appreciation for a Stanford-linked invention that's becoming a phenomenon in medical research labs, nursing facilities and TV's The Biggest Loser. The treadmill, from the Bay Area company AlterG, puts a user in shorts that zip into a hip-high inflatable bag with an airtight seal. Increasing the interior air pressure counteracts the force of gravity. The result is "unweighting," which allows users to train or undergo rehabilitation at as little as 20 percent of their body weight then work back toward 100 percent as pressure decreases in 1 percent adjustments. Exercise and rehab occur without the pain and setbacks that would happen at full body weight.
The machine is a two-generation innovation. The concept began with NASA scientist Robert Whalen, '68, MS '73, PhD '88. Everything took off in 2005 when son Sean, '04, MS '06, co-founded the firm that became AlterG, developing a commercial version of the treadmill that's still evolving technologically. Sean, operations director of AlterG Europe, now living in Estonia (the home country of his Stanford girlfriend), said in an email that there's a special thrill to seeing his father's work funneled into life-changing applications. "If AlterG were to disappear tomorrow, the joy this has brought him will have made the whole thing worth it."
The treadmill has two models with prices from $25,000 to $75,000. Stanford has one for the track and field team and one in the Human Performance Lab, where Hanten rehabbed a torn anterior cruciate ligament.
"When you're only running at 60 percent of your body weight, you can imagine that the weightlessness would be a little bizarre," she explains. "But the fact that you are able to get the sensation of running without the physical stress on your legs is really exciting and refreshing when you have barely been allowed to break a sweat in four months."