Anti-Gravity Treadmills Defy Physics For Runners

Overcome a running injury and still get workouts in with an anti-gravity treadmill.

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Overcome a running injury and still get workouts in with an anti-gravity treadmill.

Any injured runner knows the worst part of an injury is not being able to train.

That’s why when Adam Goucher, a 2000 U.S. Olympian in the 5,000 meters, had foot surgery in 2007, he found a new way to keep his fitness and speed up his recovery: the anti-gravity treadmill, or AlterG.

“It allows you to maintain your fitness to a certain extent,” Goucher said.

The AlterG uses “lower body positive pressure,” which allows runners to run at a lower simulated body weight. That’s a fancy way of saying your legs — inside neoprene shorts — are zipped into a bubble over the treadmill and pressurized air is pumped in, lifting your body up and effectively lowering your body weight.

Weight sensors allow the AlterG to be operated at anywhere from 20 to 99 percent of the runner’s body weight, in one percent increments.

The implications of weight-free running are obvious to anyone suffering from the stress of too much mileage. Those implications were also obvious to Nike Oregon Project coach Alberto Salazar, Goucher’s former coach, when he saw a prototype in the mid-2000s.

RELATED: Treadmill Workouts To Gain Speed

NASA scientist Robert Whalen previously developed negative pressure technology, the reverse of the AlterG to use in space stations. His son, Sean, while enrolled as a graduate student at Stanford, wanted to create a commercial product out of the technology. They came up with the AlterG and showed an early prototype to Salazar, who immediately invested in the product.

It was one of those early models that Goucher first ran on. Now, AlterG’s newer, nicer models can be found in many physical therapy offices, hospitals, military bases and college and professional sports training facilities throughout the U.S.

“It’s a good tool for maintaining fitness with certain injuries,” said Mark Wetmore, head cross country and track and field coach at University of Colorado, who has been using an AlterG with his athletes for the past four years.

But, it’s not just for the elite.

Rob Cavanaugh, a New Jersey runner training for the 2012 ING New York City Marathon, found himself with an oncoming stress fracture about a month before the race. His doctor recommended running on the AlterG at a local physical therapy clinic.

“I was skeptical at first,” he said. He was soon won over. Going by heart rate, he was able to get in solid workouts toward his 2:30 marathon goal. And, although the race was canceled, he was back on the road after four weeks.

“If I was injured, I would jump back on it in a heartbeat,” Cavanaugh says.

RELATED: Dealing With Stress Fractures

While most runners and coaches use the gravity-free treadmills for rehab, “there are more applications than perhaps are obvious,” AlterG Vice President Gabe Griego, said.

Increasingly, top athletes (particularly ultrarunners) use it to get in mileage without wear-and-tear on their legs. Operating the devices at a lower body weight can also allow runners to work on stride mechanics, with some equipped with foot video monitors.

AlterG, a San Francisco-based company, has relied on local elite athletes, like Shannon Rowbury, to come up with training protocols for the treadmills, all of which are available to the public. They’ve also hired professional runners and a former strength and conditioning coach for the New York Mets, who is developing an explosive strength workout using squats and jumps under the gravity-free bubble.

Additionally, a Stanford study about to be published looks at the use of the AlterG to increase an athlete’s VO2 max, Griego said. By simulating a lower body weight, a runner can run at much higher speeds with much less impact. That helps train the legs at a higher turnover and teach the musculoskeletal system to run faster.

“Anecdotally, top runners are saying it’s helping to increase their speed,” Griego said.

This piece first appeared in the March 2013 issue of Competitor magazine.


About The Author:

Kelly Dunleavy O’Mara is a journalist/reporter and a former professional triathlete. She lives in the San Francisco Bay Area and writes for a number of magazines, newspapers, and websites. You can read more about her at