Pressurized treadmill eases impact on joints

By Bill Scanlon, Rocky Mountain News (Contact)

Published August 1, 2008 at 3:03 p.m.
Updated August 1, 2008 at 3:03 p.m.

Text size  

• 0 Comments
• Email
• Print

Running in zero gravity would be great on the joints, but running on a new pressurized treadmill that effectively cuts the body's weight in half isn't bad either, a new study indicates.

A treadmill device that seals the runner's lower body in a low-gravity chamber cuts the impact on the knees, heels and back by almost half, says the study by the University of Colorado.

It's helping 2008 Olympic athletes ready for this month's games, and it can help the average runner recover from injuries, says CU Associate Professor Rodger Kram.

Running is great exercise, but the impact each time the heel strikes the road can be jarring, eventually leading to back, knee and foot problems, as millions of runners know.

If only runners could practice on the moon or, say, on board the space shuttle.

Until then, the best bet is the "G-Trainer," consisting of a treadmill surrounded by a doughnut-shaped inflatable plastic chamber. Runners are zipped into the chamber, which encases their body from the waist to the knees, Kram said.

The system pumps pressure into an air-tight tent. The runner wears a spray skirt, similar to the water-tight skirt on a kayak, that has a lip on it to zip into that tent.

"It uses air pressure to lift up on the runner, taking a 150-lb. runner down to an effective weight of 75 pounds," Kram said. "The pressure difference lifts up on the runner, basically lifting them up by their shorts," Kram said.

One of the volunteer runners for the study, integrative physiology student Andy Edwards, said, "It's a little like running in water ... but it is really comfortable."

Several former CU track stars running at Beijing this month have used the machine.

Kara Goucher, who will be running the 5-kilometer and 10-kilometer at Beijing, credits it with helping her recover from injuries. So does former CU All-American and Olympic marathoner Dathan Ritzenhein.

The study appears in this month's issue of the Journal of Applied Biomechanics. It marks the first time the actual benefits of the G-machine has ever been measured,

"We tried to find the best level of weight suppression and speed that gives you the best combination," Kram said. "The idea was to measure which levels of weight support and speeds give us the best combination of aerobic workout while reducing the impact on joints," said Kram.

"We showed that a person can run faster in the G-Trainer at a lower weight and still get substantial aerobic benefits," while maintaining good neuromuscular coordination.

Running at about 10 feet per second, or a 7-minute-mile pace, lowered the peak force of heel impact by 44 percent, said Alena Grabowski, a former doctoral candidate at CU, who worked on the study with Kram.

That's a great benefit because each foot impact at high speed can jar the body with a force equal to twice a runner's weight.

The G-Trainer is built by Alter-G Inc., of Menlo Park, Calif., using technology developed by NASA Ames Research Center to help astronauts maintain fitness in the near-zero-gravity of space travel.

For the study, the researchers attached to the treadmill a force-measuring device that Kram invented. It charts vertical and horizontal stress load on each foot, as well as biomechanical forces on the legs.

"If you can decrease the intensity of these peak forces during running, then you probably will decrease the risk of injury to the runner," Grabowski said.

Until the G-Trainer came along, coaches and trainers tried using flotation devices in swimming pools or climbing harnesses to help athletes get back into shape while recovering from stress injuries.

But pool running doesn't give the heart the aerobic exercise it needs, and the climbing harnesses are quite cumbersome, Grabowski and Kram said.

Marathon world-record holder Paula Radcliffe of Great Britain is using a G-Trainer in her high-altitude training base in Font-Remeu, France.

She needs to stay in top shape while recovering from a stress fracture to her femur in time for the Aug. 17 marathon, according to the London Telegraph.

The point isn't to get anyone to run faster, but to help an injured runner rehabilitate faster so they can get back outside where running is more fun, he said.

The future of the device "is probably in walking," Kram said.

"People coming back from knee or hip-replacement surgery can use it. That's why we're redoing the study to see the impact at different walking speeds."

Featured

• Legislature Blog

  

  Read live updates from the opening of the 2009 legislative session.

• Rocky multimedia

  

  The news comes alive in our videos and slide shows. Catch up on what's happening today.

• Who's next?

  

  Complete coverage of the Broncos' search for a new coach.

• Rocky year in photos

  

  View an audio slide show of staff selections from 2008.

• Winter Escapes

  

  Your insider’s guide to the copious joys of the coolest season.

• Sam Adams' Open Mic

  

  Open Mic: Two-man advantage with Avs

• Shanahan's career

  

  See photos from Mike Shanahan's career as Broncos coach.

• 12 days of Drew

  

  Look back at the year that has been with Drew Litton.

• A dream fulfilled

  

  A Rocky Mountain News and MediaStorm production