A study co-authored by a professor from the University of Colorado's Locomotion Laboratory shows there is no performance advantage for athletes who use prostheses made for running.

Rodger Kram, an associate professor of integrative physiology at CU, said the team of researchers examined sprinters who used the Flex-Foot Cheetah -- the running prosthesis used by Oscar Pistorius, the South African athlete who was temporarily barred from competing in the Beijing Olympics -- and similar prostheses for one leg.

The study was published in Biology Letters on Nov. 4; the lead author, Alena Grabowski, earned her doctoral degree at CU in 2007.

Using force-measuring treadmills at the Orthopedic Specialty Hospital in Murray, Utah, researchers measured ground reaction forces, or the force a runner applies to the ground, and the leg's "swing time," or the time it takes the runner to pick up a leg and put it back down.

Six unilateral-amputee runners, some of them Paralympic athletes, participated in the study, which allowed researchers to compare differences between prosthetic and biological legs in a more controlled way.

The researchers found that for the prosthetic leg, the runner's ground reaction force was lower, by an average of 9 percent.

"Vertical force to the ground is the major factor in sprinting speed," Kram said.

The team used video to compare their runners' swing times to sprinters at the Beijing Olympics. It's possible that swinging your legs faster could be an advantage for runners who use prostheses, Kram said, but they don't seem to swing their artificial leg any faster.

"The best amputee runners, the ones we analyzed from the Paralympics, are able to swing their legs as fast as runners from the Olympic games," Kram said.

"One of the runners that we studied, who was the silver medallist in the 400 meters (in the Paralympic Games), he swings his biological leg faster than his prosthetic leg," Kram said.

Last year, Kram was involved in a study that helped Pistorius fight his ban from the 2008 Olympics; ultimately, Pistorius did not qualify for the South African Olympic team.

"After that study was done, we wanted to know more, and we realized that studying one runner, who is the fastest runner with leg prostheses ever, is not good sample," Kram said. "We thought we could learn new and different things by studying bilateral amputees."

Paul Martin, of Boulder, is an Ironman and Paralympic athlete who participated in a study at the Locomotion Lab several years ago. Martin runs with a Flex-Run, the long-distance version of the Cheetah, and said he doesn't think about factors like ground reaction force when he's running -- he's just thinking about how much his leg hurts.

One day, he said, guys running on a prosthetic leg will have an advantage.

"I think it's opening up a can of worms, because I wholeheartedly think that one day, for those running on prostheses, science is going to catch up, and they're going to be better," Martin said.