Different pacing
But that doesn't mean the South African runner is better off. "He does use less energy, but it's because he has less muscle," Weyand says. In a V02 max test (the maximum amount of oxygen, in milliliters, that the body uses in one minute, per kilogram of body weight), researchers found that while Pistorius used less energy than other sprinters to achieve his maximum, his maximum level was also comparatively lower by the same amount. "It's like he's a smaller car that uses less gas, but his engine is smaller in comparison," Weyand says.
Because Pistorius runs on blades and has no muscle fibers below the knee, some speculate he doesn't get as fatigued as other runners. Fueling that idea is the fact that able-bodied runners run the first half of a 400-meter race quickly, but finish more slowly. Pistorius' modus operandi is the opposite -- he opens slowly, due to a lack of ankles and Achilles tendons, but finishes fast.
"He looks faster at the end because he is," Weyand says. "Because his pacing is different from the intact-limb athletes, that fed into the idea that he's going to have better endurance and less fatigue."
In a treadmill test for this study, all runners began at a certain speed, eliminating the start. With this method, researchers concluded that Pistorius could hold his speed over longer sprint distances the same as able-bodied runners, leading them to believe he was no less fatigued than they were.
Pistorius appears to have different sprinting mechanics than his able-bodied counterparts. Previous tests have shown, Weyand says, that the amount of time it takes for someone to lift one leg off the ground and place it down again while running is virtually the same for everyone. "Slow pokes and speed demons are the same," Weyand says. "That's the way the system works -- you can't reposition them any faster. I expected [Pistorius] to conform."
But he didn't. He spent 34% less time in the air between steps and took 21% less time to reposition his limbs than the able-bodied runners. That, according to Weyand, is likely due to the fact that he has less mass because of the prostheses. But wait -- there's more.
Pistorius does not hit the ground as hard as runners who have intact limbs, again probably due to the lighter-weight prostheses. Also, his foot stays in contact with the ground 14% longer on each sprinting step.
Dispute on results
So -- drum roll -- do Pistorius' prosthetic limbs give him an advantage or not?
"I can't answer that question," Weyand says. "Those of us who conducted the test do not agree on that."
But he adds that more information will be revealed in another study to be released some time in the future.
"It's not at all a wash, so then it becomes a matter of interpretation," Weyand says. "Could he run that fast if he had biological limbs? Or, alternatively, if you took an average person and gave them blades, would they be able to swing their legs as fast?" Couple that with the fact that running prostheses will no doubt continue to evolve and, needless to say, this will surely be continued.
--
jeannine.stein@latimes.com
