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Scientist Smackdown: Are a Sprinter's Prostethic Legs an Unfair Advantage?

By Andrew Moseman
Nov 19, 2009 10:59 PMNov 19, 2019 8:20 PM


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If you read this blog last week, you might have seen us cover a study suggesting that South African sprinter Oscar Pistorius ought to be allowed to compete in the same track and field events as everyone else because his prosthetic legs confer no advantage over a sprinter with biological legs. But if you saw a study cited by the Associated Press and many other publications yesterday, you might think that Pistorius would soon be banned from competitions, because his "blades" let him swing his legs far faster than even the world's fastest man, Usain Bolt. So what the heck is going on? The AP's study isn't actually a "study," per se. Rather, what the Journal of Applied Physiology published was a point-counterpoint (pdf), now freely available for anyone to read. In in, Peter Weyand and Matthew Bundle argue that Pistorius' prosthetics are a huge advantage, particularly in what matters most: how fast he can move his legs.

Weyand and Bundle say that the lightweight blades allow Pistorius "to reposition his limbs 15.7 percent more rapidly than five of the most recent former world-record holders in the 100-meter dash" [AP]

. There is, however, a counterpoint to this argument in the journal piece that yesterday's news reports neglected, coauthored by Alena Grabowski of the MIT Media Lab (who led the research on Pistorius' blades that 80beats covered last week). Her team has

found that the limiting factor determining an athlete's top speed was how hard the foot or prosthesis hit the ground. Their study showed this "ground force" was around 9% lower in the prosthetic limb versus the unaffected leg [The Guardian]

. Grabowski's research focused on professional runners with only one prosthetic leg. No matter, Weyand and Bundle say in a rebuttal to the counterpoint: because Pistorius swings his legs so quickly (about .28 seconds per leg, as opposed to the .36 seconds of world-class sprinters with biological legs), he needs 20 percent less ground force than an ordinary runner would to maintain the same speed. Weyand told DISCOVER that the MIT team's research is probably correct about speed and power when it comes to runners with only one prosthetic. "One limb can't go faster than the other," or the runner would go in a circle. But a runner like Pistorius with two prosthetics can learn to swing both legs at the "off-the-charts" speed of .28 seconds, he says, gaining a clear advantage. Grabowski was understandably miffed at her side's counterargument being left out of news reports. "We're all sort of shaking our heads," she said. She also questioned the validity of Weyand and Bundle's findings, saying in an email to DISCOVER that they represent an opinion and not a peer-reviewed study, that they don't consider the starting blocks and turning inherent in a 400-meter race, and Weyand and Bundle's assertion that Pistorius' blades take 10 seconds off his 400-meter time "is ridiculous and not based on data." But, Weyand tells DISCOVER, he and Bundle got their data during direct observations of Pistorius last year, during the time he was attempting to qualify for the Beijing Olympics. At that time they arrived at the same kind of conclusion Grabowski's side has arrived at now—that the sprinter ought not be banned. The reason for this odd twist in the story, Weyand says, is that he and Bundle were brought in by Pistorius' law firm during a hearing last May on the question of whether to overturn a ban on Pistorius, but the hearing could only consider the evidence used to enact the ban in the first place. So, Weyand tells DISCOVER, he and Bundle's were advocating analysis suggested the ban be overturned because its basis was shoddy insufficient scientific evidence, and at the same time their own studies convinced them that he did have a clear advantage. To make this affair even stranger, both sides—Weyand and Bundle's team, and Grabowski's—all co-authored a less controversial paper earlier this year in the same journal. However, Bundle tells DISCOVER, they left the question of advantage or no advantage out of that paper because they couldn't agree, and published this point-counterpoint instead. "The comparisons and analysis that Peter and I present in the point-counterpoint are novel, in part because our co-authors prevented them from being included in the manuscript that appeared in June," he says. As for peer review, Bundle says his argument did receive this treatment, because the journal's standards consider the editors' approval of an article to be an appropriate review. This scientist smackdown isn't going away: Grabowski told DISCOVER she would issue a press release in response to Weyand and Bundle's, and continue her prosthesis research. Though if there's one thing both sides can agree on, it's that Pistorius is a remarkable athlete, advantage or not. "What he does as an athletic feat is really an amazing thing," Weyand says. Related Content: 80beats: Prosthetic Legs Aren't Better Than the Real Thing... Yet 80beats: Scientist Smackdown: All Our Stories of Lively Scientific Debate 80beats: Toddler Gets a Telescoping, Prosthetic Arm Bone That Grows With Him Science Not Fiction: Dr. Terminator: The Prosthetics Designer Who Makes Sci-Fi Sculptures

Image: flickr/Elvar Freyr

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