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

By Andrew Moseman | November 19, 2009 11:59 am

pistorius1If  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

CATEGORIZED UNDER: Feature, Physics & Math, Technology
  • qbsmd

    I don’t understand why this is a go-no go issue. Since the issue is lighter weight leading to faster leg movement, why can’t the Olympic committee or whoever else just specify a minimum weight (or moment of inertia) for artificial legs to be used in competitions?

  • Wesley

    Woah woah woah qbsmd. Don’t try making too much sense all at once! They’re not ready for that! lol

  • Stan Wright

    If you were a promising, two-legged runner – the champion of your barrio – who was hampered only by meat legs of much less than ideal geometry, how poor would you have to be before you’d consider giving them up in exchange for protheses that could overcome this limitation and make you fast enough to win? What if your possible Olympic prowess was your family’s only chance to make it out of poverty?

  • MensaJeff

    Excellent point, Stan Wright.
    And, touching on qbsmd’s remark, if technical specs have to be written for prosthetics in competition, there will be no end to the arguments. I’m sure enterprising engineers can create race-winning prosthetics, with Olympic gold as incentive, and that means the rulebook would ultimately decide if prosthetics win or not. How fast do we *allow* them to go? There is no formula to level the playing field; in the end, it’s really apples and oranges.
    Hats off to the brave and determined athletes who work so hard to reach their potential, and compete at the highest level they can reach. And a similar salute to the amazing work being done in prosthetics. I think we all recognize and respect what great accomplishments we’re discussing. But, much as an Indy car doesn’t race against a NASCAR stock car, racing for wins and records only makes sense between equal competitors.

  • aHahn

    @ Qbsmd~ Part of the problem is the prosthese themselves. As many know, they are made for each indivigual amputee, and as a result, the system an amputee wears is coustom to their body (residual limb size and length, body wieght, height, etc.). This makes it very hard to simply ask an amputee to “add weight” to their prosthesis, or to change their chosen system to something completly new. There is actually a “window of opportunity”, so to speak, for an amputee to get used to wearing any type of prosthesis anfter their initial amputation. Generally once an amputee is using a prosthesis, and they have become used to a given system, it can be very hard for thier bodies to accept and/or get used to using a new system. Therefore aksing an athlete, or any amputee, to adjust their prosthesis by adding weight, or making other large adjustments is much easier said than done.

    I personally don’t think it’s unfair for the Olympic Comettee or other Olympic governing bodies to not allow Pistorius to compete against able-bodied athletes at the Olympic level, simply because they are not amputees themselves and therefore do not have access to prostheses. Being a college student studying to be a Prosthetics & Orthotics Practitioner, this is an issue I’m watching closely and one that really is a defining issue for both the sporting and medical communities.

  • http://diewithyourfeeton.com Nick W

    Stan Wright, if you’re poor enough to consider cutting your legs off for sprinting success, chances are you can’t afford £15,000 carbon fibre blades to strap on the end of your new stumps…

    It’s also worth bearing in mind that Pistorious has been a double-leg amputee since he was something like 11 months old. I don’t know that someone could adapt to amputation in their teens and come back to be fitter than they were; it’s not a risk many would take.

    As for the topic itself, the evidence that the blades offer an advantage is compelling enough to me that I believe he shouldn’t be allowed to compete with non-amputees. It takes nothing away from his hard work or talent, but it’s not a level playing field.

  • Angie

    If he is better than all the other runners, and obviously he is, just let him win. I think people are just furious with his success, because a guy with no legs was faster than them. But you know what? That´s life. Sometimes the most unexpected thing happens and you have to get adapted to whatever it is. Get used to it. Isn´t it only fair to let him win, when he actually is faster? The other guys can go on a diet and lose some weight that way, if they consider the whole matter unfair.

  • Jockaira

    Angie nailed it!

    I don’t believe there were or are rules that prohibit an amputee from competing with the “able-bodied” and that’s how it should be. So long as Pistorius or any other athete can run only on his own muscle power and human determination, there is no rational reason to keep him out of the race.

  • megan

    Simple logic, would those WITH prostheses have been or were near to record breaking speeds BEFORE losing their biological limbs? If not then it’s not fair. We might as well allow natural hormone enhancements for those disabled from low testosterone or too high body fat. The sports that do allow that state it than force competition between unequal participants. (ie Bodybuilding)

  • http://www.paypal.com/ Maricruz Isidoro

    Where is this blog’s contact us section because i cant seem to locate the page, maybe you might want to make it more easily viewable.

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