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Amputee Gets a Shot at the Olympics

Hugh Herr explains the scientific evidence behind the decision.

By Brittany Sauser

Wednesday, May 21, 2008

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Last week, Oscar Pistorius, a South African Paralympics runner, was granted the chance to fulfill his lifelong dream of competing in the Olympics by the Court of Arbitration for Sports (CAS), in Lausanne, Switzerland. The court upheld the appeal filed by Pistorius against the decision made on January 14 by the International Association of Athletics Federations (IAAF) that banned the "blade runner" from competing against able-bodied athletes. The CAS ruled that the IAAF did not provide "sufficient evidence of any metabolic advantage . . . [or sufficient evidence] that the biomechanical effects of using this particular prosthetic device gives Oscar Pistorius an advantage over other athletes not using the device."

Augmented humans: Hugh Herr, an MIT Media Lab professor and director of the Biomechatronics Group, led a team of researchers who evaluated the scientific validity of an IAAF study used to ban Oscar Pistorius, a Paralympics runner, from competing in able-bodied competitions.
Credit: MIT Media Lab

Pistorius is a double amputee who competes on J-shaped, carbon-fiber, Cheetah Flex-Foot prosthetics made by the Icelandic company Össur. After Pistorius performed well in an international able-bodied event in 2007, suspicion arose among members of the IAAF that his Cheetah prosthetics may give him an unfair advantage. Immediately, the institution placed a ban on using "technical devices," such as wheels and springs, in competition, and it decided to individually review Pistorius's case.

The IAAF conducted a two-day scientific study, led by German professor Gert-Peter Brüggemann, of the prostheses. Based on the resulting data, the IAAF concluded that Pistorius indeed has an unfair advantage over able-bodied athletes, claiming that he uses 25 percent less energy than they do to compete.

Astounded by such allegations, Pistorius's lawyers turned to MIT professor Hugh Herr and asked that he assess the scientific validity of the IAAF's study. Herr, the director of the Biomechatronics Group in the MIT Media Lab, and also an associate professor in the MIT-Harvard Division of Health Sciences and Technology, assembled a team that included experts in biomechanics and physiology from six universities to evaluate the scientific evidence.

Technology Review sat down with Herr and asked him to explain the scientific flaws that the team of researchers found in the IAAF study, as well as the broader implications of the CAS's ruling.

Technology Review: What were the claims made by the IAAF in its scientific report that you were tasked with assessing?

Hugh Herr: The first claim made by the IAAF was related to the metabolic energy required of Oscar to run. They claimed that Oscar, because of his Cheetah prostheses, was able to run at sprinting speeds with 25 percent less energy. In the second claim, the IAAF said the Cheetah prostheses release a greater amount of energy than the human ankle-foot complex in sprint speeds, and that that, in fact, introduces an artificial advantage to Oscar.

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TR: In regards to the first claim, how did the IAAF come to that conclusion, and what scientific evidence did you use to refute that claim?

HH: At sprinting speeds, the body uses two sources of energy: aerobic and anaerobic. The problem is that you can measure one energy source but not the other. Anaerobic energy cannot be quantified by anyone--not here in the U.S., not in Germany; it simply can't be precisely quantified. The IAAF claimed that it could be quantified, and they put a precise number on it: 25 percent energetic advantage at 400-meter-race speeds. This is deeply flawed because it can't be quantified at those speeds. No one can assess quantitatively whether there is an advantage or disadvantage.

Comments

  • able-bodied
    Since the argument is made that there is no advantage to using the Cheetah, I was wondering if able-bodied runners are allowed to use the same/similar devices in the Olympics as well.
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    dvschack
    05/21/2008
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  • Handicapped and Negligent Scientists!?
    Reading the article, I can't believe the negligent omissions in understanding what limits the speed of an athlete! Quite unimaginable ignorance. There are three things stopping an athlete travelling at unbelievable speeds, that would outpace ostriches, cheetahs and even fast cars! The weight of the athlete, working against gravity, the acceleration and deceleration of that weight and the wind resistance created when travelling forward, suggesting that the ratios of strength to weight, strength to mass of limb extremity and strength to frontal area of the limb is of paramount importance when considering this argument. I see no evidence that this has been looked at, yet this is the critical argument that need be considered.

    A runner who sprints at 27 mph must accelerate his lower legs to well over 54 mph with every stride, to compensate for the foot being stationary on the ground for a period of time with each stride. The work of acceleration and deceleration of the lower limb is resisted by the relative weight at the extremity, across the given speed range, effectively being far greater at higher speeds, 54+ mph and by the wind resistance, with energy requirements being squared as the speed doubles, as it does in this case.

    In cycling, reducing frontal area by having the cyclist reclining has seen speeds circa 70 mph, compared to the 40 mph conventionally seated. This is also the reason why the 'superman' position on the track was made illegal.

    I would like to point out also, that as a spring stores anergy for later release, the muscles around the ankle are doing actual work to absorb the shock of impact adding burden to the limitations of the cardiovascular system. This limiting factor for the speed of the runner with prosthetic limbs is removed, however, so is the burden of propulsion attributable from the lower limb. An advantage or disadvantage? Most drive comes from the muscles controlling hip and knee, but in what proportions to the lower limb it's difficult to say, but hardly what matters here to make a fair race.

    It's patently unfair to reduce your work load, by sizeable margins, by removing parts of your body, especially the fast moving, accelerating and decelerating, bits that have poor aerodynamics and yet keep the major propulsion engine relatively intact. The reduced resistance on the extremity of the limb also means that a longer prosthetic can be employed to increase leverage for the the drive coming from the upper legs, increasing stride length and reducing acceleration and deceleration cycles.

    If you want to asses athleticism, the loads on the cardiovascular system are going to be different for an amputee. Even taking the competition off the track and into the lab isn't going to create a fair and level playing field.

    Perhaps we can now get a biomechatronics specialist to argue that trucks and Formula 1 cars should compete together as there's no fundamental difference in there power output.

    Philip Grant


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    Artansoul
    05/21/2008
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