A team of experts in biomechanics and physiology that conducted experiments on Oscar Pistorius, the South African bilateral amputee track athlete, have just published their findings in the Journal of Applied Physiology. Some of their previously confidential findings were presented to the Court of Arbitration for Sport (CAS) in Lausanne, Switzerland in May of 2008. Other findings are now being presented for the first time.

A portion of the team's findings were presented at the CAS to appeal the eligibility ban imposed on Pistorius by the International Association of Athletics Federations (IAAF) barring him from sanctioned competitions, including the Olympics and World Championships. The IAAF had claimed that the Cheetah Flex-Foot prostheses (J-shaped, high-performance prostheses used for running) worn by Pistorius give him an advantage over able-bodied runners. The appeal was successfully presented on behalf of Pistorius by the international law firm of Dewey & LeBoeuf who took the case on a pro-bono basis. The CAS concluded that the IAAF failed to prove that the biomechanical effects of the Cheetah prostheses give Pistorius an advantage over other athletes not using the prostheses.

"I am delighted that the biomechanical and energetic data presented to the CAS are now published in a scientific journal and available to the public," said Hugh Herr, associate professor of Media Arts and Sciences and Health Sciences and Technology at the Massachusetts Institute of Technology (MIT), and head of the Biomechatronics research group at the MIT Media Lab. Herr presented the results at the CAS with colleague Professor Rodger Kram of the University of Colorado. Herr and Kram are two of seven authors of the study.

The other authors are Mary Beth Brown of the Georgia Institute of Technology, Matthew Bundle of the University of Wyoming, Alena Grabowski of the Massachusetts Institute of Technology, Craig McGowan of the University of Texas at Austin, and Peter Weyand of Southern Methodist University. None received compensation for the research or work on behalf of the CAS hearing. The group agreed to conduct the experiments with the understanding that they would be able to publish their scientific findings after the CAS hearing.

The scientific team compared Oscar Pistorius to track athletes with intact limbs to evaluate their:

  • Energy cost of running
  • Fatigue resistance
  • Sprinting mechanics

The team concluded that:

  • Pistorius’ maximal rate of aerobic metabolism (VO2max) is 7.6 percent lower than that of the average for intact-limb 400-meter specialists. However, he has essentially the same running speed at VO2max because his metabolic cost of running is 17 percent lower than the average for the performance-matched male sprinters. His running economy is similar to that of accomplished male distance runners.
  • Pistorius’ ability to hold his speed over longer sprint races is identical to that of intact-limb athletes.
  • Pistorius’ sprinting mechanics are markedly dissimilar to intact-limb track athletes. At top speed:
    • He exerts considerably less force on the ground in relation to his body weight than intact-limb runners.
    • His foot is in contact with the ground 14% longer on each sprinting step.
    • He spends 34% less time in the air between steps.
    • He takes 21% less time to reposition (swing) his legs between steps.

In summary, the team concluded that Pistorius’ physiology (energy cost and fatigability) is generally similar to that of intact-limb athletes, but his sprint running mechanics are markedly dissimilar.

The group’s paper in the Journal of Applied Physiology concludes:

The mechanical dissimilarities observed between Pistorius and intact-limb runners result from functional trade-offs that are perhaps inevitable for artificial vs. biological limbs. The aerial and swing time reductions observed for Pistorius may be due to his light-weight prostheses. However, the meager forces he exerts on the ground may be a critical limitation for speed. Legs must perform different functions during the stance and swing phases of the stride, as well as during the start, acceleration and relatively constant-speed phases of sprint running. Collectively, the results underscore the difficulty of providing these multiple mechanical functions with a single, relatively simple prosthetic design, and the formidable challenges involved in engineering limbs that fully mimic those produced by nature.

The full article can be obtained from the Journal of Applied Physiology Web site:

http://jap.physiology.org/cgi/reprint/00174.2009v1

Contact:
MIT Media Lab
Alexandra Kahn, 617-253-0365
akahn [at] media [dot] mit [dot] edu

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