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Oscar Pistorius' Prosthetic Legs: Do They Give Him an Advantage Over Other Olympic Runners?

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Despite finishing last in a semifinal of the Olympic 400 meters, South African Oscar Pistorius ran himself into the hearts of the public and engrained himself in the history books as the first double amputee to compete in the Olympics. Affectionately referred to as "the fastest man with no legs" or "the Blade Runner," Pistorius competes with the aid of bioengineered carbon-fiber prosthetics. While there is overwhelming admiration for his heroics, there is a faction of dissenters who believe that Pistorius is at an advantage over his able-bodied peers.

Biomechanist Roger Kram of the University of Colorado and biophysicist Hugh Herr of MIT led a team of scientists to investigate this perceived advantage. It was stated in their report, published in The Journal of Applied Physiology (JAP), that Pistorius was "physiologically similar but mechanically dissimilar" to an abled-bodied runner. So does that mean he's at an advantage? Let's examine the findings.

Physiologically

Muscle-tendon units (such as the calf-Achilles, which Pistorius lacks) are viscoelastic. In other words, they demonstrate both viscous and elastic properties when subjected to deformation. Basically, the more viscous a material, the harder it is to move. Carbon-fiber prosthetics, however, act more akin to something that is elastic and thus demonstrate relatively faster recoil. In other words, when stretched, or when a force is applied (such as pushing off the ground), it returns back to its original state much quicker than something that is more viscous (such as muscle).

As explained to Scientific American by executive vice president of research and development of Össur, the Icelandic company that manufactures Pistorius' blades, "when the user is running, the prosthesis's J curve is compressed at impact, storing energy and absorbing high levels of stress that would otherwise be absorbed by a runner's ankle, knee, hip and lower back." Thus, thanks to this elastic-like property, the use of blades would theoretically result in improved energy efficiency. In fact, this was found to be true, as a 2007 study out of Cologne, Germany, Pistorius was found to use 25-percent less energy than his peers. The report out of JAP, however, reported negligible changes in energy expenditure. The inconsistencies in the findings are attributed to a disparity in study methodology, leading Kram to state that Pistorius' "rate of energy consumption was lower than an average person but comparable to other high-caliber athletes."

Mechanically

The reduced viscosity of the blade relative to muscle, as well as its lightness, explains why Pistorius demonstrates faster leg swings than his able-bodied peers. In fact, in a competing report to the JAP study (conduct by physiologist Peter Weyland of Southern Methodist University and biomechanist Matthew Bundle of the University of Wyoming), it was found that the carbon-fiber blades allow Pistorius to reposition his limbs 15.7-percent faster than the most recent world record holders in the 100-meter dash. This enables for a 15- to 30-percent increase in sprint speed.

To make matters even more partisan, the structure of the blade appears to have a longer functional lever arm than that of the human foot (i.e., the point of contact is further away from the axes of rotation -- lower extremity joints -- than the typical contact point of the foot). This allows for a larger generation of torque when an identical magnitude of force is applied (torque = force x lever arm). The catch-22, however, is that Pistorius does not exert as much force during push-off from the ground as an able-bodied runner. While this would appear to negate any advantage that he may possess, attributed to the springy, elastic-like structure of the blades, Pistorius requires less than half of the muscle force and 20-percent less ground forces to attain the same running speeds as able-bodied runners.

Conclusion

So, when you add it up, you get a runner who has light-weight, spring-like legs that allow for more efficient movement, and a reduced requirement of force production. The question is therefore not whether he possesses an advantage but how much of an advantage is unfair. Regardless of the debate, Pistorius' remarkable journey, and the heart and spirit he has demonstrated, embody what the Olympic Games stand for. The sight of a legless sprinter utilizing the technology of today to compete in the oldest athletic event this world knows captured the hearts and minds of people of all religions, cultures, and creeds. I salute you, Oscar Pistorius -- even if you are at an advantage.