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Adventure Lab: Testing "Prosthetic Advantage"

A couple of years ago, Wired magazine put out a forward-looking article addressing whether paralympic sprinter Oscar Pistorius's artificial legs (called Cheetahs) gave him an advantage over able-bodied sprinters. After all, at the time he was close to qualifying for the Olympics with prostheses.

No one expects able-bodied runners to compete head-to-head withwheelchair-bound marathoners. The wheels confer an obvious speedadvantage, and maybe Oscar Pistorius’ Cheetahs do, too. So the realquestion is this: Do able-bodied athletes need protection from him? (Wired, March 2007)

A team of scientists from MIT took on the challenge, testing whether new advances in prosthetic technology gave athletes with artificial legs an advantage. The team put six elite sprinters with prosthetic legs on a fancy treadmill. They measured the ground reaction force of the sprinters' legs and watched videos to examine leg swing times. The article was published this week in Biology Letters.

Though prosthetic legs are lighter than real legs, the athletes equipped with them did not have faster swing times. In addition, the sprinters tested measured 9 percent less ground reaction force on their prosthesis. More force equals more speed. It could be inferred that able-bodied sprinters, using a prosthesis on one leg, would likely run slower as a result of less force. A full breakdown of the study and a video of the tests appears in this Science Now article.

The best quote in the Science Now article came from Young-Hui Chang, a comparative physiologist at the Georgia Institute ofTechnology in Atlanta.

...the debate may be missinghow much amputee athletes must overcome mechanically to competealongside able-bodied runners. These devices can't generate power ontheir own, like biological legs can, he says. "To think that[prostheses] give you an unfair advantage may be overlooking theobvious." (Science Now, November 4, 2009)

Josh McHugh addressed this point in the Wired article, and a cool Wired graphic explained how Pistorius's prostheses worked.

Now, there's a targeted study with solid results that addresses many of the issues brought up in that story.

The Takeaway: Not taking into account other considerations about lost limbs, it's not accurate to think that prostheses currently give athletes a biomechanical advantage. Elite sprinters' with prostheses have had to alter their strides and adjust their training in order to compensate for the return energy generated by their lost lower leg, or legs.

Comment: If scientists can develop legs that allow paralympians to compete at the same level as other athletes should they be allowed to compete in the Olympics?

--Joe Spring

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