MIT research: Prosthetics don't give amputee sprinters an advantage

From The Guardian in the UK:

Prosthetics worn by disabled sprinters confer no speed advantage, scientists have found. If anything, they may reduce the top speed a runner can achieve.

The research supports the case made by the South African Paralympic runner Oscar Pistorius (pictured), who uses flexible carbon-fibre blades in races. Pistorius has long argued that he should be allowed to compete alongside able-bodied athletes in races, but athletics authorities banned him from doing so in last year's Olympic games, claiming that his blades gave him an unfair advantage over able-bodied athletes.

But the new study by Alena Grabowski at the Massachusetts Institute of Technology suggests the authorities may have come to the wrong conclusion.

Grabowski and her colleagues examined how six elite sprinters, each with one amputated leg, ran with their prostheses. The researchers chose sprinters with one amputation because it allowed them to compare the action of a prosthetic limb directly against a real leg.

They 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 results are published today in the journal Biology Letters.

Simon Choppin, a sports engineer at Sheffield Hallam University, said the Pistorius controversy rested on whether his prosthetics increased the efficiency of his limbs, allowing him to achieve higher speeds for less effort.

"So, simply, you can move the prosthetic quicker and you're ready for the next step faster than someone who has a leg," said Choppin. Another possible advantage was that the prosthetics might allow the athlete to get back more of the energy they put into the track compared with able-bodied athletes. "But this [Grabowski] paper suggests you're at a disadvantage if you've got one of these blades."

Choppin suggested that the lower ground force was probably due to the relative lack of muscle in an amputee's leg. Even so, this did not mean it was inevitable that amputee sprinters would be slower runners. To compensate for the lower ground force, Grabowski found that amputees typically moved their legs more quickly to generate the same amount of power.

The research may allow athletes such as Pistorius to take their place in elite races, said Choppin. "It's hopefully good evidence that able-boded athletes will be able to compete alongside amputees such as Oscar Pistorius without that stigma that amputees are at an advantage somehow. This evidence suggests in fact they're not – they're having to compensate for the lower force by running in a different way."