Prosthetic Advantage

Olympic runner Oscar Pistorius has been the subject of discussion in the scientific community of late. Some say his carbon fibre blades give him an unfair advantage:

One of the biggest points of contention is limb-repositioning time. The average elite male sprinter moves his leg from back to front in 0.37 second. The five most recent world record holders in the 100-meter dash averaged 0.34 second. Pistorius swings his leg in 0.28 second, largely because his Cheetah's are lighter than a regular human leg. Pistorius's rivals are swinging a lower leg that weighs about 5.7 kilograms, whereas his lower leg only weighs 2.4 kilograms.

But most of the evidence would suggest otherwise:

Once Pistorius is off the blocks, he faces two distinct obstacles: navigating the two turns of the 400-meter race without an ankle, and compensating for the relative lack of energy generated by his strides. The Cheetah works like a basic spring, compressing when it hits the ground and storing potential energy, which it then releases as kinetic energy as the blade returns to its natural position. But the spring only returns about 90 percent of the energy generated by a runner's stride, according to a study released by Ossur. An able-bodied leg and foot, on the other hand, can return as much as 240 percent.

Some scientists continue to argue that Pistorius gains a degree of competitive advantage with the Cheetahs, a debate chronicled in a comprehensive Scientific American article. They reason that Pistorius' blades are much lighter than a human foot, which allows him to swing the blades faster and generate more force with each stride. But when the people who actually make and test the Cheetah say there is no competitive advantage for blade running over biological foot running, the naysayers' arguments lose a lot of credibility.

(Image: Reuters)