How Fair Are Running Prosthetics?

Jul 27 2012 @ 5:59pm

As a somewhat extreme example of how technology can improve today's athletes, South African runner Oscar Pistorius, a double amputee below the knees, runs on carbon fiber blades named "Flex-Foot Cheetahs." In order to be able to compete in the Olympics, a study was done to see whether his prosthetics offered him an unfair advantage, and though the study concluded he could enter the games, the researchers still aren't exactly in agreement about the science:

Swing time is important because it affects some central factors that determine how fast a person can run. Repositioning his legs faster means Pistorius can keep his foot on the ground longer than everyone else. It's a bit counterintuitive, but [physiologist Peter] Weyand argues that a runner's speed is largely determined by how long he can keep his feet on the ground, rather than in the air.

The longer a foot remains on the ground, the more time the person has to generate force that will propel him forward. More force generally means more speed. [Physiologist Rodger] Kram argues, however, that because the Cheetahs are made of carbon fiber, and are lighter, they can't transmit nearly as much force to the ground as a human leg can, creating less forward propulsion. So Pistorius has to push down harder than most people to get the same amount of force against the ground.

Weyand counters that Pistorius simply doesn't need to push as hard to run just as fast. Of course, other researchers have other theories about a possible advantage. Because Pistorius's Cheetah's don't tire, his lower leg stays springy throughout the entire race. For most 400-meter runners the second half of the race is where the real battle happens. Jim Matin, a researcher at the University of Utah, says that the lower leg is what weakens and slows runners. Martin thinks that if Pistorius ran in a competitive 600-meter race, Pistorius could set the world record.