'No Advantage to Being an Amputee': A Defense of Oscar Pistorius's Prostheses
Some think the Olympic runner has an unfair edge over his competitors, but the man who designed his limbs says otherwise.
Before Oscar Pistorius ever set foot inside London's Olympic Stadium, before he prepared for the 400-meter race by connecting two carbon fiber blades to the stumps of his legs, he had to move heaven and earth just to be allowed to compete. Pistorius, a South African sprinter who was born without fibulas and had both legs amputated just below the knee when he was 11 months old, had tried to enter the 2008 Olympics in Beijing, only to be rebuffed by track's international governing body. His prosthetic legs allegedly gave him a biomechanical advantage.
Pistorius quickly appealed the ruling to the Court of Arbitration for Sport, which ruled in early 2008 that he was eligible to compete in the Olympics (Pistorius missed qualifying for Beijing by 0.7 seconds). Pistorius continued to improve his times and qualified for London, racing in the 400 meters and advancing out of the preliminary round with a season-best time of 45.44 seconds on Saturday. Though Pistorius failed to qualify for the finals in the event, he will race again later this week as a part of South Africa's 4x400-meter relay team.
Pistorius is not the first amputee athlete to compete in the Olympics. Fellow South African Natalie Du Toit, who finished 16th in the 10K marathon swim in Beijing, lost her left leg below the knee in 2001. But Pistorius is the first Olympian amputee in track and field, and unlike Du Toit, he uses prosthetics.
Even as the 25-year-old South African pushed his body beyond reasonable physical limits and ultimately made it to London, scientists debated whether Pistorius' Flex-Foot Cheetahs—the J-shaped carbon blades that he runs on—give him a competitive advantage over able-bodied runners.
To the man who has designed Pistorius' prosthetics for more than 10 years, there is no debate.
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"In my opinion, there's no advantage to being an amputee," said Francois Van Der Watt, the prosthetics manager at Ossur Americas in Houston. "[The Cheetah] is not anything that's internally powered. There's no advantage that comes out of wearing it."
Van Der Watt first met Pistorius when the young runner was in high school. Back then, Pistorius sprinted in his everyday prosthetic feet, which broke easily under the strain of competitive running, Van Der Watt said.
The prosthetic expert began working with Pistorius to build an ideal apparatus for his weight and body type, refining the design as the sprinter rose to prominence in South Africa.
Pistorius now uses the Cheetah Flex Foot, the Ossur-designed carbon blades that Olympic watchers saw on Pistorius as he sprinted around the track in London this weekend. But despite earning the nickname "Blade Runner", Pistorius is working at a severe competitive disadvantage from the moment the starting gun goes off.
Because he has no ankle motion with the Cheetahs, Pistorius cannot achieve the energy gained from flexing the ankle against the starting blocks and then powering off. Of the 47 runners to finish the preliminary round of the 400 meters in London, Pistorius had the fourth-slowest reaction time at the start, no surprise given the awkward motion he must make to begin the race.
"You don't have position in the blocks to get an optimum start," Van Der Watt said of running with the Cheetahs. "You actually have a position where you have to swing [your leg] to the outside to start, so you're not pushing off as fast as an able-bodied man."
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. So while Pistorius' blades are lighter and quicker off the ground than the lower legs of the other runners, they don't make up for getting barely a third as much energy from every step, Van Der Watt noted.
On the turns, Pistorius loses even more energy because he must turn the blades with his upper legs and core muscles, rather than changing his ankle position as other runners can. On some of his strides, only part of the blade touches the ground, which means there is less kinetic energy generated.
Triathlete Sarah Reinertsen, the first woman to complete the Ironman Triathlon with a prosthetic leg, said that turning while running on prosthetics is doubly difficult because of the less-than-perfect connection between machine and human.
"When you watch the slow-motion of [Pistorius] running, you can see the prosthetics are rotating," she said. "That's a counter-force that he's working against with every step. That's energy being lost right there."
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.
For Reinertsen, who first completed the Ironman in 2005, the debate itself is a victory for amputee athletes.
"Oscar's story is being shouted across the world because it's the Olympics," she said. "People are talking about the legs and inclusion and having that debate. It's cool that we're even having this discussion."
Reinertsen woke up at 2AM on Saturday to watch Pistorius' first Olympic race live-streamed online. Though Pistorius failed to advance past the semifinals, his very presence on the track was an inspirational triumph for the human race. Step back from the scientific debate and the chattering over qualifying times, and what you have is a man with no lower legs running track in the Olympics. If that doesn't prove the old adage "anything is possible", nothing does.
"It was a proud moment," Van Der Watt said of watching Pistorius' historic run. "We've been through the trials and errors, and I know how long he's been chasing the dream. I'm glad that he was able to make that dream come true."