How Olympic 'Blade Runner' Sprints Without Feet
South Africa's Oscar Pistorius will be the first amputee to compete in the Olympics. Here's a look at the mechanics of how he runs.
- Oscar Pistorius will be the first amputee athlete to compete in the Olympics.
- His inclusion in the Olympics has sparked a debate in the scientific community about whether his blades give him an advantage.
- The future of prosthetics for runners could closely resemble a human leg.
When the start gun goes off for the individual 400 and 4X400 relay at the 2012 London Olympics, double-amputee sprinter Oscar Pistorius, the man known as the Blade Runner, will spring out of the blocks with the world's best able-bodied athletes. It marks the first time an amputee will compete in the Olympics.
Pistorius will be wearing carbon-fiber prosthetics designed for sprinting. While the debate over whether his flex-foot Cheetahs makes it harder or easier for him to sprint continues, there's no doubt that the way his body covers 400 meters is different from his competitors.
As the athletes explode from their starting blocks, the South African born without fibulas will likely get a slower start. Because he can't flex an ankle or stiffen a leg, it takes slightly longer for Pistorius to start. As the athletes gain an upright position, however, Pistorius will be able to reposition his legs much more quickly than his competitors. It's that repositioning speed that's been the point of contention of much of the debate.
In 2008, the International Association of Athletics Federations, track and field's governing body, banned Pistorius from competing against able-bodied competitors, deeming his blades an advantage.
Pistorius went to Rice University in Houston for what he hoped would be definitive testing that would prove he had no advantage. And at first, that appeared to be the case: using some of the data from the research, published in the Journal of Applied Physiology, the Court of Arbitration for Sport overturned the ban.
But later, two of the scientists pointed to key findings -- the repositioning data -- that they believe make up at least a 7-second difference in the 400-meter dash. Researchers Peter Weyand, an exercise physiologist at Southern Methodist University, and Matt Bundle, an assistant professor at the University of Montana, presented their case in a point-counterpoint article in the Journal of Applied Physiology in 2009.
The reason the data is so telling, says Weyand, is not just that it shows an advantage; it's that the comparison between Pistorius and able-bodied world class sprinters is off the charts. (Weyand and Bundle released a statement that explains their science, hoping to clear up misconceptions.)
"With the most generous assumptions, he still comes out seven seconds ahead in the 400," Weyand said. "He's a below-average high school runner without those limbs. A lot of people don't want to hear that."
Weyand stresses that he respects and admires Pistorius, but "there's no point in acquiring data if we can't report it accurately."
Hugh Herr, the director of the Biomechatronics Group at the Massachusetts Institute of Technology and another of the researchers, focuses on the lower force a runner in prosthetics creates. Without ankles, he says, amputees can't create the leg stiffness to hit the ground as forcefully as able-bodied runners.
"It's like running on a springy mattress," he says. "The ankle is an important joint for modulating whole leg stiffness, and it's been shown that a runner like Pistorius doesn't have that dramatic leg stiffness change."
The repositioning data, he says, is not enough evidence to bar him from competing (under international rules, athletes are allowed to compete unless evidence shows sufficient reason they shouldn't).
Weyand doesn't dispute that an ankle might be an advantage, but he says it's accounted for in a simple mathematical equation: speed (meters/second) = stride length (meters) X stride frequency (strides/second).
"If having no ankle affects speed, it must do so through an effect on either stride length, stride frequency or both," he says. The 7-second advantage also includes half a second for the slower start the ankle-less blades provide.
Perhaps part of the reason Pistorius' situation has attracted so much attention is because the circumstances are so unique. Bilateral amputees are rare: There are likely less than a handful of bilateral amputee runners in the world. It's hard to compare Pistorius to anyone else.
It's also hard to separate the emotional pull of the story from the scientific facts. Even Weyand isn't sure how the data should be used by the governing bodies. Having an advantage doesn't necessarily mean Pistorius shouldn't be allowed to compete, Weyand pointed out.
"It's not our place to make the policy," Weyand said. "Those are hard decisions, and it depends philosophically on what sport should be. I'm happy I'm not in their shoes."
Could legs be made that would equalize the playing field? Probably, experts say.
"We know enough about running mechanics that we can quantify it," Weyand says. "You could easily make it heavier, for example...and as you continue to refine the properties, you could get pretty close."
Pistorius' Cheetahs haven't changed much since their debut in 1997. Designed specifically for sprinting, they maintain a fixed position that makes it hard to stand still or even walk easily.
"They're missing the heel section, because sprinters are toe strikers," explains Richard Hirons, clinical specialist at Ossur, the company that makes the Cheetahs. "It has the profile of a foot, but it's pointing downward, like you're standing on tiptoes."
Running in them can still make Pistorius sore where they meet his remaining legs. He wears a more practical pair of carbon fiber feet with heels and a cosmetic cover for daily life.
Future prosthetics may minimize the differences between the two.
"In a sprint, you think of the different stages:the drive and acceleration from the blocks where you start in a squat and bend forward in transition," Hirons said. "You have the normal human anatomy working in one way, then in the run in a different way. The prosthetic is omptimized one way or another. In the future, there may be a more refined design to minimize the compromise."
And, sprinting is a small part of any runner's daily life, Hirons points out.
"Most people just see him on the starting line," he said. "But it's also about carrying his bags to the starting line, taking a bath or a shower, going up stairs. It's about what he's able to do to get to the starting line."