David Epstein
Thursday November 19th, 2009

Eighteen months ago, South African sprinter Oscar Pistorius -- famously known as the "Blade Runner" because he was born without fibulas and runs on two crescent, carbon fiber lower legs -- made global headlines when the Court of Arbitration for Sport (CAS) overturned a ban by the International Association of Athletics Federations and allowed Pistorius to compete against able-bodied runners in international competition.

The work of a group of seven scientists paved the way for Pistorius, one of the fastest South African 400-meter runners, to pursue his Olympic dream by refuting the IAAF's contention that Pistorius' artificial limbs conferred a competitive advantage. But in a report that appears today in the Journal of Applied Physiology, two of those seven scientists now say that the so-called "Cheetah" legs make Pistorius 10 seconds faster over 400 meters than he otherwise would be, a boost so significant as to make the difference between a mediocre high school runner and an Olympian. (The study was conducted before the CAS ruled. To learn why the information did not become public back then, read on.)

The researchers found that because the carbon fiber Cheetahs are about half the weight (approximately 6 ½ pounds) of an able-bodied sprinter's lower leg, Pistorius can swing his lower leg through the air between strides 15.7 percent more quickly (0.284 seconds at top speed) than the average of five former 100-meter world record holders who were studied. "Oscar is off the charts," said Peter Weyand, one of the researchers and an exercise physiologist at Southern Methodist University. "Clearly, with athletes with intact limbs, there's a lower limit to how fast they can reposition their limbs. With Oscar, if you make that lower limb twice as light, that moves that lower limit."

In fact, Weyand and co-author Matthew Bundle, assistant professor of kinesiology and health at the University of Wyoming, concluded that Pistorius has the highest stride frequency ever recorded because of how quickly the lightweight Cheetahs allow him to whip his legs through the air.

Additionally, because Pistorius repositions his limbs so quickly, and because of the way the Cheetah's support his upper body, he has the liberty of spending more time with the foot of each Cheetah on the ground, generating force all the while. "He repositions his limbs so fast that he doesn't need to get his body back up into the air so high like other sprinters, and that lowers the force he needs to generate," Weyand said. "The muscular forces he has to generate are less than half of what an intact sprinter has to generate to go the same speed."

Sound a little confusing? Mull over this example: In 1996, "clap" speed skates were introduced and revolutionized the sport of speed skating. Skaters who used them rewrote the record books in short order. Clap skates have a hinge at the toe and detachable heel, which allow the skater to keep the blade on the ice for a longer duration during each push. The longer the push time, the more force can be generated. Because Pistorius does not need to bounce himself off the ground as forcefully as other sprinters, he leaves his Cheetah on the ground and has an inordinately long push phase in each stride. "The intact guys don't have that option," Weyand said. "He can stay down longer and still bounce. The guys with intact limbs have to get off the ground fast to run fast."

Bundle and Weyand conclude in their report that "the moment in athletic history when engineered limbs outperform biological limbs has already passed."

Bundle and Weyand both said they knew even before the Court of Arbitration for Sport overturned the IAAF ban last year that Pistorius was running with an advantage. "From the instant we collected the gait-mechanics data and saw how short his swing times are, we said to the group [of scientists they were working with] that it's really clear he's got an advantage," Weyand said. (Read this for a quick history of the Pistorius controversy up through the CAS ruling.)

However, the two scientists contend that they kept the data private for two reasons:

1) The first reason amounts, essentially, to a technicality of the CAS process. The CAS hearing sought not the entire truth, but only to confirm or rebut the previous findings by an IAAF assigned scientist who said that the Cheetahs returned energy more efficiently to Pistorius' legs than the ankle joint of able-bodied sprinters, allowing Pistorius to coast at high speeds and expend little energy. (Bundle and Weyand say that the energy return is relatively meaningless for sprinters, who are seeking the mechanics for maximum speed, not energy efficiency. "It's like arguing that a Volkswagen is going to win a drag race with a Porsche," Weyand said. "[IAAF] picked the wrong issues to have the fight on.")

2) The second is a technicality of the scientific-journal publication process. Both scientists say that the peer-review and embargo process that scientific journals employ constrained how quickly they could make the information public. If researchers disclose data publicly, before the data is reviewed by other scientists, some top journals are loath to accept the work later on. "Our deal with [Pistorius'] lawyers was that we would do all this for free, but would be able to publish once we were done," Bundle said. Which begs another question: What do lawyers have to do with initiating scientific research?

Pistorius' legal team initially contacted exercise scientists in South Africa and asked to have studies conducted. Ross Tucker, a South African exercise physiologist who was contacted by the Pistorius team wrote on his The Science of Sport blog that Pistorius' team went "door-to-door ... and asked [researchers] to prove that he had no advantage." Tucker, feeling that Pistorius did have an advantage, declined to conduct a study.

Bundle and Weyand say that they were allowed to do whatever tests they saw fit, but that "we felt constrained by the [publishing] rules of the scientific community," Bundle said. After the CAS hearing, Bundle said that the group of seven scientists submitted complete data in June 2008 to the prestigious journal Science, but that it was not accepted for publication and had to remain under wraps until it could be published elsewhere. In the meantime, the language of a press release from last May was doing a great job at perpetuating a one-sided story. The subhead of the release by Rice University, where Weyand worked at the time, read: "Experts find no scientific basis for Olympic ban."

Clearly, that subhead did not represent the whole truth. The truth was that the experts, for the reasons noted above, felt that they could only divulge the part of their research that had been necessarily made public for the CAS hearing. In the release, Weyand is quoted saying that "Based on the data collected at Rice, the blades do not confer an enhanced ability to hold speed over a 400-meter race. Nor does our research support the IAAF's claims of how the blades provide some sort of mechanical advantage for sprinting."

Weyand told SI that "we painstakingly went through that press release to say that the IAAF evidence is not valid, but nowhere said that he doesn't have an advantage." On close review, the idea that the blades do not "hold speed," as Weyand said in the press release, apparently does not contradict the newly released conclusions, but it's certainly more than enough to confuse the lay sports fan. As for the subhead, only with 20/20 hindsight is it now apparent that the scientists took the wording narrowly to mean only that the precise basis presented to the CAS for an Olympic ban was not sound. (A prize is due for whichever track buff has the Rosetta Stone that deciphered that one before now.)

Weyand, while remaining tight-lipped about the full findings, occasionally cringed as just half of the story, masquerading as the full story, played out in the media. "It was tough to watch Oscar on the Today Show after the [CAS] hearing saying, 'Hey, the best guys in the world have looked at this and said I don't have an advantage'," he said. "The history and evolution of it led him to believe he doesn't have an advantage, when our conclusion is he has a very clear one."

Five scientists from the original team of seven (those other than Bundle and Weyand) published conclusions earlier this month where they said that no clear advantage was documented in the Pistorius study. The rift in the research group led today's report to be published in a multi-part point-counterpoint format that, at times, devolves into thinly veiled insults by the five -- which includes researchers from the universities of Colorado and Texas, as well as Georgia Tech and MIT -- against the two. In one counterpoint, the five wield (and attribute) a famous John McEnroe quote ("You cannot be serious!") to deprecating effect.

The group of five contends that Bundle and Weyand are unfairly reducing Pistorius' running mechanics, and not considering the fact that some aspects of Pistorius' gait may be anomalous because of adaptations required to run on two carbon fiber legs. "The notion that lightweight prostheses are the only reason for Pistorius' rapid swing times ignores that he has had many years to train and adapt his neuromuscular system to using prostheses," the scientists write in one of the counterpoints.

Bundle and Weyand say that the five researchers, including double amputee and MIT scientist Hugh Herr, never gave serious consideration to their conclusions that Pistorius has an edge. "As soon as we said he's got an advantage," Weyand said, "there was not a willingness to accept that conclusion."

The group that maintains that Pistorius has no advantage concluded in their paper earlier this month that video from Beijing of Walter Dix, an American who took bronze in the 100 and 200, showed that the swing-time of his leg was 0.274 seconds, even faster than that of Pistorius. However, in the point-counterpoint published today, Bundle and Weyand point out that the conclusion was based on NBC footage of the Olympics, not the high-speed, motion-capture video that is typically used for such research. Typical television footage displays 30 frames per second, whereas research quality footage is at least 200 frames per second, giving researchers the ability to precisely document small movements. When measured using research quality footage, Bundle and Weyand found that Dix's swing-phase took 0.318 seconds, returning him to the realm of the typically slothful sprinter, in terms of his swing-time, when compared to Pistorius.

Under normal circumstances, the Court of Arbitration for Sport's ruling would remain valid so long as Pistorius continues to compete on the same prostheses. Whether the IAAF will reconsider a new ban is unknown, and a message left with the body was not returned yesterday.

Pistorius fell 0.3 seconds short of qualifying for the 400 meters at the 2008 Olympics, but would again be in the hunt for a spot if he continues to compete through the 2012 Olympics in London. Despite not qualifying for the Olympics in Beijing, Pistorius won gold in the 100, 200, and 400 meters in the Beijing Paralympics. In those competitions, Pistorius competed almost entirely against single-leg amputees, and one question that will now arise is whether that represents a level playing field.

When Pistorius arrived on the Paralympic scene, some of his competitors immediately complained that his prostheses were too long, making his legs longer than they should be relative to the rest of his body. No conclusion has been reached on that issue, but Weyand said he believes Pistorius' leg-swing advantage persists when he competes against single-amputee runners. "Two limbs attached to the same body can't go at different speeds," he said, "so single-leg amputees are limited by their biological leg."

Where the IAAF goes from here is unclear, but any course of action will undoubtedly foist Pistorius, and the intersection of biology and technology that his feats represent, into the global limelight once more.

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