PHOTO: JOHN SUPER/AP PHOTO

OLYMPIC HOPEFUL: Oscar Pistorius runs—and wins—on two carbon-fiber prosthetic legs.

The head of R&D on foot products at Iceland-based Ossur is audibly shaken in a phone interview as she ponders the implications of carbon-fiber sprinting prostheses that might one day help an amputee exceed normal human performance on the track.

As the person in charge of designing sports prosthetics for the world's leading manufacturer of "running feet," as disabled athletes call them, Heidrun Gigja Ragnarsdottir well knows just how far things could go, though the implications give her pause. A revolution in new materials, the ever-shrinking microprocessor, and the power of CAD design tools have all pushed the technology of prostheses, in the words of Massachusetts Institute of Technology engineer Hugh Herr, to the "threshold of a new age" [see sidebar, "Building a Better Leg"]. The bionic man—or at least a microprocessor-controlled bionic leg—is already a reality. But even in the realm of passive prostheses, which by definition do not produce energy but only store and release it, recent changes have made it possible for a lower-limb amputee to run faster than ever seemed imaginable.

Maybe too fast. Is it conceivable that an amputee sprinter fitted with one, or even two, prostheses might, disability notwithstanding, gain an advantage over able-bodied competitors by virtue of using high-tech carbon-fiber leaf springs instead of feet? And if that athlete ran fast enough to qualify, for example, for the Olympics, should he or she be allowed to run?

"You don't want to disqualify someone because he is disabled—that is unfair," says Ragnarsdottir, thinking aloud. "I don't envy the people who have to decide on this question."

That would be General Secretary Istvan Gyulail and his colleagues at the International Association of Athletics Federations (IAAF), the Monaco-based body that sets the qualifying criteria for world-class competition, including the Olympics. "It would seem inhumane and against the sport to say 'go away and compete in events for the disabled,'" said Gyulail. Indeed, if a disabled sprinter can muster enough grit and gumption to give the world's fastest human being a run for their money, how could anyone possible deny that athlete the chance?

But good will is not necessarily good science, and from a strictly biomechanical point of view, it remains an open question as to whether running with a prosthesis could ever enable an athlete to surpass what would have been his able-bodied performance were he not missing one or both of his natural feet. What series of tests or experiments could possibly tease out the impact of a prosthesis from among the dozens of other variables that determine performance levels?

The IAAF has not yet taken a position on this issue, for the simple reason that an amputee running in the Olympics was "never foreseen as a realistic possibility," to quote Gyulail. But what would have seemed less than a year ago like a safely abstract and hypothetical question straight out of a graduate course in biomechanical engineering is today a real live case study.