Previous research also shows that both elite and ordinary runners with intact legs tend to move their limbs at a similar speed. Pistorius, on the other hand, “can reposition his limbs a lot faster than anyone we’ve ever measured,” says Weyand. But the scientists don’t yet know how to interpret this finding: does it represent an advantage of his comparatively light carbon limbs, or is it merely compensation for the fact that he can’t hit the ground with as much force as intact-limbed runners? “There is no real evidence he has an advantage over others, and there is some evidence the prostheses are a hindrance,” says Daniel Ferris, a biomechanist at the University of Michigan, in Ann Arbor, who was not involved in the study.
“The science is still immature, and we don’t know for certain why he’s mechanically distinct–whether it’s because of his prostheses or because of his biology,” says Herr. One way to answer that question would be to study a runner with one intact and one prosthetic leg and directly compare the biological side to the artificial side–an experiment that Herr says is in the works.
One of the major areas of controversy surrounding Pistorius’s performance is the fact that he can run the second half of the 400-meter race faster than the first half–an unusual pattern for sprinters. Some believe that this is direct evidence that his prostheses give him an advantage: they argue that because he does not have muscle below the knee, he would not suffer the same fatigue. But Weyand and his collaborators found that all runners, including Pistorius, appear to follow the same fatigue curve.
One possible explanation for Pistorius’s unusual pattern, says Herr, is that because he does not have calf muscles, the amputee runner is actually at a disadvantage during the first 200 meters–the acceleration phase of the race. It may be in the second half of the race that Pistorius’s inherent talent becomes clear. “Oscar is an outlier,” says Herr, who is a double amputee himself. “The Cheetah has been available to athletes for 15 years, but no one has been able to run as fast as Oscar.” However, Herr says that scientists haven’t yet studied Pistorius and others as they accelerate.
The research is also helping scientists better understand the basics of running. “The Oscar Pistorius case has injected a great deal of interest in the area of bipedal sprinting,” says Herr. “By looking at the differences between amputee and intact-legged runners, we can more fundamentally understand the running mechanism and what is most important for speed.” Relatively little research has been done on the mechanics of sprinting, even in intact-legged runners, partly because it’s difficult to study people moving at such fast speeds. The new research was done using a special treadmill–one of only two or three such machines in the country.
Ferris says that the findings also point to ways that running prostheses could be improved. “One thing to try would be a prosthesis with adjustable stiffness,” he says. “That way, runners may be able to generate higher forces at certain points in the race.”