Pistorius was born without fibula, or calf bone, in either leg, and at 11 months his legs were amputated below the knee. He began competing in track at 17 and quickly began racking up medals in Paralympic events. He began racing against able-bodied athletes in 2005, coming in sixth in the South African Open Championships.
He runs on the Cheetah foot manufactured by Ossur, an Icelandic prosthetic and brace manufacturer. Its J-shaped design, based on an actual cheetah foot, has been available since 2001.
But as much as amputee runners favor the artificial running foot, it can't compare to the biological version, say scientists and researchers. In a 1987 study published in Archives of Physical Medical Rehabilitation, researchers evaluated the Flex-Foot, made by Ossur and similar to the Cheetah, against a human foot. Landing on a human foot in a running stride gave a 241% spring efficiency, or energy return, because of the contraction of the calf muscles. In comparison, the Flex-Foot had an 82% spring efficiency.
"It's the muscle that will actually help propel you," specifically the calf muscle, says Robert Gailey, associate professor in the University of Miami's department of physical therapy, and director of the Functional Outcomes Rehabilitation and Evaluation Laboratory at the Miami VA Medical Center.
The bounce that Pistorius and other amputee athletes have with the Cheetah is created not by actual springs but by the bending of the carbon graphite -- the prostheses don't accelerate the runner like Inspector Gadget. An athlete still has to power his own legs, a force that in Pistorius' case comes from his hips.
Also, Pistorius' legs pound into his sockets with every stride, and though suction helps keep them in place, Gailey points out, he still has to create stability as he makes contact with the ground. Stability issues and centrifugal forces may make it more difficult for him to maneuver around a curved track. Whereas able-bodied runners are fast out of the starting blocks, a lack of ankles and Achilles tendons give Pistorius a far slower start.
But the IAAF still has some questions to answer before it determines if Pistorius can compete (no date is set for that ruling). According to spokesman Nick Davies, the organization would like to measure his VO2 max (the maximum amount of oxygen, in milliliters, that the body uses in one minute, per kilogram of body weight) and measure the mechanical efficiency of Pistorius' running style using force plates, 3-D kinematics and other techniques. All results would be compared with those of able-bodied runners. His running has already been filmed so that his stride length and speed over various parts of the track can be analyzed.
