MIT Media Lab unveils study on amputee runners

A new study provides additional evidence that amputees using specially designed prostheses "have no overall biomechanical advantages when running at top speeds compared to able-bodied sprinters," the MIT Media Lab said.

The study was conducted by a team that included Alena Grabowski and Hugh Herr of the lab's biomechatronics group; the team's findings were published today in Biology Letters, a British journal, the lab said.

Amputee runners with a prosthesis have leg-swing times similar to able-bodied runners, but prostheses generally do not yet replicate the force generated by a human leg, and one result is that a runner's top speed is affected, the study concluded.

Or as the MIT Media Lab put it in a press release: "In the new study, the researchers gathered biomechanical data from six elite, unilateral amputee sprinters using running-specific prostheses. (Unilateral sprinters have one lower-leg prosthesis and one biological leg.) Data were analyzed from jogging speeds up to top sprinting speeds on a unique high-speed instrumented treadmill at the Orthopedic Specialty Hospital in Salt Lake City, Utah. The scientists compared the forces exerted on the ground and step timing from the biological leg to the leg with the prosthesis. The results showed that the primary determinant of top speed, the force applied to the ground, was 9 percent less in the leg with the prosthesis. They also found that the time required for leg swing was not different between legs, and was similar to non-amputee sprinters. The researchers therefore concluded that while a running-specific prosthesis can partly emulate the spring-like behavior of a biological leg, unilateral amputees cannot generate and apply as much force with their prosthesis, thus impairing top speed."

The press release also noted that the biomechatronics team included researchers whose earlier work was instrumental in reversing a ban of Oscar Pistorius, a South African runner who uses J-shaped, high-performance Cheetah Flex-Foot prostheses. (Pistorius is shown in a file photo taken by Denis Farrell of the AP.)

Grabowski commented on the new work in a statement: "These new data support our previous findings that passive running-specific prostheses are not able to provide the ground forces realized by biological legs, and that we are not yet at a point in time when lower-limb prostheses outperform biological limbs. But because the biomechanical and physiological comparisons of amputee runners using prostheses to non-amputee runners are so complex, we will continue conducting additional research to better understand all the factors involved."

The study's other researchers are Craig McGowan, University of Texas at Austin; William McDermott, the Orthopedic Specialty Hospital; and Matthew Beale and Rodger Kram of the University of Colorado. (Globe Staff)