Another study weighs in on amputee runners

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Ever since South African double-amputee runner Oscar Pistorius expressed a desire to compete against runners with intact legs, it’s sparked the interest of researchers who are trying to determine if running prosthetics provide an advantage.

The latest findings come in a study recently published in the journal Biology Letters, in which researchers analyzed the force with which amputee runners’ feet hit the ground and also how fast they swung their legs, and determined that the special prosthetics gave no performance advantage over runners with biological legs.

The study participants were six elite sprinters who had one intact leg and one leg that had been amputated below the knee. Researchers decided to study these types of amputees because they could compare their affected leg to their unaffected leg.

The runners did a series of speed trials on treadmills both with and without lead strips attached to the forefoot of their prosthetics (some sprinters do this to give them a more balanced gait while running). Researchers determined that their force was on average 9% less on the prosthetic leg versus the biological leg on a range of speeds, including top speed. When they ran faster, the runners’ step force increased in both legs, but that increase was greater with the biological leg.

At faster speeds, the runners swung their legs more quickly and had less contact time on the ground. However, that didn’t differ between the two legs. Also, adding the lead strips didn’t substantially alter the leg swing time at top speed for either leg, nor did it significantly change the runners’ absolute top speed. With the weights, the average force was much less in the prosthetic leg than the biological leg.

In the study, the authors wrote, ‘Because the fastest biological-limb sprint-runners are those who can apply greater forces to the ground...a significant force impairment for the [affected leg] probably limits the ability of amputees to achieve top speeds compared with non-amputee sprinters. Our data strongly suggest that the [running-specific prosthesis] or muscle weakness/impairment due to the prosthesis limit force production rather than some other physiological factor.’

-- Jeannine Stein