As part of a case that has gripped adaptive sports, two teams of scientists have faced off in the Journal of Applied Physiology over whether running prostheses offer unfair advantages over biological legs. Their subject is Oscar Pistorius, a South African sprinter with bilateral transtibial amputations-a runner who has not only smashed Paralympic amputee world records but who narrowly missed qualifying for the South African Olympic track team.
Peter G. Weyand, PhD, and Matthew Bundle, PhD, are the authors of the article “Point: Artificial limbs do make artificially fast running speeds possible.” Some of their data was used by the Court of Arbitration for Sport (CAS) in May 2008, when it overturned Pistorius’ January 2008 ban from Olympic trials.
The team who wrote “Counterpoint: Artificial legs do not make artificially fast running speeds possible,” is led by Rodger Kram, PhD, of the University of Colorado, Boulder, Locomotion Laboratory and includes Hugh Herr, PhD, of the Massachusetts Institute of Technology Biomechatronics Laboratory. The data they present was also used in the CAS hearing.
Weyand and Bundle tested Pistorius in a lab and compared his biomechanics to four intact-limb athletes with the same top speed who were tested in the same laboratory, and to observations of two intact-limb males competing in the 100m sprint at the 1987 World Track and Field Championships. They noted that Pistorius’ stride frequencies at top speed were “greater than any previously recorded during human sprint running” and concluded that this was “the direct result of how rapidly he was able to reposition his limbs,” a result of his running-specific prostheses’ (RSP’s) mass being “less than half that of fully biological lower limbs.”
They also comment that “the combined effects of lightweight, compliant artificial limbs [were] minimum swing times of extreme brevity and moderately prolonged ground contact lengths, [which] substantially reduce the stance-averaged vertical forces required to run at any given speed.”
They propose quantifying the advantage they believed to be conferred by RSPs by “adjusting [Pistorius’] swing times and contact lengths to typical values for male track athletes with intact limbs and examining the effect on his top sprinting speed.” Doing so depicted Pistorius’ running-start 200m time as rising by nearly 6 seconds, and his running-start 400m time as rising by nearly 12 seconds.
Kram’s team, on the other hand, states that insufficient data exists to prove RSPs provide either advantage or disadvantage, basing their refutation on several criteria: that running speed is determined by factors beyond those described by Weyand and Bundle, that determinants of advantage that Weyand and Bundle describe are invalid, and that lack of evidence prohibits justifying any conclusions.
The additional factors in running speed that the Kram team considers include rates of oxygen consumption at sub-maximal running speeds, running economy (RE), and vertical ground reaction force (GRF). Data on both factors are minimal, and the team asserts, “From this scant evidence, it would be foolhardy to conclude that RSP provide a metabolic advantage or disadvantage.”
They also quote a 2009 publication in the Journal of Applied Physiology by Weyand et al. that states, “more rapid repositioning of limbs contributes little to the faster top speeds of swifter runners,” and conclude by proposing a series of experiments that would test a series of hypotheses in order to resolve the debate.
In an August 2009 interview, Kram told The O&P EDGE, “If someone is to be denied a basic human right, like being able to exercise and do sports…we should be very sure that the evidence is compelling…. I can see no good being done by an international rule [from] the IAAF [banning runners wearing RSPs], which would then become an NCAA rule, which then is adopted almost invariably by high schools, junior high schools, and youth group track…. Nothing would be gained by that.”
