Does Oscar Pistorius have an advantage or disadvantage compared to able-bodied athletes when sprinting with his running prostheses?
Researchers have published the numbers, but supporters on both sides of the debate have spoken out. Ultimately, the decision rests in the hands of the International Association of Athletics Federations (IAAF) and the Court of Arbitration for Sport (CAS).
On Jan. 14, 2008, the IAAF deemed that Ossur’s Flex-Foot Cheetah and other similar prosthetic devices should be considered technical aids and would not be permitted in competition. This decision was supported by an IAAF-sponsored scientific study from a group led by Peter Brüggemann, PhD, at the German Sport University in Cologne, Germany.
Pistorius appealed the decision to CAS and submitted to further testing at Rice University in Houston, where his athletic ability was compared with that of performance-matched able-bodied sprinters. The study was conducted by a group of seven researchers, including Peter Weyand, PhD; Matthew Bundle, PhD; Alena Grabowski, PhD; Rodger Kram, PhD; Craig McGowan, PhD; and Hugh Herr, PhD. Results of these tests, published in the June 2009 issue of the Journal of Applied Physiology, revealed that Pistorius is “simultaneously similar to intact-limb runners physiologically but dissimilar mechanically.” The authors found that Pistorius had 20% deficit in ground forces, 21% shorter leg swing times over intact-limb athletes, 33% shorter aerial times and 14% greater contact times. They wrote in the study, “the meager ground reaction forces observed during amputee running here and elsewhere identify what may be a critical limitation for speed.”
CAS concluded on May 16, 2008 — based on data about the energy return from his prosthetic devices — that the evidence considered was insufficient to prove that the prosthetic devices provided Pistorius with an advantage over able-bodied runners, and allowed him to race and try to qualify for the 2008 Olympic Games.
Despite his clearance to compete, Pistorius clocked in at 46.25 seconds in the 400 meters — his personal best but just short of the Olympics’ 45.55-second qualifying time.
But the controversy rages on over whether or not Pistorius — and other amputees who may follow him — should be allowed to compete with able-bodied runners. Thus far, the data have researchers drawing two different conclusions.
Study authors were invited to submit a manuscript, “Artificial limbs do/do not make artificially fast running speeds possible,” to the Point:Counterpoint section of the Journal of Applied Physiology. Weyand, associate professor of applied physiology and biomechanics now at Southern Methodist University, and Bundle, director of the University of Wyoming’s Biomechanics Laboratory, argued that Pistorius maintains an advantage while using these prosthetic devices; Grabowski, postdoctoral fellow in the Biomechatronics Group at Massachusetts Institute of Technology, Herr, director of the Biomechatronics Group at MIT, Kram, associate professor in the department of integrative physiology at the University of Colorado and lead author of the Counterpoint, and four of their colleagues, countered that prosthetic devices create a disadvantage for amputee sprinters.
In their point, Weyand and Bundle asserted that Pistorius’ leg swing time while sprinting is shorter than any previously recorded — 21% more brief than intact limb athletes with the same top speed, and 15.7% faster than five of the most recent world-record holders in the 100-meter dash. While elite able-bodied sprinters have swing times measuring approximately 0.35 seconds, Pistorius’ swing time measured at 0.284 seconds. Over 400 meters, Weyand said, Pistorius is approximately 10 seconds faster than he would be if he had intact limbs.
“Even in comparison to individuals with the most extreme gait adaptations for speed in recorded human history, Pistorius is not simply an outlier; he is quite literally off the biological charts,” Weyand said.
Grabowski and the others on the counterpoint stated, “an equally plausible hypothesis is that [Pistorius] has adopted rapid leg swing times to compensate for the force limitations imposed by his prostheses.” Based on previous studies — including separate work completed by Weyand — these authors maintained, “when faced with stringent force constraints, runners with biological legs choose very short leg swing times.” They argued that Weyand and Bundle’s claims are based on insufficient evidence, and proposed additional experiments.
Grabowski told O&P Business News that she and her colleagues strongly disagree with Weyand and Bundle’s conclusion.
“The data we’ve collected thus far shows that athetes using passive running-specific prostheses are not able to provide the ground forces realized by biological legs,” she said. “Lower-limb amputation and modern running prostheses do not facilitate unnaturally fast speeds or leg swing times.”
Weyand and Bundle stand by their most recent conclusion. Despite their assertion Weyand said that they consider Pistorius’ accomplishments to be substantial and valuable. — Stephanie Z. Pavlou, ELS
O&P practitioners should be proud of the accomplishments that have been made over the years in prosthetic foot and socket design; these innovations help restore the mobility of all amputees, not just the elite athletes. Even considering these technological advancements, it is, however, Oscar’s phenomenal abilities as an athlete, his dedication and his hard work that have made him the world’s #1 Paralympic sprinter. At the young age of 23, Oscar has a long career ahead of him. As he becomes faster, which he will, the controversy will continue, especially when he starts beating Olympic sprinters.
— Kevin Carroll, MS, CP, FAAOP
Vice president of prosthetics, for Hanger Prosthetics & Orthotics and O&P Business News Practitioner Advisory Council member
For more information:
- Brüggemann GP, Arampatzis A, Emrich F, Potthast W. Biomechanics of double transtibial amputee sprinting using dedicated sprint prostheses. Sports Technology. 2009;4-5: 220-227.
- Weyand PG, Sternlight DB, Bellizzi MJ, Wright S. Faster top running speeds are achieved with greater ground forces not more rapid leg movements. Journal of Applied Physiology. 2000;89(5): 1991-1999.
- Weyand PG, Bundle MW, McGowan CP, et al. The fastest runner on artificial legs: different limbs, similar function? Journal of Applied Physiology. 2009;107(3): 903-911.
- Weyand PG, Bundle MW. Point: Artificial limbs do make artificial running speeds possible [published online ahead of print November 19, 2009]. Journal of Applied Physiology. doi:10.1152/japplphysiol.01238.2009.
- Kram R, Grabowski AM, McGowan CP, et al. Counterpoint: Artificial limbs do not make artificial running speeds possible [published online ahead of print November 19, 2009]. Journal of Applied Physiology. doi:10.1152/japplphysiol.01238.2009.
- Grabowski AM, McGowan CP, McDermott WJ, Beale MT, Kram R, Herr HM. Running-specific prostheses limit ground-force during sprinting [published online ahead of print November 4, 2009]. Biology Letters. doi: 10.1098/rsbl.2009.0729.