Pistorius Limited by Prostheses, Study Says

Alena Grabowski, PhD
Alena Grabowski

Researchers continue to debate whether Oscar Pistorius has an advantage or a disadvantage over able-bodied athletes. In the second study published since Pistorius made headlines by being disqualified from competing in the 2008 Olympic trials and then having the ruling overturned, researchers found that amputees are unable to generate the same amount of force as non-amputees — and are thereby limited in their top speeds.

In the study, published Nov. 4, 2009 in Biology Letters, lead author Alena Grabowski, PhD, postdoctoral fellow in the Biomechatronics Group at Massachusetts Institute of Technology in Cambridge, Mass., along with four of her colleagues, collected data from six unilateral transtibial amputee elite Paralympic sprinters. The amputees submitted to a series of discontinuous constant speed running trials on a specialized high-speed force-measuring treadmill at the Orthopedic Specialty Hospital in Salt Lake City.

The amputees began each 10-stride running trial at a speed of 3 m per second, and increased their speeds incrementally by 1 m per second up to their top speed, determined by the speed at which they began to drift backwards on the treadmill. Researchers also added 100- and then 300-g weights to the prosthetic leg and ran two additional time trials.

They found that the average vertical force exerted on the ground was approximately 9% less for the affected leg compared with the unaffected leg over a range of speeds, including top speed. In addition, the swing time was the same in the affected and unaffected legs at all speeds. Adding mass to the prosthesis caused no significant changes to top speed or to leg swing times at top speed. Researchers also analyzed video data from the Paralympic and Olympic men’s 100- and 200-m finals and found that the swing times were not different between athletes.

Grabowski and the other authors concluded that an amputee athlete using a prosthetic device is unable to strike the ground with the same amount of force as an able-bodied runner.

“From the data collected so far, it appears that using running-specific prostheses likely impairs the ability of an athlete to exert greater force on the ground, which may be a critical limitation for achieving faster top speeds,” Grabowski told O&P Business News.

The authors also concluded that the unilateral amputees may compensate for that force deficiency by increasing their step frequency in their intact limbs or both limbs to achieve top speed.

Grabowski said that additional research is necessary.

It is up to the governing bodies of track and of the Olympics to decide if they will further investigate this matter. With a predicament this philosophical and significant, however, only one thing is certain: no answer will satisfy everyone with an opinion. — Stephanie Z. Pavlou, ELS

For more information:

  • 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.
  • Pavlou SZ. Study sparks debate over disabled or too abled. O&P Business News. 2010; 19(1):18-19.

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