How T-44 Athletes Using Cheetah Prostheses can Develop an Advantage

Thesis: Athletes with double lower limb amputations can gain a mechanical and physical advantage from their technologically advanced prostheses over their able-bodied competitors, and, as such, it is not ethical for these athletes to compete alongside those competitors in a formal International Association of Athletics Federations (IAAF) sanctioned race.

Oscar Pistorius

(“Oscar Pistorius”, 2012 Beijing Olympics)

Oscar Pistorius: A man famously known for competing in the Beijing Olympics in the 400m dash using what are known as “Cheetah Blade” Prostheses. He was the original figure that sparked such heated controversy over whether or not these legs gave him an advantage. The scientific community has been largely divided on whether or not this is true, many arguing for not but I believe an advantage has been harbored by wearers of this limb.

Hooke’s Law for Springs

(“Hooke’s Law”, 2016)

Hooke’s Law states that the force F exerted on a spring is equal to the distance x compressed or stretched multiplied by the spring constant k: F=-kx. Force is also equal to mass m times acceleration a: F=ma. So, the greater distance compressed, the greater acceleration that will be generated.

Treating Everyday Objects as Springs

(Watkins, created in Microsoft Word Dec. 2016)

In this photo is an example of how we can consider almost anything rigid to be “Hookean” or spring-like. Just like Pistorius’ legs, this pencil compresses a distance denoted x when a force is applied to it. Also, just like Pistorius limbs, this pencil now has stored potential energy within it because it wants to return to its normal state, flat.

Examining the Force Generated from the Prostheses

(Watkins, created using image from Anja Niedringhaus 2016)

When examining exactly how these blade legs procure an advantage, it is important to consider the Law of Conservation of Energy. For every action there is an equal and opposite reaction. When Pistorius compresses these legs, he stores energy in the spring, which is thus transferred into kinetic energy in the form of mass m times acceleration a. Due to the spring-like nature of the prosthetic, individuals have been able to have a 3x larger amount of energy returned to the competitor as opposed to a normal human ankle limb (Hassani). Additionally, Pistorius only has 9.3% energy loss compared to 41% energy loss in a normal human (Hassani).

Limb Re-positioning Time

(“Pendulum”, 2016)

Another important factor for runners is the Limb Re-positioning Time (LRT). This is the time it takes for the leg to start at one point, travel through its full range of motion, and then return to the starting point. Due to this, the leg can be considered a swinging pendulum. Pistorius’ prostheses allow him a LRT of 0.28 seconds, whereas the average elite male’s is 0.37 seconds (Rose). This is 67% faster for Pistorius.

Works Cited

Bournemouth University. “Running with Prosthetic Lower-limbs: Advantage or Disadvantage?” ScienceDaily. ScienceDaily, 29 June 2015. Web. 24 Oct. 2016.

Eveleth, Rose. “Should Oscar Pistorius’s Prosthetic Legs Disqualify Him from the Olympics?” Scientific American. Scientific American, 24 July 2012. Web. 25 Oct. 2016.

Hassani, Hossein, Mansi Ghodsi, Mehran Shadi, Siamak Noorozi, and Bryce Dyer. “A Statistical Perspective on Running with Prosthetic Lower-Limbs: An Advantage or Disadvantage?” MDPI. MDPI AG, 6 Nov. 2014. Web. 24 Oct. 2016.

Hooke’s Law. Digital image. NCS Pearson, 25 Jan. 2015. Web. 6 Dec. 2016.

Oscar Pistorius. Digital image., 12 July 2012. Web. 6 Dec. 2016.

Pendulum. Digital image. What Is a Pendulum? N.p., 2 Nov. 2014. Web. 6 Dec. 2016.

Simpson, Jake. “‘No Advantage to Being an Amputee’: A Defense of Oscar Pistorius’s Prostheses.” The Atlantic. Atlantic Media Company, 8 Aug. 2012. Web. 24 Oct. 2016.

Watkins, Cole. Treating Objects like Springs. Digital image. N.p., 6 Dec. 2016. Web. 6 Dec. 2016.

Watkins, Cole. Showing Forces in Prosthetic. Digital image. N.p., 6 Dec. 2016. Web. 6 Dec. 2016.

Zettler, Patricia J. “Is It Cheating to Use Cheetahs?: The Implications of Technologically Innovative Prostheses for Sports Values and Rules.” Boston University International Law Journal 1st ser. 2.2 (2009): 368–409. Web.

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