The Application of Physics in the Track and Field Paralympics

I. Introduction

Physics is commonly perceived as a means to answer fundamental questions about human existence and beyond. While this perception is true, more than the theoretical implications of physics in understanding the nature of the universe or perhaps multiverse, physics has countless practical applications. Whether we are conscious of it or not, nearly every aspect of our lives may be understood through physics. And it is an important thing to note because using the lens of physics, we can comprehend things that directly involve us such as the way our bodies work or react to certain things or how we are affected with different forces we can not even see. This is why beyond the philosophical, physics has many tangible benefits.

Such is the case of physics in Paralympics or the international arena of sports for athletes with disabilities. Through the use of principles and concepts of physics along with advancements in modern technology, athletes with disabilities are given the opportunity to still practice their passion for sports. Particularly, in double amputee sprinting, there are various ways in which physics has helped amputees in improving the way they deal with a sport that is supposedly for able-bodied individuals. However, there are also some issues surrounding the use of physics in double amputee sprinting. For example, when Oscar Pistorius the first double amputee to ever compete in the Olympic Games - participated in the race competition and won a silver medal, he was criticized for having a "racing advantage." Also, several single amputee sprinters in the Paralympics claim that double amputees are most likely to win race competitions even leading some individuals to claim that "it is actually better to be a double amputee in track and field than a single amputee." These criticisms against the alleged unfair advantage of double amputees in sprinting competitions have sparked several researches concerning the effects of prosthetic running blades on the performance of double amputees. While some researches concluded that sprinting prostheses do give an advantage, some believe otherwise.

Given these two polarizing views, the paper would then determine the effect of sprinting prosthetics in the biomechanics of disabled sprinters as described by several researchers covering the topic. The discussion would be divided into two parts. The first part would be a discussion of the kind of leg prosthetics that amputees wear during sprinting races. This would be followed by a discussion of how these sprinting prostheses work and affect the biomechanics of disabled sprinters.

II. Prosthetic Running Blades

Several developments have been made in the improvement of sprinting prostheses for disabled athletes leading some to claim that the difference in the kind of sprinting prostheses used by an athlete affect his or her chances of winning a race. Generally, there are five types of lower-limb prostheses offered to an individual depending on his or her disabiltiy which includes (1) ankle disarticulation (2) below-the-knee amputation (3) above-the-knee amputation (4) knee disarticulation and (5) hip disarticulation. The kind of prosthesis that is fit for an individual is determined by a professional prosthetist thus making all prosthetics, especially the ones given to athletes, custom-made.

One of the kinds of sprinting prostheses used by disabled athletes is called the prosthetic running blades. The type of prosthesis used by Oscar Pistorius and the one used by the second person from the left in figure two are examples of such. These running blades have sparked many controversies because of its alleged advantage over the other kinds of running prostheses as worn by the four other persons in figure two.

Running blades are made up of carbon fiber which is known to be a lightweight but resilient material. Oscar Pistorius' Flex-foot Cheetah running blades was also made of carbon fiber. Given the numerous researchers conducted on Pistorius' running blades, this paper will focus on carbon fiber prosthetic blades in determining the biomechanics of these prostheses in double amputee sprinting. As such, it will look at the several case studies conducted on Pistorius and his running blades which the next section of this paper will discuss.

III. Biomechanics of Double Amputee Sprinting: A Case Study

Generally, a running blade is composed of three main parts. The first part is the blade itself which is considered to "store kinetic energy in a similar fashion to a spring which allows the athlete to run and jump." The other parts include a socket used to attach the blade to the amputees and an artificial knee joint which is used only if the case necessitates it.

In the study entitled A Statistical Perspective on Running with Prosthetic Lower-Limbs: An Advantage or Disadvantage?, the authors claim that Pistorius' blades weigh 3.3 kilograms less than the average weight of natural lower limbs thus making Pistorius' blades more likely to produce resonance that can create some sort of a "trampoline effect." Quoting the study, In order to explain how this bouncing effect can occur, it could be added that in a prosthetic foot, when the excitation frequency (athlete muscle pressure) is increased, the inertia force will also increase until it reaches a point at which the inertia force cancels the stiffness force of spring. In this situation the excitation force acts on the system without any resistance. This will result in oscillating of the mass at its natural frequency. In the absence of any damping, the amplitude of the resulting vibration will increase. This condition is called resonance. If the frequency is increased further, the inertia force will overcome stiffness force. The magnitude of oscillation will become small, until a point where the motion is controlled by the mass and then the system is said to be in isolation.

In other words, if a system is in isolation, the momentum of that particular system is conserved thus in the case of sprinting, it makes it easier for the disabled sprinter to accelerate.

To explain further explain this, one could look at the efficiency of the running blades. According to one article, one of the potential advantages of blade runners is that it gives amputees "the ability to move the prostheses faster and with less effort because the blades weigh less than a competitor's lower legs and feet." As we know, there is a direct correlation between mass and acceleration. It is stated in Newton's Second Law of Motion that the more mass an object has, the more force is needed to accelerate that object. Given then that running blades have lesser mass than normal human limbs, less force is needed to accelerate the amputees. Since there is less force needed for acceleration, lesser effort is also exerted by the amputees to do the work of sprinting thus making the running blades more efficient.

Additionally, in the study entitled Double Amputee Sprinting - Biomechanical Challenge, Mechanical Advantage or just a Different Kind of Locomotion, there are several things that the researcher has been able to conclude which includes (1) running in prostheses is biomechanically different from able bodied athletes (2) majority of work is done in the blades without muscular work and fatigue (3) less muscular work is required at knee and hip joint and (4) other findings which ultimately made the researcher claim that double amputee sprinting is a biomechanical challenge, a mechanical advantage and a different kind of locomotion.

These claims generally justify the reasons why running blades are considered to be advantageous in double amputee sprinting. There are however other scholars who believe otherwise.

While blade prostheses share similiarities with biological limbs in the way that they mimic how normal human legs store energy as they bear a runner's weight and release it as the runner pushes off the ground, one important difference between the two is the inability of prostheses blades to have a foot that "pivot or generate its own energy"". The implication of this Figure 3. Lower Moment of Inertia Shows Smaller Amount of Mechanical or Muscular Work in the Swing absence is that it is harder for amputees using running blades to "get up to speed as a runner" such as when they are beginning from the starting blocks since the blades can not adjust the stiffness of leg muscles and accommodate changes in running surfaces through adjusting the angle to which their feet hit the ground.

Others also believe that the advantage of double amputee sprinters using running blades is not completely attributtable to their prostethetics since other natural factors such as the amputee's athleticism could also take part. 

As of now, there are still debates about the definitive advantage or disadvantage of running blades in double amputees as compared to able-bodied individuals, single amputees and amputees that do not use running blades. However, one thing is for sure. The controversy that arose out of the use of prosthetics in sports reflects the larger debate about using modern technology not only as a means to asssist humans in their daily endeavor but also to controversially enhance their abilities.

Bibliography

• Brüggemann, G.-P. "Double Amputee Sprinting - Biomechanical Challenge, Mechanical Advantage or just a Different Kind of Locomotion." Playthegame, 2009. PDF file.
• Burke, B. "Prosthetics and Athletics." Accessed May 23, 2017. Retrieved from http://amputeebladerunners.com/prosthetics-athletics/.
• Greenemeier, L. "Blade Runners: Do High-Tech Prostheses Give Runners and Unfair Advantage?" Medical & Biotech. August 5, 2016. Retrieved from https://www.scientificamerican.com/article/blade-runners-do-high-tech-prostheses-give-runners-an-unfair-advantage/.
• Hossein Hassani, et al. "A Statistical Perspective on Running with Prosthetic Lower-Limbs: An Advantage or Disadvantage?" Sports 2014, 2, 76-84. doi: 10.3390/sports2040076. PDF file.
• Reilly, J. "Blade runner' Oscar Pistorius sprints into the history books to become first double amputee to compete at the Olympic Games." Mail Online. August 4, 2012. Retrieved from http://www.dailymail.co.uk/news/article-2183556/Oscar-Pistorius-Blade-Runner-sprints-history-books-1st-double-amputee-compete-Olympics.html.
• Ross, G. "Technology at Paralympics sparks advances and controversy." 2016 Paralympic Games. September 12, 2016. Retrieved from http://commmedia.psu.edu/special-coverage/story/2016-paralympics-games/technology-at-paralympics-sparks-advances-and-controversy.
• Thomas, G. P. "Blades of Glory: What Are Paralympic Running Blades Made Of?" September 11, 2012. Retrieved from http://www.azom.com/article.aspx?ArticleID=6792.

 

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