Man or Machine (3) comments
By Francis Onwumere | Saturday, July 26 2008 | Materials
  
 Oscar Pistorius, South African and double amputee, is currently the 400 meter Para-Olympics World champion and on Friday (July 18), he lost his bid to compete alongside able-bodied athletes in the 4 x 400 meter relay event at the Beijing Olympics by a mere 0.70 seconds. Many pundits, however argue that he would have beat the 45 seconds qualifying time, if he had spent more time on the training tracks than he did in the court room. Pistorius spent a large part of this year challenging an IAAF (International Association of Athletics Federation) ruling that sought to prevent him from competing in events with able-bodied athletes.
Apparently the IAAF seemed to be going back on its word. In 2007, Pistorius was allowed to compete in a Golden League meet in Rome, his first international, able-bodied event. His performance at that race left eye-brows raised, as he finished second in his heat, beating seven other able-bodied pros.
Pistorius runs on carbon fibre prosthetic blades known as “cheetah”. The concern of the IAAF was whether the prosthetics used by him should be considered as technical aids which give him an advantage over other athletes not using them, thus contravening IAAF competition rule 144.2. The IAAF requested that Professor Peter Brüggemann at the German Sport University in Cologne study the issue.
Professor Brüggemann’s study compared biomechanical and physiological analysis of long sprint running by Pistorius using “cheetah” prosthetics with five able-bodied athletes who are capable of similar levels of performance at 400m. The results of this study showed that:
- Pistorius was able to run with his prosthetic blades at the same speed as the able-bodied sprinters with about 25% less energy expenditure. As soon as a given speed is reached, running with the prosthetics needs less additional energy than running with natural limbs.
- The positive work, or returned energy, from the prosthetic blade is close to three times higher than with the human ankle joint in maximum sprinting.
- The energy loss in the prosthetic blade was measured at 9.3% during the stance phase while the average energy loss in the ankle joint of the able bodied control athletes was measured at 41.4%. This means that the mechanical advantage of the blade in relation to the healthy ankle joint of an able bodied athlete is higher than 30%.
Based on these results the IAAF ruled in January that Oscar Pistorius is ineligible to compete in the Beijing Olympics because his prosthetic racing legs gave him a clear competitive advantage. At the core of this ruling is the introduction of technology to the sport, and the future consequences of that decision.
The cheetah prostheses is made from Carbon fiber reinforced plastic (CFRP or CRP), a composite that is a very strong, light and expensive. Composite materials are commonly referred to by the name of its reinforcing fibres (carbon fibre, in this case). It has many applications in aerospace and automotive fields, and now athletic prosthetics, where its high strength to weight ratio is of importance.
Prosthetic manufacturer Ossur explains the workings of their carbon fibre blades:
“Vertical forces generated at heel contact are stored and translated into a linear motion described as Active Tibial Progression, from the foot-flat to toe-off phase. This action reduces the need to actively push the body forward using the contra-lateral foot as well as equalizing stride length”.
Thus effectively the prosthetic limb is able to take the forces that are generated during landing, store them and then translate this into forward movement albeit in a more efficient way than the human limb.
There remains no doubt that Pistorius is a talented athlete but the question that remains is how much of the machine is in the man?
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