August 6, 2012

We Really Are Living in the Future, or The Real Hero of the Games

You can have your Michael Phelps, your Andy Murray, and your Usain Bolt.  Oscar Pistorius is my new sports idol.  He personifies so many noble human qualities that it's hard to do the real person justice by trying to list them all here.  We'd all be a little better if we behaved more like Oscar.  WWOD?

I won't repeat a lot of what's been said about him already, but we can put to bed the whole myth that he somehow gets an advantage from his prosthetic legs.  Having years of experience designing high-performance sport implements with carbon fiber reinforced materials, as well as a few developing orthopedic braces for athletes, I think I can shed some unique insights on the "controversy" surround his inclusion in the Olympics.

First, despite what marketing execs have led you to believe, carbon fiber composites are not magic.  All that carbon fiber gives you is a very stiff, and a very strong material per unit of mass.  That allows engineers to design structures that are much lighter than their metallic counterparts, and much stronger and stiffer than their plastic counterparts.  From the simplest analytic point of view, Oscar's "legs" would be too heavy to be practical made from an alloy, or too weak make from just plastics.  It is only the combination of properties that composite materials have that allow his high-performance running legs to be fully realized.

The next question is inevitably, does it give him an advantage over biologic legs that most of us are born with.  There really is no simple way to answer that question, but the main point is that they do not.  The blade-like design of his prostheses act like a spring.  They simply store and return the energy that he generates on each stride.  Just like the muscles, tendons, ligaments and bones that he doesn't have would ordinarily.  The only possible advantage that I could imagine would be if he decided to "grow" several inches by ordering longer prostheses that were a little stiffer.  Theoretically, he would have a little more leverage with each stride (just like taller people do), but that raises ethical issues and any self-respecting doctor or prosthetist would refuse to go along.  Plus, he would simply have to train harder to generate more force to effectively load his longer legs anyway.  So, we'll call that a wash, hypothetical though it may be.

On the flip side, however, we can clearly see how he is disadvantaged by his prostheses: no ankle joints.  His blade-like legs only replicate the muscles of the lower leg, foot arch and ball.  While carbon fiber is strong and light, it is only so in one direction.  At present is would be extremely difficult to design a composite structure that mimics the flexibility and strength of the human ankle.  In order to do that we are probably talking about metal and/or plastic components, and we're back to the initial design problem: strength to weight ratio.  If you watched him run you could see he lacked the fluidity and agility of the other runners.  Pistorius' gait is more analogous to someone on stilts rather than a silky smooth world class sprinter.

Finally, we can instantly know the obvious truth that Oscar's legs provide him no advantage.  Just count the number of his competitors that have elected to become amputees to gain the same "advantage".

I don't mean in my explanation to minimize the amazing accomplishment of running world class 400m times as a double amputee.  And shame on the gatekeepers of international athletics for attempting to keep him out of competition for so long.  We have witnessed some remarkable achievements at these games, but none more so than Oscar Pistorius making the semifinals in the 400m sprint.  Here's hoping his team earn a medal in the relay.

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