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Monday, September 03, 2012

Oscar Pistorius: Counting strides (as requested) and more thoughts

Oscar Pistorius beaten, and then invites debate on someone else's technology

Talk about irony.  Within minutes of being upset by Brazil's Alan Oliveira in the final of the men's T44 200m, Oscar Pistorius claimed in this interview that he's "not running a fair race here".  The crux of his argument, which he also stated yesterday before even losing this final, is that his rivals are artificially extending the length of their legs, and he pointed out in this interview that "it's very clear that the guys have got very long strides".

To add to that case, he is quoted after the final as saying the following: "I can't compete with Alan's stride length".

Now, let me start upfront by saying that there is a lot more to running that stride length.  If all it took was big strides, then the running world would be dominated by the tallest men, and shorter runners like Tyson Gay would stand no chance.  What matters is not just stride length, or height, but rather the length of the leg relative to height, and the ground contact length, which is a function of the leg length (partly).  Plus there is force applied to the ground, leg turnover rates and all those things, but let's take one component at a time here!

Read more. . .

As requested - a cursory look at the strides

So, since Oscar Pistorius has made it a point to emphasize how long his rivals' strides are (it's "very clear that they have got very long strides", he said), and to say that he "can't compete with Alan's (Oliveira - the Brazilian who beat him) stride length", I watched the race over and did the obvious thing - I counted the strides.

It turns out that Pistorius took 92 steps during the race (2.2m per stride), and Oliveira took 98 steps to win gold (2.0m per stride).  To break it down further:

In the first 100m, Pistrorius took 49 steps (2.0m per stride), with 43 steps in the straight (2.3m per stride).

Oliveira, on the other hand, took SHORTER strides - 52 in the first 100m (1.92m each) and 46 in the second 100m (2.2m each).

So, a simple count shows that Pistorius has longer strides than Alan, and they are consistently longer - on the bend, and in the straight, for those who are wondering.   It's Oliveira who "can't compete with Oscar's stride length".  His faster speed, then, is the result of faster leg movement, because speed, as you will appreciate, is the result of stride length and stride rate.

And here again, let me repeat, there is much more to the debate that simply the stride length, as I'll get to shortly.  But the point there is that once again, you have this misinformation from Pistorius, and the media are too lazy to interrogate it further, they just report and allow the uninformed debate to go on.  Already on Twitter I got numerous responses saying "Look how long Oliveira's stride is"!  And it's not - it's shorter than Pistorius', by some margin!

It's not (just) about the stride length.  And welcome to the slippery slope

Right, so having dealt with that over simplification, let's talk briefly about the issue here.  Is it possible that the Brazilian has increased his stride length as a result of increasing the length of his blades?  Of course it is.  This is part of the problem with the prosthetic limbs, and there's no way to know this unless you go back to the IPC World Championships in 2011 and measure the height of the athlete and compare it to today.

You could count Oliveira's strides and find that his stride length has increased, but now you have another problem - you can't confidently attribute any increase to the leg length.  It may be that he has gotten stronger, and is covering more ground per stride as a result.  If that were true, then his stride length relative to his height would be much greater, with no explanation other than many hours of good training (This is how Pistorius explained his own performance improvements, incidentally)

So, for Oliveira, his improved performance may be due to the blade length, it may be due to his technical skill, it may be due to his improved strength, it may be due to some weight loss.  You see the slippery slope here?  Only if his height was measured and is continuously measured can one know with certainty this answer.

But even then, an athlete may discover that they are a few inches shorter than the upper limit imposed by some rule based on ratios, and they can, quite legally, add to their blades.  What is wrong with that?  I'd say nothing - they are simply correcting and then optimizing what nature did not provide, aren't they?  Their mistake was making their prosthetics too short the first time, and they should be allowed to add height within reason.  Again, welcome to the slippery slope of technology in sport.

So then your response may be to say "Surely there is an ideal leg length for someone's height?".  The answer is that there IS a range, but in elite athletes, the limits have to be wide because ranges that you'd find in the normal population don't apply.  There is pretty substantial evidence, for example, to show that elite runners (Kenyan and West African runners in particular) have disproportionately long legs relative to height, and so this may be a factor that predicts running success.  I'd bet that if you look at the likes of Usain Bolt, Kirani James and Asbel Kiprop, you'll find that they have longer than normal legs for their height.

The double problem in a double amputee is that you don't have a height - without prosthetic limbs, there's no reference point against which to "anchor" leg length.  So then, you can start using arm length and say that the "normal" leg length is a certain factor of the arm length.  But again, that doesn't work because the ranges are large enough that you can "artificially" get longer legs without violating the upper limit of what is found normally.  Again, I'd be willing to bet that in the elite athletic population, you'll find many of the best runners are guys with disproportionately long legs relative to arms.  It's worth checking all the athletes, of course, but the end result of this (and I'm going to get this data for you - it's just that it's 12.44am here in SA) is that the kind of accusation Pistorius is making is pretty baseless.  Not to mention the timing, which is another matter.

As for the fast finish, I'd love to see the splits from the race, measured accurately.  Doing it off the TV set is weak, and it gives splits of 11.1s and 10.4s for Pistorius, and 11.5s and 10.0s for Oliveira.  That's fairly meaningless because you'll see many 200m races with a 0.6s swing.  It's unusual, certainly, for a leader to be reeled in that strongly, but it's the kind of finish that has carried Pistorius to a few gold medals in his time - I remember a Commonwealth 100m race where he gave up about 5m (0.5s at that speed) in a 100m race and still won.  Today was no different, so the claim that you can't win from behind is equally misguided.

The bottom line is that whatever the rules of prosthetic limbs, if Oliveira is within them (and we have good reason to think that he is, given his compliance with the IPC and even Pistorius' accusation is not that he is cheating, but that the rules are wrong), it just re-introduces the same debate - how do we know, with 100% certainty, that we are not seeing the result of some technological battle?

The answer is that we can't.  The leg length issue is an 'advantage' that Pistorius has always had, and we've been watching him compete for years not knowing if he's done the exact same thing as he is now accusing Oliveira of.  Remember, the leg:arm ratio is a flawed way to establish these boundaries for elite athletes.

And it does beg the question - why does Pistorius not just push his length up to the limit if the rules allow it?  If Pistorius is below whatever limit exists for leg length, then he should just increase his length and run a 44s 400m in 2013.  Or, if Pistorius is already there (which I strongly suspect, given the R&D backing he has), then all we've seen tonight is that Oliveira has corrected his length and managed to create an equal race with Pistorius.

The bigger issue is that of technology.  The advantage for Oliveira tonight was NOT his stride length, despite Pistorius' claims.  The advantage was stride rate.  And remember, this is the factor that Peter Weyand concluded gave Oscar Pistorius an enormous advantage over able-bodied runners who simply cannot move their limbs at the same rate, because Pistorius was able to achieve leg repositioning times that no able-bodied human ever could.  That advantage is still in play, except now we have another runner who is benefitting from it, and possibly exploiting it even better than Pistorius.

Pistorius doesn't enjoy that compay.  I look forward to the emergence of even more of these runners, and perhaps one day, sooner rather than later, we'll be seeing the first even sub-21s 200m time by a double amputee, and then it's matter of time before we see a sub-45s 400m time, and so on.  Are we just seeing the emergence of the next generation of athlete, equally capable of using the technology, but with greater athletic potential than Pistorius?   Have the floodgates opened?  I'd be willing to say that there is already an athlete who has begun training who will beat both Oliveira and Pistorius by some margin and force these same questions, all over again.

If you're wondering tonight about whether Pistorius has a valid argument, then welcome to the slippery slope that is the introduction of technology with no clear answers to the sport.  We've been here for eight years.

Feel free to discuss, I'll get more thoughts on it tomorrow.