The compensation factor – or why shoes might just be bad for your feet

10 06 2011

There are many modern innovations around which we take for granted as good, that are, indeed, not.

Some interventions, such as seat belts, are shown by statistics to save lives, and as the cost of strapping in is not too high, so the case in favour is strong.

But what about modern running shoes? It may be turning out that nice cushiony running shoes actually cause more injuries than they prevent – and for a similar reason that taking out all the safety features from a traffic intersection may actually make it safer.

Why is this so?

It seems in these latter cases that making people safer only leads them to take more risks, sometimes cancelling out the benefit completely – this is has been termed “risk compensation” – but how does that apply to running shoes?

It turns out the cushioning makes us feel safe – safe to slam down our heels without feeling the shock. It also turns out that while it may feel ok, it allows us to use our foot in a way it was never intended, and results in far greater forces going up our legs.

Think for a moment about the foot of a cheetah, or a deer, or a dog. Ask yourself, where is the heel?

Of course, it is clear once you think about it, it’s way up the leg, far from the floor! And do you think a cheetah has thuds of force going up its spine? I don’t!

Ok, so someone could point out we did not evolve from gazelles and they could also point out that no other primates show a raised heel; true enough – but primates started off as rubbish runners, and it was only the humans that  started down the road to better feet for running during all those years hunting on the African savanna. Whenever there is selective pressure to run, that great engineer (evolution) eventually finds that a raised heel is the optimal solution – remembering of course that the engineer has only the stump of a redundant old fin to work with. Of course, the invention of shoes (and ultimately cars) has completely removed the shaping forces, so I guess our heels will fall once more.

Don’t agree? Ok, pop on those big comfy shoes, and just like a beemer driver cruising at 100mph, tell yourself its safe to slam down those heels 😉

Some interesting sources:

  1. Walking robot – gee look, to make it work, they abandoned heels: http://www.youtube.com/watch?v=sv35ItWLBBk
  2. Walking robot “with heels” seems to need bizarre extra hip mobility: http://www.youtube.com/watch?v=67CUudkjEG4&NR=1
  3. Even Nike, they who started the whole thing now seem to admit openly that bare is best, and sell you the shoe that does it for $90: http://inside.nike.com/blogs/nikerunning_news-en_CA/2009/07/12/engineering-the-nike-free-50
  4. Take a sneak-peek into the barefoot community: http://www.barefootted.com
  5. Oh, and I got put on the scent of this by Christopher McDougall’s excellent book, Born to Run: http://www.chrismcdougall.com/
  6. In the wiki for Risk Compensation it interesting to learn that in Sweden, traffic collision rates dropped for 18 months after they changed which side of the road they drove on. Wow!
  7. The classic tale about how making roads seem more dangerous made them safer: http://www.wired.com/wired/archive/12.12/traffic.html