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We've known for a long time that a lower rate of energy consumption at any given speed means an athlete can run farther. This is the idea behind all sorts of new training methods that measure caloric intake against mileage outtake and such, but what we haven't known is why.
Until now.
Melanie Scholz of the Free University of Amsterdam, Netherlands began to wonder if this measure of efficiency was actually a measure of stored energy—specifically of elastic energy stored in a runner's Achilles tendon.
The idea is pretty simple. When a foot lands it compresses the tendon, storing energy that gets released the next time the runner lifts that foot, thus helping to power the next stride. But what's really interesting here is that the amount of energy available for storage turns out to be directly related to the size of one's heel.
Scholz figured this out by mathematically modeling the effects of heel length (measured as the distance between the Achilles and the inside and outside ends of the ankle bone) on distance running prowess.
What she discovered is that the shorter the heel, the greater the amount of stored elastic energy.
She then hooked up 15 pro runners to a treadmill and measured their oxygen consumption as they ran. Turns out that those with shorter heels used less oxygen—indicating greater efficiency.
One of the things that makes this research seem a bit curious is that there don't tend to be many Malay or Aboriginee (two ethnic groups with shorter heels) professional runners, but this may have more to do with cultural biases etc. than anything that has to do with running, though it does strike me as curious.
