Friday, October 30, 2009

Can a human being outrun a horse?

Apparently over long distances.

I was listening to Ira Flatow on NPR, in my car today. Since the New York marathon is tomorrow he was talking about it, and one of his guests claimed that when it comes to long distances, human beings can essentially outrun all other animals - including horses.

Since I heard only that snippet (I reached my destination), and I had a few minutes, I googled, and no kidding! Here is a fascinating NYT link on the topic.

Some interesting numbers.

The fastest marathon was run just under 2:04 hours by Haile Gebrselassie of Ethiopia which translates to an average speed of 12.67 mph, or 4:44 minutes per mile. A horse can gallop at about 25-30 mph over short distances, but like I said before, they often underperform humans in marathons.

Over short distances, Usain Bolt of Jamaica ran a 9:58 at the 100m dash, which translates to 23.35 mph, or 2.57 minutes per mile, while a cheetah can go at a top speed of 60mph, which is about three times as fast.

We clearly weren't built to outrun such predators.

So what tilts the balance in our favor as distance increases? Apparently it has all to do with cooling.

When a horse gallops, it produces heat at a rate greater than what it can easily dissipate. Humans are much better at dissipating energy.

A simple energy balance tells us that if the input is greater than the output, there is accumulation of heat which leads to a rise in temperature - which is clearly undesirable. The evidence for this hypothesis is the fact that humans have a much better chance of beating animals in marathons when it is hot, sunny, and humid - conditions that make heat dissipation even harder for the poor animals.

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