Wednesday, April 30, 2008

Running after Antelope

You may be familiar with the radio show This American Life. If not, then you'll just have to listen to it because it is hard to describe. Each week they have a number of stories loosely based around a theme.

Best of all they stream practically all their shows on the web. (There is an option to pay to download a show but you can also just listen to it for free just by clicking on 'Full episode'.)

Back in 1997 one of their perennial favorites Scott Carrier told a great story about his attempt to run down an antelope. (It's actually the second story in the show but takes up the majority of the hour long show and starts at about 5:40 if you want to skip straight to it). For reasons a little too complicated to explain Scott and his brother are trying to show it would have been possible to hunt down antelope on foot simply by doggedly chasing them until the antelope become exhausted.

But don't take my word for it, listen to the story. It's got some interesting observations on biology, grad school and life generally and it is a great example of storytelling.

Oh yes, and it's relevant to class because I was reading about the physiology of the pronghorn antelope. This is one of those animals that someone has managed to get onto a tread mill in the lab. In the wild pronghorns will trot along at 40mph and could polish off a 10k race in about 10 minutes. In stress tests they tend to increase the incline and in this case they got the antelope to do about 25mph up an 11% slope and recorded a maximum oxygen consumption of 300ml of oxygen per kg per minute. Compare that to the highest values ever recorded in a human (93ml of oxygen per kg per minute in a Scandinavian cross country skier). 'Normal' values are more likely to be closer to 45 or 50 in a fit person or as low as 20 to 30 in a sedentary person. Humans, at rest, need 3.5 ml of oxygen, every minute, for each kilogram of body weight just to support the cellular activities in the tissues that keep us alive so the increase in oxygen use during exercise is impressive.

Another interesting fact about Pronghorn is that there is nothing remotely fast enough to chase them in the current American fauna. Whatever drove their evolution to higher speed and endurance is long gone.

Cheetahs by the way are far less impressive. Although they can exceed 60mph in a sprint they cannot run at this speed for more than 20 or 30 seconds without overheating. To catch a cheetah all you need to do is follow it for a few minutes and it will soon become exhausted, overheated and, apparently, also very tame in this state. Yes, this is the class that teaches you useful information.

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