Malcolm Gladwell:

With those figures, coaches in Kenya can train their athletes to the outer limits of endurance–up to 150 miles a week–without worrying that their pool of talent will be meaningfully depleted. Even if four out of every five runners break down, the fifth will convert that training into performance…

We’ve always known that running is culturally important in Kenya, in a way it isn’t anywhere else in the world. But these are staggering numbers. A million 10 to 17 year olds running 10 to 12 miles a day? I’m guessing the United States doesn’t have more than 5,000 or so boys in that age bracket logging that kind of mileage. 70 miles a week is an enormous amount of running–even for an adult. I ran middle distance at a nationally competitive level as a teenager, and never got close to 70 miles a week.