A runner needs not just to be skinny but - more specifically - to have skinny calves and ankles, because every extra pound carried on your extremities costs more than a pound carried on your torso. That's why shaving even a few ounces off a pair of running shoes can have a significant effect.

In cognitively demanding fields, there are no naturals. Nobody walks into an operating room straight out of a surgical rotation and does world-class neurosurgery.

The paradox of endurance sports is that an athlete can never work as hard as he wants, because if he pushes himself too far, his hematocrit will fall.

Malcolm Gladwell Quotes