Gina Kolata looks at The Bicycling Paradox and how fit doesn’t have to mean thin:
He came to realize, he said, that cycling is a lot more forgiving of body type and age than running. The best cyclists going up hills are those with the best weight-to-strength ratio, which generally means being thin and strong. But heavier cyclists go faster downhill. And being light does not help much on flat roads.James Hagberg, a kinesiology professor at the University of Maryland, explains that the difference between running on a flat road and cycling on a flat road has to do with the movement of the athlete’s center of gravity.
“In running, when you see someone who is obviously overweight, they will be in trouble,” Dr. Hagberg said. “The more you weigh, the more the center of gravity moves and the more energy it costs. But in cycling, there are different aerodynamics — your center of gravity is not moving up and down.”