Feet in the Clouds: A Story of Fell Running and Obsession by Richard Askwith is about the British pass time of running up and down very steep peaks, fells and hilltops. He says fell runners usually peak in their mid-thirties to fifties. Youngsters don't have the stamina that a Bob Graham (http://en.wikipedia.org/wiki/Bob_Graham_Round) or Joss Naylor (http://en.wikipedia.org/wiki/Joss_Naylor) have.