I think there really is something to the idea of running giving you time to reflect and think. And it's not just the time alone; the "runner's high" and just being in motion seems to help. Even driving does it to some extent.

Read The Making of the Atomic Bomb, and you might be surprised to note how many of the great scientific insights of the last century happened like a flash out of nowhere to someone who was walking, riding on a tram, or just somehow *moving*...

Humans are born runners. We literally are born to run on the African savannah. We're not sprinters like lions, but long-distance, run-down-the-prey-till-it-collapses type hunters like dogs.