I don't run but I do a lot of walking. My mind wanders a huge amount during my walks, which I find nice. I am usually so focused on preventing my mind from wandering, even in leisure activities, for example by focusing on a movie or book. Sometimes I stay up later because it means I'll fall asleep quicker and not be alone with my thoughts waiting for sleep for as long. But I think there's a definite need in the human mind for time to sort things out internally, even if (and maybe especially if) there's thoughts you're trying to escape from.