>Running has a similar, but immensely stronger, effect. Generally, I have near constant dialogue between my characters going on in the back of my head. When I run, it simply engulfs my mind, making it hard to concentrate on anything else. I cannot have "jogging buddies" for this reason. It's simply too difficult to listen/react to them when I have an overwhelming stream of imaginary conversation filling my skull.
I found the opposite effect for myself. While walking and basic physical exercise tends to improve my ability to tackle problems more creatively, running or high intensity exercise gets me in a survival mode where I can't think about complex and abstract problems deeply. Was a downside because I always wished I could multitask on 40-60 minute runs, killing two birds with one stone. Instead I can't get anything done but an intense cardio exercise.