I'm a runner too, but I found out that it is not the best activity to stop thinking about a topic. My mind keeps wandering around, unless I run so fast that I'm totally exhausted for the rest of the day.

As I recently discovered that activities which require your undivided attention work better for me. My meditation is motorcycling and downhill biking :)

I'm the same way. I use to have a "running mix" on my iphone. But one day the earphones broke and I just listened to the sounds around me. It really helped me relax. Almost like a moving meditation. I definitely recommend the music-less run!