When I'm excited about an idea I have a compulsion to walk around in basically circles. I don't know exactly why but i assume when body enters such elavated alertness you have to let out steam somehow.

Otherwise, i prefer running as it to me gives more bang for the buck. It's crucial if you have a sedentary job to elevate your blood-circulation to be able work productively through the day. Regular anaerobic exercise seems quite ideal for that.