I can't think about anything but combat when I do combat - I'm super uncoordinated and would probably kill myself or someone else if I tried - but I find I come up with lots of great writing motivation while on the spin bike. Often whole scenes come to me, fully formed while I'm tackling a steep hill, or racing through a speed section.
Then all I need to do is write it down when I get home, dripping sweat across my keyboard as I do.
What exercise do you do? Does it help with your creative pursuits?