I would like to add, since I can no longer edit my post, that 10-15 minutes of full-out intense exercise is plenty. I like to look at it as trading one kind of pain for another - for a kind that may be helpful to me. Logically, that appeals to me, and it's a break from the tedium of unclear mind and no energy. Yes, it's hard to start, but as an experiment for a few minutes, I can push myself.