Brain shifts from glucose to lactate fuel source during exercise.

I had that thought as well. I do know that some of the people in the medical field whom I have talked to say that exercise tends to shift the brain in to more predominant Alpha wave patterns which correlates to creative thought. That explains why stepping away from the computer and taking a walk can be very helpful for solving problems.

It's especially interesting in that when muscles work really hard they make lactic acid - which is then used by the brain when <i>it</i> is working hard.

I wonder if that is related to the beneficial effects of exercise on mood.