I definitely had problems with ADHD, and still do to some extent. I was listening to a book, The Sports Gene, and the touched on exercise and attention deficit.

I definitely had problems with ADHD, and still do to some extent. I was listening to a book, The Sports Gene, and the touched on exercise and attention deficit. A proposed theory is that in the attention deficit brain you don't have enough dopamine. Exercise produces the dopamine you need to get to "normal". Therefore, exercise for some people is very rewarding and helps them out a lot. In other individuals who already have normal levels of dopamine it is a very "meh" experience for them, maybe even counter productive. They don't get the boost of dopamine as strongly since they already had "enough" to function well. And, since they had to endure, potentially higher, cognitive load to do the exercise its a net negative for them. Anyway, I don't know if this mechanism explains all of it, but anecdotally this matches extremely well with my experience. Later in life I have come to rely on routine physical exercise as it keeps me on an even keel and productive. Caffeine and Ritalin both just made me go into the zone just the same way hard exercise does. I find that if I do not exercise hard and regular I have a hard time staying productive and I might seek towards other dopamine producing behaviors (Alcohol, junk foods). I have found a middle ground of moderate exercise, but it is never as fulfilling as being full tilt into a training cycle. edit: Found a quote from the author of The Sports Gene: "Here at Axon Sports, we talk a lot about the brain’s role in playing sports. From vision to perception to decision making to emotions, the brain plays a critical role in sports success. What have we learned about neurogenetics that can influence an athlete’s performance from a cognitive perspective? DE: One of the most surprising things I learned in my reporting was that scientists know quite well that not only does the dopamine system in the brain—which is involved in the sense of pleasure and reward—respond to physical activity, but it can also drive physical activity. One of the scientists I quote in the book suggests that this may be why very active children who take Ritalin, which alters dopamine levels, suddenly have less drive to move around. That’s precisely what he sees when he gives Ritalin to the rodents he breeds for high voluntary running, anyway. And it appears that different versions of genes involved in the dopamine system influence the drive to be active. (Interestingly, native populations that are nomadic and that migrate long distances tend to have a higher prevalence of a particular dopamine receptor gene; the same one that predisposes people to ADHD. I discuss in the book the possible link.) "