Exercise doesn't have an effect for me. In high school I played two varsity sports and in college I played in some club/recreational leagues. Now I swim and weightlift, but I wouldn't say any of these activities improve my quality of sleep or ability to induce it.

This is because, for me, "sleepiness" is not the same as "tiredness." I can be extremely exhausted, both mentally and physically, but I'll still never feel sleepy.

I would say one of the most frustrating aspects of being an insomniac is that is makes activities like weightlifting much more difficult. I'll never be able to achieve my weightlifting goals because I simply don't sleep enough hours to let my body fully recover. I've found I still have a strong stamina for aerobic sports, but building raw strength and muscle has been really hard.