When I would have sleepovers as a kid, my mom would always tell us that we were not allowed to run around like monkeys before bed because then we would not be able to fall asleep. Being the angelic child that I was, my friends and I would start doing jumping jacks as soon as mom left the room in hopes of staying up all night long, only to be asleep soon thereafter. Turns out mom was wrong (sorry mom) -- I have never had any hard evidence against it, until I dug a little.
A professor from the University of South Carolina, Shawn Younstedt who researches physical activity and sleep, says that evidence indicates that [evening exercise] does not disturb sleep for most people. Furthermore, any initial sleep disturbances may resolve within a few weeks. This is great news for any of you that work crazy hours but still want to fit in a workout. You may have always felt you couldn't do it right before bed because it would mess up your sleeping patterns but that should no longer be a worry.
This also gives further evidence that 24 hour gyms are not so crazy after all, now are they.