I think as long as one does not train as soon as (or very soon after) they get up, then it should be fine. When I was training twice a day as a weightlifter, the 10am workout (which for me was 3 hours after waking up) was always less intense than the 4pm workout. There was less volume (less sets) and less weight (load) lifted in the am vs. the pm. That may not mean much for a bodybuilder, since in this game, it's effort above all else and not the number of plates on the bar. By effort I mean what your muscles feel. And feel does not necessarily have to rely (and most often it does not) rely on weight for progressive overload but other factors such as time, reps, sets, and even the elimination of momentum in a given exercise.
Currently, I'm working out at 02:35, which is 5 minutes after arriving home from work.
Fadi.