I'll go out on a limb here and say that training first thing in the morning is for crazy people. And my CNS takes more than just time to wake it up. But depending on your reason for training, it might behoove you to slap it around a little, especially if job requirements dictate that you are not always able to control the time when you have to use the aforementioned sleepy CNS. Combat personnel, firefighters, LEO, etc., often do not have the luxury of choosing when to exert, and are best prepared for this contingency by doing an occasional workout very early.