I've done it before. Depends on my daily schedule, but I hate working out that late. I try to workout during the afternoons or evenings. I've found that if I workout after 10pm I don't have a lot of energy to give it 100%. I've read about the subject and what most bodybuilders do is that they try to do their cardio early in the morning on an empty stomach before they start the day and then if they can't do weights at that time they move the weight training session to the afternoons. But those are bodybuilders I don't know why I just can't workout in the morning. Even when I've had the opportunity to do it I just can't bring myself to wake up early to exercise. I also read that most people prefer to workout in the afternoon/evening and I fit into that category, but if I know I have the energy and I couldn't workout earlier I've been known to exercise at crazy hours.