First thing in the morning for me, as that’s really the only way I can fit it into my work schedule. I work 10-12 hour days and don’t typically get done with work until at least 9, sometimes much later. After that there isn’t time or energy to train. Even if I was at a 24 hour gym(which I’m not), training late makes it hard to get to sleep at a decent time. I’ve done it on occasion and it throws my sleep off cycle bigtime.