I used to workout at lunch time at my previous job which is my favorite time to workout. I always came back more energized and afternoons went a lot faster. But that only worked because my gym was right next door and I was able to take longer lunch breaks (made up the time, of course)...
I just read this yesterday in our local paper's fitness section:
Which time of day is optimal for exercise? Exercise scientists and those looking at chronobiology — how biological rhythms change in a daily cycle — nearly always give the same initial response in answering the question.
"For...