I do my upper body days (really just my lifting days as I tend to do full body most times in the gym) on days when I have the time. Whether it is "optimal" or not is a distant second to actually getting it done. Generally that means either Tuesday or Wednesday at lunch, once on the weekend and possibly Friday at lunch as well. Over the winter, my intense cycling workouts have been on the other day of Tuesday/Wednesday and the other day of the weekend. But, if I was doing upper body only, I would have no problems doing it on the same day as a hard cycling workout.