A few men only do one workout a week and that is usually full body workouts. Seems to be making a bit of a comeback for some. But most will split the body parts up, to upper and lower, and train each one on separate workout day; example Monday-upper...Thursday-lower. It's two workouts a week, but one workout for the upper and lower body.
Fewest times for me has been once a week. Usually a Push workout. Next workout (that same week) a Pull workout. Legs are worked with the Pull sessions. So that's one workout per upper or lower body. Other times I have trained; Monday-Push. Wednsday-legs Friday-Pull.
I've also made good gains by just doing one exercise per workout, sometimes once, some times twice a week Like pullover and press, squat cleans, clean and press, etc. These heavy compound exercises are like money in the bank for increasing mass & strength, an in a somewhat shorter period of time. Working with serious intent, on these movements, also enters into this also.
People who actually were there (opposed to what others may have read in magazines) and watch Mentzer, said he would do 3 or 4 warm-ups sets with some respectable weight. Than hit that 1 set max. Doing forced reps, which included negatives when positive reps were done.....sometimes doing static holds after the negatives..extremely intense work load.
Another guy watched as Mentzer took a client, who flew over from Germany, through one of the most brutal workout he had ever seen. Using the above positives, negatives and static holds. Was working back at the time.
Mentzer changed a lot of his view about training in later years, even to the extent of suggesting 3 to 4 (or more) weeks between training sessions. Guess his declining mental state, in later years, is well known to most on GB.
Good Luck.