monday: chest-triceps-abs
tuesday:legs-calves
thursday: shoulders-traps
friday: back-biceps-forearms
If you have a brains, you would mix thigs up by doing it right:
Monday= back-shoulders-traps-abs
Wendsday=chest-triceps-biceps
Thursday=legs-calves-abs
Friday= back-shoulders-traps
Monday=chest-triceps-biceps
etc.
This is how you can get two workouts for muscle group within on week without overdoing it. You still get plenty of rest but you have to use "light weeks" every now and then to prevent over training. Once a month would be enough. I am with no hurry, so I train three times a week, and keep weekends off:
Monday= back-shoulders-traps-abs
Wednesday= chest-triceps-biceps-abs
Friday=legs-calves-abs
This way I can always put 110% effort on it with no fear of over training. I do crunches and hyper extensions before every workout for warming up.
What comes to theory of the subject, it is 100% correct. As a natural bodybuilder you should not use training schedule which make you work out overlapping muscle groups, because of the simple rule of the thumb, which says that your muscle grows while it is resting. You don't work out to get bigger muscles, that is only the stimulant and growing takes it's place between the stimulants, mostly while you sleep. If you use gear, this has nothing to do with you.