Considering the fact that each muscle gets used to a workout by the third training session, I have found a better form of progression is to change the workout rather than increasing the weight, this way the body cannot adjust to routine and has to increase strength and muscle size to handle the unaccustomed work it is asked to do!
As I mentioned before, the body adjusts to routine very quickly and in bodybuilding, this should be avoided.
In short, keep the muscles confused. I tell my students that if you do not see changes in each workout, you should ask questions and I will find the reason changes are not occurring, (i.e. overwork, nutritional, not forcing reps, etc.)
(Musclemag Vol2 issue 1)