In regards to the Advanced Dual Factor 5x5:
I'll paraphrase: "Weeks one through four are placing enough stress on the body to force adaptation, and weeks five through eight function allowing for rest and adaptation and the demonstration of increased performance." - Practical Programming
Basically, the first four weeks are very demanding, placing a lot of stress on your body. From the deloading on through the intensity phase, your body is actually resting from your high volume loading phase, and utilizing the higher fitness levels your body gained from those first four weeks. So if you compare weeks 1-4 with 5-8, your going from 25 total reps down to 9 reps as well as dropping Day 2's squats altogether. A nice vacation.
