"Another very commonly accepted idea is that to progress you need to completely change your workout very often (authorities recommend anywhere between changing every 2 to 6 weeks). If you listen to them, if you do not do that, you are an idiot doomed to a life of stagnation in the gym. As you might tend to believe, I do not agree with them. Here are a few reasons why.
1. Look at some of the most successful athletes and bodybuilders; they stick to the same program for very long. Oh, sometimes they might change the number of reps or sets that they do (within reason) but most of them stick to the same lifts week in and week out.
All elite olympic lifters only do the snatch, clean & jerk, squat and front squat (a minority will throw in a few assistance exercises) and most of them don't vary their reps much. Yet their strength goes up.
Dorian Yates stuck to the same training program for all his Olympia wins, except for some minor changes because of injuries.
Ed Coan and many top powerlifters from the 80s and 90s used the same exercises year round, only varying the reps.
2. Often times frequent training revamping is (like the 1-hour rule) a way for trainers to make more money. Since it's good for business, it is in their interest to promote the myth that you need to change your training (and thus BUY a new program) frequently. When a lot of people say the same thing, that thing eventually begin to be seen as factual, even if the guys doing the talking have an interest.
3. When you first start a program it takes you a week or two to get used to it, learn the exercises and master them. Even if you know the exercises, if you've been away from them for a while you have quick "progress" for 2 or 3 weeks. That progress isn't due to better muscle stimulation, simply to an improved coordination and efficiency on that lift.
After 3 weeks or so, the "quick" gains (neural adaptations) stop and your progress slows down. You then change your program completely and you start improving your lifts again... not because you are getting stronger or bigger... because you are getting used to the new lifts. It gives an ILLUSION of progress but in reality very little growth will be stimulated.
I'm not saying that you shouldn't vary your training, far from it. I include a lot of variation in my own training. But these are micro-variations... doing a few more or a few less sets... varying the reps a bit ... adding or removing an assistance lift, etc. I stick with the basic movements for a while. It is not until you are very efficient at them that your body will need to build more tissue to adapt. If you change these exercises too often then they will not give you their full benefits.
I always stick to the same movement "core"... for me these are the push press, bench press, power snatch, squat and a form of pulldown. These will stick with me almost year round. The assistance work is then adjusted daily on a need-to basis.
Remember only DOING A LOT OF HARD WORK will bring real muscle growth... frequent changes (complete revamping of program) only gives the illusion of progresss"