Chris Aceto article from RXmuscle.com

This is a great read for anyone questioning their weight training program.  If you have been following my site for the past year I fell into the habit of constantly changing workouts up.  Never doing the same workout twice.  Thinking that I was keeping my body in constant shock to always get better results was bullshit.  Read this and find out why. - Tyler

"If you are a personal trainer, bodybuilder, fitness enthusiast or just a guy that looks like he works out, chances are that you have been asked how many exercises to do for each body part. Frankly, this is probably one of the most often asked questions by people who don't train and people who do train. To pop this year off like a bottle of champagne, I am going to endeavor to answer this "enigma".

What most people believe is that the bodybuilder should do at least three different exercises for each body part that is being trained. I would tend to agree with that as different exercises exert different angles on the muscle being worked, thereby causing different recruitment patterns. Muscles respond and grow to a number of stimuli. Some of these are: the weight you use, the rep range, the total number of sets you do and the angles/exercises used to exert stress.

It should be noted that some bodybuilders fall into the trap of changing the angles all the time and try to never do the same workout twice. A consequence is that they never get heavy with the weight. In other words, they mix the angles up, always changing the workout and forget that using heavy weights plays the biggest role in muscle fiber recruitment. This is a primary reason strong bodybuilders often have an easier time adding serious amounts of muscle mass. Those who tend to be stronger, naturally recruit far more muscle fibers than those bodybuilders who, genetically, lack a lot of muscle strength. That's not to say the strongest bodybuilder will always be the very biggest. Look no further than Ronnie himself... oh wait, bad example, he's a freak. Simply, this is a very important analogy that I believe a lot of bodybuilders should understand in order to gain mass.

Beginners and intermediates should stay with very basic exercises. I wouldn't get too fancy and change the workouts around all the time; continuously changing the angles. First, you have to figure out what is working. When you change the angles all the time, it's hard to establish what is causing the muscles to grow. When you stay with just one to two exercises for each body part, you can easily figure out what is working and what is not working. For example, if you are doing chins and bent over rows for back; flat bench presses and incline dumbbell presses for chest. If you are making good progress, then you obviously know you do not have to change around the angles/exercises to stimulate growth. In this case, basic exercises without great variances in angles, is sufficient to cause growth. On the other hand, if you are doing two exercises and not seeing solid gains, you should change your routine to include more exercises.

Overall, I think it's somewhat of a myth that muscles respond and grow by constantly changing angles. There are other variables that are more important that you can implement before altering the routine to include multiple exercises. You can try to add more weight, you can alter the rep range to include fewer reps and more weight, or you can work at a higher rep range while still trying to train to failure with heavy weights. In addition to those strategies, you can decrease rest periods between sets which can add stress to the muscles or you can include drop sets where you perform a heavy set of three to four reps and rack the weight; rest for ten seconds and try to squeeze out another two to three reps. These are all very effective ways to stimulate growth without varying the exercises or angles you are currently doing.

Although my main emphasis when working with bodybuilders is diet, I also find myself correcting training misconceptions with bodybuilders who still believe silly things. One such silly thing is that pre-contest, you absolutely have to always change your workouts around to keep the body changing. Shockingly, there is an idea that amongst some bodybuilders that changing angles or increasing rep ranges leads to greater muscularity, less body fat with greater visibly muscular detail. The truth is, varying the angles a lot or adding high reps to your training does not add much in terms of definition and detail. Detail within muscle is mostly a body fat issue. If you lose all your fat, you'll see a heck of a lot more in terms of definition and cuts then if you have not shed all your body fat." - Chris Aceto