During the Golden Era of Bodybuilding (1900-1980’s), the three movements that make up the sport of powerlifting were used by virtually every bodybuilder during their preparation. These three movements are the Squat, Bench Press, and the Deadlift. Now, whether its the overwhelming plethora of machines that may be more aesthetically pleasing to the eye (especially to gym owners who may have never TRAINED a day in their life) or that the equipment needed to perform the big three in a safe manner can no longer be found in gyms across the country (absence of the power rack), we just don't see these lifts being performed as frequently. Especially by bodybuilders - but if your number one goal is muscle growth, these 3 lifts maybe the missing link.
Motor Unit Involvement means how muscle by way of your brain and nerves are being utilized in the activity/exercise. The Deadlift utilizes approximately 70%+ , Squat approximately 65%+, and although I think it would be much more if done powerlifting style, the Bench Press involves approximately 45%+ of an athletes total motor units. The motor units involved in Isolated Supplemental Exercises (Leg Curls and Extensions, Calf Raises, DB Curls, etc.) is less than 20%.
I'm not suggesting that you abandon all isolation movements, I'm simply saying that your time would be better spent basing your program off the big three mentioned above. The “Big 3” will enable you to use heavier loads in your Isolated Supplemental lifts. For example, if your Squat numbers are going up you could expect the loads you are using in the Leg Extension increase. This is a one-way street. Increase in Leg Extension “strength” does not necessarily equal in increased loads in the squat.
Testosterone and Growth Hormone both play a large role in your body’s ability to increase muscle size (hypertrophy). Research has shown that lifting heavy loads (above 85% of ones 1RM) has a large effect on releasing these hormones. Squatting, Bench Pressing and Deadlifting allow you to accomplish this. 85% of 1RM usually means fewer than 6 repetitions. I don’t see how this could be done safely and effectively with machine training and isolation work.
The Term “Powerbuilder” is name that has been floating around which was coined by a friend and colleage of mine Jared Daigre (CEO of BOAD Apparel). Basically it refers to an athlete that is strong like a powerlifter while looking like a bodybuilder. It has been stated with the exception of a few names that for the most part bodybulders are “fancy sports cars with lawnmower engines”. All show no go if you will. Becoming efficent in the Squat, Bench Press and Deadlift may be the key in unlocking your potential to grow while avoiding the classification of “Athletic Mannequin.”