This is an excerpt from M.A.X. Muscle Plan, The by Brad Schoenfeld.
The MAX Muscle Plan begins with a MAX strength phase. During this phase you'll focus on lifting heavy weights in a low repetition range. The goal here is to get as strong as possible; increasing muscle size is of secondary concern at this point.
Why is it important to build strength when the overall goal is to maximize muscle development? The short answer is that getting stronger ultimately fosters better muscle growth. Quite simply, if you aren't physically strong, muscle development is bound to suffer.
I equate the process to building a house. Before erecting the frame of the house and laying down the hardwood flooring you must first construct a rock-solid foundation. Without a strong foundation, the house will ultimately crumble. Similarly, to achieve maximal muscle development you must build your body on a foundation of strength. Stronger muscles allow you to use heavier weights—and thus generate greater muscle tension—in the moderate repetition ranges that optimally stimulate hypertrophy. By increasing muscle tension without compromising metabolic stress, you set the stage for enhanced growth.
The most important adaptation to heavy lifting is an improvement in the response of your nervous system. You see, muscles are innervated—that is, activated—by nerve cells called neurons, which transmit electrical and chemical signals to a given number of fibers within a muscle. A single neuron and all the corresponding fibers it innervates are called a motor unit. The major muscles in your body are innervated by multiple motor units, often many thousands.
How does all this physiology relate to muscle growth? The ability of your muscles to exert force is governed by three distinct neural mechanisms: recruitment, rate coding, and synchronization. Let's take a brief look at how heavy strength training affects each of these factors.
Recruitment refers to the ability of your nervous system to activate motor units. Recruitment is generally governed by the size principle, which suggests that smaller motor units (primarily made up of endurance-oriented slow-twitch fibers) are recruited first and that larger motor units (primarily made up of strength-oriented fast-twitch fibers) are progressively recruited thereafter if and when additional force is required. Although many studies show that advanced trainees are able to recruit all available fibers at approximately 80 percent of 1RM, some believe that heavy weight training may help condition stubborn high-threshold motor units, thereby allowing their recruitment at lower percentages of 1RM. This leads to greater muscle fatigue across the full spectrum of fibers and thus greater muscle growth.
Rate coding refers to the frequency at which nerve impulses are stimulated during a lift. Nerve impulses that fire with a high frequency produce more muscle tension than do lower frequency impulses. Rate coding is widely considered the most important determinant of your ability to produce force. The good news is that heavy strength training increases the rate at which nerve impulses fire, and it can extend the firing period. The upshot is a greater sustained muscle tension during your lifts.
Synchronization refers to the coordinated timing between different motor units within a muscle (intramuscular coordination) or between different synergists (intermuscular coordination). As an analogy, think of synchronization as similar to a symphony orchestra. If the string section is not in sync with the percussion section or the violins are not in sync with each other, the end result is a hodgepodge of sounds. To produce sweet music, all the instruments must play harmoniously. Similarly, if the impulses reaching different motor units are out of phase, then muscle force is compromised. Fibers must contract as a unit in precise accord to maximize force production. Heavy lifting helps foster both intramuscular and intermuscular harmony in the fibers within both the target muscles and the stabilizing muscles.
By enhancing the efficiency of recruitment, rate coding, and synchronization, the MAX strength phase lays the groundwork for future muscle growth. It provides a strong base on which to build your body. As long as you follow the program in a step-by-step fashion, you will maximize muscle development during the MAX muscle phase.