The five factors that stimulate muscle growth

To be successful in building muscle, people taking part in strength training activities need to keep their focus on the elements that directly stimulate muscle growth. This may sound like common sense, but according to powerlifting champion Frédéric Delavier, many of the things people think of as important regarding strength training—such as lifting heavier weights, doing additional repetitions, and completing more sets—are actually no more than the means to an end. “If you want to make training productive, you must be sure that you truly understand and not lose sight of the final goal, which is muscle development,” Delavier says.

Delavier, whose first book, Strength Training Anatomy, has sold more than a million copies worldwide, pinpoints five factors that stimulate muscle growth. They are featured in his new title, The Strength Training Anatomy Workout II, a more advanced way of creating power and mass that expands on his first edition:

1. Stretching tension. When a contracted muscle is not ready to lengthen to its stretched position, and the muscle is moved forcefully by a weight, the confrontation of those two resistances causes a lot of cellular damage. That is exactly what happens during the negative phase of a repetition, a weight-muscle confrontation that damages the fibers and forces the body to repair itself and grow. “The stretching tension is a powerful signal for growth,” Delavier says. “To exploit this potential for growth, you need to accentuate the negative phase for each repetition.”
2. Contraction tension. When a muscle has difficulty contracting because of the force exerted by a very heavy weight, the muscle must strengthen itself. Delavier stresses, “To ensure that you provoke a significant muscle-building response, you must continually apply force on your muscles by using heavier and heavier weights.”
3. Time under tension. The weight used during a workout is not the only factor that affects muscle growth. The amount of time that the muscle remains under tension also plays a fundamental role. If too light a weight is used, the time under tension will be longer, but the force of the contraction will be too weak for muscles to take notice of the growth signal. Delavier says that people must find an ideal compromise between absolute tension and time under tension. Scientific research shows the compromise to be a weight that is about 70 to 80 percent of the maximum strength.
4. Muscle burn. The arrival of lactic acid in the muscles means that they have reached the end of what they can endure metabolically. Enduring this burn for as long as possible takes the muscles to the edge of metabolic rupture. Muscle burn is another means of progressing that is different from the heavy, traumatic work that exploits stretching tension, contraction tension, and time under tension.
5. Muscle pump. As someone continues doing repetitions, his or her muscles fill with blood. Called muscle pump, this blood flow brings nutrients and “deforms” the muscles in an unusual fashion. The more intense the muscle pump is, the more the muscle fibers are pressed together. “Because muscle pump training is not traumatic, it can be done frequently, especially as a way of accelerating recuperation,” comments Delavier.

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