Chapter 3: The Specificity of Hypertrophy
In Chapters 1 and 2, we established that the non-negotiable trigger for muscle growth is the combination of high-threshold motor unit recruitment and high fiber-level mechanical tension. Any training method that checks both boxes will stimulate hypertrophy, regardless of the load on the bar, the number of reps, or the subjective sensation of burn and pump. But once those fundamental conditions are met, two more nuanced points need to be addressed before we can get into the practical application of exercise selection and programming.
Hypertrophy is:
- Task-specific: The specific exercises you perform will determine which muscle fibers grow and how they grow. This is not just a matter of targeting different muscles, but also of how the load is applied to those muscles.
- Fiber-specific: muscles do not grow as uniform blocks. Instead, different fibers located in different regions of the muscle may grow more or less depending on the exercise selection and how the load is applied.
In this chapter we will also try to address the question of whether the different type of fibers (Type I vs. Type II) respond differently to different training methods, and whether there are any practical implications for how we should structure our training to maximize growth across all fiber types.
The practical application of these principles—which exercises to pick and how to program them—will then be the subject of Chapters 4 and 5.