What actually happens when you gain new skeletal muscle

When you engage in an effective muscle-building training program, there is a wide range of physiological adaptations that occur to cause new skeletal muscle to grow. In turn, your muscle size increases, as does your muscle strength and power. Let’s take a look at what is happening in the body when you gain new skeletal muscle following consistent and well-thought-out weightlifting.

Muscle fiber hypertrophy

The primary mechanism behind muscle growth is hypertrophy, which involves an increase in the size of each muscle fiber. Resistance training (weightlifting) causes microscopic tears in the muscle fibers, and when these tears are repaired, a growth process is initiated in the muscles.

Muscle fiber recruitment

When you lift weights, your body recruits motor units, which comprise a motor neuron and the muscle fibers that it innervates. With progressive overload (increasing resistance or intensity over time), your body begins to recruit more motor units and activates a higher number of muscle fibers when you lift, leading to increased muscle strength and size.

Protein synthesis

Protein synthesis (protein production) occurs in the body all the time, including when your body is increasing skeletal muscle fiber size and strength. When you perform resistance exercises, the body increases protein synthesis to repair and rebuild damaged muscle fibers. Protein synthesis is stimulated by factors such as mechanical tension (resistance training) and dietary protein intake.

Satellite cell activation

Satellite cells are specialized cells involved in muscle repair and growth. When muscle fibers are damaged, satellite cells become activated and fuse with existing muscle fibers, contributing to the repair and hypertrophy process. This fusion increases the number of nuclei within the muscle fibers, supporting their growth.