Muscle fibers primarily grow through changes in size, rather than in number. Here's how:
Understanding Muscle Growth
Muscle growth, also known as muscle hypertrophy, generally refers to an increase in the size of muscle cells. There are three primary ways a muscle can grow:
- Increase in the number of fibers (hyperplasia)
- Increase in the length of fibers
- Increase in the girth (diameter) of fibers (hypertrophy)
Skeletal Muscle Fiber Growth
Fiber Number Increase: Limited
According to research, skeletal muscle fibers cannot divide. Therefore, new skeletal muscle fibers are not created by cell division. Instead, more of them can be made only by the fusion of myoblasts, which happens during development, notably before birth in humans. This means that the total number of multinucleated skeletal muscle fibers is generally established early in life.
Fiber Length Increase
Muscles can grow in length to some extent, which is especially noticeable during overall body growth and development, such as in childhood and adolescence. This allows the muscles to adjust as the bones lengthen.
Fiber Girth Increase (Hypertrophy)
The most common way muscle fibers increase in size is through an increase in their girth (diameter), also called hypertrophy. This happens when:
- Muscle fibers are damaged or stressed: Weightlifting or other forms of resistance exercise create micro-tears in the muscle fibers.
- The body repairs the damage: In response to these micro-tears, the body repairs and rebuilds the muscle fibers. This repair process leads to an increase in the size of the fibers.
- Protein synthesis increases: Adequate protein intake is essential for muscle growth. The body uses amino acids (from proteins) to synthesize new muscle proteins, leading to increased fiber size.
Key Takeaways on Fiber Growth
| Aspect | Description |
|---|---|
| Fiber Number | Limited increase after birth. New fibers form by fusion of myoblasts, which occurs mainly during prenatal development. |
| Fiber Length | Increases during overall growth and development. |
| Fiber Girth | Increases in size (hypertrophy) through damage and repair, and increased protein synthesis. This is the most common method of muscle growth. |
Practical Application
To promote muscle growth, you should:
- Engage in resistance training exercises (such as weightlifting).
- Consume sufficient protein to support muscle repair and synthesis.
- Allow adequate rest for muscle recovery.
