Science
How do muscles grow?
Muscles grow when exercise creates tiny tears in muscle fibers, and the body repairs them slightly bigger and stronger. With enough protein, rest, and progressively harder training, this repeat-and-rebuild cycle gradually builds muscle size and strength.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how muscle growth works.
Step by step
- 1Hard exercise causes tiny tears in muscle fibers.
- 2The body repairs them thicker and stronger.
- 3Protein supplies the building blocks.
- 4Rest and progressive overload drive growth.
Frequently asked questions
- How do muscles grow?
- Exercise damages muscle fibers slightly; the body repairs them bigger and stronger, given protein and rest.
- Why is rest important for muscle growth?
- Muscles rebuild during recovery, not during the workout itself, so rest is when growth happens.
- Does protein build muscle?
- Protein provides the amino acids needed to repair and grow muscle, supporting the process alongside training.