Final answer:
Muscles grow through hypertrophy, not mitosis. During exercise, muscle fibers experience microscopic damage, and during rest and recovery, the body adds more structural proteins to repair and adapt the muscle fibers, resulting in muscle growth.
Step-by-step explanation:
Muscles grow through a process called hypertrophy, where structural proteins are added to muscle fibers, increasing their size. This process occurs when muscle cells change in size but do not undergo mitosis to create new cells. Instead, the diameter of existing muscle cells increases.
With exercise, the muscle fibers experience microscopic damage. To repair this damage and adapt to the increased demand, the body adds more structural proteins to the damaged fibers during the rest and recovery process. Over time, this leads to muscle growth and increased strength.