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nmdcat.online July 28, 2026

An increase in physical training induces hypertrophy in skeletal muscle. The biological mechanism behind this increase in muscle size is primarily:

A. An increase in the total number of muscle fibers through mitosis
B. An increase in the size of individual muscle fibers due to more myofibrils
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C. The conversion of smooth muscle cells into skeletal muscle cells
D. An increase in the amount of extracellular matrix and fat tissue

📝 Explanation

Muscle hypertrophy (growth due to exercise) occurs not by cell division (hyperplasia), but by the enlargement of existing individual muscle fibers. The cells synthesize more actin and myosin, creating more myofibrils, which increases the thickness and strength of the fiber.

📖 Additional Information

  • An increase in the total number of muscle fibers through mitosis
  • An increase in the size of individual muscle fibers due to more myofibrils
  • The conversion of smooth muscle cells into skeletal muscle cells
  • An increase in the amount of extracellular matrix and fat tissue

Muscle hypertrophy (growth due to exercise) occurs not by cell division (hyperplasia), but by the enlargement of existing individual muscle fibers. The cells synthesize more actin and myosin, creating more myofibrils, which increases the thickness and strength of the fiber.

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