What is Myofibrillar Hypertrophy?

Myofibrillar Hypertrophy
Man with big muscles sitting and lifting dumbbells


Myofibrillar hypertrophy refers to muscle growth that occurs from increasing the number and density of myofibrils, the long protein chains that make up muscle fibers.


  • Myofibrils are thickened and multiplied with progressive overload training, especially higher weight and lower rep ranges.
  • This expands the cells’ capability for contractile force and power output. It makes up ‘quality muscle.’
  • Myofibrillar hypertrophy leads to gains in strength that accompany size gains with heavy, compound lifting.
  • Sets of 1-8 reps recruit the highest threshold motor units in Type II fast twitch fibers to stimulate myofibrillar growth.


  • The sustainable muscle built using heavy weights with enough time under tension.
  • Powerlifters’ predominantly myofibrillar hypertrophy increasing contractile strength.

Related Terms

  • Sarcomeres, Type II muscle fibers, contractile elements, 1RM strength

Common Questions

  • Does myofibrillar hypertrophy make you appear bigger? Less than sarcoplasmic growth, but provides dense muscle cell strength.
  • Is it better than sarcoplasmic hypertrophy? They complement each other. Myofibrillar provides strength and function.

Do Not Confuse With

  • Sarcoplasmic hypertrophy – Increased volume of sarcoplasm fluid around fibers.
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Categorized as obesity