The BEST Way to Gain Muscle? Myofibrillar vs. Sarcoplasmic Hypertrophy

The Structure of Skeletal Muscle

In the figure below, you can see a muscle divided into its component parts. You can see there is a sarcolemma, which is the surrounding tissue of a muscle fiber, and inside the sarcolemma, there are the myofibrils – the contractile portions of the muscle fiber.

Take Away – Sarcoplasmic hypertrophy is the growth of components within the sarcolemma, while myofibrillar hypertrophy is the growth of the myofibrillar components.

 Sarcoplasmic Hypertrophy

Sarcoplasmic hypertrophy can be thought of as a more long-lasting form of hyperemia (a.k.a. cell fluid increase). Increases in non-contractile substances such as intracellular fluid or muscle glycogen increase the size of a muscle.

An often used analogy is to compare this to filling a balloon with water to increase its size.

Sarcoplasmic hypertrophy can often be caused by hyperemia, or the pump. When a pump is large enough, it makes the sarcolemma expand, literally blowing up the muscle fiber to the point where it must grow, or risk bursting. This process is often the goal of bodybuilding-style exercise programs.

Myofibrillar Hypertrophy

Myofibrils are the contractile portions of a muscle fiber, and myofibrillar hypertrophy is defined as the increase in the myofibrillar content of a muscle. The increase in myofibrils can be thought of as increasing the density of a muscle fiber (think, the thickening of the ‘skin’ of a balloon) — not the volume like sarcoplasmic hypertrophy — a process which leads to greater gains in strength. This is where people will commonly relate olympic lifters, and sprinters, who tend to be immensely strong without being very big — a result of their training methods, which aim to maximize myofibrillar hypertrophy.



Sarcoplasmic Hypertrophy – Traditional ‘bodybuilder” style workouts.

  • Higher Volume (sets/reps)
  • Shorter Rest Periods
  • Lower Intensity (% of 1RM)
  • Time Under Tension (TUT) 45-70 seconds
  • Larger Variety of Exercises

Myofibrillar Hypertrophy  – Traditional ‘power-lifter’ style workouts.

  • Lower Volume (sets/reps)
  • Longer Rest Periods
  • Higher Intensity (% of 1RM)
  • Time Under Tension (TUT) sub 20 seconds
  • Smaller Variety of Exercises

The reality is you must train in both aspects to make consistent progress. If you only train myofibrillar hypertrophy you will be missing out on the benefits of sarcoplasmic!

This is why we take a deeper look into proper program design and macro/micro cycling programs with our clients. This ensures constant progression, limits repetitive injuries, reduces imbalance and leads to overall healthier clients!

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