What happens when we exercise

The terms hypertrophy and hyperplasia refer to an increase in the size of living tissues.

Both are concepts related to muscle growth, but they have their differences.

This article describes the differences between hypertrophy and hyperplasia and how to achieve each.

What is hypertrophy?

Hypertrophy is the increase in the volume of a tissue or organ due to the rise in the size of the permanent cells. Hypertrophy occurs due to inflammation of individual cells. This includes the muscles.

Muscle hypertrophy is the growth of the muscles due to the increased size of existing muscle fibers.

From a genetic point of view, hypertrophy is achieved when the synthesis of contractile protein is superior to its degradation. (1,2)

The traditional way to achieve muscle hypertrophy is to combine a routine with free weights and bars, a caloric surplus, and 8 hours of rest per day.

What is hyperplasia?

By definition, hyperplasia increases the amount of tissue due to cell proliferation. Growth hormones control cells undergoing hyperplasia. (3)

Muscle hyperplasia is the increase in the size of the muscles due to the rise in the number of muscle fibers.

Examples of naturally occurring hyperplasia are in the mammary glands during lactation and in the endometrium during the menstrual cycle. It can also happen as a pathology in the prostate of men.

Differences between hypertrophy and hyperplasia

From the differences in its mechanism, we can conclude that hyperplasia increases the size of a tissue or an organ due to a more significant number of cells. At the same time, hypertrophy is an increase in the size of an organ due to the inflammation of individual cells. (3)

To see it more clearly, below is a table with the differences between hypertrophy and hyperplasia:

Increased volume due to the size of individual cellsIncrease in size due to a greater number of cells
Occurs in permanent cellsOccurs in labile cells
By greater functional demandBy excessive cellular stimulation
Increases the size of cellular componentsIncreases the amount of tissue by cell division

What happens when we exercise – hypertrophy or hyperplasia?

In the case of muscles, there is no doubt that muscle hypertrophy is a process that occurs with exercise.

Whether it is possible to achieve muscle hyperplasia is still controversial for the scientific community.

What is known today is that there are two mechanisms by which new muscle fibers can form:

  1. One fiber splits and becomes two or more fibers. This does not happen with exercise.
  2. Satellite cells become activated and create myoblast cells. These myoblast cells then fuse with the existing muscle fiber to grow, or they can form with each other to create a new muscle fiber. Thus reaching hyperplasia.

Whether it is possible to achieve hyperplasia with exercise is still controversial. Although recent research suggests that it could occur with eccentric exercises, more studies are still needed to confirm this. (5.6)

The most important thing for both hypertrophy and possible hyperplasia is that the exercises are performed at a controlled speed and emphasize the neuromuscular connection.


  • Hypertrophy and hyperplasia are two terms related to the enlargement of an organ. This includes the muscles.
  • Hypertrophy occurs due to the increase in the size of existing fibers, and hyperplasia due to the generation of new muscle fibers.
  • There is no doubt that with the exercises, muscular hypertrophy is achieved. Whether it is possible to achieve hyperplasia is still controversial in the scientific community. Some studies suggest that it could occur with concentric contractions.


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