How do muscles grow?

What causes muscle to grow faster?

We all know that doing sports makes muscles grow. However, from the point of view of anatomy, this is not entirely accurate, since the muscles themselves do not grow substantially( only their volume increases), and without sufficient nutrition, even the best strength exercises are completely useless.

Muscle growth is a complex process of changing the muscle fiber and surrounding tissues, requiring both regular increases in physical exertion, as well as a sufficient amount of energy and time for recovery. Only the right combination of these factors causes the muscles to grow faster.

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Physiology of muscle growth

From the scientific point of view, it is more correct to speak not about the growth of muscles, but about increasing their volume - the very number of muscle fibers practically does not change during life and is set genetically( 1).Strength training really makes fibers stronger, but they do not provoke their growth.

Visual growth of muscles is an increase in sarcoplasm( nutrient fluid surrounding muscle fibers), glycogen depots and hypertrophy( proliferation) of connective tissues. In fact, the athlete's body learns to more effectively use and energize the existing muscle fibers.

How many muscles grow after training?

Studies show that the process of muscle growth begins 3-4 hours after training( 2), and ends in 36-48 hours - which is why it makes no sense to train the same group of muscles more often. The main assistants for rapid growth and muscle recovery are nutrition and sleep.

Immediately after strength training, the body requires both digestible proteins to stop catabolic processes and carbohydrates in an amount of at least 100-150 g. The period when the body prefers to send food energy to the muscles is called the metabolic or carbohydrate window.

Carbohydrates - the main food for the muscles

The correct strength training starts in the body various physiological processes, leading to an increase in the strength of muscle fibers. However, without sufficient energy intake in the form of carbohydrates, fats and proteins( in this sequence), no muscle growth will occur.

Carbohydrates are needed for the body to create glycogen stores( the main source of energy for muscles), fats - for the synthesis of testosterone and other hormones. The role of proteins in the process of muscle growth is often overestimated - in fact, even athletes have enough 100-150 grams of protein per day.

Power before training

For muscles to function, they need a fast energy supply. That is why the body needs preliminary supplies of nutrients in energy depots. Before starting the exercise in the form of glycogen, there must be carbohydrates, which will then be consumed.

Totally in the body of an athlete can store up to 400-500 g of glycogen( 100-150 g in the liver and 350-400 g in sarcoplasm).Importantly, the lack of carbohydrates in the diet does not allow the body to form glycogen reserves for training and significantly limits the processes of muscle recovery and growth.

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The best training for muscle growth

The so-called "basic training" is most effective for muscle growth and glycogen synthesis, which consists in performing multi-joint basic exercises that involve several large muscle groups at once. Exercises are performed with great weight and in 5-7 repetitions.

Such strength training provokes microdamages of muscle tissue, and the restoration of connective tissue after these microdamages leads to muscle growth. In addition, they increase the production of hormones that affect the growth of muscles - especially testosterone.

Features of sports metabolism

The main difference between the athlete's metabolism and the metabolism of an unsportsman is the ability to more effectively use carbohydrates and regulate the level of insulin in the blood. Carbohydrates are processed into glycogen and sent to the muscles, rather than to fat stores.

This is why the increased calorie content of food( at least 20% above the norm) is extremely important for muscle growth - otherwise the body will simply have neither energy nor the stimulus for launching complex, labor-consuming and energy-consuming processes to increase the musculature.


Muscle growth occurs due to the proliferation of connective tissues, and by increasing the volume of energy depots of muscles. At the same time, nutrition is more important than strength training itself, and it is not so much proteins that are important, as are the correct sources of carbohydrates and fats.

Scientific sources:

  1. How do muscles grow? Young sub Kwon, M.S.and Len Kravitz, Ph. D., source
  2. Muscle Growth Part I: Why, And How, Does A Muscle Grow And Get Stronger? Casey Butt, Ph. D., source