How muscles grow: Part II

Due to what muscles grow?

In the first part of the material it was said that the number of muscle fibers is determined genetically, and the muscles grow due to an increase in volume( "hypertrophy").It is believed that more than 80% of growth is due to an increase in connective tissue( 1).

The remaining 20% ​​growth is due to the increase in storage of nutrients in the muscles. But despite the fact that it's only 20%, without nutrient supply, muscle growth is simply impossible. As always, the Pareto 80/20 rule applies.

The role of nutrition in the muscle set

In response to strength training, the body increases the amount of energy and nutrients in the muscles, which allows you to train longer and more efficiently, and heal microdamages and build new connective tissue faster.

Strengthened nutrition after exercise( "carbohydrate window") is important for the development of the body's abilities to transform and store energy for stronger training the next time. If you do not eat enough, it significantly impairs muscle growth.

Muscle growth and hormones

To assimilate amino acids and grow, the muscle cell needs special enzymes;the ability of a cell to produce these enzymes is very limited, but in some cases, surrounding satellite cells are able to give it this valuable enzyme.

In the first place, satellite cells are activated by hormones( growth hormone, testosterone, IGF-1 and others), the production of which increases with force training;secondly, the activity of the satellite cells increases with the intake of creatine( 2).

Strength Training

Although the increase in muscle strength is directly related to the increase in its volume, performing exercises with a high weight and with a small number of repetitions involves a specific type of muscle fibers - the fastest fibers( Type II).

If your goal is to increase strength, then you need to perform exercises with a weight of 85% of 1MP in the amount of 3-5 repetitions( 3).Such training activates the work of the nervous system and increases the production of hormones, on which, for example, a basic program is built.

Training for weight increase

If your main goal is to increase muscle volume, then you need 6-12 repetitions of exercise and working weight in the border of 70-85% of 1MP( 3).In this case, consider that the smaller the muscle group, the more it needs repetition, and vice versa.

Training with an average number of repetitions involves fast muscle fibers of the middle type( Type IIB) reacting to glycogen, which together with increased blood circulation and sufficient nutrients in the blood will give an increase in muscle volume.

Optimal training frequency

The duration of recovery of muscle fibers after training and accompanying growth takes 36-48 hours, so it is strictly not recommended to train the same muscle group more often. But once again we note that without food this growth is impossible.

First, before carbohydrate training, carbohydrates are important, allowing you to fill the glycogen stores for this workout;secondly, protein nutrition, calcium and vitamins are necessary for muscle growth;third, creatine to improve the energy of muscle cells.


Exercising with heavy weights at low repetitions increases primarily the strength, and execution with an average weight and an average number of repetitions - the mass and volume of muscles. But without sufficient nutrition and restoring muscle growth will not.


  1. Muscle Growth: Why, And How, Does A Muscle Grow And Get Stronger, Casey Butt, Ph. D., source
  2. Creatine supplementation augments in human skeletal muscle,source
  3. Rational and Irrational Hypertrophy: Why Are not Olympic Lifters Bigger Than Bodybuilders? , source