Muscle building - 3 key factors

Muscles feel good, make sexy and even improve our health. But they don't come by themselves. Here I explain which factors play a role in muscle growth.

What is muscle growth? 

In terms of muscle growth, one often speaks of hypertrophy. In medicine, hypertrophy is an independent increase in the size or growth of an organ or tissue. Logically, muscle tissue or muscle cells grow during muscle growth. So if you've heard the word hypertrophy training before, you're talking about training to build muscle.

What happens during muscle growth?

Muscle fibres are single cells, but have several nuclei. Each of these cell nuclei has a certain "sphere of influence" in which the nuclei can expand. Due to the stress the muscle cells are exposed to during training, this area of influence of the cell nuclei can increase the storage of protein. This is also called anabolism, because substances (protein) are built up in the body.

What causes muscle growth?

Basically, muscle growth (hypertrophy) is dominated by 3 decisive influencing factors: Mechanical tension, muscle damage and metabolic stress.

Mechanical tension

Mechanically induced tension in the muscle, generated by the use of force, is an essential stimulus for muscle growth. More precisely, the muscle has to be overloaded so that the growth stimulus aims at increased performance. (Goldberg, Etlinger, Goldspink, & Jablecki, 1975)

The tension in the muscle during strength training „disturbs“ the integrity of the muscle and consequently adjustment mechanisms are initiated. (Toigo & Boutellier, 2006)

Whether an induced tension alone is sufficient to induce hypertrophy is unlikely, but neuronal adaptation symptoms can be observed.

Muscular damage

Strength training can lead to local damage to the muscles. The damage can occur on the smallest level (molecular level), up to large damages (tears in the musculature), which become noticeable through sore muscles. (Vierck, et al., 2013)

The reaction to these micro-traumas can be compared to an inflammatory reaction. As soon as the damage is noticed by the body, cells necessary for the repair move to the site of the event and ensure the healing process. In addition, a large number of cells necessary for muscle growth (satellite cells) are stored in the affected area. This means that damage to muscles promote hypertrophy. (Vierck, et al., 2013)

Metabolic stress

The energy production during strength training takes place mainly through the anaerobic energy metabolism. When all energy reserves are exhausted and/or the supply of new energy is too slow, metabolic stress occurs. The body reacts to this stress with adaptation processes that trigger an increased hypertrophy reaction. (Goto, Ishii, Kizuka, & Takamatsu, 2005)


The best results can be achieved by combining all 3 influencing factors. In contrast to the assumption that one influencing factor dominates, all three have an additive effect in the body.


Marc Neuhoff (CEO)

Marc graduated from the DSHS Cologne and the KIT with a master's degree in sports science. His personal trainer background and more than 14 years of training experience contribute to his expertise.