The Biology of Muscle Exercise: How Are New Muscles Formed?

The Evolutionary Significance of Muscle Development

The muscles developed by individuals through exercise or strength training correspond to a biological change type known as modification. In other words, muscles develop under physical stress, but if this activity is stopped for a long enough period, muscles revert to their natural state determined by genes (or approach it over time). At no point in this change is genetic; that is, the child of someone who builds muscles is not born more muscular.

Therefore, modifications like muscle development cannot directly contribute to the course of evolution; however, they can certainly have indirect advantages of being fit in the wild.

How Do Our Muscles Develop? How Are New Muscles Formed?

It's a question that will confuse scientists.

Temporary "Swelling" of Muscles After Exercise

Firstly, how do our existing muscles develop? The answer to this question is not that difficult. Our muscles are composed of muscle fibers, and we can think of these as simple cellular structures.

Muscles have two fundamental types of contraction: isometric contraction and isotonic contraction. For example, let's assume you're trying to lift a 40-kilogram mass. At the beginning of the lift, your muscles contract until the mass moves, but there is no displacement. The contraction during this process is called isometric contraction. Later, when we apply enough force, the mass starts to move, and our muscles contract by applying the same force (or increasing force). This is called isotonic contraction.

The continuous repetition of this process, that is, the constant stimulation of certain muscles, results in a continuous accumulation of nutrients and proteins in these muscles. Therefore, the cells here will develop more and increase in volume. This is how the development of our existing muscles occurs. When you go to a gym and work out for about 2 hours, feeling that your muscles are 'pumped' is because of this. This swelling is a sensation resulting from the volume increase of muscle cells due to constant stimulation, and it does not have significant permanence. In fact, it is thought that the main responsible for early-stage (first 1-3 weeks of exercise initiation) muscle hypertrophy might be edema-related muscle swelling, and thus, it may not be a real muscle hypertrophy. This hypertrophy is not linearly related to the muscle mass you will ultimately acquire and cannot be used to predict the future.
Therefore, much more training will be required for this sensation to become permanent and turn into meaningful muscle growth.

Muscle Mathematics

Regarding the development of muscles, there are some very basic, almost "muscle mathematics," extremely simple truths. We can summarize them in 3 main points:

1. Muscle development depends on the balance between muscle breakdown and muscle building. For muscle development to occur, muscle building must be higher than muscle breakdown. This is possible when protein synthesis is higher than protein breakdown. Therefore, muscle development is built on protein mathematics.
2. Both protein synthesis and protein breakdown are controlled through cellular mechanisms associated with these processes. Therefore, understanding these cellular mechanisms is a necessity to increase protein synthesis and decrease protein breakdown.
3. Resistance exercises (lifting weights) significantly enhance muscle development. However, sustainable muscle development is a somewhat slow and long process; hence, consistent and regular training for at least a few months is inevitable. In contrast, even a single session of muscle exercise accelerates protein synthesis for 2-4 hours after the exercise, and according to some studies, this period can extend up to 24 hours.

The impact of muscle resistance exercises on protein synthesis is much higher than its impact on protein breakdown; hence, the primary source of the lasting muscle building effect of muscle training is its impact on protein synthesis.