Why do muscles grow

When we talk about muscle growth, we often think of a person going to the gym, lifts heavy dumbbells, drinks protein drinks, maybe even takes a photo in the mirror and occasionally uploads the photo to one of the social networks... but seriously, is this the only possible way of muscle growth? What really happens to muscles during physical exercise?

The muscles in the human body are divided into three main categories - smooth, skeletal, and cardiac. In the context of this post, we mean only skeletal muscles. These are one of the main components of the human locomotor system and allow our skeleton to move. Each such muscle is attached to the skeleton from both ends by a tendon. Skeletal muscles are also the only muscles that can be controlled by the will.

Skeletal muscle is composed of several bundles of muscle cells that represent muscle fibers. The muscle cell is multinucleate, which, as we will see below, plays a role in muscle growth. There are other, fiber-like, structures in the cytoplasm of muscle cells called myofibrils. Myofibrils are transversely divided, hence the name for striated muscle, into individual basic functional muscle units called sarcomeres. Sarcomeres play another important role in muscle growth.

Muscle is made up of proteins that are constantly degrading and new ones are forming. The rate of protein conversion in muscles is called protein balance. It can be negative, we are talking about atrophy - loss of muscle mass, or positive, we are talking about hypertrophy - gain of muscle mass.

Muscles can be strengthened in two different ways, aerobically and anaerobically. Aerobic exercise is an activity in which the muscles work with a constant force for a long period of time, i.e. for example when running, swimming, or cycling. Anaerobic exercise is then an activity in which the muscles work with great force for a very short period of time, i.e. typically during bodybuilding or weightlifting. The muscles get stressed during the unusual load on the body and the body tries to compensate for this experience for the next time. During aerobic exercise, the number of muscle cell nuclei increases, which increases the amount of ATP (adenosine triphosphate) that the muscle is able to accumulate. This ultimately increases the muscle's ability to withstand longer work before fatigue occurs. During anaerobic exercise, the number of sarcomeres in myofibrils increases, which we perceive as physical muscle growth. As a result, the muscle tries to adapt to lifting heavy things, such as dumbbells. However, it should be noted that almost no exercise is exclusively strength or endurance. It is rather a combination of both and one of the components in the given exercise predominates.

A person who strengthens does not need to eat more protein than is specified in the principles of proper diet, i.e. about 12 to 15 % of the total energy intake, or 1.6 g of protein per kilogram of total body weight. It turns out that the athlete's body gains more protein with increased efficiency of metabolism. Higher protein consumption has no effect on muscle growth. However, it is important that the person eats more energy than he expends.^[1]

When it comes to food intake, in the short term, with regard to muscle growth, it is better to eat protein-rich food before physical activity itself than after it. The time lag between food intake and exercise is not that important.^[1]