Muscle growthInside the muscles, the muscle fibres are damaged when exercising, and, during their regeneration, the body creates new, stronger fibres, resulting in muscle growth. We gain muscle volume through an increase in muscle mass, i.e. Muscle hypertrophy We achieve muscle hypertrophy with a greater volume of strength training. To increase muscle volume, weight (resistance) training is the most appropriate form of exercise. It is better to weight train with heavier weights, but even after low-intensity training with a high number of repetitions the muscle will grow.
Although all muscle fibres grow and strengthen as a result of training, different types of fibre grow with differing intensities. Fast twitch muscle fibres, responsible for muscle strength and speed, are higher in volume and grow faster than slow twitch muscle fibres with the impact of intense resistance training. Everyone has a certain ratio of fast twitch muscle fibres in their muscles, which is largely determined genetically. Therefore, some people who have a higher number of fast twitch fibres respond to resistance training faster than people with a higher ratio of slow twitch fibres (which does give them an advantage, however, when it comes to endurance sports). This fact is one reason why strength-speed athletes (e.g. sprinters) tend to have more muscle bulk than endurance athletes (e.g. marathon runners).
Muscle proteins responsible for contraction are completely rebuilt by the body in 7–15 days. Training influences the speed of rebuilding as well as the number of proteins incorporated into the muscle. This affects the speed at which the muscles increase in volume.
The impact of age on muscle volumeMuscle loss starts to occur after 50 years of age. Young men have an average of a kilo of muscle or more in each leg than older men. The average decline in muscle strength over a decade is around 12–14%.
Myosatellite cells are small cells stored in the connective tissue of the skeletal muscles and act as a regenerative reservoir for muscle recovery. If muscles are damaged or, as a result of mechanical stress (e.g. when training), the satellite cells, which start to divide and convert into muscle cells, are activated. At a specific stage of this conversion, they will merge with pre-existing muscle cells (cell fibres). That is why, during training, the number of muscle fibres does not increase in the muscle. Only the volume of previously existing fibres increases and their effectiveness (strength) increases. When joining satellite cells with muscle fibres, the cell nucleus is added to the already existing nuclei in the muscle fibre. An increase in the number of nuclei allows the muscle to make more muscle proteins.
Nutrition and muscle growth
For muscles to grow, you need to have a positive energy intake – this means that you have to take in more energy in your food than you expend during the day. Although many athletes focus mainly on increasing protein intake when training for muscle volume and strength, this approach is not always ideal. According to studies, the total calorie intake together with the protein intake, which stimulates muscle growth partially independently of each other, is important.
According to some studies, a greater energy intake, roughly 15–25% above the value needed to maintain the existing muscle volume (usually value from 500 to 2000 kcal/day), has proven to be the most beneficial for increasing net muscle volume. However, when increasing energy intake, there is often an increase in body fat alongside the increase in the muscle (up to 60% of the total weight gained). The recommended amount of protein should be around 12–15% of the total calorie intake, which is approximately 1g of protein per kg of body mass.
According to scientific studies, the consumption of dietary protein supplements for untrained individuals in the first weeks of resistance training is a waste of time. However, by increasing the length and frequency of exercise, as well as the load, protein supplements can help stimulate muscle growth and increase muscular strength. Furthermore, it seems that protein supplements can speed up the increase in anaerobic and aerobic performance.