Human muscle hypertrophy – how do our muscles grow?

Those who regularly lift heavy weights are likely to often come across technical terms that represent the essence of methods for gaining and increasing muscle mass. Two terms that are used regularly are sarcoplasmic and myofibrillar hypertrophy. Do you know what they mean and how they relate to training? In this article we will clarify this issue.

Content

• 1 Mechanisms of skeletal muscle hypertrophy 1.1 Hypertrophy is the adaptation of muscles to load
• 1.2 Types of muscle fiber hypertrophy

How to stimulate hypertrophy

If your goal is to quickly gain muscle mass, focus on myofibrillar hypertrophy. After all, fast fibers provide about 60% of muscle volume.

Remember that growth stimulation is a two-phase process:

1. The first phase is the launch of the hypertrophy mechanism

Classic strength training in the gym is best suited for this.

• Give priority to basic exercises with free weights (barbell, dumbbells, body weight)
• Number of working approaches – 3
• Rep range – 8-12
• Weight weight – 70-85% of one repetition maximum

1. Second phase – supercompensation

This is the process of hypertrophy itself. It is during rest that the muscles begin to increase in volume. Therefore, it is important to use the optimal frequency of training and rest.

Excessive fanaticism can slow down progress!

During rest, the body recovers and stores excess nutrients in the cells.

The duration of this process takes 2-3 days for beginners, and 3-5 days for experienced athletes.

In order for your muscles to grow, your body must create an excess of nutrients (plastic material).

The main component of muscles is protein. Therefore, for their growth it is necessary to consume the required amount of protein food. And also carbohydrates, fats, vitamins and minerals so that protein is better absorbed.

Mechanisms of skeletal muscle hypertrophy[edit | edit code]

Causes of muscle atrophy with age
Skeletal muscle hypertrophy

(Greek
hyper
- more and Greek
trophe
- nutrition, food) is an adaptive increase in the volume or mass of skeletal muscle. A decrease in skeletal muscle volume or mass is called atrophy. A decrease in skeletal muscle volume or mass in old age is called sarcopenia.

Hypertrophy is the adaptation of muscles to load[edit | edit code]

Hypertrophy determines the speed of skeletal muscle contraction, maximum strength, and the ability to resist fatigue, all of which are important physical attributes that are directly related to athletic performance. Due to the high variability of various characteristics of muscle tissue, such as the size and composition of muscle fibers, as well as the degree of tissue capillarization, skeletal muscles are able to quickly adapt to changes that occur during the training process. At the same time, the nature of adaptation of skeletal muscles to strength and endurance exercises will be different, which indicates the existence of different response systems to load.

Thus, the adaptive process of skeletal muscles to training loads can be considered as a set of coordinated local and peripheral events, the key regulatory signals to which are hormonal, mechanical, metabolic and neural factors. Changes in the rate of synthesis of hormones and growth factors, as well as the content of their receptors, are important factors in the regulation of the adaptive process, which allows skeletal muscles to satisfy the physiological needs of various types of motor activity.

Read more:

Adaptation of muscles to load.

Types of muscle fiber hypertrophy[edit | edit code]

The structure of muscle fiber
Two extreme types of muscle fiber hypertrophy can be distinguished [1] [2]: myofibrillar hypertrophy and sarcoplasmic hypertrophy.

• Myofibrillar hypertrophy of muscle fibers
  is an increase in the volume of muscle fibers due to an increase in the volume and number of myofibrils. At the same time, the packing density of myofibrils in the muscle fiber increases. Hypertrophy of muscle fibers leads to a significant increase in maximum muscle strength. Fast (type IIB) muscle fibers[1] and to a lesser extent type IIA are most predisposed to myofibrillar hypertrophy.

• Sarcoplasmic hypertrophy of muscle fibers
  is an increase in the volume of muscle fibers due to a predominant increase in the volume of sarcoplasm, i.e., their non-contractile part. Hypertrophy of this type occurs due to an increase in the content of mitochondria in muscle fibers, as well as: creatine phosphate, glycogen, myoglobin, etc. Slow (I) and fast oxidative (IIA) muscle fibers are most predisposed to sarcoplasmic hypertrophy [1]. Sarcoplasmic hypertrophy of muscle fibers has little effect on the growth of muscle strength, but it significantly increases the ability to work for long periods of time, i.e., it increases their endurance.

Myofibrillar and sarcoplasmic muscle hypertrophy
In real situations, muscle fiber hypertrophy is a combination of the two named types with a predominance of one of them. The predominant development of one or another type of muscle fiber hypertrophy is determined by the nature of the training. Exercises with significant external weights (more than 70% of the maximum) contribute to the development of myofibrillar hypertrophy of muscle fibers. This type of hypertrophy is typical for strength sports (weightlifting, powerlifting). Long-term performance of motor actions that develop endurance with a relatively small force load on the muscles causes mainly sarcoplasmic hypertrophy of muscle fibers. This hypertrophy is typical for middle and long distance runners. Bodybuilding athletes are characterized by both myofibrillar and sarcoplasmic hypertrophy of muscle fibers[3].

Muscle hyperplasia is often referred to as hypertrophy.

(increase in the number of fibers), however, recent studies[4] have shown that the contribution of hyperplasia to muscle volume is less than 5% and is more significant only when using anabolic steroids. Growth hormone does not cause hyperplasia. Thus, people prone to hypertrophy tend to have a larger number of muscle fibers. The total number of fibers is genetically determined and practically does not change throughout life without the use of special pharmacology.

Training for myofibrillar hypertrophy

We know that weights of 70% and above involve all slow and almost all fast muscle fibers. As you get tired or the weight of the weight increases, unused fast fibers will be activated. It turns out that for myofibrillar hypertrophy you should work with heavy weights in a small number of repetitions. You should perform powerful reps with heavy weights so that the time per set is about 20 seconds, usually about 8 reps.

Methodology for assessing the degree of hypertrophy[edit | edit code]

In order to assess the degree of skeletal muscle hypertrophy, it is necessary to measure the change in its volume or mass. Modern research methods (computer or magnetic resonance imaging) make it possible to assess changes in the volume of skeletal muscles in humans and animals. For this purpose, multiple “slices” of the cross-section of the muscle are performed, which makes it possible to calculate its volume. However, until now, the degree of skeletal muscle hypertrophy is often judged by changes in the maximum cross-sectional value of the muscle obtained by computed tomography or magnetic resonance imaging.

In bodybuilding, muscle hypertrophy is assessed by measuring the coverage of the arms (at the level of the forearm and biceps), thighs, legs, and chest using a meter tape.

Some practical recommendations.

Thus, from all of the above, several practical tips can be emphasized:

• To build muscle mass, use 8-12 reps per set.
• Perform exercises with maximum amplitude.
• Take relatively short rest periods (30-90 seconds).
• Once a week, overload an isolated muscle group (12 - 20 repetitions). This method will help increase the volume and increase the effectiveness of training.
• Always work according to plan.
• Consume enough calories with a minimum of 15% protein or 1.0 grams of protein per kilogram of body weight.
• And never forget about sleep, you should sleep 7-9 hours a day!

Indicators that determine the volume of skeletal muscles[edit | edit code]

The main component of skeletal muscle is muscle fibers, which make up approximately 87% of its volume[5]. This component of the muscle is called contractile, since the contraction of muscle fibers allows the muscle to change its length and move parts of the musculoskeletal system, carrying out the movement of parts of the human body. The rest of the muscle volume (13%) is occupied by non-contractile elements (connective tissue formations, blood and lymphatic vessels, nerves, tissue fluid, etc.).

To a first approximation[6], the volume of the entire muscle (Vm) can be expressed by the formula:

Vm = Vmv × Nmv + Vns

where: Vmv – muscle fiber volume; Nmf – number of muscle fibers; Vns – the volume of the non-contractile part of the muscle (that is, the volume that is occupied by all components of the muscle, except muscle fibers)

The influence of training on the parameters that determine the volume of skeletal muscles[edit | edit code]

It has been proven that under the influence of strength and endurance training, the volume of muscle fibers (Vmv) and the volume of the non-contractile part of the muscle (Vns) increase. There has been no evidence of an increase in the number of muscle fibers (muscle fiber hyperplasia) in humans under the influence of strength training, although muscle fiber hyperplasia has been proven in animals (mammals and birds)[7].

Structure of skeletal muscles

You can’t do without biochemistry this time either, but what to do, you need to gain knowledge. So, the muscle is a case of dense connective tissue - epimysium, in which muscle fibers are placed. These fibers are combined into bundles, which are also surrounded by their own connective tissue - perimysium. The muscle fibers themselves consist of myofibrils - the contractile protein elements of the muscle. And even they are surrounded by connective tissue called endomysium. Around the myofibrils there is sarcoplasm, which can be characterized as an energetic substance for the myofibrils. Sarcoplasm consists of water, glycogen, phosphates, and also contains mitochondria and ribosomes. Each bundle of muscle fibers is innervated by a motor neuron.

Mechanisms of skeletal muscle hypertrophy[edit | edit code]

Myofibrillar hypertrophy of muscle fibers is based on intensive synthesis and reduced breakdown of muscle proteins. There are several hypotheses for myofibrillar hypertrophy:

• acidosis hypothesis;
• hypoxia hypothesis;
• hypothesis of mechanical damage to muscle fibers.

Acidosis hypothesis

suggests that the trigger for increased protein synthesis in skeletal muscles is the accumulation of lactic acid (lactate) in them. An increase in lactate in muscle fibers causes damage to the sarcolemma of muscle fibers and organelle membranes, the appearance of calcium ions in the sarcoplasm of muscle fibers, which causes activation of proteolytic enzymes that break down muscle proteins. The increase in protein synthesis in this hypothesis is associated with the activation and subsequent division of satellite cells.

Hypoxia hypothesis

suggests that the trigger for increased protein synthesis in skeletal muscle is a temporary restriction of oxygen supply (hypoxia) to skeletal muscle, which occurs during resistance exercise with heavy weights. Hypoxia and subsequent reperfusion (restoration of oxygen flow to skeletal muscles) causes damage to the membranes of muscle fibers and organelles, the appearance of calcium ions in the sarcoplasm of muscle fibers, which causes activation of proteolytic enzymes that break down muscle proteins. The increase in protein synthesis in this hypothesis is associated with the activation and subsequent division of satellite cells.

Hypothesis of mechanical damage to muscle fibers

suggests that the trigger for increased protein synthesis is high muscle tension, which leads to severe damage to the contractile and cytoskeletal proteins of the muscle fiber. It has been proven[8] that even a single session of strength training can damage more than 80% of muscle fibers. Damage to the sarcoplasmic reticulum causes an increase in calcium ions in the sarcoplasm of the muscle fiber and the subsequent processes described above.

According to the above hypotheses, muscle fiber damage causes delayed onset muscle soreness (DOMS)

, which is associated with their inflammation.

Androgens (male sex hormones) play a very important role in regulating the volume of muscle mass, in particular in the development of muscle hypertrophy. In men they are produced by the gonads (testes) and in the adrenal cortex, and in women - only in the adrenal cortex. Accordingly, men have more androgens in their bodies than women.

Age-related development of muscle mass occurs in parallel with an increase in the production of androgenic hormones. The first noticeable increase in the volume of muscle fibers is observed at 6-7 years of age, when the formation of androgens increases. With the onset of puberty (11–15 years), an intensive increase in muscle mass begins in boys, which continues after puberty. In girls, the development of muscle mass generally ends with puberty.

Animal experiments have established that the administration of androgenic hormones (anabolic steroids) causes a significant intensification of muscle protein synthesis, resulting in an increase in the mass of trained muscles and, as a result, their strength. However, skeletal muscle hypertrophy can occur without the participation of androgen and other hormones (growth hormone, insulin and thyroid hormones).

The effect of training on the composition and hypertrophy of muscle fibers of various types.

It has been proven[9][10][11] that strength training and endurance training do not change the ratio of slow (type I) and fast (type II) muscle fibers in the muscles. However, these types of training are able to change the ratio of the two types of fast fibers, increasing the percentage of type IIA muscle fibers and correspondingly decreasing the percentage of type IIB muscle fibers.

As a result of strength training, the degree of hypertrophy of fast muscle fibers (type II) is much greater than that of slow fibers (type I), while endurance training leads to hypertrophy primarily of slow fibers (type I). These differences indicate that the degree of muscle fiber hypertrophy depends both on the extent of its use during training and on its ability to hypertrophy.

Strength training involves a relatively small number of repeated maximal or near maximal muscle contractions, involving both fast-twitch and slow-twitch muscle fibers. However, a small number of repetitions is enough to develop hypertrophy of fast fibers, which indicates their greater predisposition to hypertrophy (compared to slow fibers). A high percentage of fast-twitch fibers (type II) in muscles is an important prerequisite for significant increases in muscle strength with targeted strength training. Therefore, people with a high percentage of fast-twitch fibers in their muscles have a higher potential for developing strength and power.

Endurance training involves a large number of repeated muscle contractions of relatively low force, which are mainly provided by the activity of slow-twitch muscle fibers. Therefore, during endurance training, the hypertrophy of slow muscle fibers (type I) is more pronounced compared to the hypertrophy of fast fibers (type II).

Sports nutrition for muscle fiber hypertrophy

Remember that in addition to sports nutrition, the role of food and nutrient ratios for muscle growth cannot be overemphasized.

Only if all the principles are followed: high-calorie, frequent meals high in complex carbohydrates (about 40–50%), proteins (20–30%) and fats (20%), you can additionally take sports supplements.

Creatine

This supplement is not necessary for muscle growth, with the exception of men with an asthenic body type who find it difficult to gain weight. Creatine is able to retain excess fluid in the sarcoplasm, which will help increase muscle endurance and speed up recovery. That is, creatine does not directly affect hypertrophy, but serves as a necessary boost during strength training.

Full cycle amino acids and BCAAs

The construction of new cells in the body is impossible without proteins. Regular nutrition is sometimes not enough for muscle growth, so athletes must resort to taking such supplements. Proteins that are broken down into amino acids speed up the absorption time of substances, allow you to quickly replenish lost energy reserves, build new fibers and prevent catabolism.

Read more about BCAA supplement →

Protein shakes and gainers

Supplements enrich the diet with proteins (amino acids), and in the case of gainers, fast carbohydrates (energy), which are needed as a meal replacement or for use before or after strength training. The proteins and carbohydrates in these products, depending on the manufacturer, are both simple and complex, that is, with different rates of absorption. Some are designed to be taken before bed or in the morning, preventing muscle breakdown at night or after sleep. Quick gainers and protein shakes are especially necessary immediately after training, closing the protein-carbohydrate window with them. In this case, the muscles receive all the necessary nutrients for further growth.

Factors of hypertrophy[edit | edit code]

Synthesis of contractile proteins[edit | edit code]

Increasing the synthesis of contractile proteins is an absolute condition for increasing the size of muscle cells in response to training load. During the growth of skeletal muscles, not only the intensity of protein synthesis changes, but also the rate of its degradation [12]. In humans, an increase in protein synthesis above the resting level occurs very quickly, within 1–4 hours after completion of a single training session[13]. At the onset of muscle hypertrophy, increased protein synthesis correlates with increased RNA activity [14]. The transmission of mRNA is facilitated by those factors whose activity is known to be regulated by their phosphorylation[15]. In parallel with these changes, after a training session, there is an increase in the transport of amino acids into the muscles subjected to stress. From a theoretical point of view, this increases the availability of amino acids for protein synthesis[16].

Ribonucleic acid (RNA)[edit | edit code]

Some evidence suggests that after this initial stage, a necessary condition for continued muscle hypertrophy is an increase in RNA levels (as opposed to the increase in RNA activity that occurred initially). Here, the increased amount of mRNA may be due to either increased gene transcription in cell nuclei or an increase in the number of nuclei. The muscle fibers of an adult human contain hundreds of nuclei, and each nucleus carries out protein synthesis in a limited volume of cytoplasm, called the “nuclear component”[17]. It is important to note that although the nuclei of a muscle cell have undergone mitosis, they are able to provide an increase in fibrils only to a certain limit, after which the recruitment of new nuclei becomes necessary. This assumption is supported by human and animal studies demonstrating that hypertrophy of skeletal muscle fibers is accompanied by a significant increase in the number of nuclei[18]. In well-trained people, such as heavyweights, the number of nuclei in the hypertrophied skeletal muscle fibril is greater than in people who lead a sedentary lifestyle. The existence of a linear relationship between the number of nuclei and the cross-sectional area of ​​the myofibril has been established [19]. The appearance of new nuclei in an enlarged myofibril plays a role in maintaining a constant nuclear-cytoplasmic ratio, i.e., a stable size of the nuclear component. The appearance of new nuclei in hypertrophied myofibrils has been reported for individuals of different ages[20].

Hyperplasia (satellite cells)[edit | edit code]

Along with hypertrophy (increase in cell volume), under the influence of physical training, the process of hyperplasia is observed - an increase in the number of fibers due to the division of satellite cells. It is hyperplasia that ensures the development of muscle memory.

Satellite cells or satellite cells

The functions of satellite cells are to facilitate growth, support vital functions and repair damaged skeletal (non-cardiac) muscle tissue. These cells are called satellite cells because they are located on the outer surface of the muscle fibers, between the sarcolemma and the basal lamina (the upper layer of the basement membrane) of the muscle fiber. Satellite cells have one nucleus, which occupies most of their volume. Normally these cells are in a resting state, but they are activated when the muscle fibers receive any type of injury, such as from strength training. The satellite cells then multiply and the daughter cells are attracted to the damaged muscle area. They then fuse with the existing muscle fiber, donating their cores which help regenerate the muscle fibers. It is important to emphasize that this process does not create new skeletal muscle fibers (in humans), but increases the size and amount of contractile proteins (actin and myosin) within the muscle fiber. This period of satellite cell activation and proliferation lasts up to 48 hours after injury or after a strength training session[21].

The effect of androgenic anabolic steroids[edit | edit code]

Results from animal studies have shown that the use of androgenic anabolic steroids is associated with significant increases in muscle size and muscle strength[22]. The use of testosterone in concentrations exceeding physiological levels in men with different levels of physical fitness for 10 weeks was accompanied by a significant increase in muscle strength and cross-section of the quadriceps femoris muscle [23]. Androgenic anabolic steroids are known to increase protein synthesis and promote muscle growth both in vivo and in vitro[24]. In humans, long-term use of anabolic steroids increases the degree of muscle fiber hypertrophy in well-trained weightlifters[25]. The skeletal muscles of weightlifters who have taken anabolic steroids are characterized by extremely large muscle fiber sizes and a large number of nuclei in the muscle cells[26]. A similar pattern has been observed in animal models, where androgenic anabolic steroids have been found to mediate their myotrophic effects by increasing the number of nuclei in muscle fibers and increasing the number of muscle fibers[27]. Thus, anabolic steroids promote an increase in the number of nuclei in order to promote protein synthesis in extremely hypertrophied muscle fibers[28]. The primary mechanism by which androgenic anabolic steroids induce muscle hypertrophy is the activation and induction of proliferation of myosatellite cells, which subsequently fuse with existing muscle fibers or with each other to form new muscle fibers. This conclusion is consistent with the results of immunohistochemical localization of androgen receptors in cultured satellite cells, demonstrating the possibility of direct effects of anabolic steroids on myosatellite cells [29].

Effect of additives

Dietary supplements include 1 or more food ingredients. Their components are intended for oral administration in the form of tablets, capsules, tablets or liquid.

Based on the type of impact on the body and effect, the following main types of sports supplements are distinguished:

• Aimed at increasing the body's endurance - especially important for athletes who engage in aerobic types of training;
• Energy supplements – used to improve performance in the short term. It's the same as eating food - the supplement contains energy. The difference is that the sports supplement is absorbed much faster.
• supplements that help restore damaged muscles and compensate for microtrauma. This is, for example, whey protein or amino acids.

Energy nutritional supplements are used by athletes to increase their athletic abilities for a short period and to train more often.

They are aimed at restoring muscle energy resources:

• caffeine is a common substance that is even found in tea and coffee;
• guarana;
• vitamin B12 - can be obtained not only through supplements, but also from food, for example, from meat;
• carbohydrates – found in large quantities in sweet, refined foods, and are also easily digested;
• Asian ginseng.

Guarana is a plant native to the Amazon. Its rhizomes and stems are dried, crushed and used by athletes as a nutritional supplement that increases endurance and strength in athletes.

Caffeine has a similar effect: it temporarily stimulates the nervous system and body tone, adding endurance and strength. Caffeine is found in everyday drinks and is sold in pharmacies. This is the most common energy supplement.

The main sports supplements that help athletes recover after training are protein and amino acid supplements. These are basically protein shakes or supplements with a lot of protein.

Excessive protein intake causes:

• loss of calcium and, as a result, dehydration of the body;
• gout;
• damage to the liver and kidneys, the cardiovascular system suffers greatly;
• constipation due to lack of complex carbohydrates, in particular fiber;
• bloating, occasional flatulence.

The most common and popular performance enhancing supplements are:

• Creatine – found in most protein shakes;
• glutamine is a naturally occurring substance found in food products;
• androstenedione is a hormonal substance;
• chromium is a vitamin that can also be found in food;
• ephedra.

Creatine increases physical strength, which is why it is popular among bodybuilders. Glutamine, found in whey fiber supplements, is the most abundant free amino acid discovered by scientists in the human body.

The effect of insulin, amino acids and exercise on hypertrophy[edit | edit code]

PI3K - mTOR (phosphatidylinositol 3-kinase - mammalian target of rapamycin) signaling pathway Activation of the PI3K - mTOR (phosphatidylinositol 3-kinase - mammalian target of rapamycin) signaling pathway
Insulin, amino acids and resistance exercise all lead to increased protein synthesis in the brain. skeletal muscles[30]. Although insulin, amino acids, and exercise individually activate multiple signal transduction pathways in skeletal muscle, one pathway, PI3K–mTOR (mammalian target of rapamycin 3-kinase), is a target of all three. Activation of the PI3K–mTOR signal transduction pathway results in both immediate (from several minutes to several hours) and prolonged (from hours to several days) effect of regulation of protein synthesis through modulation of several stages, including the initiation of mRNA translation and, as a consequence, biosynthesis on ribosomes . The common endpoint in signaling from each stimulus is the protein kinase mTOR. Inhibition of mTOR by rapamycin or by genetic methods (eg, RNA interference in cultured cells) prevents the increase in protein synthesis caused by any of the three designated stimuli. Moreover, rapamycin dramatically attenuated the hypertrophy observed in the synergistic ablation model of resistance exercise. In fact, in both cell types, both cultured and in vivo animals, inhibition of mTOR resulted in a reduced cell phenotype. Overall, the available evidence strongly suggests a central role for mTOR in the control of cell growth. Now that the importance of the role of mTOR in the hypertrophy process has been identified, future studies should soon provide more detailed information regarding the mechanisms by which amino acids and exercise promote signaling through this kinase. In addition, the study of the downstream reactions activated by mTOR and leading to gene expression should also be addressed in future studies. Together, such studies targeting both mTOR input and output signaling will lead to a better understanding of how insulin, amino acids, and resistance exercise increase protein synthesis and hypertrophy in skeletal muscle.

Other anabolic agents[edit | edit code]

• A growth hormone
• Insulin
• Mechanical growth factor
• Fibroblast growth factors
• Insulin-like growth factors and their receptors
• Sports nutrition for muscle growth

Sources[edit | edit code]

1. ↑ 1,01,11,2 Kots Ya.M. Sports physiology Textbook for physical education institutes. - M.: Physical culture and sport, 1998.
2. Solodkov A.S., Sologub E.B. Human physiology. General. Sports. Age: Textbook. - M.: Terra-Sport, Olympia press, 2001.
3. Solodkov A.S., Sologub E.B. Human physiology. General. Sports. Age: Textbook. - M.: Terra-Sport, Olympia press, 2001.
4. Kraemer, William J.; Zatsiorsky, Vladimir M. (2006). Science and practice of strength training. Champaign, IL: Human Kinetics. p. 50. ISBN 0-7360-5628-9.
5. MacDougall JD, Sale DG, Alway SE, Sutton JR Muscle fiber number in biceps brachii in bodybuilders and control subjects // Journal Applied Physiology, 1984. V 57. No. 5. P. 1399-1403.
6. Samsonova A.V. Hypertrophy of human skeletal muscles: Textbook. — 3rd ed. - St. Petersburg: Politekhnika, 215.
7. MacDougall JD Hypertrophy and Hyperplasia // In: The Encyclopedia of Sport Medicine. Strength and Power in Sport. - Bodmin, Cornwall: Blackwell Publishing, 2003.
8. Gibala, MJ, MacDougall JD, Tarnopolsky MA, Stauber WT, Elorriaga A. Changes in human skeletal muscle ultrastructure and force production after acute resistance exercise // Journal of Applied Physiology. - 1995. - P. 702-708.
9. MacDougall JD, Elder GCB, Sale DG, Moroz JR & Sutton, JR Effects of strength training and immobilization on human muscle fibers // European Journal of Applied Physiology. - 1980. - No. 43. - P. 25–34.
10. Yazvikov V.V. The influence of sports training on the composition of muscle fibers of mixed human skeletal muscles // Theory and practice of physical culture. - 1988. - No. 2. - P. 48-50.
11. Yazvikov V.V., Morozov S.A., Nekrasov A.N. Correlation between the content of slow fibers in the vastus externus muscle and athletic performance // Human Physiology. - 1990. - T. 16, No. 4. - P. 167-169.
12. Goldbeig et al., 1975
13. Wong and Booth, 1990; Chcsley et al., 1992; Biolo ct al., 1995; Philips et al., 1997
14. Laurent et al., 1978; Wong, Booth, 1990
15. Frederickson, Sonebcig, 1993; Wada et al., 1996
16. Biolo et al., 1997
17. Cheek, 1985; Hall, Ralston, 1989; Allen et al., 1999
18. Goldberg et al., 1975; Cabric, James, 1983; Winchester, Gonyea, 1992; Allen et al., 1995; Kadi, 2000
19. Kadi et al., 1999a; Kadi, 2000
20. Hikida et al., 1998; Kadi, Tomcll, 2000
21. Hawke, T. J., and D. J. Garry. Myogenic satellite cells: physiology to molecular biology. Journal of Applied Physiology. 91:534-551, 2001.
22. Egginton, 1987; Salmons, 1992
23. Basin et al., 1996
24. Powers, Florini, 1975; Rogozkin, 1979
25. Kadi et al., 1999b
26. Kadi et al., 1999b
27. Galavazi, Szirmai, 1971; Sassoon, Kelley, 1986; Joubcrt, Tobin, 1989; Joubert, Tobin, 1995
28. Kadi et al., 1999b
29. Doumit et al., 1996
30. Douglas R. Bolster, Leonard S. Jefferson and Scot R. Kimball. Regulation of protein synthesis associated with skeletal muscle hypertrophy by insulin-, amino acid- and exercise-induced signaling. Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, PO Box 850, Hershey, PA 17033, USA