Indicators of muscle system activity. Muscle activity Muscle activity

Welcome, welcome, is anyone there? The ABCs of Bodybuilding are in touch! And on this Friday we will examine an unusual topic called electrical activity of muscles.

After reading, you will learn what EMG is as a phenomenon, what and for what purposes this process is used, why most studies on the “better” exercises operate specifically on electrical activity data.

So, make yourself comfortable, it will be interesting.

Electrical activity of muscles: questions and answers

This is the second article in the “Muscle inside” series, in the first we talked about, but in general the cycle is dedicated to the phenomena and events that take place (may leak) inside the muscles. These notes will allow you to better understand the pumping processes and make faster progress in improving your physique. Why did we actually decide to talk specifically about the electrical activity of muscles? It's very simple. In our technical (and not only) articles, we constantly provide lists of the best exercises, which are formed precisely on the basis of EMG research data.

For almost five years now, we have been providing you with this information, but not once during this time have we revealed the very essence of the phenomenon. Well, today we will fill this gap.

Note:
All further narration on the topic of electrical activity of muscles will be divided into subchapters.

What is electromyography? Muscle activity measurement

EMG is an electrodiagnostic medicine technique for assessing and recording electrical activity produced by skeletal muscles. The EMG procedure is performed using a device called an electromyograph to create a recording called an electromyogram. The electromyograph detects the electrical potential generated by muscle cells when they are electrically or neurologically activated. To understand the essence of the EMG phenomenon, it is necessary to have an idea of ​​the structure of the muscles and the processes occurring inside them.

A muscle is an organized “collection” of muscle fibers (MF), which in turn are made up of groups of components known as myofibrils. In the skeletal system, nerve fibers initiate electrical impulses in the m.v., known as muscle action potentials. They create chemical interactions that activate myofibril contraction. The more activated fibers in a muscle part, the stronger the contraction that the muscle can produce. Muscles can only create force when they contract/shorten. Pull and push forces in the musculoskeletal system are generated by the coupling of muscles that act in an antagonistic pattern: one muscle contracts and the other relaxes. For example, when lifting a dumbbell for the biceps, the biceps brachii muscle contracts/shortens when lifting the apparatus, and the triceps (antagonist) is in a relaxed state.

EMG in various sports

The method of assessing the basic muscle activity that occurs during physical movement has become widespread in many sports, especially fitness and bodybuilding. By measuring the number and magnitude of impulses generated during muscle activation, it is possible to assess how much a muscle unit is stimulated to produce a particular force. An electromyogram is a visual illustration of the signals generated during muscle activity. And further in the text we will look at some “portraits” of EMG.

EMG procedure. What does it consist of and where is it carried out?

For the most part, it is possible to measure the electrical activity of muscles only in special sports research laboratories, i.e. specialized institutions. Modern fitness clubs do not provide such an opportunity due to the lack of qualified specialists and low demand from the club’s audience.

The procedure itself consists of:

• placement on the human body in a certain area (on or near the muscle group being studied) special electrodes connected to a unit that measures electrical impulses;
• recording and transmission of signals to a computer through a wireless transmission unit for EMG data from located surface electrodes for subsequent display and analysis.

In the picture version, the EMG procedure looks like this.

Muscle tissue at rest is electrically inactive. When a muscle voluntarily contracts, action potentials begin to appear. As the force of muscle contraction increases, more and more muscle fibers fire action potentials. When the muscle contracts fully, a random group of action potentials with varying speeds and amplitudes should appear. (full set and interference pattern).

Thus, the process of obtaining a picture comes down to the fact that the subject performs a specific exercise according to a specific scheme (sets/reps/rest), and the devices record electrical impulses generated by the muscles. Ultimately, the results are displayed on the PC screen in the form of a specific pulse graph.

Purity of EMG results and the concept of MVC

As you probably remember from our technical notes, sometimes we gave different values ​​for muscle electrical activity even for the same exercise. This is due to the intricacies of the procedure itself. In general, the final results are influenced by a number of factors:

• choosing a specific muscle;
• the size of the muscle itself (men and women have different volumes);
• correct electrode placement (in a specific place of the superficial muscle - muscle belly, longitudinal midline);
• human body fat percentage (the more fat, the weaker the EMG signal);
• thickness - how strongly the central nervous system generates the signal, how quickly it enters the muscle;
• training experience - how well developed a person is.

Thus, due to these initial conditions, different studies may produce different results.

Note:

More accurate results of muscle activity in a specific movement are provided by the intramuscular assessment method. This is when a needle electrode is inserted through the skin into the muscle tissue. The needle is then moved to several points in the relaxed muscle to assess both insertion and resting activity in the muscle. By assessing resting and insertion activity, the electromyograph evaluates muscle activity during voluntary contraction. The shape, size and frequency of the resulting electrical signals indicate the degree of activity of a particular muscle.

In the electromyography procedure, one of its main functions is how well the muscle can be activated. The most common method is to perform a maximum voluntary contraction (MVC) of the muscle being tested. It is MVC, in most studies, that is accepted as the most reliable means of analyzing peak force and force produced by muscles.

However, the most complete picture of muscle activity can be provided by providing both sets of data. (MVC and ARV - average) EMG values.

Actually, we’ve dealt with the theoretical part of the note, now let’s dive into practice.

Electrical activity of muscles: the best exercises for each muscle group, research results

Now we will begin to collect cones :) from our dear audience, and all because we will engage in a thankless task - proving that a specific exercise is the best for a specific muscle group.

And why it is ungrateful, you will understand as the story progresses.

So, by taking EMG readings during various exercises, we can paint an illustrative picture of the level of activity and arousal within the muscle. This can indicate how effective a particular exercise is at stimulating a particular muscle.

I. Research results (Professor Tudor Bompa, Mauro Di Pasquale, Italy 2014)

The data is presented according to the template, muscle group-exercise-percentage of activation m.v.:

Note:

The percentage value indicates the proportion of fibers activated, a value of 100% indicates complete activation.

No. 1. Latissimus dorsi muscles:

• – 91 ;
• – 89 ;
• – 86 ;
• – 83 .

No. 2. Pectoral muscles (greater pectoral):

• – 93 ;
• – 87 ;
• – 85 ;
• – 84 .

No. 3. Front deltoid:

• standing dumbbell press – 79 ;
• – 73 .

No. 4. Middle/side delta:

• straight arm raises through the sides with dumbbells - 63 ;
• raises straight arms through the sides on the upper block of the crossover - 47 .

No. 5. Rear deltoid:

• standing bent over raise with dumbbells - 85 ;
• Bent-over arms raise while standing from the lower block of the crossover – 77 .

No. 6. Biceps (long head):

• curling arms on a Scott bench with dumbbells - 90 ;
• curling arms with dumbbells while sitting on a bench at an upward angle - 88 ;
• (narrow grip) – 86 ;
• – 84 ;
• – 80 .

No. 7. Quadriceps (rectus femoris muscle):

• – 88 ;
• – 86 ;
• – 78 ;
• – 76 .

No. 8. Back surface (biceps) of the thigh:

• – 82 ;
• – 56 .

No. 9. Rear surface (semitendinosus muscle) hips:

• – 88 ;
• deadlift on straight legs - 63 .

With respect and gratitude, Dmitry Protasov.

The muscular system is figuratively defined as a person’s biological key to the outside world.

Electromyography - method for studying the functional state of movement organs by recording muscle biopotentials. Electromyography is the recording of electrical processes in muscles, actually recording the action potentials of muscle fibers that cause it to contract. A muscle is a mass of tissue made up of many individual muscle fibers connected together and working in concert. Each muscle fiber is a thin thread, only about 0.1 mm thick and 300 mm long. When stimulated by an electrical action potential coming to a fiber from a motor neuron, the fiber sometimes shortens to about half its original length. Muscles involved in fine motor corrections (fixation of an object with the eyes) can have only 10 fibers in each unit. In the muscles that carry out more coarse adjustments when maintaining posture, one motor unit can have up to 3000 muscle fibers.
The surface electromyogram (EMG) summarily reflects the discharges of the motor units that cause contraction. EMG recording allows one to detect the intention to start a movement a few seconds before it actually begins. In addition, the myogram acts as an indicator of muscle tension. In a state of relative rest, the relationship between the actual force developed by the muscle and the EMG is linear.
The device with which muscle biopotentials are recorded is called an electromyograph, and the recording recorded with it is an electromyogram (EMG). EMG, in contrast to bioelectrical activity of the brain (EEG), consists of high-frequency discharges of muscle fibers, for undistorted recording of which, according to some ideas, a bandwidth of up to 10,000 Hz is required.

Indicators of respiratory system activity

The respiratory system consists of the airways and lungs.
The main motor apparatus of this system consists of the intercostal muscles, the diaphragm and the abdominal muscles. The air entering the lungs during inhalation supplies the blood flowing through the pulmonary capillaries with oxygen. At the same time, carbon dioxide and other harmful metabolic products leave the blood and are expelled when exhaled. There is a simple linear relationship between the intensity of muscular work performed by a person and oxygen consumption.
In psychophysiological experiments, breathing is now recorded relatively rarely, mainly to control for artifacts.

To measure the intensity (amplitude and frequency) of breathing, a special device is used - a pneumograph. It consists of an inflatable belt chamber wrapped tightly around the subject's chest and a discharge tube connected to a pressure gauge and recording device. Other methods of recording respiratory movements are possible, but in any case, tension sensors must be present to record changes in chest volume.
This method provides a good record of changes in breathing rate and amplitude. Using this recording, it is easy to analyze the number of breaths per minute, as well as the amplitude of respiratory movements under different conditions. We can say that breathing is one of the insufficiently assessed factors in psychophysiological research.

Eye reactions

For a psychophysiologist, three categories of eye reactions are of greatest interest: constriction and dilation of the pupil, blinking and eye movements.
Pupillometry - method of studying pupillary reactions. The pupil is the hole in the iris through which light enters the retina. The diameter of a person's pupil can vary from 1.5 to 9 mm. The size of the pupil fluctuates significantly depending on the amount of light falling on the eye: in the light the pupil narrows, in the dark it expands. Along with this, the size of the pupil changes significantly if the subject reacts emotionally to the influence. In this regard, pupillometry is used to study the subjective attitude of people to certain external stimuli.
Pupil diameter can be measured by simply photographing the eye during an examination or using special devices that convert the size of the pupil into a constantly varying potential level recorded on a polygraph.
Flashing (blink) - periodic closure of eyelids. The duration of one blink is approximately 0.35 s. The average blink rate is 7.5 per minute and can vary from 1 to 46 per minute. Blinking performs different functions in maintaining the vital functions of the eyes. However, for a psychophysiologist it is important that the frequency of blinking varies depending on the mental state of a person.
Eye movement widely studied in psychology and psychophysiology. These are varied in function, mechanism and biomechanics of rotation of the eyes in the orbits. There are different types of eye movements that serve different functions. However, the most important function of eye movements among them is to maintain the image of interest to a person in the center of the retina, where visual acuity is highest. The minimum speed of tracking movements is about 5 arc. min/s, the maximum reaches 40 degrees/s.
Electrooculography - method of recording eye movements, based on graphical recording of changes in the electrical potential of the retina and eye muscles. In humans, the anterior pole of the eye is electrically positive and the posterior pole is negative, so there is a potential difference between the fundus of the eye and the cornea that can be measured. When the eye turns, the position of the poles changes, and the resulting potential difference characterizes the direction, amplitude and speed of eye movement. This change, recorded graphically, is called an electrooculogram. However, eye micromovements are not recorded using this method; other techniques have been developed for their recording. (see picture)

Lie detector

Lie detector - the conventional name of a polygraph device that simultaneously records a complex of physiological indicators (GSR, EEG, plethysmogram, etc.) in order to identify the dynamics of emotional stress. A person undergoing a polygraph examination is interviewed, during which, along with neutral ones, they ask questions that constitute a subject of special interest. By the nature of the physiological reactions that accompany answers to various questions, one can judge a person’s emotional reactivity and, to some extent, the degree of his sincerity in a given situation. Since in most cases a specially untrained person does not control his vegetative reactions, a lie detector gives, according to some estimates, up to 71% of cases of deception detection.
It should be borne in mind, however, that the interview (interrogation) procedure itself can be so unpleasant for a person that the physiological changes that arise along the way will reflect the person’s emotional reaction to the procedure. It is impossible to distinguish emotions provoked by the testing procedure from emotions caused by target questions. At the same time, a person with high emotional stability will be able to feel relatively calm in this situation, and his vegetative reactions will not provide solid grounds for making an unambiguous judgment. For this reason, the results obtained with the help of a lie detector must be treated with a due degree of criticality (see video).

Selection of methods and indicators

Ideally, the choice of physiological methods and indicators should logically follow from the methodological approach adopted by the researcher and the goals set for the experiment. However, in practice, they are often based on other considerations, for example, the availability of instruments and the ease of processing experimental data.
Arguments in favor of choosing methods seem more powerful if the indicators extracted with their help receive a logically consistent meaningful interpretation in the context of the psychological or psychophysiological model being studied.

Psychophysiological models. In science, a model is understood as simplified knowledge that carries certain, limited information about an object/phenomenon, reflecting certain of its properties. Using models, you can simulate the functioning and predict the properties of the objects, processes or phenomena being studied. In psychology, modeling has two aspects: mental modeling And situation modeling. The first means a symbolic or technical imitation of mechanisms, processes and results of mental activity, the second means the organization of one or another type of human activity by artificially constructing the environment in which this activity is carried out.
Both aspects of modeling find a place in psychophysiological research. In the first case, the simulated features of human activity, mental processes and states are predicted on the basis of objective physiological indicators, often recorded without direct connection with the phenomenon being studied. For example, it has been shown that some individual characteristics of perception and memory can be predicted from the characteristics of brain biocurrents. In the second case, psychophysiological modeling involves simulating certain mental activities in laboratory conditions in order to identify its physiological correlates and/or mechanisms. In this case, it is obligatory to create some artificial situations in which the studied mental processes and functions are somehow included. An example of this approach is numerous experiments to identify physiological correlates of perception, memory, etc.
When interpreting the results in such experiments, the researcher must clearly understand that the model is never completely identical to the phenomenon or process being studied. As a rule, it takes into account only certain aspects of reality. Consequently, no matter how comprehensive, for example, any psychophysiological experiment to identify the neurophysiological correlates of memory processes may seem, it will provide only partial knowledge about the nature of its physiological mechanisms, limited by the framework of this model and the methodological techniques and indicators used. It is for this reason that psychophysiology is replete with a variety of unrelated and sometimes simply contradictory experimental data. Such data obtained in the context of different models represent fragmentary knowledge, which in the future should probably be combined into an integral system describing the mechanisms of psychophysiological functioning.

Interpretation of indicators. The question of what importance the experimenter attaches to each of the indicators he uses deserves special attention. In principle, physiological indicators can perform two main roles: target (semantic) and service (auxiliary). For example, when studying brain biocurrents during mental activity, it is advisable to simultaneously record eye movements, muscle tension and some other indicators. Moreover, in the context of such work, only indicators of brain biocurrents carry a semantic load associated with this task. The remaining indicators serve to control artifacts and the quality of registration of biocurrents (registration of eye movements), control of the emotional states of the subject (registration of GSR), since it is well known that eye movements and emotional stress can introduce interference and distort the picture of biocurrents, especially when the subject decides what or a task. At the same time, in another study, registration of both eye movements and GSR may play a semantic rather than a service role. For example, when the subject of research is a visual search strategy or the study of the physiological mechanisms of the human emotional sphere.
Thus, the same physiological indicator can be used to solve different problems. In other words, the specific use of an indicator is determined not only by its own functionality, but also by the psychological context in which it is included. A good knowledge of the nature and all the possibilities of the physiological indicators used is an important factor in organizing a psychophysiological experiment.

The significance of experiments performed on animals. As noted above, many problems in psychophysiology have been and continue to be solved in experiments on animals. (First of all, we are talking about studying the activity of neurons.) In this regard, the problem formulated by L.S. acquires special significance. Vygotsky. This is the problem of the human-specific relationship between structural and functional units in brain activity and the determination of new principles for the functioning of systems, intra- and intersystem interactions compared to animals.
It should be directly stated that the problem of “human-specific correlation of structural and functional units in brain activity and the determination of new principles of system functioning compared to animals,” unfortunately, has not yet received productive development. As O.S. writes Andrianov (1993): “The rapid “immersion” of biology and medicine... into the depths of living matter has pushed into the background the study of the most important problem - the evolutionary specifics of the human brain. Attempts to find at the molecular level a certain material substrate that is characteristic only of the human brain and determines the characteristics the most complex mental functions have not yet been crowned with success."
Thus, the question arises about the legitimacy of transferring data obtained on animals to explain brain functions in humans. A widely accepted point of view is that there are universal mechanisms of cellular functioning and general principles of information coding, which allows for interpolation of results (see, for example: Fundamentals of Psychophysiology, edited by Yu.I. Aleksandrov, 1998).
One of the founders of Russian psychophysiology E.N. Sokolov, solving the problem of transferring the results of research performed on animals to humans, formulated the principle of psychophysiological research as follows: man - neuron - model. This means that psychophysiological research begins with the study of behavioral (psychophysiological) reactions of a person. Then it moves on to the study of the mechanisms of behavior using microelectrode recording of neural activity in experiments on animals, and in humans using an electroencephalogram and evoked potentials. Integration of all data is carried out by building a model from neural-like elements. In this case, the entire model as a whole must reproduce the function under study, and individual neuron-like elements must have the characteristics and properties of real neurons. The prospects for research of this kind lie in the construction of models of “specifically human types,” such as, for example, neurointelligence.

Conclusion. The above materials indicate a wide variety and different levels of psychophysiological methods. The scope of competence of a psychophysiologist includes much, from the dynamics of neuronal activity in the deep structures of the brain to local blood flow in a finger. The question naturally arises of how to combine such indicators, which are so different in their methods of obtaining and content, into a logically consistent system. Its solution, however, rests on the lack of a single generally accepted psychophysiological theory.
Psychophysiology, which was born as an experimental branch of psychology, largely remains so to this day, compensating for the imperfection of the theoretical foundation with the variety and sophistication of its methodological arsenal. The wealth of this arsenal is great, its resources and prospects seem inexhaustible. The rapid growth of new technologies will inevitably expand the possibilities of penetration into the secrets of human physicality. It will lead to the creation of new processing devices capable of formalizing a complex system of dependence of variables used in objective physiological indicators, naturally related to human mental activity. Regardless of whether new solutions will be the result of further development of electronic computing technology, heuristic models or other methods of cognition still unknown to us, the development of science in our time anticipates a radical transformation of psychophysiological thinking and working methods

Glossary of terms

1. alpha rhythm
2. pacemaker
3. reticular formation
4. afferentation
5. corticolimbic interaction
6. galvanic skin response (GSR)

Self-test questions

1. How are the rhythmic components of the electroencephalogram related to the human condition?
2. What causes the galvanic skin response?
3. How are pneumography and spirography different?
4. What does assessing the condition of peripheral vessels provide?
5. How are lie detector scores interpreted?

References

1. Anokhin P.K. Essays on the physiology of functional systems. M.: Medicine, 1975.
2. Buresh Y., Bureshova O., Huston D.P. Methods and basic experiments for studying the brain and behavior. M.: Higher School, 1991.
3. Belenkov N.Yu. The principle of integrity in brain activity. M.: Medicine, 1980.
4. Bernstein N.A. Essays on the physiology of movements and the physiology of activity. M.: Medicine, 1966.
5. Bekhtereva N.P., Bundzen P.V., Gogolitsyn Yu.L. Brain codes of mental activity. L.: Nauka, 1977.
6. Gnezditsky V.V. Evoked brain potentials in clinical practice. Taganrog: TSTU, 1997.
7. Danilova N.N. Psychophysiology. M.: Aspect Press, 1998.
8. Dubrovsky D.I. psyche and brain: results and prospects of research // Psychological journal. 1990. T.11. No. 6. P. 3-15.
9. Natural scientific foundations of psychology / Under. ed. A.A. Smirnova, A.R. Luria, V.D. Nebylitsyna. M.: Pedagogy, 1978.
10. Ivanitsky A.M., Strelets V.B., Korsakov I.A. Information processes of the brain and mental activity. M.: Nauka, 1984.
11. Lomov B.F. methodological and theoretical problems of psychology. M.: Nauka, 1984.
12. Neurocomputer as the basis of thinking computers. M.: Nauka, 1993.
13. Merlin V.S. Essay on an integral study of individuality. M.: Pedagogy, 1986.
14. Methodology and technique of psychophysiological experiment. M.: Nauka, 1987.
15. Fundamentals of psychophysiology / Ed. Yu.I. Alexandrova. M., 1998.
16. Tikhomirov O.K. Psychology of thinking. M.: MSU, 1984.
17. Chuprikova N.I. psyche and consciousness as a function of the brain. M.: Nauka, 1985.
18. Hassett J. Introduction to psychophysiology. M.: Mir, 1981.
19. Yarvilehto T. Brain and psyche. M.: Progress, 1992.

Have you ever thought about why absolutely all beginners, when they come to the gym, cannot gain muscle mass in the first year of their training? Once upon a time this same thought came to me and I tried to understand it in more detail. And I realized that in fact everything is quite simple and that the whole point turns out to be in our muscular activity.

What is muscle activity?

Muscle activity is, by and large, nothing more than your interaction between the strength of your muscles being used at the moment with their maximum capacity.

I'll explain it a little simpler to you. In ordinary life, we usually do not use the strength of our muscles to their full potential. And therefore it all comes down to the fact that a person outside the gym in everyday life works and lifts a maximum of, say, 5 - 10 kg, and even then only when he goes to the store for groceries.

It is precisely this kind of load that the muscles of an ordinary person who does not go to the gym and does not lift weights are accustomed to...

Therefore, our muscles have long adapted to such a minimal load and are not activated at full capacity, but at most by 5% - 10% percent.

But their power capabilities are much higher, but with all this, they will not get involved in the work just because you wanted it. To do this they need to be trained.

The muscle activity of an untrained person is approximately 30% - 40% percent, which is more than 2-3 times lower than the strength capabilities and potential of the muscles themselves.

If an untrained person puts his maximum effort into something, then his current maximum muscle activity will be approximately 30% - 40% percent, in fact, this is even less than half of the capacity of the muscles themselves.

And that’s when such a person decides to go to the gym in order to start actively exercising. And after 3-4 months he sees that he has not gained much muscle during all this time, but at the same time he has significantly increased his strength, then a reasonable question arises: why?

The answer is that he simply did not gain muscle mass because he did not develop sufficient potential of his muscles at this point in time.

We all have known for a long time that muscle growth directly depends on an increase in strength, so the stronger your muscles are, the larger they will be in volume.

And this has long been a proven fact!

Muscle mass, or rather muscle hypertrophy, occurs only when the muscles experience extreme stress, or rather even a huge muscle overload.

What do we usually see in practice? So this is that all beginners basically sit on exercise machines, and as a rule, they begin to pump up the most common muscles, such as biceps, triceps and abs, sometimes doing bench press.

• They squat - NO
• They do deadlifts - NO
• They do standing presses - also NO

Most gym newbies don't do heavy compound exercises at all. They do not work hard and do not perform really difficult basic exercises, but, as a rule, always perform isolated exercises while working mainly on simulators.

And most importantly, they don’t even try to somehow increase their strength, but only constantly exhaust their muscles with light weights and a large number of repetitions.

In other words, their muscle potential has not exhausted its strength capabilities for their further growth at the moment. This means that at the moment all their muscle activity will be below 100% percent.

Therefore, many athletes, and this is almost 90% percent, even after a year or even two years do not see any growth in muscle mass...

In order for any muscle growth to occur, at the initial stage you must first increase the strength of your muscles, and not everyone understands this fact...

I'll give you an example.

Let's say that a person comes to the gym. Moreover, before this he had never done anything and therefore at the moment his maximum muscle activity is at the level of 30% - 40% percent of their maximum 100% percent potential at the moment of the muscles that he has now.

• Green stripe- shows muscle activity at a level of 5% - 10% percent used in everyday life.
• Blue stripe– shows the muscle activity (strength) of an untrained person at a level of 30% - 40% percent.
• Red stripe— shows the maximum 100% percentage potential of the muscles and their capabilities at the moment.
• Blue stripe- shows the passage of your strength maximum and the subsequent hypertrophy of your muscles.

And if he does not increase the strength of his muscles and does not involve muscle activity at 100% percent, then there will simply be no hypertrophy in the future.

If he increases the strength of his muscles, then muscle activity will also increase to 100% percent, and as soon as he reaches this mark and exceeds it, then only after this will muscle hypertrophy follow, that is, the muscles themselves will begin to increase.

Let's try to figure out why at the initial stage of your training you should always work only to increase your strength indicators.

Let's go back to the fact that a person has only recently started working out and his maximum bench press is currently 50 kg, but his muscles are capable and can press 80 kg, but at the moment he cannot do this, now he can only do 50 kg in your bench press.

It turns out that at the moment these same 80 kg are essentially his muscle potential. In other words, these 80 kg are his 100% muscle potential and the muscle activity that his muscles are able to cope with in this exercise.

And relatively speaking, until he reaches these 80 kg in the bench press, his muscles will not grow because he has not exhausted his muscle potential, at which his muscles are able to work at the moment, without resorting to hypertrophy and an increase in the very volume of it muscle fibers.

And only when he reaches this weight and overcomes it, only after that will the process of muscle growth begin because his muscle activity will be overloaded at 100%.

• This is why all beginners coming to the gym are able to immediately add 30-40 kg or even more in a few months, for example, in the bench press, as well as in other exercises.

• And that is why, at the very beginning, all novice athletes so rapidly increase their strength indicators over the course of a whole year, almost doubling them.

This is due to the fact that before the gym they already had the initially undeveloped potential of their muscles, which they only turned on when they began to actively exercise and increase their strength indicators and increase the strength of their muscles.

But I will disappoint you, because this period of rapid growth in your strength is just a temporary period, followed by that limit and that bar that many then cannot overcome for a very long time.

That is why many beginners, having achieved a certain increase in their strength capabilities in one exercise or another, then for a very long time cannot increase their strength.

And all because before this, even if you were working out anyhow, you still added and increased your strength indicators, but then as soon as you reached a certain limit, i.e. to that point of 100% percent muscle potential, which you initially already had, by the way, then after that you can no longer overcome it for a long time.

Moreover, this can even extend to several years of empty training, when an athlete cannot add, for example, even a couple of kg to his bench press, and many of you have probably encountered this problem.

In order to avoid all this, first of all, you need to learn how to competently structure your workouts and your training cycles, and only then will you further increase your strength indicators and be able to always progress in muscle mass.

Energy of muscle activity.

One muscle fiber can contain 15 billion thick filaments. While muscle fibers are actively contracting, approximately 2,500 molecules of ATP (a nucleotide that plays an important role in the metabolism of energy and substances in the body) per second break down in each thick thread. Even small skeletal muscles contain thousands of muscle fibers.

The main function of ATP is to transfer energy from one place to another, rather than long-term storage of energy. At rest, skeletal muscle fibers produce more ATP than they need. Under these conditions, ATP transfers energy to creatine. Creatine is a small molecule that muscle cells assemble from amino acid fragments. The transfer of energy creates another high-energy compound, creatine phosphate (CP).

ATP + creatine ADP + creatine phosphate

During muscle contraction, ATP compounds are broken down, resulting in the formation of adenosine diphosphate (ADP). The energy stored in creatine phosphate is then used to “recharge” ADP, converting it back into ATP through the reverse reaction.

ADP + creatine phosphate + creatine

The enzyme creatine phosphokinase (CPK) facilitates this reaction. When muscle cells are damaged, CPK leaks through the cell membranes into the bloodstream. Thus, high blood concentrations of CPK usually indicate serious muscle damage.

Resting skeletal muscle fibers contain approximately six times more creatine phosphate as ATP. But when muscle fibers are under sustained tension, these energy reserves will be depleted in only about 15 seconds. Muscle fibers must then rely on other mechanisms to convert ADP to ATP.

Most cells in the body generate ATP through aerobic metabolism in the mitochondria and through glycolysis in the cytoplasm. Aerobic metabolism (accompanied by oxygen consumption) typically provides 95% of the ATP in a resting cell. In this process, mitochondria absorb oxygen, ADP, phosphate ions and organic substrates from the surrounding cytoplasm. The substrates then introduce the tricarboxylic acid cycle (also known as the citric acid cycle or Krebs cycle), an enzymatic pathway that breaks down organic molecules. The carbon atoms are released as carbon dioxide, and the hydrogen atoms are shuttled by respiratory enzymes into the inner mitochondrial membrane, where their electrons are removed. After a series of intermediate steps, protons and electrons combine with oxygen to form water. In this efficient process, large amounts of energy are released and used to create ATP.

Resting skeletal muscle fibers rely almost exclusively on aerobic fatty acid metabolism to generate ATP. When the muscle begins to contract, the mitochondria begin breaking down the pyruvic acid molecule instead of the fatty acids. Pyruvic acid is provided by the enzymatic pathway of glycolysis. Glycolysis is the breakdown of glucose to pyruvic acid in the cytoplasm of the cell. This process is called anaerobic because it does not require oxygen. Glycolysis provides an increase in ATP and generates 2 molecules of pyruvic acid from every molecule of glucose. ATP is formed during glycolysis. Because glycolysis can occur in the absence of oxygen, it may be especially important when the presence of oxygen limits the rate of mitochondrial ATP production. In most skeletal muscle, glycolysis is the main source of ATP during peak periods of activity. The breakdown of glucose under these conditions occurs mainly from glycogen reserves in the sarcoplasm. Glycogen is a polysaccharide of chains of glucose molecules. Typical skeletal muscle fibers contain large glycogen stores, which can account for 1.5% of total muscle weight.

Energy consumption and level of muscle activity.

In skeletal muscles, when they are at rest, the demand for ATP is low. With more than enough oxygen available to the mitochondria to meet this demand, they end up producing excess ATP. The extra ATP is used to build glycogen stores. Resting muscle fibers absorb fatty acids and glucose that are delivered by the bloodstream. Fatty acids are broken down in the mitochondria and ATP is generated to convert creatine into creatine phosphate and glucose into glycogen.

With moderate levels of physical activity, the need for ATP increases. This demand is met by the mitochondria when the rate of mitochondrial ATP production increases, which increases the rate of oxygen consumption. Oxygen availability is not a limiting factor because oxygen can diffuse (combine, mix) within the muscle fiber quickly enough to meet mitochondrial demands. Skeletal muscle at this point depends primarily on aerobic pyruvic acid metabolism to generate ATP. Pyruvic acid is formed during glycolysis, which breaks down glucose molecules derived from glycogen in muscle fibers. If glycogen stores are low, the muscle fiber may also break down other substrates such as lipids or amino acids. While the demand for ATP can be met by mitochondrial activity, the provision of ATP by glycolysis remains a minor contributor to the overall energy production of the muscle fiber.

At peak levels of activity, a lot of ATP is required, causing ATP production in the mitochondria to increase to its maximum. This maximum speed is determined by the availability of oxygen, and oxygen cannot diffuse through the muscle fibers quickly enough to allow the mitochondria to produce the required ATP. At peak levels of workload, mitochondrial activity can provide only about one-third of the required ATP. The rest is accounted for by glycolysis.

When glycolysis produces pyruvic acid faster than it can be used by the mitochondria, the level of pyruvic acid in the sarcoplasm increases. Under these conditions, pyruvic acid is converted into lactic acid.

The anaerobic process of glycolysis allows the cell to generate additional ATP when mitochondria are unable to meet current energy demands. However, anaerobic energy production has its disadvantages:

Lactic acid is an organic acid that is found in body fluids
dissociates into hydrogen ions and the negatively charged lactate ion. Thus, the production of lactic acid can lead to a decrease in intracellular pH. Buffers in the sarcoplasm can resist pH shifts, but these protections are limited. Eventually, changes in pH will alter the functional characteristics of key enzymes.
Glycolysis is a relatively inefficient way to generate ATP. Under anaerobic conditions, each molecule of glucose generates 2 molecules of pyruvic acid, which are converted to lactic acid. In turn, the cell receives 2 ATP molecules through glycolysis. If those pyruvic acid molecules were catabolized aerobically in the mitochondria, the cell would receive 34 additional ATP molecules.

Muscle fatigue. Skeletal muscle fibers fatigue when they can no longer contract despite the continuation of the nerve impulse. The cause of muscle fatigue varies depending on the level of muscle activity. After short peak levels of activity, such as a 100-meter time trial, fatigue may be
the result of depletion of ATP reserves or a drop in pH, which is accompanied by the accumulation of lactic acid. After prolonged exertion, such as a marathon, fatigue may involve physical damage to the sarcoplasmic reticulum, which interferes with the regulation of intracellular Ca2+ ion concentrations. Muscle fatigue accumulates and the effects become more pronounced as more muscle fibers begin to be recruited by the condition. The result is a gradual decrease in the capabilities of all skeletal muscles.

If muscle fiber contracts at moderate levels and ATP demands can be met through aerobic metabolism, fatigue will not occur until glycogen, lipid, and amino acid stores are depleted. This type of fatigue occurs in the muscles of long-term athletes, such as marathon runners, after several hours of long-distance running.

When a muscle produces a sudden, intense burst of activity at peak levels, most of the ATP is provided by glycolysis. After a few seconds to a minute, the rise in lactic acid levels lowers the pH of the tissues and the muscles can no longer function normally. Athletes who experience rapid, powerful loads, such as 100-meter sprinters, experience this type of muscle fatigue.

For normal muscle function you need: 1) significant intracellular energy reserves, 2) normal blood circulation and 3) normal oxygen concentration in the blood. Anything that interferes with one or more of these factors will contribute to premature muscle fatigue. For example, decreased blood flow from tight clothing, poor circulation, or blood loss slows the delivery of oxygen and nutrients while accelerating the buildup of lactic acid and also contributes to muscle fatigue.

Recovery period. When muscle fibers contract, the conditions in the sarcoplasm change. Energy reserves are consumed, heat is released and, if the contraction was peak, milk is generated. During the recovery period, conditions in the muscle fibers return to normal. It may take several hours for muscle fibers to recover from a period of moderate activity. After prolonged activity at higher activity levels, full recovery may take a week. During the recovery period, when oxygen is abundant, lactic acid can be processed by converting back to pyruvic acid.

Pyruvic acid can be used either by the mitochondria to generate ATP, or as a substrate for enzymes that synthesize glucose and restore glycogen stores.

During periods of exercise, lactic acid diffuses from muscle fibers into the bloodstream. This process continues after the strain has ended because intracellular lactic acid concentrations are still relatively high. The liver absorbs lactic acid and converts it into pyruvic acid. Approximately 30% of these pyruvic acid molecules are broken down, providing the ATP needed to convert other pyruvic acid molecules into glucose. The glucose molecules are then released into circulation, where they are taken up by skeletal muscle fibers and used to restore their glycogen stores. This shuffling of lactic acid to the liver and glucose to the muscle cells is called the Cori cycle.

During the recovery period, oxygen is readily available and the body's oxygen demand remains elevated, above normal resting levels. The recovery period is fueled by ATP. The more ATP required, the more oxygen will be needed. The oxygen debt, or excess post-exercise oxygen consumption created during exercise, is the same amount of oxygen needed for normal recovery. Skeletal muscle fibers, which must restore ATP, creatine phosphate and glycogen, to the concentration of their previous levels, and liver cells, whichgenerate the ATP needed to convert excess lactic acid into glucose and are responsible for most of the additional oxygen consumption. While the oxygen debt is replenished, the frequency and depth of breathing increase. As a result, you will continue to breathe heavily long after you stop intense exercise.

Thermal losses of muscle activity generate significant amounts of heat. When a catabolic reaction occurs, such as glycogen breakdown or glycolysis reactions, muscle fibers capture only a portion of the released energy. The rest is released as heat. Resting muscle fibers, relying on aerobic metabolism, capture about 42% of the energy released in catabolism. The other 58% warms the sarcoplasm of tissue fluid and circulating blood. Active skeletal muscles release about 85% of the heat needed to maintain normal body temperature.

When muscles become active, their energy consumption increases dramatically. As anaerobic energy production becomes the primary method of ATP, muscle fibers are less efficient at absorbing energy. At peak levels of exercise, only about 30% of the energy released is stored as ATP, with the remaining 70% warming the muscles and surrounding tissues.

Hormones and muscle metabolism. Metabolic activity in skeletal muscle fibers is regulated by hormones of the endocrine system. Growth hormone from the pituitary gland and testosterone (the main sex hormone in men) stimulate the synthesis of contractile proteins and the expansion of skeletal muscles. Thyroid hormones increase the rate of energy consumption during rest. During intense physical activity, adrenal hormones, especially adrenaline, stimulate muscle metabolism and increase the duration of stimulation and the force of contraction.

V. N. Seluyanov, V. A. Rybakov, M. P. Shestakov

Chapter 1. Models of body systems

1.1.4. Physiology of muscle activity

The biochemistry and physiology of muscle activity during physical work can be described as follows. Using simulation, we will show how physiological processes unfold in a muscle when performing a step test.

Let us assume that a muscle (for example, the quadriceps femoris muscle) has an MMV of 50%, the amplitude of the step is 5% of the maximum alactic power, the value of which is taken to be 100%, and the duration is 1 min. At the first step, due to low external resistance, low-threshold MUs (MUs) are recruited, according to Hanneman’s “size rule”. They have high oxidative capabilities; their substrate is fatty acids. However, for the first 10–20 s, energy supply comes from the reserves of ATP and CrP in active MFs. Already within one step (1 min.) the recruitment of new muscle fibers takes place, thanks to this it is possible to maintain the given power on the step. This is caused by a decrease in the concentration of phosphogens in active MVs, that is, the force (power) of contraction of these MVs, an increase in the activating influence of the central nervous system, and this leads to the involvement of new motor units (MUs). A gradual stepwise increase in external load (power) is accompanied by a proportional change in some indicators: heart rate, oxygen consumption, pulmonary ventilation increase, the concentration of lactic acid and hydrogen ions does not change.

When the external power reaches a certain value, a moment comes when all the IMF are involved in the work and the intermediate muscle fibers (IMF) begin to be recruited. Intermediate muscle fibers can be called those in which the mass of mitochondria is not enough to ensure a balance between the formation of pyruvate and its oxidation in the mitochondria. In the PMV, after a decrease in the concentration of phosphogens, glycolysis is activated, part of the pyruvate begins to be converted into lactic acid (more precisely, into lactate and hydrogen ions), which enters the blood and penetrates into the PMV. The entry of lactate into the IMF (OMV) leads to inhibition of fat oxidation; glycogen becomes the substrate of oxidation to a greater extent. Consequently, a sign of the recruitment of all MMVs (OMVs) is an increase in lactate concentration in the blood and increased pulmonary ventilation. Pulmonary ventilation increases due to the formation and accumulation of hydrogen ions in the PMV, which, when released into the blood, interact with the blood buffer systems and cause the formation of excess (non-metabolic) carbon dioxide. An increase in the concentration of carbon dioxide in the blood leads to increased respiration (Human Physiology, 1998).

Thus, when performing a step test, a phenomenon occurs that is commonly called the aerobic threshold (AeT). The appearance of AeP indicates the recruitment of all OMVs. By the magnitude of external resistance, one can judge the strength of OMVs, which they can exhibit during the resynthesis of ATP and CrP due to oxidative phosphorylation (Seluyanov V.N. et al., 1991).

A further increase in power requires the recruitment of higher threshold MUs (HMUs), in which there are very few mitochondria. This enhances the processes of anaerobic glycolysis, and more lactate and H ions enter the blood. When lactate enters the OMV, it is converted back to pyruvate by the enzyme LDH H (Karlsson, 1971,1982). However, the power of the mitochondrial OMV system has a limit. Therefore, first there is a limiting dynamic equilibrium between the formation of lactate and its consumption in the OMV and PMV, and then the balance is disturbed, and uncompensated metabolites - lactate, H, CO 2 - cause a sharp intensification of physiological functions. Breathing is one of the most sensitive processes and reacts very actively. When blood passes through the lungs, depending on the phases of the respiratory cycle, it should have a different partial tension of CO 2. A “portion” of arterial blood with a high CO 2 content reaches chemoreceptors and directly modular chemosensitive structures of the central nervous system, which causes an intensification of respiration. As a result, CO 2 begins to be washed out of the blood so that, as a result, the average concentration of carbon dioxide in the blood begins to decrease. When the power corresponding to AnP is reached, the rate of lactate release from the working glycolytic MVs is compared with the rate of its oxidation in the MVs. At this moment, only carbohydrates become the substrate of oxidation in the OM (lactate inhibits the oxidation of fats), some of them are glycogen from the OM, the other part is lactate formed in glycolytic MV. The use of carbohydrates as oxidation substrates ensures the maximum rate of energy production (ATP) in the mitochondria of the OMV. Therefore, oxygen consumption and/or power at the anaerobic threshold (AnP) characterizes the maximum oxidative potential (power) of OMV(Seluyanov V.N. et al., 1991).

A further increase in external power necessitates the involvement of increasingly high-threshold motor units innervating glycolytic MVs. The dynamic balance is disrupted, the production of H and lactate begins to exceed the rate of their elimination. This is accompanied by a further increase in pulmonary ventilation, heart rate and oxygen consumption. After ANP, oxygen consumption is mainly related to the work of the respiratory muscles and myocardium. When the limits of pulmonary ventilation and heart rate are reached or when local muscle fatigue occurs, oxygen consumption stabilizes and then begins to decrease. At this moment, the MIC is recorded.