Aerobic mechanism of energy supply. Energy supply to the body: methods of energy supply. Aerobic mechanism of energy supply to muscle activity

Rubric "Biochemistry". Aerobic and anaerobic factors of sports performance. Bioenergy criteria physical performance. Biochemical indicators of the level of development of aerobic and anaerobic components of sports performance. Correlation in the levels of development of aerobic and anaerobic components of sports performance in representatives of various sports. Features of biochemical changes in the body under critical conditions of muscle activity.

Among the leading biochemical factors that determine sports performance, the most important are the bioenergetic (aerobic and anaerobic) capabilities of the body. Depending on the intensity and nature of the support, it is proposed to divide the work into several categories:

anaerobic (alactate) load power zone;
anaerobic (glycolytic) zone;
zone of mixed anaerobic-aerobic supply (an aerobic processes);
zone of mixed aerobic-anaerobic supply (aerobic processes predominate);
zone aerobic energy supply.

Anaerobic work of maximum power (10-20 sec.) is performed mainly on intracellular reserves of phosphagen (creatine phosphate + ATP). The oxygen debt is small, has an alactic nature and must cover the resynthesis of spent macroergs. There is no significant accumulation of lactate, although glycolysis may be involved in providing such short-term loads and the lactate content in working muscles increases.

Operation of submaximal powers depending on the pace and duration, it lies in the zones of anaerobic (glycolytic) and anaerobic-aerobic energy supply. The leading contribution is from anaerobic glycolysis, which leads to the accumulation of high intracellular lactate concentrations, acidification of the environment, development of NAD deficiency and autoinhibition of the process. Lactate has a good, but finite, rate of penetration through membranes and the balance between its content in muscles and plasma is established only after 5-10 minutes. from the start of work.

When working high power prevails aerobic pathway of energy supply (75-98%). Work of moderate power is characterized by almost complete aerobic energy supply and the possibility of long-term performance from 1 hour. up to many hours depending on the specific power. There are a significant number of indicators used to identify the level of development, aerobic and anaerobic mechanisms of energy conversion.

Some of them provide an integral assessment of these mechanisms, others allow us to characterize their various aspects (speed of deployment, power, capacity, efficiency) or the state of any individual link or stage. The most informative are the indicators recorded when performing testing loads that cause close to maximum activation of the corresponding energy conversion processes. It should be taken into account that anaerobic processes are highly specific and are included to the greatest extent in the energy supply only for the type of activity in which the athlete has undergone special training. This means that to assess the possibilities of using anaerobic processes to provide energy for work, bicycle ergometer tests are most suitable for cyclists, running for runners, etc.

Of great importance for identifying the possibilities of using various energy supply processes are the power, duration and nature of the testing exercise performed. For example, to assess the level of development of the alactic anaerobic mechanism, the most suitable are short-term (20-30 seconds) exercises performed with maximum intensity. The greatest changes associated with the participation of the glycolytic anaerobic mechanism of energy supply to work are found when performing exercises lasting 1-3 minutes. with maximum intensity for this duration. An example would be work consisting of 2-4 repeated exercises, lasting about 1 minute, performed at equal or decreasing rest intervals. Each repetition exercise should be performed with the highest possible intensity. The state of aerobic and anaerobic processes of energy supply to muscle work can be characterized using a test with a stepwise increase in load until “failure”.
Indicators characterizing the level of anaerobic systems are the values of alactic and lactate oxygen debt, the nature of which was discussed earlier. Informative indicators of the depth of glycolytic anaerobic shifts are the maximum concentration of lactic acid in the blood, indicators of the active blood reaction (pH) and the shift of buffer bases (BE).

To assess the level of development of aerobic mechanisms of energy production, the definition is used maximum consumption oxygen (MIC) - the highest oxygen consumption per unit time that can be achieved under conditions of intense muscular work.
MIC characterizes the maximum power of the aerobic process and is integral (generalized) in nature, since the ability to produce energy in aerobic processes is determined by the combined activity of many organs and systems of the body responsible for the utilization, transport and use of oxygen. In sports where the main source of energy is the aerobic process, along with power, its capacity is of great importance. The holding time of maximum oxygen consumption is used as an indicator of capacity. To do this, together with the MPC value, the value of “critical power” is determined - the lowest power of the exercise at which the MPC is achieved. For these purposes, a test with a stepwise increase in load is most convenient. Then (usually the next day) athletes are asked to perform work at the critical power level. The time during which the “critical power” can be maintained is recorded and oxygen consumption changes. The operating time at “critical power” and the MIC retention time correlate well with each other and are informative regarding the capacity of the aerobic pathway for ATP resynthesis.

As you know, the initial stages of any fairly intense muscular work are provided with energy due to anaerobic processes. The main reason for this is the inertia of aerobic energy supply systems. After the aerobic process has developed to a level corresponding to the power of the exercise being performed, two situations may arise:

aerobic processes fully cope with the energy supply of the body;
Along with the aerobic process, anaerobic glycolysis is involved in energy supply.

Research has shown that in exercises whose power has not yet reached “critical” and, therefore, aerobic processes have not developed to the maximum level, anaerobic glycolysis can participate in the energy supply of work throughout its entire duration. The lowest power, starting from which glycolysis takes part in energy production throughout the entire work, along with aerobic processes, is called the “threshold of anaerobic metabolism” (PANO). The power of ANNO is usually expressed in relative units - the level of oxygen consumption (as a percentage of MIC) achieved during operation. Improved fitness for aerobic exercise is accompanied by an increase in PANO. The value of PANO depends primarily on the characteristics of aerobic mechanisms of energy production, in particular, on their efficiency. Since the efficiency of the aerobic process can undergo changes, for example, due to changes in the coupling of oxidation with phosphorylation, it is of interest to assess this aspect of the functional readiness of the organism. The most important are individual changes in this indicator at different stages training cycle. The effectiveness of the aerobic process can also be assessed in a test with a stepwise increase in load when determining the level of oxygen consumption at each step.
So, the participation of anaerobic and aerobic processes in the energy supply of muscle activity is determined, on the one hand, by the power and other features of the exercise performed, and on the other hand, by the kinetic characteristics ( maximum power, maximum power retention time, maximum capacity and efficiency) of energy generation processes.
The considered kinetic characteristics depend on the joint action of many tissues and organs and change differently under the influence of training exercises. This feature of the response of bioenergetic processes to training loads must be taken into account when designing training programs.

Any muscular work requires energy. The mechanical energy expended during muscle tension is taken from its own reserves of chemical energy. The energy that is released as a result of complex biochemical reactions is delivered to thin protein threads (muscle fibers), causing them to change their position, connect to each other and shorten. Thus, the muscle, shortening, produces movement in the joint.

The energy required for muscle work, resulting from biochemical reactions, is based on the use three types energy generation: 1) aerobic, 2) anaerobic-glycolytic, 3) anaerobic-alactate. Bioenergetic substances (fuel) when performing muscular work are carbohydrates, fats and creatine phosphate. Proteins are necessary for the body, primarily as building materials for new cells.

Nutrients, passing through the gastrointestinal tract, are absorbed by the blood and sent further to “storage areas”. Fats, which can be considered as “low-actane fuel”, are deposited mainly in subcutaneous tissues. Carbohydrates (glycogen) – high-actane fuel, accumulate in muscles and liver.

If the power of the work performed is small (moderate), then energy for working muscles is generated by combustion (oxidation) of carbohydrates and fats with the help of inhaled oxygen. As a result of combustion, the energy necessary for working muscles is released and by-products are formed - carbon dioxide and water.

If the work power is much higher (high or submaximal), then the energy released during the combustion of carbohydrates (glycogen) will not be enough and therefore the energy required for such work is formed by the breakdown of glycogen (without the participation of oxygen). We can say that in muscle there are two mechanisms of biochemical reactions - combustion and splitting.

Combustion (oxidation) mechanism

The mechanism of combustion of carbohydrates and fats can be called an aerobic process of energy formation (aerobic - with the participation of oxygen). The development of aerobic processes occurs gradually, this process reaches its maximum 1-2 minutes after the start of work. Complete combustion of carbohydrates and fats occurs, which produces energy, carbon dioxide CO2 and water H2O, which are transported in the blood.

Carbohydrates and fats + oxygen → combustion = energy + carbon dioxide + water.

In order for combustion (oxidation) to occur, in addition to “fuel” (carbohydrates and fats), muscles and tissues must be constantly supplied with oxygen and freed from “decomposition” products (water and carbon dioxide). Transportation of these substances is carried out by blood. The more oxygen the muscles receive, the more energy can be produced and the more intense work can be done. Therefore, aerobic capacity is limited by the respiratory and cardiovascular systems. Fatigue sets in when the fuel runs out. If these conditions are met, the muscle environment remains constant and you can work for 2-3 hours or more. The combustion (oxidation) mechanism is the dominant source of energy during prolonged low-intensity and moderate-intensity work (as well as at rest).

Table No. 2. The relationship between the duration of the competitive distance and the functional activity of various body systems characterizing aerobic capabilities.

Decomposition mechanism (anaerobic - without the participation of oxygen).

The mechanism of breakdown of bioenergetic substances in the human body occurs in two ways: 1) breakdown of glycogen located in the muscles - anaerobic-glycolytic mechanism; 2) the breakdown of creatine phosphate (CrP), also located in the muscle - anaerobic-alactate mechanism.

Anaerobic - glycolytic mechanism. The release of energy occurs due to the instantaneous breakdown of glycogen contained in the muscle (a more complex form of carbohydrates).

Glycogen→ breakdown = Energy + lactic acid (lactate).

This mechanism provides much more energy per unit time than the aerobic mechanism and is used when performing work of submaximal power, with a duration separate exercise from 30 seconds to 2-3 minutes. The advantage of this mechanism, which can be compared to discharging an electric battery, is that it is located in the muscle itself and is used instantly. The disadvantage is that a large amount of lactic acid accumulates in working muscles and it becomes difficult for them to cope with the effects of an acidic environment.

Table No. 3. The relationship between the duration of the competitive distance and the functional activity of various body systems characterizing anaerobic-glycolytic capabilities.

Anaerobic-alactate mechanism.

To perform exercises with maximum speed(power) a mechanism is needed that releases the greatest amount of energy per unit of time, but acts for a short time (no more than 15-20 seconds). This mechanism is anaerobic-alactate (creatine phosphate).

Creatine phosphate (CrP)→ breakdown = Energy + Creatine (Cr.).

Table No. 4. The relationship between the duration of the competitive distance and the functional activity of various body systems characterizing anaerobic-alactate capabilities.

General characteristics of the aerobic energy supply system

The aerobic energy supply system is significantly inferior to the alactic and lactate systems in terms of the power of energy production and the speed of inclusion in supporting muscle activity, but is many times superior in capacity and efficiency (Table 1).

Table No. 1. Energy supply for muscle work

Sources	Paths of Education	Activation time to maximum level	Validity	Duration of maximum energy release
Alactate anaerobic	ATP, creatine phosphate	0	Up to 30 s	Up to 10 s
Lactate anaerobic	Glycolysis to form lactate	15 – 20 s	From 15 – 20 s to 6 – 6 min	From 30 s to 1 min 30 s
Aerobic	Oxidation of carbohydrates and fats by air oxygen	90 – 180 s	Up to several hours	2 – 5 minutes or more

A feature of the aerobic system is that the formation of ATP in cellular organelles, mitochondria, located in muscle tissue occurs with the participation of oxygen delivered by the oxygen transport system. This predetermines the high efficiency of the aerobic system, and sufficiently large reserves of glycogen in muscle tissue and liver, as well as practically unlimited reserves of lipids – its capacity.

In the most simplified form, the activity of the aerobic energy supply system is carried out as follows. At the first stage, as a result of complex processes, both glycogen and free fatty acids (FFA) are converted into acetyl-coenzyme A (acetyl-CoA) - the active form of acetic acid, which ensures that all subsequent energy generation processes proceed according to a single scheme. However, until the formation of acetyl-CoA, the oxidation of glycogen and FFA occurs independently.

All the numerous chemical reactions occurring in the process of aerobic resynthesis of ATP can be divided into three types: 1 – aerobic glycolysis; 2 – Krebs cycle, 3 – electron transport system (Fig. 7).

Rice. 7. Stages of ATP resynthesis reactions in the aerobic process

The first stage of the reactions is aerobic glycolysis, which results in the breakdown of glycogen with the formation of CO2 and H2O. The course of aerobic glycolysis occurs according to the same pattern as the course of anaerobic glycolysis discussed above. In both cases, as a result of chemical reactions, glycogen is converted into glucose, and glucose into pyruvic acid with the resynthesis of ATP. Oxygen does not participate in these reactions. The presence of oxygen is detected later when, with its participation, pyruvic acid is not converted into lactic acid into lactic acid, and then into lactate, which takes place in the process of anaerobic glycolysis, but is sent to the aerobic system, the end products of which are carbon dioxide (CO2), excreted from the body by the lungs, and water (Fig. 8)

Rice. 8. Schematic flow of anaerobic and aerobic glycolysis

The breakdown of 1 mole of glycogen into 2 moles of pyruvic acid releases energy sufficient for the resynthesis of 3 moles of ATP: Energy + 3ADP + Pn → 3ATP

CO2 is immediately removed from the pyruvic acid formed as a result of the breakdown of glycogen, transforming it from a three-carbon compound into a two-carbon one, which, when combined with coenzyme A, forms acetyl-CoA, which is included in the second stage of aerobic ATP formation - the citric acid cycle or the Krebs cycle.

In the Krebs cycle, a series of complex chemical reactions occur, as a result of which pyruvic acid is oxidized - the removal of hydrogen ions (H+) and electrons (e-), which ultimately enter the oxygen transport system and participate in ATP resynthesis reactions at the third stage, forming CO2, which diffuses into the blood and is transported to the lungs, from which it is excreted from the body. In the Krebs cycle itself, only 2 moles of ATP are formed (Fig. 9).

Rice. 9. Schematic representation of carbon oxidation in the Krebs cycle

The third stage occurs in the electron transport chain ( respiratory chain). The reactions that occur with the participation of coenzymes are generally reduced to the following. Hydrogen ions and electrons released as a result of reactions in the Krebs cycle and, to a lesser extent, glycolysis, are transported to oxygen to form water. The simultaneously released energy in a series of coupled reactions is used for the resynthesis of ATP. The entire process that occurs along the chain of electron transfer to oxygen is called oxidative phosphorylation. In the processes occurring in the respiratory chain, about 90% of the oxygen supplied to the cells is consumed and the largest amount of ATP is formed. In total, the oxidative electron transport system provides the formation of 34 ATP molecules from one glycogen molecule.

Digestion and absorption of carbohydrates into the bloodstream occurs in the small intestine. In the liver they are converted into glucose, which in turn can be converted into glycogen and stored in the muscles and liver, and is also used by various organs and tissues as a source of energy to maintain activity. In a healthy body with sufficient levels physical fitness men weighing 75 kg contain 500–550 g of carbohydrates in the form of muscle glycogen (about 80%), liver glycogen (approximately 16–17%), blood glucose (3–4%), which corresponds to energy reserves of about 2000–2200 kcal .

Liver glycogen (90 - 100 g) is used to maintain the level of blood glucose necessary to ensure the normal functioning of various tissues and organs. During prolonged aerobic work, which leads to depletion of muscle glycogen stores, part of the liver glycogen can be used by the muscles.

It should be taken into account that glycogen reserves of muscles and liver can increase significantly under the influence of training and nutritional manipulations involving carbohydrate depletion and subsequent carbohydrate saturation. Under the influence of training and special nutrition, the concentration of glycogen in the liver can double. Increasing the amount of glycogen increases its availability and rate of utilization during subsequent muscle work.

For prolonged periods physical activity At average intensity, the formation of glucose in the liver increases 2–3 times compared to its formation at rest. Strenuous work over a long period of time can lead to a 7 to 10-fold increase in glucose production in the liver compared to data obtained at rest.

The efficiency of the process of energy supply from fat reserves is determined by the rate of lipolysis and the speed of blood flow in adipose tissue, which ensures intensive delivery of free fatty acids (FFA) to muscle cells. If work is performed at an intensity of 50 – 60% VO2 max, there is maximum blood flow in adipose tissue, which contributes to maximum entry of FFA into the blood. More intense muscle work is associated with an intensification of muscle blood flow while simultaneously reducing the blood supply to adipose tissue and, consequently, with a deterioration in the delivery of FFAs to muscle tissue.

Although lipolysis unfolds during muscle activity, already at 30–40 minutes of work of average intensity, its energy supply is equally carried out due to the oxidation of both carbohydrates and lipids. Further continuation of work, leading to the gradual depletion of limited carbohydrate resources, is associated with an increase in the oxidation of FFA; for example, energy supply for the second half marathon distance in running or road cycling (over 100 km) is predominantly associated with the use of fat.

Despite the fact that the use of energy from lipid oxidation is of real importance for ensuring endurance only during prolonged muscular activity, starting from the first minutes of work at an intensity exceeding 60% of VO2max, there is a release of FFA from triacylglycerides, their intake and oxidation in contracting muscles. 30 - 40 minutes after the start of work, the rate of FFA consumption increases 3 times, and after 3 - 4 hours of work - 5 - 6 times.

Intramuscular utilization of triglycerides increases significantly under the influence of aerobic training. This adaptive reaction manifests itself both in the rapid development of the process of energy formation due to the oxidation of FFAs supplied from muscle tricerides, and in the increase in their utilization from muscle tissue.

An equally important adaptive effect of trained muscle tissue is an increase in its ability to utilize fat reserves. Thus, after a 12-week aerobic training, the ability to utilize triglycerides in working muscles increased sharply and reached 40%.

The role of proteins for ATP resynthesis is not essential. However, the carbon skeleton of many amino acids can be used as energy fuel in the process of oxidative metabolism, which manifests itself during prolonged moderate-intensity exercise, during which the contribution of protein metabolism to energy production can reach 5–6% of the total energy requirement.

Due to the significant reserves of glucose and fats in the body and the unlimited possibility of consuming oxygen from their atmospheric air, aerobic processes, having less power compared to anaerobic processes, can ensure the performance of work for a long time (i.e., their capacity is very large with very high efficiency) . Research shows that, for example, marathon running Due to the use of muscle glycogen, muscle work continues for 80 minutes. A certain amount of energy can be mobilized from liver glycogen. In total, this can provide 75% of the time required to complete the marathon distance. The rest of the energy comes from the oxidation of fatty acids. However, the rate of their diffusion from the blood into the muscles is limited, which limits the energy production from these acids. The energy produced as a result of the oxidation of FFA is sufficient to maintain the intensity of muscle work at the level of 40 - 50% VO2max, while the strongest marathon runners are able to cover a distance with an intensity exceeding 80 - 90% VO2max, which indicates a high level of adaptation of the aerobic energy supply system, allowing not only ensure an optimal combination of the use of carbohydrates, fats, individual amino acids and metabolites for energy production, but also the economical use of glycogen.

Thus, the entire set of reactions that ensure aerobic oxidation of glycogen is as follows. At the first stage, as a result of aerobic glycolysis, pyruvic acid is formed and a certain amount of ATP is resynthesized. In the second, in the Krebs cycle, CO2 is produced, and hydrogen ions (H+) and electrons (e-) are introduced into the electron transport system, also with the resynthesis of a certain amount of ATP. And finally, The final stage associated with the formation of H2O from H+, e- and oxygen with the release of energy used for resynthesis of the overwhelming amount of ATP. Fats and proteins used in fuel for ATP resynthesis also pass through the Krebs cycle and electron transport system (Fig. 10).

Rice. 10. Schematic representation of the functioning of the aerobic energy supply system

Lactate energy supply system.

In the lactate energy supply system, ATP resynthesis occurs due to the breakdown of glucose and glycogen in the absence of oxygen. This process is commonly referred to as anaerobic glycolysis. Anaerobic glycolysis is a much more complex chemical process compared to the mechanisms of phosphogene breakdown in the alactic energy supply system. It involves the occurrence of a series of complex sequential reactions, as a result of which glucose and glycogen are broken down into lactic acid, which in a series of conjugate reactions is used for the resynthesis of ATP (Fig. 2).

Rice. 2. Schematic representation of the process of anaerobic glycolysis

As a result of the breakdown of 1 mole of glucose, 2 moles of ATP are formed, and the breakdown of 1 mole of glycogen produces 3 moles of ATP. Simultaneously with the release of energy, pyruvic acid is formed in the muscles and body fluids, which is then converted into lactic acid. Lactic acid quickly decomposes to form its salt, lactate.

The accumulation of lactic acid as a result of intense activity of the glycolytic mechanism leads to a large formation of lactate and hydrogen ions (H+) in the muscles. As a result, despite the action of buffer systems, muscle pH gradually decreases from 7.1 to 6.9 and even to 6.5 - 6.4. Intracellular pH, starting from a level of 6.9 - 6.8, slows down the intensity of the glycolytic reaction to restore ATP reserves, and at pH 6.5 - 6.4, the breakdown of glycogen stops. Thus, it is the increase in the concentration of lactic acid in the muscles that limits the breakdown of glycogen in anaerobic glycolysis.

Unlike the alactic energy supply system, the power of which reaches maximum levels already in the first second of work, the process of activation of glycolysis unfolds much more slowly and reaches high levels of energy production only in 5–10 seconds of work. The power of the glycolytic process is significantly inferior to the power of the creatine phosphokinase mechanism, but is several times higher than the capabilities of the aerobic oxidation system. In particular, if the level of ATP energy production due to the breakdown of CP is 9 – 10 mmol/kg bw/s (wet tissue mass), then when glycolysis is activated, the volume of ATP produced can increase to 14 mmol/kg bw. t./s. Due to the use of both sources of ATP resynthesis during 3 minutes of intense work, the human muscular system is capable of producing about 370 mmol/kg bw. At the same time, glycolysis accounts for at least 80% of total production. The maximum power of the lactate anaerobic system appears at 20–25 seconds of work, and at 30–60 seconds the glycolytic pathway of ATP resynthesis is the main one in the energy supply of work.

The capacity of the lactate anaerobic system ensures its predominant participation in energy production when performing work lasting up to 30–90 s. With longer work, the role of glycolysis gradually decreases, but remains significant even with longer work - up to 5 - 6 minutes. The total amount of energy that is generated due to glycolysis can be visually assessed by blood lactate indicators after performing work that requires extreme mobilization of the lactate energy supply system. In untrained people, the maximum concentration of lactate in the blood is 11 – 12 mmol/l. Under the influence of training, the capacity of the lactate system increases sharply and the concentration of lactate in the blood can reach 25 – 30 mmol/l and higher.

The maximum values of energy production and lactate in the blood in women are 30–40% lower compared to men of the same sports specialization. Young athletes Compared to adults, they have low anaerobic capabilities. the maximum concentration of lactate in the blood under extreme anaerobic loads does not exceed 10 mmol/kg, which is 2–3 times lower than in adult athletes.

Thus, adaptive reactions of the lactate anaerobic system can proceed in different directions. One of them is an increase in the mobility of the glycolytic process, which is manifested in a much faster achievement of its maximum productivity (from 15–20 to 5–8 s). The second reaction is associated with an increase in the power of the anaerobic glycolytic system, which allows it to produce a significantly larger amount of energy per unit time. The third reaction comes down to increasing the capacity of the system and, naturally, the total volume of energy produced, as a result of which the duration of work increases, mainly provided by glycolysis.

The maximum values of lactate and pH in arterial blood during competitions in some sports are presented in Fig. 3.

Fig.3. Maximum values of lactate and pH in arterial blood in athletes specializing in various types sports: a – running (400, 800 m); b – speed running skating (500, 1000m); c – rowing (2000 m); d – swimming 100 m; d – bobsleigh; e – cycling race (100 km)
(Eindemann, Keul, 1977)

They give a fairly complete picture of the role of lactate anaerobic energy sources for achieving high sports results different types sports and about the adaptive reserves of the anaerobic glycolysis system.

When choosing the optimal duration of work that ensures the maximum concentration of lactate in the muscles, it should be taken into account that the maximum lactate content is observed when using maximum loads, the duration of which ranges from 1 to 6 minutes. An increase in work duration is associated with a decrease in lactate concentration in muscles.

To select the optimal method for increasing anaerobic capacity, it is important to trace the characteristics of lactate accumulation during intermittent work of maximum intensity. For example, one-minute maximum loads with four-minute pauses lead to a constant increase in blood lactate (Fig. 4) while simultaneously reducing acid-base levels (Fig. 5).

Rice. 4. Change in blood lactate concentration during intermittent maximal exercise (one-minute exercise at 95% intensity, separated by 4-minute rest periods) (Hermansen, Stenswold, 1972)

Rice. 5. Change in blood pH during intermittent one-minute exercise of maximum intensity (Hollman, Hettinger, 1980)

A similar effect is observed when performing 15-20 second exercises of maximum power with pauses of about 3 minutes (Fig. 6).

Rice. 6. Dynamics of biochemical changes in athletes during repeated performance of short-term exercises of maximum power (N. Volkov et al., 2000)

Alactate energy supply system.

This energy supply system is the least complex, differs high power release of energy and short duration of action. Energy generation in this system occurs due to the breakdown of energy-rich phosphate compounds - adenosine triphosphate (ATP) and creatine phosphate (CP). The energy generated as a result of the breakdown of ATP is fully included in the process of energy supply to work already in the first second. However, already in the second second, work is performed due to creatine phosphate (CP) deposited in muscle fibers and containing energy-rich phosphate compounds. The breakdown of these compounds leads to an intense release of energy. The end products of CP breakdown are creatine (Cr) and inorganic phosphate (Pn). The reaction is stimulated by the enzyme creatine kinase and is schematically as follows:

The energy released during the breakdown of CP is available for the process of ATP resynthesis, therefore, the rapid breakdown of ATP during muscle contraction is immediately followed by its resynthesis from ADP and Fn with the involvement of energy released during the breakdown of CP:

Another mechanism of the alactic energy supply system is the so-called myokinase reaction, which is activated during significant muscle fatigue, when the rate of ATP breakdown significantly exceeds the rate of its resynthesis. The myokinase reaction is stimulated by the enzyme myokinase and consists of the transfer of a phosphate group from one molecule to another and the formation of ATP and adenosine monophosphate (AMP):

Adenosine monophosphate (AMP), a byproduct of the myokinase reaction, contains the last phosphate group and, unlike ATP and ADP, cannot be used as an energy source. The myokinase reaction is activated under conditions when, due to fatigue, other pathways of ATP resynthesis have exhausted their capabilities.

CF reserves cannot be replenished during the work process. For its resynthesis, only the energy released as a result of the breakdown of ATP can be used, which turns out to be possible only in the recovery period after the end of work.

The alactic system, distinguished by a very high rate of energy release, is at the same time characterized by an extremely limited capacity. The level of maximum alactic anaerobic power depends on the amount of phosphates (ATP and CP) in the muscles and the rate of their use. Under the influence of sprint training, alactic anaerobic power can be significantly increased. Influenced special training the capacity of the alactic anaerobic system can be increased by 40-80%. For example, sprint training for 8 weeks in runners led to an increase in ATP and CP content in skeletal muscle at rest by about 10%.

Under the influence of training in the muscles, not only the amount of ATP and Kf increases, but also the ability of muscle tissue to break them down significantly increases. Another adaptive reaction that determines the power of the alactic anaerobic system is the acceleration of phosphate resynthesis due to increased activity of enzymes, in particular creatine phosphokinase and myokinase.

Under the influence of training, the maximum capacity of the alactic anaerobic energy supply system also increases significantly. The capacity of the alactic anaerobic system under the influence of targeted long-term training can increase by 2.5 times. This is confirmed by the indicators of the maximum alactic O2 debt: in beginner athletes it is 21.5 ml/kg, in high-class athletes it can reach 54.5 ml/kg.

An increase in the capacity of the alactic energy system is also manifested in the duration of work at maximum intensity. Thus, in persons not involved in sports, the maximum power of the alactic anaerobic process, achieved 0.5 - 0.7 s after the start of work, can be maintained for no more than 7 - 10 s, while in top-class athletes specializing in sprint disciplines, it can appear within 15–20 s. At the same time, a longer operating time is accompanied by significantly greater power, which is determined by high speed decomposition and resynthesis of high-energy phosphates.

The concentration of ATP and CP in men and women is almost the same - about 4 mmol/kg ATP and 16 mmol/kg CP. However, the total amount of phosphogenes that can be used during muscle activity is significantly greater in men than in women, which is due to large differences in the total volume of skeletal muscles. Naturally, men have a much larger capacity of the alactic anaerobic energy supply system.

In conclusion, it should be noted that persons with high level alactic anaerobic performance, as a rule, have low aerobic capacity and endurance for long-term work. At the same time, runners long distances alactic anaerobic capacity is not only not comparable to that of sprinters, but is often inferior to the indicators recorded in persons who do not engage in sports.

General characteristics of energy supply systems for muscle activity

Energy, as is known, is a general quantitative measure that links together all natural phenomena and different forms of motion of matter. Of all the types of energy generated and used in various physical processes (thermal, mechanical, chemical, etc.) in relation to muscle activity, the main attention should be focused on the chemical energy of the body, the source of which is food products and its conversion into mechanical energy motor activity person.

The energy released during the breakdown of food is used to produce adenosine triphosphate (ATP), which is stored in muscle cells and provides fuel for the production of mechanical energy during muscle contraction.

The energy for muscle contraction comes from the breakdown of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and inorganic phosphate (P). The amount of ATP in the muscles is small and is sufficient to ensure high-intensity work for only 1–2 s. To continue work, ATP resynthesis is necessary, which is produced due to energy-releasing reactions three types. Replenishing ATP reserves in muscles allows you to maintain a constant level of its concentration, necessary for full muscle contraction.

ATP resynthesis is ensured in both anaerobic and aerobic reactions using creatine phosphate (CP) and ADP reserves contained in muscle tissue, as well as energy-rich substrates (muscle and liver glycogen, lipid tissue reserves, etc.). Chemical reactions leading to the provision of energy to muscles occur in three energy systems: 1) anaerobic alactic, 2) anaerobic lactate (glycolytic), 3) aerobic.

Energy is generated in the first two systems through chemical reactions that do not require the presence of oxygen. The third system provides energy supply to muscle activity as a result of oxidation reactions occurring with the participation of oxygen. The most general ideas about the sequence of inclusion and quantitative relationships in the energy supply of muscle activity of each of these systems are shown in Fig. 1.

The capabilities of each of these energy systems are determined by power, i.e., the rate of energy release in metabolic processes, and capacity, which is determined by the size and efficiency of use of substrate funds.

Rice. 1. Sequence and quantitative relationships of the processes of energy supply to muscle activity in qualified athletes in various energy systems (diagram): 1 – alactic; 2 – lactate; 3 – aerobic

General characteristics of the aerobic energy supply system

Table No. 1. Energy supply for muscle work

Sources	Paths of Education	Activation time to maximum level	Validity	Duration of maximum energy release
Alactate anaerobic	ATP, creatine phosphate	0	Up to 30 s	Up to 10 s
Lactate anaerobic	Glycolysis to form lactate	15 – 20 s	From 15 – 20 s to 6 – 6 min	From 30 s to 1 min 30 s
Aerobic	Oxidation of carbohydrates and fats by air oxygen	90 – 180 s	Up to several hours	2 – 5 minutes or more

Rice. 7. Stages of ATP resynthesis reactions in the aerobic process

Rice. 8. Schematic flow of anaerobic and aerobic glycolysis

The breakdown of 1 mole of glycogen into 2 moles of pyruvic acid releases energy sufficient for the resynthesis of 3 moles of ATP: Energy + 3ADP + Pn → 3ATP

Rice. 9. Schematic representation of carbon oxidation in the Krebs cycle

The third stage occurs in the electron transport chain (respiratory chain). The reactions that occur with the participation of coenzymes are generally reduced to the following. Hydrogen ions and electrons released as a result of reactions in the Krebs cycle and, to a lesser extent, glycolysis, are transported to oxygen to form water. The simultaneously released energy in a series of coupled reactions is used for the resynthesis of ATP. The entire process that occurs along the chain of electron transfer to oxygen is called oxidative phosphorylation. In the processes occurring in the respiratory chain, about 90% of the oxygen supplied to the cells is consumed and the largest amount of ATP is formed. In total, the oxidative electron transport system provides the formation of 34 ATP molecules from one glycogen molecule.

Digestion and absorption of carbohydrates into the bloodstream occurs in the small intestine. In the liver they are converted into glucose, which in turn can be converted into glycogen and stored in the muscles and liver, and is also used by various organs and tissues as a source of energy to maintain activity. The body of a healthy man with a sufficient level of physical fitness with a body weight of 75 kg contains 500 - 550 g of carbohydrates in the form of muscle glycogen (about 80%), liver glycogen (about 16 - 17%), blood glucose (3 - 4%), which corresponds to energy reserves of about 2000 – 2200 kcal.

With prolonged physical activity of moderate intensity, the formation of glucose in the liver increases by 2–3 times compared with its formation at rest. Strenuous work over a long period of time can lead to a 7 to 10-fold increase in glucose production in the liver compared to data obtained at rest.

Although lipolysis unfolds during muscle activity, already at 30–40 minutes of work of average intensity, its energy supply is equally carried out due to the oxidation of both carbohydrates and lipids. Further continuation of work, leading to the gradual depletion of limited carbohydrate resources, is associated with an increase in the oxidation of FFA; for example, energy supply for the second half of a marathon distance in running or road cycling (over 100 km) is predominantly associated with the use of fat.

Due to the significant reserves of glucose and fats in the body and the unlimited possibility of consuming oxygen from their atmospheric air, aerobic processes, having less power compared to anaerobic processes, can ensure the performance of work for a long time (i.e., their capacity is very large with very high efficiency) . Research shows that, for example, in marathon running, due to the use of muscle glycogen, muscle work continues for 80 minutes. A certain amount of energy can be mobilized from liver glycogen. In total, this can provide 75% of the time required to complete the marathon distance. The rest of the energy comes from the oxidation of fatty acids. However, the rate of their diffusion from the blood into the muscles is limited, which limits the energy production from these acids. The energy produced as a result of the oxidation of FFA is sufficient to maintain the intensity of muscle work at the level of 40 - 50% VO2max, while the strongest marathon runners are able to cover a distance with an intensity exceeding 80 - 90% VO2max, which indicates a high level of adaptation of the aerobic energy supply system, allowing not only ensure an optimal combination of the use of carbohydrates, fats, individual amino acids and metabolites for energy production, but also the economical use of glycogen.

Thus, the entire set of reactions that ensure aerobic oxidation of glycogen is as follows. At the first stage, as a result of aerobic glycolysis, pyruvic acid is formed and a certain amount of ATP is resynthesized. In the second, in the Krebs cycle, CO2 is produced, and hydrogen ions (H+) and electrons (e-) are introduced into the electron transport system, also with the resynthesis of a certain amount of ATP. And finally, the final stage is associated with the formation of H2O from H+, e- and oxygen with the release of energy used for resynthesis of the overwhelming amount of ATP. Fats and proteins used in fuel for ATP resynthesis also pass through the Krebs cycle and electron transport system (Fig. 10).

Rice. 10. Schematic representation of the functioning of the aerobic energy supply system

Lactate energy supply system.

Rice. 2. Schematic representation of the process of anaerobic glycolysis

The maximum values of energy production and lactate in the blood in women are 30–40% lower compared to men of the same sports specialization. Young athletes have low anaerobic capabilities compared to adults. the maximum concentration of lactate in the blood under extreme anaerobic loads does not exceed 10 mmol/kg, which is 2–3 times lower than in adult athletes.

The maximum values of lactate and pH in arterial blood during competitions in some sports are presented in Fig. 3.

Fig.3. Maximum values of lactate and pH in arterial blood in athletes specializing in various sports: a – running (400, 800 m); b – speed skating (500, 1000m); c – rowing (2000 m); d – swimming 100 m; d – bobsleigh; e – cycling race (100 km)
(Eindemann, Keul, 1977)

They provide a fairly complete understanding of the role of lactate anaerobic energy sources for achieving high athletic results in various sports and the adaptive reserves of the anaerobic glycolysis system.

A similar effect is observed when performing 15-20 second exercises of maximum power with pauses of about 3 minutes (Fig. 6).

Rice. 6. Dynamics of biochemical changes in athletes during repeated performance of short-term exercises of maximum power (N. Volkov et al., 2000)

Alactate energy supply system.

This energy supply system is the least complex, characterized by high energy release power and short duration of action. Energy generation in this system occurs due to the breakdown of energy-rich phosphate compounds - adenosine triphosphate (ATP) and creatine phosphate (CP). The energy generated as a result of the breakdown of ATP is fully included in the process of energy supply to work already in the first second. However, already in the second second, work is performed due to creatine phosphate (CP), deposited in muscle fibers and containing energy-rich phosphate compounds. The breakdown of these compounds leads to an intense release of energy. The end products of CP breakdown are creatine (Cr) and inorganic phosphate (Pn). The reaction is stimulated by the enzyme creatine kinase and is schematically as follows:

The alactic system, distinguished by a very high rate of energy release, is at the same time characterized by an extremely limited capacity. The level of maximum alactic anaerobic power depends on the amount of phosphates (ATP and CP) in the muscles and the rate of their use. Under the influence of sprint training, alactic anaerobic power can be significantly increased. Under the influence of special training, the power of the alactic anaerobic system can be increased by 40-80%. For example, 8 weeks of sprint training in runners resulted in an approximately 10% increase in resting skeletal muscle ATP and CP content.

An increase in the capacity of the alactic energy system is also manifested in the duration of work at maximum intensity. Thus, in persons not involved in sports, the maximum power of the alactic anaerobic process, achieved 0.5 - 0.7 s after the start of work, can be maintained for no more than 7 - 10 s, while in top-class athletes specializing in sprint disciplines, it can appear within 15–20 s. At the same time, a longer duration of work is accompanied by a significantly greater power, which is determined by the high rate of decomposition and resynthesis of high-energy phosphates.

In conclusion, it should be noted that individuals with a high level of alactic anaerobic performance, as a rule, have low aerobic capacity and endurance for long-term work. At the same time, the alactic anaerobic capacity of long-distance runners is not only not comparable to that of sprinters, but is often inferior to the indicators recorded in persons who do not engage in sports.

General characteristics of energy supply systems for muscle activity

Energy, as is known, is a general quantitative measure that links together all natural phenomena and different forms of motion of matter. Of all the types of energy generated and used in various physical processes (thermal, mechanical, chemical, etc.) in relation to muscular activity, the main attention should be focused on the chemical energy of the body, the source of which is food products and its conversion into mechanical energy of motor activity person.

The energy for muscle contraction comes from the breakdown of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and inorganic phosphate (P). The amount of ATP in the muscles is small and is sufficient to ensure high-intensity work for only 1–2 s. To continue work, ATP resynthesis is necessary, which is produced due to energy-releasing reactions of three types. Replenishing ATP reserves in muscles allows you to maintain a constant level of its concentration, necessary for full muscle contraction.

ATP resynthesis is ensured in both anaerobic and aerobic reactions using creatine phosphate (CP) and ADP reserves contained in muscle tissue, as well as energy-rich substrates (muscle and liver glycogen, lipid tissue reserves, etc.) as energy sources. Chemical reactions leading to the provision of energy to muscles occur in three energy systems: 1) anaerobic alactic, 2) anaerobic lactate (glycolytic), 3) aerobic.

General characteristics of the aerobic energy supply system

Table No. 1. Energy supply for muscle work

All the numerous chemical reactions occurring in the process of aerobic resynthesis of ATP can be divided into three types: 1 - aerobic glycolysis; 2 - Krebs cycle, 3 - electron transport system (Fig. 7).

Rice. 7. Stages of ATP resynthesis reactions in the aerobic process

Rice. 8. Schematic flow of anaerobic and aerobic glycolysis

The breakdown of 1 mole of glycogen into 2 moles of pyruvic acid releases energy sufficient for the resynthesis of 3 moles of ATP: Energy + 3ADP + Pn → 3ATP

In the Krebs cycle, a series of complex chemical reactions occur, as a result of which pyruvic acid is oxidized - the removal of hydrogen ions (H+) and electrons (e-), which ultimately enter the oxygen transport system and participate in ATP resynthesis reactions in the third stage, forming CO2, which diffuses into the blood and is transported to the lungs, from which it is excreted from the body. In the Krebs cycle itself, only 2 moles of ATP are formed (Fig. 9).

Rice. 9. Schematic representation of carbon oxidation in the Krebs cycle

The third stage occurs in the electron transport chain (respiratory chain). The reactions that occur with the participation of coenzymes are generally reduced to the following. Hydrogen ions and electrons released as a result of reactions in the Krebs cycle and, to a lesser extent, glycolysis, are transported to oxygen to form water. The simultaneously released energy in a series of coupled reactions is used for the resynthesis of ATP. The entire process that occurs along the chain of electron transfer to oxygen is called oxidative phosphorylation. In the processes occurring in the respiratory chain, about 90% of the oxygen supplied to the cells is consumed and the largest amount of ATP is formed. In total, the oxidative electron transport system provides the formation of 34 ATP molecules from one glycogen molecule.

Digestion and absorption of carbohydrates into the bloodstream occurs in the small intestine. In the liver they are converted into glucose, which in turn can be converted into glycogen and stored in the muscles and liver, and is also used by various organs and tissues as a source of energy to maintain activity. The body of a healthy man with a sufficient level of physical fitness with a body weight of 75 kg contains 500 - 550 g of carbohydrates in the form of muscle glycogen (about 80%), liver glycogen (about 16 - 17%), blood glucose (3 - 4%), which corresponds to energy reserves of about 2000 - 2200 kcal.

During prolonged physical activity of moderate intensity, the formation of glucose in the liver increases by 2 - 3 times compared with its formation at rest. Strenuous work over a long period of time can lead to a 7 to 10-fold increase in glucose production in the liver compared to data obtained at rest.

The efficiency of the process of energy supply from fat reserves is determined by the rate of lipolysis and the speed of blood flow in adipose tissue, which ensures intensive delivery of free fatty acids (FFA) to muscle cells. If work is performed at an intensity of 50 - 60% VO2 max, there is maximum blood flow in the adipose tissue, which contributes to the maximum entry of FFA into the blood. More intense muscle work is associated with an intensification of muscle blood flow while simultaneously reducing the blood supply to adipose tissue and, consequently, with a deterioration in the delivery of FFAs to muscle tissue.

Although lipolysis unfolds during muscle activity, already at the 30th - 40th minute of work of average intensity, its energy supply is equally carried out due to the oxidation of both carbohydrates and lipids. Further continuation of work, leading to the gradual depletion of limited carbohydrate resources, is associated with an increase in the oxidation of FFA; for example, energy supply for the second half of a marathon distance in running or road cycling (over 100 km) is predominantly associated with the use of fat.

Due to the significant reserves of glucose and fats in the body and the unlimited possibility of consuming oxygen from their atmospheric air, aerobic processes, having less power compared to anaerobic processes, can ensure the performance of work for a long time (i.e., their capacity is very large with very high efficiency) . Research shows that, for example, in marathon running, due to the use of muscle glycogen, muscle work continues for 80 minutes. A certain amount of energy can be mobilized from liver glycogen. In total, this can provide 75% of the time required to complete the marathon distance. The rest of the energy comes from the oxidation of fatty acids. However, the rate of their diffusion from the blood into the muscles is limited, which limits the energy production from these acids. The energy produced as a result of the oxidation of FFA is sufficient to maintain the intensity of muscle work at the level of 40 - 50% VO2max, while the strongest marathon runners are able to cover a distance with an intensity exceeding 80 - 90% VO2max, which indicates a high level of adaptation of the aerobic energy supply system, allowing not only ensure an optimal combination of the use of carbohydrates, fats, individual amino acids and metabolites for energy production, but also the economical use of glycogen.

Thus, the entire set of reactions that ensure aerobic oxidation of glycogen is as follows. At the first stage, as a result of aerobic glycolysis, pyruvic acid is formed and a certain amount of ATP is resynthesized. In the second, in the Krebs cycle, CO2 is produced, and hydrogen ions (H+) and electrons (e-) are introduced into the electron transport system, also with the resynthesis of a certain amount of ATP. And finally, the final stage is associated with the formation of H2O from H+, e- and oxygen with the release of energy used for resynthesis of the overwhelming amount of ATP. Fats and proteins used in fuel for ATP resynthesis also pass through the Krebs cycle and electron transport system (Fig. 10).

Rice. 10. Schematic representation of the functioning of the aerobic energy supply system

Lactate energy supply system.

Rice. 2. Schematic representation of the process of anaerobic glycolysis

Unlike the alactic energy supply system, the power of which reaches maximum levels already in the first second of work, the process of activation of glycolysis unfolds much more slowly and reaches high levels of energy production only in 5 - 10 seconds of work. The power of the glycolytic process is significantly inferior to the power of the creatine phosphokinase mechanism, but is several times higher than the capabilities of the aerobic oxidation system. In particular, if the level of ATP energy production due to the breakdown of CP is 9 - 10 mmol/kg b.w./s (wet tissue mass), then when glycolysis is activated, the volume of ATP produced can increase to 14 mmol/kg b.w. t./s. Due to the use of both sources of ATP resynthesis during 3 minutes of intense work, the human muscular system is capable of producing about 370 mmol/kg bw. At the same time, glycolysis accounts for at least 80% of total production. The maximum power of the lactate anaerobic system appears at 20-25 seconds of work, and at 30-60 seconds the glycolytic pathway of ATP resynthesis is the main one in the energy supply of work.

The capacity of the lactate anaerobic system ensures its predominant participation in energy production when performing work lasting up to 30 - 90 s. With longer work, the role of glycolysis gradually decreases, but remains significant even with longer work - up to 5 - 6 minutes. The total amount of energy that is generated due to glycolysis can be visually assessed by blood lactate indicators after performing work that requires extreme mobilization of the lactate energy supply system. In untrained people, the maximum concentration of lactate in the blood is 11 - 12 mmol/l. Under the influence of training, the capacity of the lactate system increases sharply and the concentration of lactate in the blood can reach 25 - 30 mmol/l and higher.

The maximum values of energy production and lactate in the blood in women are 30 - 40% lower compared to men of the same sports specialization. Young athletes have low anaerobic capabilities compared to adults. the maximum concentration of lactate in the blood under extreme anaerobic loads does not exceed 10 mmol/kg, which is 2 - 3 times lower than in adult athletes.

Thus, adaptive reactions of the lactate anaerobic system can proceed in different directions. One of them is an increase in the mobility of the glycolytic process, which is manifested in a much faster achievement of its maximum productivity (from 15 - 20 to 5 - 8 s). The second reaction is associated with an increase in the power of the anaerobic glycolytic system, which allows it to produce a significantly larger amount of energy per unit time. The third reaction comes down to increasing the capacity of the system and, naturally, the total volume of energy produced, as a result of which the duration of work increases, mainly provided by glycolysis.

The maximum values of lactate and pH in arterial blood during competitions in some sports are presented in Fig. 3.

Fig.3. Maximum values of lactate and pH in arterial blood in athletes specializing in various sports: a - running (400, 800 m); b - speed skating (500, 1000m); c - rowing (2000 m); g - swimming 100 m; d - bobsleigh; e - bicycle race (100 km)
(Eindemann, Keul, 1977)

A similar effect is observed when performing 15-20 second exercises of maximum power with pauses of about 3 minutes (Fig. 6).

Rice. 6. Dynamics of biochemical changes in athletes during repeated performance of short-term exercises of maximum power (N. Volkov et al., 2000)

Alactate energy supply system.

The alactic system, distinguished by a very high rate of energy release, is at the same time characterized by an extremely limited capacity. The level of maximum alactic anaerobic power depends on the amount of phosphates (ATP and CP) in the muscles and the rate of their use. Under the influence of sprint training, alactic anaerobic power can be significantly increased. Under the influence of special training, the power of the alactic anaerobic system can be increased by 40-80%. For example, 8 weeks of sprint training in runners resulted in an approximately 10% increase in resting skeletal muscle ATP and CP content.

An increase in the capacity of the alactic energy system is also manifested in the duration of work at maximum intensity. Thus, for people not involved in sports, the maximum power of the alactic anaerobic process, achieved 0.5 - 0.7 s after the start of work, can be maintained for no more than 7 - 10 s, while for top-class athletes specializing in sprint disciplines, it can appear within 15 - 20 s. At the same time, a longer duration of work is accompanied by a significantly greater power, which is determined by the high rate of decomposition and resynthesis of high-energy phosphates.

General characteristics of energy supply systems for muscle activity

Energy, as is known, is a general quantitative measure that links together all natural phenomena and different forms of motion of matter. Of all the types of energy generated and used in various physical processes (thermal, mechanical, chemical, etc.) in relation to muscular activity, the main attention should be focused on the chemical energy of the body, the source of which is food products and its conversion into mechanical energy of motor activity person.

The energy for muscle contraction comes from the breakdown of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and inorganic phosphate (P). The amount of ATP in the muscles is small and is sufficient to ensure high-intensity work for only 1 - 2 s. To continue work, ATP resynthesis is necessary, which is produced due to energy-releasing reactions of three types. Replenishing ATP reserves in muscles allows you to maintain a constant level of its concentration, necessary for full muscle contraction.

ATP resynthesis is ensured in both anaerobic and aerobic reactions using creatine phosphate (CP) and ADP reserves contained in muscle tissue, as well as energy-rich substrates (muscle and liver glycogen, lipid tissue reserves, etc.) as energy sources. Chemical reactions leading to the provision of energy to muscles occur in three energy systems: 1) anaerobic alactic, 2) anaerobic lactate (glycolytic), 3) aerobic.

Rice. 1. Sequence and quantitative relationships between the processes of energy supply to muscle activity in qualified athletes in various energy systems (diagram): 1 - alactic; 2 - lactate; 3 - aerobic