Aerobic resynthesis of atf. Anaerobic pathways for ATP resynthesis Hydrolysis and ATP resynthesis

Quantitative criteria for ATP resynthesis pathways. Aerobic pathway for ATP resynthesis. Anaerobic pathways for ATP resynthesis. Relationships between different pathways of ATP resynthesis during muscle work.

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Lecture 8. Topic: ENERGY PROVIDING MUSCLE CONTRACTION.

Questions:

1. Quantitative criteria for ATP resynthesis pathways.

4. Relationships between different pathways of ATP resynthesis during muscle work. Zones of relative power of muscle work.

Subject : BIOCHEMICAL SHIFT DURING MUSCULAR WORK.

Questions:

1. Basic mechanisms of neurohumoral regulation of muscle activity.

2. Biochemical changes in skeletal muscles.

3. Biochemical changes in the brain and myocardium.

4. Biochemical changes in the liver.

5. Biochemical changes in the blood.

6. Biochemical changes in urine.

Quantitative criteria for ATP resynthesis pathways.

Contraction and relaxation of muscles require energy, which is generated whenhydrolysis of ATP molecules.

However, ATP reserves in the muscle are insignificant; they are enough to operate the muscle for 2 seconds. The production of ATP in muscles is called ATP resynthesis.

Thus, two parallel processes take place in the muscles: ATP hydrolysis and ATP resynthesis.

ATP resynthesis, in contrast to hydrolysis, can occur in different ways, and in total, depending on the energy source, they are divided into three: aerobic (basic), creatine phosphate and lactate.

For quantitative characteristics of various ATP resynthesis pathwaysUsually several criteria are used.

1. Maximum power or maximum speedthis is the largest amount of ATP that can be formed per unit time due to a given resynthesis pathway. Maximum power is measured in calories or joules, based on the fact that one mmol of ATP corresponds to physiological conditions of approximately 12 cal or 50 J. Therefore, this criterion has the dimension cal/min-kg muscle tissue or J/min-kg muscle tissue.

2. Deployment timethis is the minimum time required for ATP resynthesis to reach its highest speed, that is, to achieve maximum power. This criterion is measured in units of time.

3. Time to save or maintain maximum powerthis is the longest time for a given ATP resynthesis pathway to function with maximum power.

4. Metabolic capacitythis is the total amount of ATP that can be formed during muscle work due to a given ATP resynthesis pathway.

Depending on oxygen consumption resynthesis pathways are divided into aerobic and anaerobic.

2. Aerobic pathway for ATP resynthesis.

Aerobic pathway for ATP resynthesisotherwise calledtissue respirationthis is the main method of ATP formation that occurs in mitochondria muscle cells. During tissue respiration, two hydrogen atoms are removed from the oxidized substance and transferred through the respiratory chain to molecular oxygen delivered to the muscles by the blood, resulting in the formation of water. Due to the energy released during the formation of water, ATP molecules are synthesized from ADP and phosphoric acid. Typically, for every water molecule formed, three ATP molecules are synthesized.

Most often, hydrogen is taken away from intermediate products of the tricarboxylic acid cycle (TCA cycle). The TCA cycle is the final stage of catabolism during which acetyl coenzyme A is oxidized to carbon dioxide and water. During this process, four pairs of hydrogen atoms are removed from the acids listed above and therefore 12 molecules of ATP are formed from the oxidation of one molecule of acetyl coenzyme A.

In turn, acetyl coenzyme A can be formed from carbohydrates, fats, amino acids, that is, through this compound, carbohydrates, fats and amino acids are involved in the TCA cycle.

The rate of aerobic ATP metabolism is controlled by the content of muscle cells A DF, which is an activator of tissue respiration enzymes. During muscular work, accumulation occurs A DF. Excess A DF accelerates tissue respiration, and it can reach maximum intensity.

Another activator of ATP resynthesis is carbon dioxide. An excess of this gas in the blood activates the respiratory center of the brain, which ultimately leads to an increase in blood circulation and improved oxygen supply to the muscles.

Maximum poweraerobic pathway is 350-450 cal/min-kg. Compared to anaerobic pathways of ATP resynthesis, tissue respiration is lower, which is limited by the rate of oxygen delivery to the muscles. Therefore, due to the aerobic pathway of ATP resynthesis, only moderate physical activity can be carried out.

Deployment timeis 3 4 minutes, but for well-trained athletes it can be 1 minute. This is due to the fact that the delivery of oxygen to mitochondria requires the restructuring of almost all body systems.

Operating time at maximum poweris tens of minutes. This makes it possible to use this path during prolonged muscle work.

Compared to other ATP resynthesis processes occurring in muscle cells, the aerobic pathway has a number of advantages.

1. Economical: from one glycogen molecule 39 ATP molecules are formed, with anaerobic glycolysis only 3 molecules.

2. Versatility: various substances act as initial substrates here: carbohydrates, fatty acid, ketone bodies, amino acids.

3. Very long operating time. At rest, the rate of aerobic resynthesis of ATP may be low, but during physical activity it can become maximum.

However, there are also disadvantages.

1. Mandatory oxygen consumption, which is limited by the rate of oxygen delivery to the muscles and the rate of oxygen penetration through the mitochondrial membrane.

2. Long deployment time.

3. Small maximum value power.

Therefore, muscle activity characteristic of most sports cannot be completely obtained by this route of ATP resynthesis.

In sports practice, the following indicators are used to assess aerobic resynthesis:maximum oxygen consumption (MOC), aerobic metabolic threshold (AMT), anaerobic metabolic threshold (ANT) and oxygen supply.

IPC This is the maximum possible rate of oxygen consumption by the body when performing physical work. The higher the MIC, the higher the rate of tissue respiration. The more trained a person is, the higher the VO2 max. MOC is usually calculated per 1 kg of body weight. In people who do not engage in sports, the MIC is 50 ml/min-kg, and in trained people it reaches 90 ml/min-kg.

In sports practice, MOC is also used to characterize the relative power of aerobic work, which is expressed as a percentage of MOC. For example, the relative power of work performed with an oxygen consumption of 3 l/min by an athlete with a VO2 max of 6 l/min will be 50% of the VO2 max level.

PJSC this is the highest relative power of work, measured by oxygen consumption as a percentage relative to the MOC. Large PAO values indicate better development aerobic resynthesis.

PANO this is the minimum relative power of work, also measured by oxygen consumption as a percentage of the VO2 max. A high PANO indicates that aerobic resynthesis is higher per unit time, so glycolysis is turned on at much higher loads.

Oxygen arrivalthis is the amount of oxygen (above the pre-working level) used during a given load to ensure aerobic resynthesis of ATP. Oxygen supply characterizes the contribution of tissue respiration to the energy supply of all work done. Oxygen gain is often used to evaluate all aerobic work done.

Under the influence of systematic training, the number of mitochondria in muscle cells increases, the oxygen transport function of the body improves, and the amount of myoglobin in the muscles and hemoglobin in the blood increases.

3. Anaerobic pathways for ATP resynthesis.

Anaerobic pathways for ATP resynthesisthese are additional paths. There are two such pathways: the creatine phosphate pathway and the lactate pathway.

Creatine phosphate pathwayassociated with substancecreatine phosphate. Creatine phosphate consists of the substance creatine, which binds to the phosphate group via a high-energy bond. Creatine phosphate in muscle cells is contained at rest at 15 20 mmol/kg.

Creatine phosphate has a large energy reserve and high affinity for ADP. Therefore, it easily interacts with ADP molecules that appear in muscle cells during physical work as a result of the ATP hydrolysis reaction. During this reaction, a phosphoric acid residue with a reserve of energy is transferred from creatine phosphate to an ADP molecule with the formation of creatine and ATP.

Creatine phosphate + ADP → creatine + ATP.

This reaction is catalyzed by the enzyme creatine kinase . This ATP resynthesis pathway is sometimes called creatikinase.

The creatine kinase reaction is reversible, but is biased toward ATP production. Therefore, it begins to take place as soon as the first ADP molecules appear in the muscles.

Creatine phosphate is a fragile substance. The formation of creatine from it occurs without the participation of enzymes. Creatine not used by the body is excreted from the body in urine. In men, urinary creatinine excretion ranges from 18-32 mg/day. kg body weight, and for women 10-25 mg/day. kg (this is the creatinine coefficient). Creatine phosphate synthesis occurs during rest from excess ATP. During moderate muscular work, creatine phosphate reserves can be partially restored. The reserves of ATP and creatine phosphate in muscles are also called phosphagens.

Maximum powerThis path is 900-1100 cal/min-kg, which is three times higher than the corresponding indicator for the aerobic path.

Deployment time only 1 2 sec.

Operating time at maximum speedonly 8 10 sec.

The main advantage of the creatine phosphate pathway for ATP formation is

short deployment time (1-2 sec);
high power.

This reaction is the main source of energy for maximum power exercises: sprinting, throwing jumps, lifting a barbell. This reaction can be triggered repeatedly during execution physical exercise, which makes it possible to quickly increase the power of the work performed.

Biochemical assessment of the state of this ATP resynthesis pathway is usually carried out by two indicators: creatine ratio and alactic debt.

Creatine ratioThis is the release of creatine per day. This indicator characterizes the reserves of creatine phosphate in the body.

Alactate oxygen debt this increase in oxygen consumption in the next 4 5 minutes, after performing a short-term exercise of maximum power.This excess oxygen is required to ensure a high rate of tissue respiration immediately after the end of the load to create an increased concentration of ATP in muscle cells. In highly qualified athletes, the value of alactic debt after performing maximum power loads is 8 10 liters.

Glycolytic pathway ATP resynthesis , just like creatine phosphate is an anaerobic pathway. The source of energy necessary for ATP resynthesis in this case is muscle glycogen. During the anaerobic breakdown of glycogen, the terminal glucose residues in the form of glucose-1-phosphate are alternately cleaved from its molecule under the action of the enzyme phosphorylase. Next, glucose-1-phosphate molecules, after a series of sequential reactions, are converted intolactic acid.This process is called glycolysis As a result of glycolysis, intermediate products are formed containing phosphate groups connected by high-energy bonds. This bond is easily transferred to ADP to form ATP. At rest, glycolysis reactions proceed slowly, but with muscular work, its speed can increase 2000 times, and already in the pre-start state.

Maximum power750 850 cal/min-kg, which is two times higher than with tissue respiration. Such high power is explained by the content of a large supply of glycogen in the cells and the presence of a mechanism for activating key enzymes.

Deployment time 20-30 seconds.

Operating time at maximum power 2 -3 minutes.

The glycolytic method of ATP formation has several advantages before the aerobic route:

it reaches maximum power faster,
has a higher maximum power,
does not require the participation of mitochondria and oxygen.

However, this path also has its own flaws :

the process is uneconomical,
the accumulation of lactic acid in the muscles significantly disrupts their normal functioning and contributes to muscle fatigue.

The overall result of glycolysis can be represented in the form of the following equations:

C 6 H 12 O 6 + ADP + 2 H 3 PO 4 C 3 H 6 O 3 + 2 ATP + 2 H 2 O;

Glucose Milk

Acid

[ C 6 H 10 O 5 ] n + 3 ADP + 3 H 3 PO 4 C 3 H 6 O 3 + [ C 6 H 10 O 5 ] n_ 1 + 3 ATP + 2 H 2 O

Glycogen Dairy

Acid

Scheme of anaerobic and aerobic glycolysis

Two biochemical techniques are used to assess glycolysis measurement of lactate concentration in the blood, measurement of the blood hydrogen index and determination of the alkaline reserve of the blood.

The lactate content in urine is also determined. This provides information about the total contribution of glycolysis to providing energy for the exercises performed during training.

Another important indicator islactate oxygen debt.Lactate oxygen debt is an increased oxygen consumption in the next 1 1.5 hours after the end of muscular work. This excess oxygen is necessary to eliminate lactic acid formed during muscle work. In well-trained athletes, the oxygen debt is 20 22 liters. The size of the lactic debt is used to judge the capabilities of a given athlete under submaximal power loads.

4. The relationship between different pathways of ATP resynthesis during muscle work. Zones of relative power of muscle work.

During any muscular work, all three pathways of ATP resynthesis function, but they are turned on sequentially.In the first seconds of work, ATP resynthesis occurs due to the creatine phosphate reaction, then glycolysis turns on and, finally, as work continues, tissue respiration replaces glycolysis.

The specific contribution of each of the mechanisms of ATP formation to the energy supply of muscle movements depends on the intensity and duration of physical activity.

During short-term, but very intense work (for example, running 100 m), the main source of ATP is the creatine kinase reaction. During longer intensive work (for example, at medium distances), most of the ATP is formed through glycolysis. When performing exercises of long duration, but of moderate power, the energy supply to the muscles is carried out mainly due to aerobic oxidation.

Currently, various classifications of muscle work power have been adopted. In sports biochemistry, the classification most often used is based on the fact that power is determined by the relationship between the three main pathways of ATP resynthesis. According to this classification there are four zones of relative power of muscle work:maximum, submaximal, large and moderate.

Maximum powercan develop during work lasting 15 20 seconds. The main source of ATP during this work is creatine phosphate. Only at the very end is the creatine kinase reaction replaced by glycolysis. Examples of physical exercises performed in the maximum power zone are sprinting, long and high jumps, some gymnastic exercises, lifting barbells, and some others. The maximum power during these exercises is denoted asmaximum anaerobic power.

Work in the zone submaximal aerobic powerhas a duration of up to 5 minutes. The leading mechanism of ATP resynthesis is glycolysis. Initially, until the glycolytic reactions reached maximum speed, the formation of ATP occurs due to creatine phosphate, and at the end tissue respiration is included in the process. Work in this zone is characterized by a high oxygen debt of 20-22 liters. An example of physical activity in this power zone is middle-distance running, middle-distance swimming, track cycling, sprint speed skating, etc. Such loads are called lactate.

Work in the zone high power has a maximum duration of up to 30 minutes. Work in this zone is characterized by the same contribution of glycolysis and tissue respiration. The creatine phosphate pathway is involved only at the very beginning of work. Examples of exercises in this zone are 5000 m running, ice skating long distances, ski race, middle-distance swimming, etc. Here, loads are distinguished eitheraerobic-anaerobic, or anaerobic-aerobic.

Work in the temperate zone lasting over 30 minutes occurs predominantly aerobically. This includes marathon running, athletics cross-country, road cycling, race walking, long-distance cross-country skiing, hiking, etc.

In acyclic and situational sports (martial arts, gymnastic exercises, sport games) the power of the work performed changes many times. For example, soccer players alternate running at moderate speed (high power zone) with running short distances at sprint speed (maximum or submaximal power zone). At the same time, football players have periods of play when the power of work decreases to moderate.

When preparing athletes, it is necessary to use training loads that develop the ATP resynthesis pathway, which is the leading one in energy supply for work in the relative power zone characteristic of a given sport.

Topic: BIOCHEMICAL SHIFT DURING MUSCULAR WORK.

1. Basic mechanisms of neurohumoral regulation of muscle activity.

Any physical work is accompanied by changes in the speed of metabolic processes. The necessary restructuring of metabolism during muscle activity occurs under the influence of neurohumoral regulation.

The following mechanisms of neurohumoral regulation of muscle activity can be distinguished:

During muscular work, the tone of the sympathetic division of the autonomic system increases nervous system who is responsible for the work internal organs and muscles.

In the lungs, under the influence of sympathetic impulses, the respiratory rate increases and the bronchi expand. As a result, pulmonary ventilation increases, which leads to improved oxygen supply to the body.

Under the influence of the sympathetic nervous system, the heart rate also increases, which results in an increase in the speed of blood flow and an improvement in the supply of organs, primarily muscles, with oxygen and nutrients.

The sympathetic system increases sweating, thereby improving thermoregulation.

It has a slowing effect on the functioning of the kidneys and intestines. Under the influence of the sympathetic nervous system, fat is mobilized.

Hormones play an equally important role in restructuring the body during muscle work. Adrenal hormones play the greatest role in biochemical changes.

The adrenal medulla producescatecholamines adrenaline and norepinephrine.The release of medulla hormones into the blood occurs during various emotions and stress. The biological role of these hormones is to create optimal conditions for performing muscular work of great power and duration by influencing physiological functions and metabolism.

Once in the blood, catecholamines duplicate the actions of sympathetic impulses. They cause an increase in breathing rate and dilation of the bronchi. Under the influence of adrenaline, the heart rate and strength increase. Under the influence of adrenaline in the body, blood is redistributed in the vascular bed.

In the liver, these hormones cause accelerated breakdown of glycogen. In adipose tissue, catecholamines activate lipases, thereby accelerating the breakdown of fat. In muscles they activate the breakdown of glycogen.

Hormones of the cortical layer are also actively involved in the activation of muscle work. Their effect is that they suppress the action of the enzyme hexokinase, which contributes to the accumulation of glucose in the blood. Since these hormones do not act on nerve cells, this makes it possible to nourish nerve cells, since glucose is practically the only source of energy for them. Hormones glucocorticoids inhibit anabolic processes and, first of all, protein biosynthesis. This makes it possible to use the released ATP molecules for muscle work. In addition, they stimulate the synthesis of glucose from non-carbohydrate substrates.

2. Biochemical changes in skeletal muscles.

When performing physical workprofound changes occur in the muscles, primarily due to the intensity of ATP resynthesis processes.

The use of creatine phosphate as an energy source leads to a decrease in its concentration in muscle cells and the accumulation of creatine in them.

Almost any exercise uses muscle glycogen to produce ATP. Therefore, its concentration in the muscles decreases regardless of the nature of the work. By doing intense loads in the muscles there is a rapid decrease in glycogen reserves and the simultaneous formation and accumulation of lactic acid. Due to the accumulation of lactic acid, the acidity inside muscle cells increases. An increase in lactate content in muscle cells also causes an increase in osmotic pressure in them. An increase in osmotic pressure leads to water entering the muscle cell from the capillaries and intercellular space, and the muscles swell or, as athletes say, “clog.”

Prolonged muscular work of low power causes a gradual decrease in the concentration of glycogen in the muscles. In this case, the breakdown occurs aerobically, with the consumption of oxygen. The end products of this breakdown, carbon dioxide and water, are removed from the muscle cells into the blood. Therefore, after performing work of moderate power, a decrease in glycogen content is detected in the muscles without the accumulation of lactate.

Another important change that occurs in working muscles is an increase in the rate of protein breakdown. The breakdown of proteins is especially accelerated when performing strength exercises, and this primarily affects the contractile proteins of myofibrils. Due to the breakdown of proteins in muscle cells, the content of free amino acids and their breakdown products - keto acids and ammonia - increases.

Another characteristic change caused by muscle activity is a decrease in the activity of muscle cell enzymes. One of the reasons for the decrease in enzymatic activity may be increased acidity caused by the appearance of lactic acid in the muscles.

Finally, muscle activity can lead to damage to intracellular structures such as myofibrils, mitochondria and other biomembranes. Thus, disruption of the membranes of the sarcoplasmic chain leads to disruption of the conduction of nerve impulses to cisterns containing calcium ions. Violations of the integrity of the sarcolemma are accompanied by the loss of many important substances from the muscles, which leave the damaged cell into the lymph and blood. The work of enzymes built into the membranes is also disrupted. The functioning of the calcium pump and tissue respiration enzymes located on the inner surface of mitochondrial membranes is disrupted.

3. Biochemical changes in the brain and myocardium.

Brain. During muscle activityIn the motor neurons of the cerebral cortex, the formation and subsequent transmission of a motor nerve impulse occurs. Both of these processes (formation and transmission of nerve impulses) are carried out with the consumption of energy in the form of ATP molecules. The formation of ATP in nerve cells occurs aerobically. Therefore, during muscle work, the brain's consumption of oxygen from the flowing blood increases. Another feature of energy metabolism in neurons is that the main substrate of oxidation is glucose, which comes with the bloodstream.

Due to this specific energy supply to nerve cells, any disruption in the supply of oxygen or glucose to the brain inevitably leads to a decrease in its functional activity, which in athletes can manifest itself in the form of dizziness or fainting.

Myocardium. During muscle activity, the heart rate increases and increases, which requires a large amount of energy compared to the resting state. However, the energy supply to the heart muscle is carried out mainly through aerobic resynthesis of ATP. Only at a heart rate of more than 200 beats/min does anaerobic ATP synthesis turn on.

The great potential for aerobic energy supply in the myocardium is due to the structural features of this muscle. Unlike skeletal muscles, the myocardium has a more developed and dense network of capillaries, which allows it to extract more oxygen and oxidation substrates from the blood. In addition, cardiac muscle cells contain more mitochondria containing tissue respiration enzymes. Cardiac muscle cells use glucose, fatty acids, ketone bodies, and glycerol as energy sources. The myocardium stores glycogen for a “rainy day” when other energy sources are depleted.

During intense work, accompanied by an increase in the concentration of lactate in the blood, the myocardium extracts lactate from the blood and oxidizes it to carbon dioxide and water.

When one lactic acid molecule is oxidized, up to 18 ATP molecules are synthesized. The ability of the myocardium to oxidize lactate is of great biological importance. This allows the body to maintain the required concentration of glucose in the blood longer, which is very important for the bioenergetics of nerve cells, for which glucose is almost the only substrate of oxidation. Oxidation of lactate in the myocardium also helps to normalize the acid-base balance, since the concentration of this acid in the blood decreases.

4. Biochemical changes in the liver.

During muscle activity, liver functions are activated, aimed primarily at improving the supply of working muscles with extramuscular sources of energy carried by the blood. The most important ones are described belowbiochemical processes occurring in the liver during operation.

1. Under the influence of adrenaline, the rate of breakdown of glycogen increases with the formation of free glucose. The resulting glucose leaves the liver cells into the blood, which leads to an increase in its concentration in the blood. At the same time, glycogen content decreases. The highest rate of glycogen breakdown is observed in the liver at the beginning of work, when glycogen reserves are still large.

2. During physical exercise, liver cells actively extract fat and fatty acids from the blood, the content of which in the blood increases due to the mobilization of fat from fat depots. The fat entering the liver cells is immediately hydrolyzed and converted into glycerol and fatty acids. Fatty acids are then broken down by β-oxidation to acetyl coenzyme A, from which ketone bodies are then formed. Ketone bodies are an important source of energy. With the blood flow they are transferred from the liver to working organs - the myocardium and skeletal muscles. In these organs, ketone bodies are again converted into acetyl coenzyme A, which is immediately aerobically oxidized in the tricarboxylic acid cycle to carbon dioxide and water, releasing a large amount of energy.

3. Another biochemical process that occurs in the liver during muscular work is the formation of glucose from glycerol, amino acids, and lactate. This process involves the expenditure of energy from ATP molecules. Typically, such glucose synthesis occurs during prolonged work, leading to a decrease in the concentration of glucose in the bloodstream. Thanks to this process, the body manages to maintain the required level of glucose in the blood.

4. During physical work, the breakdown of muscle proteins increases, leading to the formation of free amino acids, which are further deaminated, releasing ammonia. Ammonia is a cellular poison; its neutralization occurs in the liver, where it is converted into urea. The synthesis of urea requires a significant amount of energy. Under debilitating loads that do not correspond to the functional state of the body, the liver may not cope with the neutralization of ammonia, in which case the body becomes intoxicated with this poison, leading to a decrease in performance.

5. Biochemical changes in the blood.

Changes in the chemical composition of the blood are a reflection of the biochemical changes that occur during muscular activity in various internal organs, skeletal muscles and myocardium.

Biochemical changes that occur in the blood largely depend on the nature of the work, so their analysis should be carried out taking into account the power and duration of physical activity.

When performing muscular work, the following changes are most often found in the blood.

1. Changes in the concentration of proteins in the blood plasma. There are two reasons for this. Firstly, increased sweating leads to a decrease in the water content in the blood plasma and, consequently, to its thickening. This causes an increase in the concentration of substances contained in the plasma. Secondly, due to damage to cell membranes, intracellular proteins are released into the blood plasma. In this case, part of the proteins in the bloodstream passes into the urine, and the other part is used as energy sources.

2. The change in blood glucose concentration during work goes through a number of phases. At the very beginning of work, the glucose level increases. Glucose leaves the liver, where it is formed from glycogen. In addition, muscles that have glycogen reserves do not urgently need glucose from the blood at this stage. But then there comes a stage when the glycogen in the liver and muscles runs out. Then comes the next phase, when blood glucose is used to extract energy. Well, at the end of the work, a phase of exhaustion begins and, as a result, hypoglycemia decrease in the concentration of glucose in the blood.

3. An increase in the concentration of lactate in the blood is observed at almost any sports activities, but the degree of lactate accumulation largely depends on the nature of the work performed and the athlete’s training. The greatest increase in the level of lactic acid in the blood is observed when performing physical activity in the submaximal power zone. Since in this case the main source of energy for working muscles is anaerobic glycolysis, leading to the formation and accumulation of lactate.

It should be remembered that lactate accumulation does not occur immediately, but several minutes after finishing work. Therefore, measurement of lactate level should be carried out 5 7 minutes after finishing work. If the lactate level at rest does not exceed 1 2 mmol/l, then in highly trained athletes after training it can reach 20 30 mmol/l.

4. Hydrogen index (pH). When performing exercises of submaximal power, the pH level can decrease quite significantly (by 0.5 units)

5. Physical exercise is accompanied by an increase in the concentration of free fatty acids and ketone bodies in the blood. This is due to the mobilization of fat in the liver and the release of the products of this process into the blood.

6. Urea. During short-term work, the concentration of urea in the blood changes slightly; during long-term work, the level of urea increases several times. This is due to increased protein metabolism during exercise.

6. Biochemical changes in urine.

Physical exercise affects the physicochemical properties of urine, changes in which are explained by significant shifts in the chemical composition of urine.

Substances that are usually absent appear in the urine. These substances are calledpathological components.Athletes experience the following pathological components after hard work.

1. Protein. Usually there is no more than 100 mg of protein in the urine. After exercise, there is a significant amount of protein excreted in the urine. This phenomenon is called proteinuria. The heavier the load, the higher the protein content. The cause of this phenomenon may be damage to the kidney membranes.However, reducing the load completely restores the normal composition of urine.

2. Glucose. At rest, there is no glucose in the urine. After completing a workout, glucose is often found in the urine. This is due to two main reasons. First, excess glucose in the blood during physical activity. Secondly, disruption of the renal membranes causes disruption of the reabsorption process.

3. Ketone bodies. Before work, ketone bodies are not detected in the urine. After exercise, ketone bodies can be excreted in the urine in large quantities. This phenomenon is called ketonuria. It is associated with an increase in the concentration of ketone bodies in the blood and an increase in their reabsorption by the kidneys.

4. Lactate. The appearance of lactic acid in the urine is usually observed after exercise involving submaximal power exercises. By the release of lactate in the urine, one can judge the overall contribution of glycolysis to the energy supply of all the work performed by the athlete during training.

Along with the effect on the chemical composition of urine, physical activity also changes the physicochemical properties of urine.

Density. Urine volume tends to be smaller after exercise because most of the water is lost through sweat. This affects the density of urine, which increases. An increase in urine density is also associated with the appearance of substances in it that are usually absent in urine.

Acidity. Ketone bodies and lactic acid excreted in the urine change its acidity. Typically, urine pH is 5 6 units. After work it can drop to 4 4.5 units.

The more intense the physical activity, the morechanges observed in the composition of urine and blood are more significant.

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Aerobic pathway for ATP resynthesis

The aerobic pathway of ATP resynthesis is the main, basic method of ATP formation that occurs in the mitochondria of muscle cells. During tissue respiration, two hydrogen atoms are removed from the oxidized substance and transferred through the respiratory chain to molecular oxygen - 02, delivered by the blood to the muscles from the air, resulting in the formation of water. Due to the energy released during the formation of water, ATP is synthesized from ADP and phosphoric acid. Typically, for every water molecule formed, three ATP molecules are synthesized.

In a simplified form, aerobic ATP resynthesis can be represented by the following diagram:

Most often, hydrogen is taken away from intermediate products of the tricarboxylic acid cycle - the Krebs cycle. The Krebs cycle is the final stage of catabolism, during which acetyl coenzyme A is oxidized to CO2 and H20. During this process, 4 pairs of hydrogen atoms are removed from the acids listed above and therefore 12 ATP molecules are formed during the oxidation of one molecule of acetyl coenzyme A.

In turn, acetyl-CoA can be formed from carbohydrates, fats and amino acids, i.e. Through acetyl-CoA, carbohydrates, fats and amino acids are involved in the Krebs cycle:

The rate of the aerobic pathway of ATP resynthesis is controlled by the content of ADP in muscle cells, which is an activator of tissue respiration enzymes. At rest, when there is almost no ADP in the cells, tissue respiration occurs at a very low rate. During muscle work, due to the intensive use of ATP, the formation and accumulation of ADP occurs. The resulting excess ADP accelerates tissue respiration, and it can reach maximum intensity.

Another activator of the aerobic pathway of ATP resynthesis is CO2. Carbon dioxide produced in excess during physical work activates the respiratory center of the brain, which ultimately leads to an increase in blood circulation and improved oxygen supply to muscles.

The aerobic pathway of ATP formation is characterized by the following criteria.

The maximum power is 350-450 cal/min-kg. Compared to anaerobic pathways of ATP resynthesis, tissue respiration has the lowest maximum power. This is due to the fact that the capabilities of the aerobic process are limited by the delivery of oxygen to mitochondria and their quantity in muscle cells. Therefore, due to the aerobic pathway of ATP resynthesis, it is possible to perform physical activity of only moderate intensity.

Deployment time - 3-4 minutes. Such a long deployment time is explained by the fact that in order to ensure the maximum rate of tissue respiration, a restructuring of all body systems involved in the delivery of oxygen to muscle mitochondria is necessary.

Operating time at maximum power is tens of minutes. As already indicated, the energy sources for aerobic resynthesis of ATP are carbohydrates, fats and amino acids, the breakdown of which is completed by the Krebs cycle. Moreover, for this purpose, not only intramuscular reserves of these substances are used, but also carbohydrates, fats, ketone bodies and amino acids delivered by blood to the muscles during physical work. In this regard, this ATP resynthesis pathway functions at maximum capacity for such a long time.

Compared to other ATP resynthesis processes occurring in muscle cells, aerobic resynthesis has a number of advantages. It is highly economical: during this process there is a deep decomposition of oxidized substances to the final products - CO2 and H20 and therefore a large amount of energy is released. For example, during the aerobic oxidation of muscle glycogen, 39 ATP molecules are formed per each glucose molecule split off from glycogen, while during the anaerobic breakdown of this carbohydrate, only 3 ATP molecules are synthesized per one glucose molecule. Another advantage of this resynthesis route is its versatility in the use of substrates. During aerobic resynthesis of ATP, all the main organic substances of the body are oxidized: amino acids, carbohydrates, fatty acids, ketone bodies, etc. Another advantage of this method of ATP formation is the very long duration of its work: practically it functions constantly throughout life. At rest, the rate of aerobic resynthesis of ATP is low; during physical exercise, its power can reach its maximum.

However, the aerobic method of ATP formation also has a number of disadvantages. Thus, the effect of this method is associated with the mandatory consumption of oxygen, the delivery of which to the muscles is ensured by the respiratory and cardiovascular systems. The functional state of the cardiorespiratory system is the limiting factor that limits the duration of operation of the aerobic pathway of ATP resynthesis with maximum power and the value of the maximum power.

The possibilities of the aerobic pathway are also limited by the fact that all enzymes of tissue respiration are built into the inner membrane of mitochondria in the form of respiratory ensembles and function only ffPH in the presence of an intact membrane. Any factors influencing the state and properties of membranes disrupt the formation of ATP in an aerobic manner. For example, disturbances in oxidative phosphorylation are observed during acidosis, swelling of mitochondria, and during the development in muscle cells of free radical oxidation of lipids that are part of mitochondrial membranes.

Another disadvantage of aerobic ATP formation can be considered the long deployment time and small maximum power in absolute value. Therefore, muscle activity, characteristic of most sports, cannot be fully ensured by this way of ATP resynthesis, and muscles are forced to additionally include anaerobic methods of ATP formation, which have a shorter deployment time and greater maximum power.

In sports practice, three indicators are often used to assess aerobic phosphorylation: maximum oxygen consumption, anaerobic metabolism threshold and oxygen supply.

MOC is the maximum possible rate of oxygen consumption by the body when performing physical work. This indicator characterizes the maximum power of the aerobic pathway of ATP resynthesis: the higher the MIC value, the greater the value of the maximum rate of tissue respiration, this is due to the fact that almost all the oxygen entering the body is used in this process. MIC is an integral indicator that depends on many factors: on the functional state of the cardiorespiratory system, on the content of hemoglobin in the blood, and myoglobin in the muscles, on the number and size of mitochondria. In untrained young people, MOC is usually 3-4 l/min, in athletes high class performing aerobic exercise, MPC - 6-7 l/min. In practice, to exclude the influence of body weight on this value, MIC is calculated per kg of body weight. In this case, in young people who are not involved in sports, the MOC is 40-50 ml/min-kg, and in well-trained athletes it is 80-90 ml/min-kg.

In sports practice, MOC is also used to characterize the relative power of aerobic work, which is expressed by oxygen consumption as a percentage of MOC. For example, the relative power of work performed with an oxygen consumption of 3 l/min by an athlete with a VO2 max of 6 l/min will be 50% of the VO2 max level. PANO is the minimum relative power of work, measured by oxygen consumption as a percentage relative to MIC, at which the glycolytic pathway of ATP resynthesis begins to turn on. in untrained people, PANO is 40-50% of MOC, and in athletes, PANO can reach 70% of MOC. Higher values of PANO in trained people are explained by the fact that aerobic phosphorylation in them produces more ATP per unit time, and therefore the anaerobic pathway of ATP formation - glycolysis - is turned on at high loads. Oxygen intake is the amount of oxygen used during a given load to ensure aerobic resynthesis of ATP. Oxygen supply characterizes the contribution of tissue respiration to the energy supply of the work done.

Under the influence of systematic training aimed at developing aerobic performance, the number of mitochondria in myocytes increases, their size increases, and they contain more tissue respiration enzymes. At the same time, the oxygen transport function is improved: the content of myoglobin in muscle cells and hemoglobin in the blood increases, the performance of the respiratory and cardiovascular systems of the body increases.

Anaerobic pathways for ATP resynthesis

Anaerobic pathways for ATP resynthesis are additional ways of producing ATP in cases where the main pathway for producing ATP - aerobic - cannot provide muscle activity with the required amount of energy. This happens in the first minutes of any work, when tissue respiration has not yet fully developed, as well as when performing high-power physical activity.

Creatine phosphate pathway for ATP resynthesis (opheatin kinase, alactate)

Muscle cells always contain creatine phosphate, a compound containing a phosphate group linked to the creatine residue by a macroenergetic bond. The content of creatine phosphate in muscles at rest is 15-20 mmol/kg. Creatine phosphate has a large energy reserve and high affinity for ADP. Therefore, it easily interacts with ADP molecules that appear in muscle cells during physical work as a result of ATP hydrolysis. During this reaction, a phosphoric acid residue with a reserve of energy is transferred from creatine phosphate to an ADP molecule with the formation of creatine and ATP:

This reaction is catalyzed by the enzyme creatine kinase. In this regard, this pathway of ATP resynthesis is also called creatine kinase.

The creatine phosphate reaction is reversible, but its equilibrium is shifted towards the formation of ATP, and therefore it begins to occur as soon as the first portions of ADP appear in myocytes.

During muscular work, the activity of creatine kinase increases significantly due to the activating effect of calcium ions on it, the concentration of which in the sarcoplasm under the influence of a nerve impulse increases almost 1000 times. Another mechanism for regulating the creatine phosphate reaction is associated with the activating effect of creatine formed during this reaction on creatine kinase. Due to these mechanisms, the activity of creatine kinase at the beginning of muscle work increases sharply and the creatine phosphate reaction very quickly reaches its maximum speed.

Creatine phosphate, having a large supply of chemical energy, is a fragile substance. Phosphoric acid can easily be split off from it, resulting in cyclization of the creatine residue, leading to the formation of creatinine:

The formation of creatinine occurs spontaneously without the participation of enzymes. This reaction is irreversible. The resulting creatinine is not used in the body and is excreted in the urine. Therefore, by the excretion of creaquinine in the urine, one can judge the content of creatine phosphate in the muscles, since they contain the main reserves of this compound.

Creatine phosphate synthesis in muscle cells occurs during rest through the interaction of creatine with excess ATP:

Creatine phosphate reserves can be partially restored during muscular work of moderate power, during which ATP is synthesized due to tissue respiration in such an amount that is sufficient to ensure the contractile function of myocytes and to replenish creatine phosphate reserves. Therefore, during physical work, the creatine phosphate reaction can be turned on many times.

The total reserves of ATP and creatine phosphate are often referred to as phosphagens.

Creatine is formed in the liver using three amino acids: glycine, methionine and arginine. In sports practice, glycine and methionine preparations are used as food additives to increase the concentration of creatine phosphate in muscles.

The creatine phosphate pathway of ATP resynthesis is characterized by the following values of accepted quantitative criteria:

The maximum power is 900-1100 cal/min-kg, which is three times higher than the corresponding figure for aerobic resynthesis. This large value is due to the high activity of the creatine kinase enzyme and, therefore, the very high rate of the creatine phosphate reaction.

Deployment time is only 1-2 s. As already indicated, the initial reserves of ATP in muscle cells are sufficient to ensure muscle activity for just 1-2 s, and by the time they are exhausted, the creatine phosphate pathway for ATP formation is already functioning at its maximum speed. This short deployment time is explained by the action of the mechanisms described above for regulating the activity of creatine kinase, which make it possible to sharply increase the rate of this reaction.

The operating time at maximum speed is only 8-10 s, which is due to the small initial reserves of creatine phosphate in the muscles.

The main advantages of the creatine phosphate pathway for ATP formation are a very short deployment time and high power, which is extremely important for speed-strength sports. The main disadvantage of this method of ATP synthesis, which significantly limits its capabilities, is the short time of its operation. The time to maintain maximum speed is only 8-10 s; by the end of the 30th s, its speed is halved. And by the end of the 3rd minute of intense work, the creatine phosphate reaction in the muscles practically stops.

Based on this characteristic of the creatine phosphate pathway for ATP resynthesis, it should be expected that this reaction will be the main source of energy to provide short-term exercises of maximum power: sprinting, jumping, throwing, lifting weights, etc. The creatine phosphate reaction can be turned on repeatedly during physical activity, which makes it possible to quickly increase the power of the work performed, develop acceleration over a distance and the finishing jerk.

Biochemical assessment of the state of the creatine phosphate pathway for ATP resynthesis is usually carried out using two indicators: creatinine coefficient and alactic oxygen debt.

Creatinine ratio is the excretion of creatinine in urine per day per 1 kg of body weight. In men, creatinine excretion ranges from 18-32 mg/day-kg, and in women - 10-25 mg/day-kg. The creatinine coefficient characterizes the reserves of creatine phosphate in the muscles, since there is a linear relationship between the content of creatine phosphate and the formation of creatinine from it, since this conversion occurs non-enzymatically and is irreversible. Therefore, using the creatinine coefficient, it is possible to assess the potential of this ATP production pathway, including its metabolic capacity.

Alactate oxygen debt is an increased oxygen consumption in the next 4-5 minutes after performing a short-term exercise of maximum power. This excess oxygen is required to ensure a high rate of tissue respiration immediately after the end of the load to create an increased concentration of ATP in muscle cells. Under these conditions, creatine is phosphorylated to form creatine phosphate:

Thus, the use of creatine phosphate during work leads to the accumulation of creatine, the conversion of which back into creatine phosphate requires a certain amount of oxygen. It follows that the alactic oxygen debt characterizes the contribution of the creatine phosphate pathway of ATP resynthesis to the energy supply of the performed work. physical activity and provides an estimate of its metabolic capacity. An idea of the power of this method of ATP formation is given by the indicator obtained by dividing the amount of alactic debt by the time the load is performed.

In qualified athletes, the value of alactic oxygen debt after maximum power loads is usually 8-10 liters.

As a result of systematic training aimed at developing speed-strength qualities, the concentration of creatine phosphate in the muscles increases and the activity of creatine kinase increases, which is reflected in an increase in the amount of alactic oxygen debt and daily creatinine excretion.

Glycolytic pathway for ATP resynthesis

This resynthesis pathway, like the creatine phosphate one, belongs to the anaerobic methods of ATP formation. The source of energy necessary for ATP resynthesis in this case is muscle glycogen, the concentration of which in the sarcoplasm ranges from 0.2-3%. During the anaerobic breakdown of glycogen, the terminal glucose residues in the form of glucose-1-phosphate are alternately cleaved from its molecule under the influence of the enzyme phosphorylase. Next, the glucose-1-phosphate molecules through a series of successive stages are converted into lactic acid, which in its chemical composition is like half of a glucose molecule. During the anaerobic breakdown of glycogen to lactic acid, called glycolysis, intermediate products are formed containing a phosphate group with a high-energy bond, which is easily transferred to ADP to form ATP.

The final equation for the anaerobic breakdown of glycogen is as follows:

All glycolytic enzymes are found in the sarcoplasm of muscle cells.

Glucose entering the muscles from the bloodstream can also undergo glycolysis. Anaerobic breakdown of glucose proceeds according to the Equation:

Regulation of the rate of glycolysis is carried out by changing the activity of two enzymes: phosphorylase and phosphofructokinase. Phosphorylase catalyzes the first reaction of glycogen breakdown - the cleavage of glucose-1-phosphate from it. This enzyme is activated by adrenaline, AMP and calcium ions, and inhibited by glucose-6-phosphate and excess ATP. The second regulatory enzyme of glycolysis, phosphofructokinase, is activated by ADP and especially AMP, and inhibited by excess ATP and citric acid. The presence of such regulatory mechanisms leads to the fact that at rest glycolysis proceeds very slowly; with intense muscular work, its rate increases sharply and can increase compared to the resting level by almost 2000 times, and an increase in the rate of glycolysis can be observed already in the pre-start state due to the release of adrenaline.

Quantitative criteria for the glycolytic pathway of ATP resynthesis:

The maximum power is 750-850 cal/min-kg, which is approximately twice the corresponding rate of tissue respiration. The high value of the maximum power of glycolysis is explained by the content of a large supply of glycogen in muscle cells, the presence of mechanisms for activating key enzymes, leading to a significant increase in the rate of glycolysis, and the lack of oxygen requirement.

Deployment time - 20-30 s. This is due to the fact that all participants in glycolysis are located in the sarcoplasm of myocytes, as well as the possibility of activation of glycolytic enzymes. As already noted, phosphorylase, the enzyme that triggers glycolysis, is activated by adrenaline, which is released into the blood immediately before work begins. Calcium ions, the concentration of which in the sarcoplasm increases approximately 1000 times under the influence of a motor nerve impulse, are also powerful activators of phosphorylase.

Operating time with maximum power is 2-3 minutes. There are two main reasons for such a small value of this criterion. Firstly, glycolysis occurs at a high rate, which quickly leads to a decrease in the concentration of glycogen in the muscles and, consequently, to a subsequent decrease in the rate of its breakdown. Secondly, the process of glycolysis produces lactic acid, the accumulation of which leads to increased acidity inside muscle cells. Under conditions of increased acidity, the catalytic activity of enzymes, including glycolytic enzymes, decreases, which also leads to a decrease in the rate of this ATP resynthesis pathway.

The glycolytic method of ATP formation has a number of advantages over the aerobic way. It reaches maximum power faster, has a higher maximum power and does not require the participation of mitochondria and oxygen.

However, this path also has significant drawbacks. This process is not economical. The breakdown of one glucose residue cleaved from glycogen to lactate produces only 3 ATP molecules, while the aerobic oxidation of glycogen to water and carbon dioxide produces 39 ATP molecules per glucose residue. This inefficiency, combined with high speed, quickly leads to the depletion of glycogen stores.

Another serious drawback of the glycolytic pathway of ATP resynthesis is the formation and accumulation of lactate, which is the end product of this process. Increased lactate concentration in muscle fibers causes a pH shift to the acidic side, while conformational changes occur in muscle proteins, leading to a decrease in their functional activity. Thus, the accumulation of lactic acid in muscle cells significantly disrupts their normal functioning and leads to the development of fatigue.

With a decrease in the intensity of physical work, as well as during rest periods during training, the resulting lactate can partially leave the muscle cells into the lymph or blood, which makes it possible to restart glycolysis.

Currently known biochemical methods for assessing the use of the glycolytic pathway of ATP resynthesis during physical work are based on the assessment of biochemical changes in the body caused by the accumulation of lactic acid. This is primarily the determination of the concentration of lactate in the blood after physical exercise. At rest, i.e. before starting work, the lactate concentration in the blood is usually 1-2 mmol/l. After intense short-term exercise, the concentration of lactic acid in the blood increases sharply and can reach 18-20 mmol/l, and in athletes highly qualified even greater values. Another indicator reflecting the accumulation of lactic acid in the bloodstream is the blood pH value. At rest, this figure is 7.36-7.40, after intense work it decreases to 7.2-7.0, and an even more significant decrease in pH is noted in the literature - to 6.8. The greatest changes in lactate concentration and blood pH observed after exercise “to failure” in the zone of submaximal power characterize the metabolic capacity of glycolysis. The maximum power of glycolytic resynthesis of ATP can be assessed by the rate of increase in the concentration of lactate in the blood or by the rate of decrease in pH.

Another method for assessing the rate of glycolysis, which records the consequences of the formation and accumulation of lactic acid, is the determination of the alkaline reserve of the blood. Alkaline blood reserve is the alkaline components of all blood buffer systems. When lactic acid enters the blood during muscular work, it is first neutralized by interacting with the blood buffer systems, and therefore the alkaline reserve of the blood decreases.

The contribution of glycolysis to the energy supply of physical work performed can also be assessed by determining lactate in urine. At rest, there is practically no lactate in the urine. After exercise, especially intense exercise, large amounts of lactic acid are excreted in the urine. It should be taken into account that during training, glycolysis is turned on many times and therefore urine analysis provides information about the total contribution of the glycolytic resynthesis pathway to providing energy for all loads performed during training.

Along with the study of blood and urine, determination of lactate oxygen debt can also be used to assess the glycolytic pathway of resynthesis. Lactate oxygen debt is an increased oxygen consumption in the next 1-1.5 hours after the end of muscular work. This excess oxygen is necessary to eliminate lactic acid formed during work. The largest values of lactate oxygen debt are determined after physical activity lasting 2-3 minutes, performed with maximum intensity. In well-trained athletes, the lactate oxygen debt can reach 20 liters.

The magnitude of the lactate oxygen debt can be used to judge the capabilities of the glycolytic pathway for ATP resynthesis. Thus, the value of lactate debt indicates the metabolic capacity of glycolysis, and its maximum power can be assessed by the ratio of the value of lactate debt to the time of performing the maximum load of submaximal power.

As a result of systematic training using submaximal loads, the concentration of glycogen in muscle cells increases and the activity of glycolytic enzymes increases. Highly trained athletes develop tissue and blood resistance to a decrease in pH, and therefore they can relatively easily tolerate a shift in blood pH to 70 and below.

Adenylate kinase reaction

The adenylate kinase reaction occurs in muscle cells under conditions of significant accumulation of ADP in them, which is usually observed with the onset of fatigue. The adenylate kinase reaction is accelerated by the enzyme adenylate kinase, which is located in the sarcoplasm of myocytes. During this reaction, one ADP molecule transfers its phosphate group to another ADP, resulting in the formation of ATP and AMP:

For a long time, this pathway of ATP formation was considered as an emergency mechanism that ensures the synthesis of ATP in conditions when other methods of producing ATP become ineffective. In addition, it was believed that the adenylate kinase reaction leads to a decrease in the total amount of adenyl nucleotides in myocytes, since the AMP formed in this reaction can be deaminated and converted into inosinic acid:

However, at present, this reaction is assigned not an energetic, but a regulatory role. This is due to the fact that AMP is a powerful activator of carbohydrate breakdown enzymes - phosphorylase and phosphofructokinase, which are involved both in the anaerobic breakdown of glycogen and glucose to lactic acid, and in their aerobic oxidation to water and carbon dioxide. It also turned out that the conversion of AMP to inosinic acid has a positive effect on muscle activity. The ammonia formed as a result of deamination can neutralize lactic acid and thereby prevent the onset of changes in myocytes associated with its accumulation. At the same time, the total content of adenyl nucleotides in cells does not change, since inosinic acid, when interacting with one of the amino acids - aspartic acid, is again converted into AMP.

In table The values of the criteria for the ATP Resynthesis pathways described above are given. Quantitative criteria for the main pathways of ATP resynthesis:

The relationship between different pathways of ATP resynthesis during muscle work

During any muscular work, all three pathways of ATP resynthesis function, but they are turned on sequentially. In the first seconds of work, ATP resynthesis occurs due to the creatine phosphate reaction, then glycolysis turns on and, finally, as work continues, tissue respiration replaces glycolysis.

Inclusion of ATP resynthesis pathways during physical work

The figure shows that the transition of energy supply to muscle activity from anaerobic to aerobic pathways leads to a decrease in the total production of ATP per unit of time, which is reflected in a decrease in the power of the work performed.

The specific contribution of each of the mechanisms of ATP formation to the energy supply of muscle movements depends on the intensity and duration of physical activity.

During short-term, but very intense work, the main source of ATP is the creatine kinase reaction; during longer intensive work, most of the ATP is formed through the glycolytic pathway. When performing exercises of long duration, but of moderate power, the energy supply to the muscles is carried out mainly due to aerobic oxidation.

Zones of relative power of muscle work

Currently, various classifications of muscle activity power have been adopted. One of them is the B.C. classification. Farfel, based on the position that the power of physical activity performed is determined by the relationship between the three main pathways of ATP resynthesis functioning in the muscles during work. According to this classification, four zones of relative power of muscle work are distinguished: maximum, submaximal, large and moderate power.

Work in the maximum power zone can continue for 15-20 s. The main source of ATP under these conditions is creatine phosphate. Only at the end of the work is the creatine phosphate reaction replaced by glycolysis. An example of physical exercises performed in the maximum power zone is sprinting, long and high jumps, some gymnastic exercises, lifting barbells, etc.

Work in the submaximal power zone lasts up to 5 minutes. The leading mechanism of ATP resynthesis is glycolytic. At the beginning of work, until glycolysis has reached its maximum speed, the formation of ATP occurs due to creatine phosphate, and at the end of work, glycolysis begins to be replaced by tissue respiration. Work in the submaximal power zone is characterized by the highest oxygen debt - Up to 20 liters. Examples of physical activities in this power zone include middle-distance running, short-distance swimming, track cycling, and ice skating. sprint distances and etc.

Work in a high power zone has a maximum duration of up to 30 minutes. Work in this zone is characterized by approximately equal contributions from glycolysis and tissue respiration. The creatine phosphate pathway of ATP resynthesis functions only at the very beginning of work, and therefore its share in the total energy supply of this work is small. An example of exercises in this power zone is running at 5000 centimeters, skating for stayer distances, cross-country skiing, middle and long distance swimming, etc.

Work in the moderate power zone continues for over 30 minutes. Energy supply to muscle activity occurs predominantly aerobically. An example of such power is marathon running, athletics cross-country, race walking, road cycling, long-distance cross-country skiing, hiking, etc.

In acyclic and situational sports, the power of the work performed changes many times. So, a football player alternates running at a moderate speed with running short distances at a sprint speed; You can also find segments of the game when the power of work is significantly reduced. Such examples can be given in relation to many other sports.

Attention is the problem. Checking the presence of medicinal substances in the human body while performing work

Selecting sports and physical exercise systems for active recreation

In a simplified form, aerobic ATP resynthesis can be represented by the following diagram:

In turn, acetyl-CoA can be formed from carbohydrates, fats and amino acids, i.e. Through acetyl-CoA, carbohydrates, fats and amino acids are involved in the Krebs cycle:

The aerobic pathway of ATP formation is characterized by the following criteria.

In sports practice, three indicators are often used to assess aerobic phosphorylation: maximum oxygen consumption, anaerobic metabolism threshold and oxygen supply.

MOC is the maximum possible rate of oxygen consumption by the body when performing physical work. This indicator characterizes the maximum power of the aerobic pathway of ATP resynthesis: the higher the MIC value, the greater the value of the maximum rate of tissue respiration, this is due to the fact that almost all the oxygen entering the body is used in this process. MIC is an integral indicator that depends on many factors: on the functional state of the cardiorespiratory system, on the content of hemoglobin in the blood, and myoglobin in the muscles, on the number and size of mitochondria. In untrained young people, the VO2 max is usually 3-4 l/min, in high-class athletes performing aerobic exercise, the VO2 max is 6-7 l/min. In practice, to exclude the influence of body weight on this value, MIC is calculated per kg of body weight. In this case, in young people who are not involved in sports, the MOC is 40-50 ml/min-kg, and in well-trained athletes it is 80-90 ml/min-kg.

A person, in order to constantly maintain the performance and vital activity of muscle tissue.

The release of necessary elements and acids during resynthesis makes it possible, for example, for athletes, to keep muscle tissue in tension for a long period.

While at rest, in order to maintain its condition and current metabolic processes, muscles need constant resynthesis of ATP and the production of the corresponding ones.

The mechanism of adenosine triphosphate formation is a process that must constantly occur in the human body to ensure muscle performance at rest. At the same time, their consumption of adenophosphates increases at the moment when muscle contraction occurs.

ATP resynthesis supplies tissues with the necessary energy for performance and the actomyosin complex of elements, and in the active state provides them with the necessary amount of calcium ions.

To achieve this, the amount of adenositrophosphorus in muscle tissue is constantly restored. In this case, the efficiency of restoration is equal to the time of consumption; this process occurs due to certain biochemical mechanisms of resynthesis.

Elements that act as sources of ongoing APT resynthesis in the body can be the “backbone” muscles and some other tissues. It is these energy sources that are rich in phosphate-containing elements:

Creatine phosphate
Adenosine phosphate

In addition, in the process of catabolism, the following are formed:

Glycogen
Energy components

As a result of the oxidation process in an aerobic environment, gradient elements appear in the body. Approximately 0.20% of ATP is located in the muscles, while the concentration value “%” increases and the myosin mass is suppressed, as a result of which the occurrence of muscle adhesions is ensured.

But the concentration of ATP in the muscles should not decrease, less than 0.1%, otherwise the muscles will contract until they are completely exhausted. This is ensured due to the fact that at this moment calcium in the sarcoplasmic reticulum stops working.

If the muscle is depleted, rigora begins to develop, i.e., a systemic, persistent contraction.

Anaerobic and aerobic processes of resynthesis in muscles

ATP resynthesis is a reaction under conditions of aerobic and anaerobic mechanisms.

The course of the reaction, during the active period, can occur, as a result of the reaction, in the presence of anaerobic conditions.

Anaerobic resynthesis processes occur without the participation of oxygen, subject to the presence of oxygen - the reaction is called aerobic.

At constant rates, ATP resynthesis occurs with the participation of oxygen, therefore, an aerobic process is observed.

Due to intense physical labor, the process of ATP resynthesis does not occur, since oxygen access to the muscles is excluded. In the “backbone” muscles, only three anaerobic and one aerobic are observed - the reduction of adenosine triphosphate.

Such a process includes mechanisms such as:

Creatine phosphokinase
Alactate
Lactated
Myokinase

The aerobic process itself includes the course of oxidative phosphation, and the number of mitochondria increases significantly. During aerobic oxidation, the production of an energy substrate is observed:

Glucose
Fatty acid
Some amino acids
Lactic acid
Ketone bodies

The aerobic mechanism, or as it is also called the acid mechanism, is an important process for athletes, as it provides speed and endurance. It is the aerobic reaction that can maintain constant tension over a long period of time.

Oxygen reactions in muscles provide energy for their performance, mainly due to the chemical interaction of nutrients such as fats and carbohydrates directly with oxygen. All the necessary components enter the athlete’s body along with food and accumulate in storage until they are needed.

For example, sugar and starch, which act as carbohydrates, form the element glycogen. On average, in the human body, glycogen can provide submaximal performance for up to 70-80 minutes. But at the same time, the level of fat in the body is never exhausted.

Namely, carbohydrates are the most energy suppliers for the body when compared to fats.

This is due to the fact that with the same consumption, 10% less oxygen is required for their oxidation. This fact is very relevant for situations with a lack of oxygen during severe physical exertion.

Due to the fact that the reserves of carbohydrates in the body tend to be depleted over time, the endurance and achievements (capabilities) of athletes decrease. After all reserves have been exhausted, fats join the maintenance process and fuel uninterrupted performance.

Actually, the contribution of components such as fats and carbohydrates to providing muscles with energy directly depends on performance and the level of energy expended.

But, at the same intensity of exercise, under conditions of an aerobic reaction, the body will consume less carbohydrates and a higher level of fat. This rule mainly applies to athletes, since their muscles are systematically exposed to stress when compared with untrained people.

Thus, we can conclude that a person with trained muscles expends much less energy, since he has large amounts of carbohydrates in his body.

The oxygen system can produce as much oxygen as the body can consume, and the higher the level of oxygen consumed when performing strenuous work, the more efficiency increases. In comparison with the analogue reactions occurring, the processes of ATP resynthesis, it is the aerobic mechanism that is characterized by great advantages:

High level of efficiency, since 30 ATP molecules are produced from one molecule, compared to the anaerobic process, in which only 3 molecules are formed.
Multifunctionality, since amino acids, carbohydrates, ketone bodies, etc. act as energy components.
The duration of the process is significantly longer, since at the moment of rest, AT resynthesis is relatively small, but with increasing loads, it instantly grows to its maximum value.

But, despite obvious advantages, the aerobic process is also characterized by some disadvantages:

The constant consumption of oxygen molecules significantly limits the speed of its passage to the muscles and the process of its absorption through the mitochondrial membrane.
Large deployment rate over time.
Minimum maximum power.

Certain processes occur in muscles during the resynthesis of APT. The most important and fastest is the creatine kinase reaction, which produces phosphoryl elements when ATP is depleted.

In an environment with a low acidity level, the activation of respiration elements mainly occurs and at the same time, inhibition of enzymes responsible for the work of muscle tissue and ATP resynthesis reactions occurs. At the very beginning of the process, ATP is transferred into the intermembrane space using the inner membrane.

At this point, ATP resynthesis is the link between creatine entering from crane kinase. It is this interaction that promotes metochondrial creatine kinase, which is located in the mitochondrial membrane and thereby produces creatinosphate.

Thus, the emerging element again enters the sarcoplasm, in which it rejects the remainder of the phosphorus elements from ATP to sarcoplasmic ADP.

The maximum period of the process does not exceed 30 seconds, and maximum power is achieved in 2 minutes.
This method is characterized by advantages in comparison with analogues:

Maximum power achieved much faster
The maximum power indicator is much greater than that of the aerobic method
Occurs without the need to use oxygen and mitochondria

Although, even the glycolytic method has a number of disadvantages:

The mechanism has a low efficiency indicator
A large accumulation of acid in the muscles can interfere with their normal functioning and even stimulate muscle fatigue.

The myokinase mechanism occurs when there is a large amount of ADP in the sarcoplasm and appears as an auxiliary method, under conditions that other possibilities have already exhausted themselves and in this moment are already close to this figure.

Myokinase in tissues most often occurs with a significant increase in the level of ADP.

Basically, this situation can occur with severe muscle fatigue.

In this word, we can say that the aerobic and anaerobic reactions that occur provide the high required level of energy.

General indicators and energy capabilities of ongoing reactions

ATP resynthesis proceeds and the incoming mechanism itself is characterized by energy supply indicators that differ from each other, which proceed based on the following criteria:

"Max" power
Flow rate
Capacity according to the indicator of mathematics
"Max" efficiency

“Max” is the highest value of the rate of occurrence of ATP elements in one of the metabolic reactions, which limits the intensity limit of the actions performed, due to the applied features of the reaction mechanism. flow determines the maximum time during which highest level capacity of adenosine triphosphate resynthesis.

Metabolic capacity is an indicator of the holistic value of ATP, which can arise during the use of a chain of ongoing processes of ATP resynthesis, taking into account the value of a constant number of elements that provide energy supply to the muscles.

The full amount of capacity limits the scope of the action performed. Thus, such efficiency occurs with a limited amount of energy that accumulates in the macroergic bonds of adenositrifosphate.

Namely, this characterizes the efficiency of the work being done at this moment, and in this case the criterion is the general indicator of useful action.

The value of the efficiency coefficient, in this case, will be the ratio of the total useful energy expended to its total amount that arises during the above process. The general coefficient of PD during energy metamorphoses, during metabolic processes, mainly depends on:

Phospholation level
Indicator of chemomechanical processes

The “max” efficiency of such chemomechanical couplings proceeds almost identically and amounts to 1/2 of the total reaction.

“Max” efficiency of the phosphorylation level is the highest value in the alactic anaerobic process, and is 80%, and the minimum indicator is 40%, when the glycolysis reaction occurs, it increases to 42%. In a stationary aerobic process the figure is 58%.

Thus, we can conclude that processes under anaerobic conditions are characterized by a significantly increased maximum power of ATP generation, but at the same time they have a practically minimal retention period of accumulated components.

You can see what ATP synthesis is in the video::

Tissue respiration is the main method of producing ATP, used by all cells of the body (except red blood cells).

In the process of tissue respiration, two hydrogen atoms (two protons and two electrons) are removed from the oxidized substance and transferred through the respiratory chain, consisting of enzymes and coenzymes, to molecular hydrogen - O 2, delivered by the blood from the air to all tissues of the body. As a result of the addition of hydrogen atoms to oxygen, water is formed. Due to the energy released during the movement of electrons along the respiratory chain, ATP is synthesized from ADP and phosphoric acid in mitochondria. Typically, the formation of one water molecule is accompanied by the synthesis of three ATP molecules.

In a simplified form, tissue respiration can be represented by the following diagram.

Various intermediate products of the breakdown of proteins, carbohydrates and fats are used as oxidation substrates (i.e. substances from which hydrogen is removed) in tissue respiration. However, the intermediate products of the tricarboxylic acid cycle (TCA cycle) - the Krebs cycle (isocitric, ketoglutaric, succinic and malic acids) are most often subject to oxidation. The Krebs cycle is the final stage of catabolism, during which the oxidation of the acetic acid residue included in acetyl coenzyme A occurs - this is a universal metabolite of the body into which, during its decomposition, the main organic substances - proteins, carbohydrates and fats - are converted.

In some cases, the removal of hydrogen atoms from oxidized substances occurs in the cytoplasm, and here the separated hydrogen joins not to oxygen (as in the case of tissue respiration), but to some other substance. The most common hydrogen acceptor is pyruvic acid, which arises from the breakdown of carbohydrates and amino acids. As a result of the addition of hydrogen atoms, pyruvic acid is converted into lactic acid (lactate). Thus, with this type of oxidation, instead of the final product - water - another final product is formed - lactic acid, and this occurs without the consumption of oxygen, i.e. anaerobic. Due to the energy released in the cytoplasm, ATP is synthesized, which is called anaerobic, or substrate phosphorylation, or anaerobic ATP synthesis. The biological purpose of this type of oxidation is to produce ATP without the participation of tissue respiration and oxygen.

Muscle contraction is a complex mechanochemical process during which the chemical energy of the hydrolytic breakdown of ATP is converted into mechanical work performed by the muscle.

The process of muscle relaxation, or relaxation, as well as the process of muscle contraction, is carried out using the energy of ATP hydrolysate. Both phases of muscle activity - contraction and relaxation - occur with the obligatory use of energy, which is released during ATP hydrolysation.

However, ATP reserves in muscle cells are insignificant (at rest, the concentration of ATP in muscles is about 5 mmol/l) and are sufficient for muscle work for 1-2 s. Therefore, to ensure longer muscle activity, ATP reserves must be replenished in the muscles. The formation of ATP in muscle cells directly during physical work is called ATP resynthesis and comes with energy consumption. Depending on the energy source, there are several pathways for ATP resynthesis.

The following criteria are usually used to quantitatively characterize various ATP resynthesis pathways:

Maximum power, or maximum speed, is the largest amount of ATP that can be formed per unit time due to a given resynthesis pathway. Maximum power is measured in calories or joules, based on the fact that 1 mmol of ATP (506 mg) corresponds under physiological conditions to approximately 12 cal or 50 J (1 cal = 4.18 J). Therefore, this criterion has the dimension cal/min kg muscle tissue or, respectively, J/min kg muscle tissue;

The deployment time is the minimum time required for ATP resynthesis to reach its highest speed, i.e. to achieve maximum power. This criterion is measured in time units (s, min);

The time of preservation or maintenance of maximum power is the longest time of functioning of a given ATP resynthesis pathway with maximum power. Units of measurement - s, min, h;

Metabolic capacity is the total amount of ATP that can be produced during muscle work by a given ATP resynthesis pathway.

Depending on oxygen consumption, resynthesis pathways are divided into aerobic and anaerobic /24/.

Aerobic pathway for ATP resynthesis

(synonyms: tissue respiration, aerobic or oxidative phosphorylation) is the main, basic method of ATP formation that occurs in the mitochondria of muscle cells. During tissue respiration, two hydrogen atoms (two protons and two electrons) are removed from the oxidized substance and transferred through the respiratory chain to molecular oxygen - O 2, delivered by the blood to the muscles from the air, resulting in the formation of water. Due to the energy released during the formation of water, ATP is synthesized from ADP and phosphoric acid. Typically, for every water molecule formed, three ATP molecules are synthesized. In turn, acetyl-CoA can be formed from carbohydrates, fats and amino acids, i.e. Through acetyl-CoA, carbohydrates, fats and amino acids are involved in the Krebs cycle.

The rate of the aerobic pathway of ATP resynthesis is controlled by the content of ADP in muscle cells, which is an activator of the enzyme of tissue respiration. At rest, when there is almost no ADP in the cells, tissue respiration occurs at a very low rate. During muscle work, due to the intensive use of ATP, the formation and accumulation of ADP occurs. The resulting excess ADP accelerates tissue respiration, and it can reach maximum intensity.

Another activator of the aerobic pathway of ATP resynthesis is CO. Carbon dioxide produced in excess during physical work activates the respiratory center of the brain, which ultimately leads to an increase in blood circulation and improved oxygen supply to muscles.

The aerobic pathway of ATP formation is characterized by the following criteria:

Maximum power (350-450 cal/min kg);

Deployment time (3-4 minutes, for well-trained athletes it can be about 1 minute);

Operating time at maximum power (tens of minutes).

As already indicated, the energy sources for aerobic resynthesis of ATP are carbohydrates, fats and amino acids, the breakdown of which is completed by the Krebs cycle. Moreover, for this purpose, not only intramuscular reserves of these substances are used, but also carbohydrates, fats, ketone bodies and amino acids delivered by blood to the muscles during physical work. In this regard, this ATP resynthesis pathway functions at maximum capacity for such a long time.

However, the aerobic method of ATP formation also has a number of disadvantages. The functional state of the cardiorespiratory system is a limiting factor that limits the duration of operation of the aerobic pathway of ATP resynthesis with maximum power and the value of the maximum power. The capabilities of the aerobic pathway are also limited by the fact that all enzymes of tissue respiration are built into the inner membrane of mitochondria in the form of respiratory ensembles and function only in the presence of an intact membrane. Any factors affecting the state and properties of membranes disrupt the formation of ATP aerobically. For example, disturbances in oxidative phosphorylation are observed during acidosis (increased acidity), swelling of mitochondria, and during the development in muscle cells of free radical oxidation of lipids that make up the mitochondrial membranes.

Another disadvantage of aerobic ATP formation can be considered the long deployment time (3-4 minutes) and the small maximum power in absolute value /24/.

Anaerobic pathways for ATP resynthesis

Anaerobic pathways for ATP resynthesis (creatine phosphate, glycolytinic) are additional methods of ATP formation in cases where the main pathway for ATP production - aerobic - cannot provide muscle activity with the required amount of energy. This happens in the first minutes of any work, when tissue respiration has not yet fully developed, as well as when performing high-power physical activity.

Creatine phosphate pathway for ATP resynthesis

(creatine kinase, alactate)

Muscle cells always contain creatine phosphate, a compound containing a phosphate group linked to the creatine residue by a high-energy bond. The content of creatine phosphate in muscles at rest is 15-20 mmol/kg.

The creatine phosphate reaction is reversible, but its equilibrium is shifted towards the formation of ATP, and therefore it begins to occur as soon as the first portions of ADP appear in the myocytase. This reaction is catalyzed by the enzyme creatine kinase. During muscular work, the activity of creatikinase increases significantly due to the activating effect on it of calcium ions and creatine, formed during this reaction. Due to these mechanisms, the activity of creatine kinase at the beginning of muscle work increases sharply and the keatine phosphate reaction very quickly reaches its maximum speed.

The formation of creatine occurs spontaneously without the participation of enzymes. This reaction is irreversible. The resulting creatinine is not used in the body and is excreted in the urine.

Creatine phosphate synthesis in muscle cells occurs during rest by reacting creatine with excess ATP. Creatine phosphate reserves can be partially restored during muscular work of moderate power, during which ATP is synthesized due to tissue respiration in such an amount that is sufficient to ensure the contractile function of myocytes and to replenish the creatine phosphate barrier. Therefore, during physical work, the creatine phosphate reaction can be turned on many times. Creatine is formed in the liver using the amino acids glycine, methionine and arginine.

The creatine phosphate pathway of ATP synthesis is characterized by the following values of accepted quantitative criteria:

Maximum power (900-1100 cal/min kg);

Deployment time (only 1-2 s);

Operating time at maximum speed (only 8-10 s).

The main advantages of the creatine phosphate pathway for ATP formation are its very short deployment time and high power, which is extremely important for speed-strength sports. The main disadvantage of this method of ATP synthesis, which significantly limits its capabilities, is the short time of its operation. The time to maintain maximum speed is only 8-10 s, by the end its speed is halved, and by the end of the 3rd minute of intense work, the creatine phosphate reaction in the muscles practically stops.

Biochemical assessment of the state of the creatine phosphate pathway for ATP resynthesis is usually carried out using two indicators: creatinine coefficient and alactic oxygen debt.

The creatinine coefficient characterizes the reserves of creatine phosphate in the muscles, since there is a linear relationship between the content of creatine phosphate and its formation from creatinine, since this conversion occurs non-enzymatically and is irreversible.

Alactic oxygen debt is an increase (above the resting level) in oxygen consumption in the next 4-5 minutes after performing a short-term exercise of maximum power. This excess oxygen is required to ensure a high rate of tissue respiration immediately after the end of the load to create an increased concentration of ATP in muscle cells. Thus, the use of creatine phosphate during work leads to the accumulation of creatine, the conversion of which back into creatine phosphate requires a certain amount of oxygen.

Glycolytic pathway of ATP resynthesis (glycolysis)

Glycolysis is also an anaerobic way of producing ATP. The source of energy necessary for ATP resynthesis is muscle glycogen. During anaerobic breakdown, glycogen is converted into lactic acid through a series of successive stages under the influence of the phosphorylase enzyme. During the process of glycolysis, intermediate products are formed containing a phosphate group with a high-energy bond, which is easily transferred to ADP to form ATP.

All glycolytic enzymes are found in the sarcoplasm of muscle cells. Glucose entering the muscles from the bloodstream can also undergo glycolysis.

The enzymes phosphorylase and phosphofructokinase regulate the rate of glycolysis. Moreover, at rest, glycolysis proceeds very slowly; with intense muscular work, its speed increases sharply and can increase compared to the rest level by almost 2000 times, and an increase in the rate of glycolysis can be observed already in the pre-start state due to the release of adrenaline.

Maximum power - 750-850 cal/min kg.

Deployment time - 20-30 s.

Operating time with maximum power is 2-3 minutes.

The advantages of glycolysis over the aerobic pathway of ATP formation: it reaches maximum power faster, proceeds at high speed, has a higher maximum power and does not require the participation of mitochondria and oxygen in the process.

Disadvantages of glycolysis: the high speed of the process quickly leads to a decrease in the concentration of glycogen in the muscles, and the accumulation of lactic acid during glycolysis leads to an increase in acidity inside muscle cells, which reduces the catalytic activity of glycolytic enzymes; Glycolysis is uneconomical. An increase in the concentration of lactate in muscle fibers causes a shift in pH to the acidic side, while conformational changes occur in muscle proteins, leading to a decrease in their functional activity, i.e. leads to the development of fatigue.

With a decrease in the intensity of physical work, as well as during rest periods during training, the resulting lactate can partially leave the muscle cells into the lymph and blood, which makes it possible to restart glycolysis.

Zones of relative power of muscle work

Currently, various classifications of muscle activity power have been adopted. One of them is the classification according to V.S. Farfel, based on the position that the power of physical activity performed is determined by the relationship between the three main pathways of ATP resynthesis that function in the muscles during work. According to this classification, four zones of relative muscle work power are distinguished: maximum, submaximal, large and moderate.

Work in the high power zone lasts up to 30 minutes. Work in this zone is characterized by approximately equal contributions from glycolysis and tissue respiration. The creatine phosphate pathway for ATP resynthesis functions only at the very beginning.

Work in the moderate power zone continues for over 30 minutes. Energy supply to muscle activity occurs predominantly aerobically /24/.