Oxygen consumption (OC) is an indicator that reflects the functional state of the cardiovascular and respiratory systems.
With an increase in the intensity of metabolic processes during physical exertion, a significant increase in oxygen consumption is necessary. This places increased demands on the function of the cardiovascular and respiratory systems.
At the beginning of dynamic work of submaximal power, oxygen consumption increases and after a few minutes reaches a steady state. Cardiovascular and respiratory systems are included in the work gradually, with some delay. Therefore, at the beginning of work, oxygen deficiency increases. It persists until the end of the load and stimulates the activation of a number of mechanisms that provide the necessary changes in hemodynamics.
Under conditions of steady state, the body's consumption of oxygen is fully satisfied, the amount of lactate in the arterial blood does not increase, and ventilation of the lungs, heart rate, and atmospheric pressure also do not change. The time to reach a steady state depends on the degree of preload, intensity, work of the athlete. If the load exceeds 50% of the maximum aerobic power, then a steady state occurs within 2-4 minutes. With increasing load, the time to stabilize the level of oxygen consumption increases, while there is a slow increase in ventilation of the lungs, heart rate. At the same time, the accumulation of lactic acid in the arterial blood begins. After the end of the load, oxygen consumption gradually decreases and returns to the initial level of the amount of oxygen consumed in excess of the basal metabolic rate in the recovery period, called oxygen debt (OD).
Oxygen debt consists of 4 components:
Aerobic Elimination of Anaerobic Metabolism Products (initial KD)
Increase in oxygen debt by the heart muscle and respiratory muscles (to restore the initial heart rate and respiratory rate)
An increase in tissue oxygen consumption depending on a temporary increase in body temperature
Replenishment of myoglobin oxygen
The size of the oxygen debt depends on the amount of effort and training of the athlete. With a maximum load lasting 1–2 minutes, an untrained person has a debt of 3–5 liters, and an athlete has 15 liters or more. Maximum oxygen debt is a measure of the so-called anaerobic capacity. It should be borne in mind that CA rather characterizes the total capacity of anaerobic processes, that is, the total amount of work done at maximum effort, and not the ability to develop maximum power.
Maximum oxygen consumption
Oxygen consumption increases in proportion to the increase in load, however, there comes a limit at which a further increase in load is no longer accompanied by an increase in AC. This level is called maximum oxygen consumption or oxygen limit.
Maximum oxygen uptake is the maximum amount of oxygen that can be delivered to working muscles in 1 minute.
The maximum oxygen consumption depends on the mass of the working muscles and the state of the oxygen transport systems, respiratory and cardiac performance, and peripheral circulation. The value of the BMD is associated with heart rate, stroke volume, arterio-venous difference - the difference in oxygen content between arterial and venous blood (AVR)
MPK = HR * WOK * AVRO2
The maximum oxygen consumption is determined in liters per minute. In childhood, it increases in proportion to height and weight. In men, it reaches its maximum level by 18-20 years. Starting from the age of 25-30, it steadily decreases.
On average, the maximum oxygen consumption is 2-3 l / min, and for athletes 4-7 l / min
To assess the physical condition of a person, the oxygen pulse is determined - the ratio of oxygen consumption per minute to the pulse rate for the same minute, that is, the number of milliliters of oxygen that is delivered in one heartbeat. This indicator characterizes the efficiency of the work of the heart. The less the oxygen pulse increases, the more efficient the hemodynamics, the lower the heart rate the required amount of oxygen is delivered.
At rest, the CP is 3.5-4 ml, and with intense physical activity, accompanied by oxygen consumption of 3 l / min, it increases to 16-18 ml.
11. biochemical characteristics of muscle activity of different power (zone of maximum and submaximal power)
Relative Power Zones of Muscular Work
Currently, various classifications of the power of muscle activity are accepted. One of them is the B.C. classification. Farfel, based on the position that the power of physical activity performed is due to the ratio between the three main ATP resynthesis pathways that function in the muscles during work. According to this classification, four zones of relative power of muscular work are distinguished: maximum, submaximal, high and moderate power.
Work in the zone maximum power may continue for 15-20 s. The main source of ATP under these conditions is creatine phosphate. Only at the end of the work, the creatine phosphate reaction is replaced by glycolysis. An example of physical exercises performed in the zone of maximum power is sprinting, long and high jumps, some gymnastic exercises, lifting a barbell, etc.
Work in the zone submaximal power has a duration of up to 5 minutes. The leading mechanism of ATP resynthesis is glycolytic. At the beginning of work, until glycolysis has reached its maximum rate, the formation of ATP is due to creatine phosphate, and at the end of work, glycolysis begins to be replaced by tissue respiration. Work in the zone of submaximal power is characterized by the highest oxygen debt - up to 20 liters. An example of physical activity in this power zone is middle-distance running, short-distance swimming, track cycling, sprint skating, etc.
12. biochemical characteristics of muscle activity of various power (zone of high and moderate power)
Work in the zone high power has a maximum duration of up to 30 minutes. Work in this zone is characterized by approximately the same contribution of 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 exercise in this power zone is 5000-hour running, distance skating, cross-country skiing, middle and long distance swimming, etc.
Work in the zone moderate power lasts over 30 minutes. Energy supply of muscle activity occurs mainly in the aerobic way. An example of the work of such power is marathon running, track and field cross-country, race walking, road cycling, long-distance skiing, hiking, etc.
In acyclic and situational sports, the power of the work performed changes many times. So, for a football player, running at a moderate speed alternates with running for short distances at a sprint speed; you can also find such segments of the game when the power of work is significantly reduced. Such examples can be given in relation to many other sports.
However, in a number of sports disciplines, physical loads related to a certain power zone still prevail. So, the physical work of skiers is usually performed with high or moderate power, and in weightlifting, maximum and submaximal loads are used.
Therefore, in the preparation of athletes, it is necessary to apply training loads that develop the ATP resynthesis pathway, which is the leading one in the energy supply of work in the relative power zone characteristic of this sport.
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oxygen debt- rus oxygen debt (m), oxygen debt (g) eng oxygen debt fra dette (f) d oxygène deu Sauerstoffschuld (f) spa deuda (f) de oxígeno … Occupational safety and health. Translation into English, French, German, Spanish
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As physical activity increases, oxygen consumption increases up to the individual maximum (IPC).
In untrained people, the MIC is usually 3-4 L/min or 40-50 ml/min/kg; in well-trained athletes, the MIC reaches 6-7 l / min or 80-90 ml / min / kg. Due to fatigue, the maximum oxygen consumption cannot be maintained for a long time (up to 15 minutes).
During operation, the need for oxygen increases. Figure 14 reflects the availability of oxygen:
A - light work;
B - hard work;
B - exhausting work.
Oxygen demand (O 2 -request) - the amount of oxygen necessary for the body to fully meet the energy needs that arise in work due to oxidative processes.
Oxygen income (O 2 -income) - the amount of oxygen used for aerobic ATP resynthesis during work. Oxygen income is limited by the MPC (Fig. 14 B) and the speed of deployment of aerobic processes of energy supply.
Thus, when operating at high power, the oxygen demand may exceed the oxygen supply (Fig. 14 C). In this case, to oxygen deficiency (O 2 -deficiency) - the difference between oxygen demand and oxygen income persists throughout the entire operation and leads to a significant oxygen debt.
Under conditions of oxygen deficiency, anaerobic reactions of ATP resynthesis are activated, which leads to the accumulation of anaerobic decay products in the body, primarily lactate. During work, in which a steady state is possible, some of the lactate can be utilized during work due to increased aerobic reactions in which lactate is utilized, converted to pyruvate and oxidized. The other part is eliminated after the work [Holloshi D.O., 1982].
If a steady state does not occur, then the concentration of lactate in the course of work increases all the time, which leads to a refusal to work. In this case, lactate is eliminated at the end of work. These processes require an additional amount of oxygen, so for some time after the end of work, its consumption continues to be increased compared to the rest level [Volkov N.I., Nessen E.N., Osipenko A.A., Korsun, 2000].
Oxygen debt (O 2 -debt) - the amount of oxygen necessary for the oxidation of metabolic products accumulated in the body during intense muscular work with insufficient aerobic energy supply, as well as to replenish the reserve oxygen consumed during physical activity.
Anaerobic energy supply is carried out in two ways:
Creatine phosphate (without lactate formation);
Glycolytic (with the formation of lactate).
1- "alactate" fraction of oxygen debt;
2- "lactate" fraction of oxygen debt
Fig.14. Formation and elimination of oxygen debt
during operation of different power [according to N.I. Volkov 2000]
Therefore, oxygen debt has two fractions:
- alactic O 2 -debt - the amount of O 2 necessary for the resynthesis of ATP and creatine phosphate and replenishment of oxygen directly in muscle tissue;
- lactate О 2 -debt - the amount of О 2 necessary to eliminate lactic acid accumulated during work.
And, if alactic O 2 -debt is eliminated quickly enough, in the first minutes after the end of work, then the elimination of lactate O 2 -debt can last up to two hours.
Methodical conclusions:
1. Alactate oxygen debt is formed during any work and is eliminated quickly, within 2-3 minutes.
2. Lactate oxygen debt increases significantly when the value of the oxygen demand of the MIC is exceeded.
3. Insufficient rest time between repetitions of loads of increased power translates the process of energy supply into a glycolytic "channel".
Features of muscle adaptation
To work on endurance
Skeletal muscles in cross section are a mosaic of fast, intermediate and slow fibers. White would 
strict fibers are larger, but not very uniform in thickness. They are not so well supplied with blood capillaries, there are few mitochondria in them. As a result, they do not adapt to long-term work, and their role in increasing endurance is very small. On the contrary, red slow fibers are usually surrounded by an abundant capillary network and the number of mitochondria is very large. In addition, red fibers are much thinner (3-4 times). Intermediate type fibers are fast red fibers with a pronounced ability to both anaerobic and aerobic energy generation mechanisms.
Under the influence of endurance training, intermediate muscle fibers acquire the properties of slow fibers with a corresponding decrease in the properties of fast muscle fibers. With the help of immunohistochemical methods that make it possible to determine "fast" and "slow" myosin, it was found that the fibers of the intermediate type contain both types of myosin and that their ratio can change during training. However, such changes are not detected in the red slow and white fast fibers. The approximate content of slow red fibers in the wide external muscle of the thigh in speed skaters-all-rounders is about 56%, stayers - about 75% [Meyerson F.Z., 1986]. The efficiency of aerobic provision at the peripheral level is largely determined by the oxidative potential of the muscles, which, in turn, is determined by the development of the mitochondrial system.
The power of the skeletal muscle mitochondrial system, which determines both the ability to resynthesize ATP and utilize pyruvate, is a link that limits the intensity and duration of muscle work. The ability of mitochondria to use pyruvate as an energy substrate, preventing its conversion to lactate and the subsequent accumulation of lactate, is the most important condition for increasing the level of strength endurance. At the same time, the rate of pyruvate formation in fast glycolytic fibers is approximately the same as the rate of its use in “aerobic” fibers, and in this case, the total effect may be due to the simultaneous operation of fibers of one and another type. This is beneficial both from a mechanical and metabolic point of view [Meyerson F.Z., Pshennikova M.G., 1988].
The absence of hypertrophy of slow muscle fibers does not mean the absence of adaptive biosynthesis processes in them. During endurance training, mitochondrial protein synthesis is preferred, and not only in slow, but also in intermediate fibers. With oxidative energy supply, metabolism occurs through the mitochondrial membranes. Consequently, the greater the total surface of mitochondrial membranes, the more efficient the oxidative processes. With different intensity and volume of physical activity, mitochondrial biosynthesis proceeds in different ways.
1. Hypertrophy- an increase in the volume of mitochondria - occurs during "emergency" adaptation to sharply increased loads. This is a fast but inefficient way. Although the total surface of mitochondrial membranes increases, their structure changes, impairing their functioning.
2. Hyperplasia- increase in the number of mitochondria. The volume of the mitochondrion does not change, but the total surface area of the membranes increases. This effective option for long-term adaptation to aerobic exercise is achieved by long-term training.
At the same time, the total surface area of mitochondrial membranes can increase even more due to the formation crist- folds on the inner membrane of the mitochondria.
Rice. 15. Increasing diffuse distances
in hypertrophied muscle
If strength training causes hypertrophy of intermediate and fast muscle fibers, then slow muscle fibers under the influence of endurance loads not only do not hypertrophy, but can also decrease in thickness, which leads to an increase in the density of mitochondria and capillaries and a decrease in diffuse distances.
Thus, during prolonged work, when the supply of oxygen, energy substrates, and the removal of metabolic products are decisive factors, muscle hypertrophy will adversely affect endurance.
This circumstance directs the search for ways to increase the aerobic performance of highly trained athletes from the center to the periphery, that is, from the cardio-respiratory system to the neuromuscular system.
Methodical conclusions:
1. A decrease in muscle volume contributes to an increase in endurance.
2. The increase in endurance is directly related to the development of the mitochondrial system in muscle fibers.
At rest, the average human energy expenditure is approximately 1.25 kcal / min, i.e. 250 ml of oxygen per minute. This value varies depending on the body size of the subject, his gender and environmental conditions. During exercise, energy consumption can increase by 15-20 times.
With calm breathing, young adults expend about 20% of the total energy expenditure. Less than 5% of total oxygen consumption is required to move air in and out of the lungs (P.D. Sturkie, 1981). The work of the respiratory muscles and the expenditure of energy for respiration with an increase in ventilation of the lungs are here to a greater extent than the minute volume of respiration.
It is known that the work of the respiratory muscles goes to overcome the resistance to air flow in the respiratory tract and the elastic resistance of the lung tissue and chest. Observations show that elasticity also changes in connection with the blood filling of the lungs, training increases the number of capillaries in the lungs, without noticeably affecting the alveolar tissue (J. Minarovjech, 1965).
During physical exertion, ventilation of the lungs, ventilation equivalent, heart rate, oxygen pulse, blood pressure and other parameters change in direct proportion to the intensity of the load or the degree of its increase, the age of the athlete, his gender and fitness.
With great physical exertion, people with a very good functional state are able to perform work due to only aerobic mechanisms of energy production.
After the end of the load, oxygen consumption gradually decreases and returns to its original level. The amount of oxygen that is consumed in excess of the basal metabolic rate during the recovery period is called oxygen debt. Oxygen debt is repaid in four ways:
1) aerobic elimination of anaerobic metabolism (“true oxygen debt”); increased oxygen consumption by the heart muscle and respiratory muscles (until the initial heart rate and respiration are restored);
increased oxygen consumption by tissues, depending on the temporary increase in temperature and the content of catecholamines in them;
replenishment of myoglobin with oxygen.
The amount of oxygen debt at the end of work depends on the amount of effort and fitness of the subject. With a maximum load lasting 1-2 minutes, an untrained person can develop an oxygen debt of 3-5 liters, a highly qualified athlete - 15 liters or more. The maximum oxygen debt is a measure of the so-called anaerobic capacity. Oxygen debt characterizes the total capacity of anaerobic processes, i.e., the total amount of work done at maximum effort.
The share of anaerobic energy production is reflected in the concentration of lactic acid in the blood. Lactic acid is formed directly in the muscles during exercise, but it takes some time for it to diffuse into the blood. Therefore, the highest concentration of lactic acid in the blood is usually observed at the 3-9th minute of the recovery period. The presence of lactic acid lowers the pH of the blood. After performing heavy loads, a decrease in pH to 7.0 is observed.
In people 20-40 years old with average physical fitness, it ranges from 11 to 14 mmol / l. In children and the elderly, it is usually lower. As a result of training, the concentration of lactic acid at a standard (same) load increases less. However, in highly trained athletes after maximum (especially competitive) physical activity, lactic acid sometimes exceeds 20 mmol/l. In a state of muscle rest, the concentration of lactic acid in the arterial blood ranges from 0.33-1.1 mmol / l. In athletes, due to the adaptation of the cardiorespiratory system to physical exertion, oxygen deficiency at the beginning of work is less.
IN the process of muscular work consumes the oxygen supply of the body, phosphagens (ATP and CRF), carbohydrates (muscle and liver glycogen, blood glucose) and fats. After work, they are restored. The exception is fats, recovery of which may not be.
IN the restorative processes that occur in the body after work find their energy reflection in the increased (p "compared to the pre-working state) oxygen consumption - oxygen debt (see Fig. 12). According to the original theory of A. Hull (1922), oxygen debt is excess O2 consumption above the pre-workout resting level, which provides energy for the body to restore to the pre-working state, including the restoration of energy reserves consumed during work and the elimination of lactic acid.The rate of O2 consumption after work decreases exponentially: during the first 2-3 minutes very quickly (rapid , or lactate, component of oxygen debt), and then more slowly (slow, or lactate, component of oxygen debt), until it reaches (after 30-60 minutes) a constant value close to pre-working.
P After operation with a capacity of up to 60% of the MIC, the oxygen debt does not much exceed the oxygen deficit. After more intense exercise, the oxygen debt significantly exceeds the oxygen deficit, and the more, the higher the power of work (Fig. 24).B The fast (alactic) component of O2-debt is associated mainly with the use of O2 for the rapid recovery of high-energy phosphagens consumed during work in working muscles, as well as with the restoration of normal O2 content in venous blood and with the saturation of myoglobin with oxygen.
M The slow (lactate) component of O2-debt is associated with many factors. To a large extent, it is associated with the post-working elimination of lactate from the blood and tissue fluids. In this case, oxygen is used in oxidative reactions that ensure the resynthesis of glycogen from blood lactate (mainly in the liver and partly in the kidneys) and the oxidation of lactate in the heart and skeletal muscles. In addition, a long-term increase in O2 consumption is associated with the need to maintain an increased activity of the respiratory and cardiovascular systems during the recovery period, increased metabolism and other processes that are caused by a long-term increased activity of the sympathetic nervous and hormonal systems, increased body temperature, which also slowly decrease by throughout the recovery period.
Restoration of oxygen reserves. Oxygen is found in muscles in the form of a chemical bond with myoglobin. These reserves are very small: each kilogram of muscle mass contains about 11 ml of O2. Consequently, the total reserves of "muscle" oxygen (per 40 kg of muscle mass in athletes) do not exceed 0.5 liters. In the process of muscular work, it can be quickly consumed, and after work it can be quickly restored. The rate of restoration of oxygen reserves depends only on its delivery to the muscles.
WITH once after the cessation of work, the arterial blood passing through the muscles has a high partial tension (content) of O2, so that the restoration of O2-myoglobin occurs, probably, in a few seconds. The oxygen consumed in this case constitutes a certain part of the fast fraction of oxygen debt, which also includes a small amount of O2 (up to 0.2 l), which goes to replenish its normal content in venous blood.
T Thus, within a few seconds after the cessation of work, oxygen "reserves" in the muscles and blood are restored. The partial tension of O2 in the alveolar air and arterial blood not only reaches the pre-working level, but also exceeds it. The content of O2 in the venous blood flowing from the working muscles and other active organs and tissues of the body is also quickly restored, which indicates their sufficient oxygen supply in the post-work period. Therefore, there is no physiological reason to use breathing with pure oxygen or a mixture with a high content oxygen after work to speed up recovery processes.
Recovery of phosphagens (ATP and CRF). Phosphagens, especially ATP, are restored very quickly (Fig. 25). Already within 30 s after the cessation of work, up to 70% of the consumed phosphagens are restored, and their complete replenishment ends in a few minutes, and almost exclusively due to the energy of aerobic metabolism, i.e. due to oxygen consumed in the fast phase of O2-debt. Indeed, if immediately after work, the working limb is tourniqueted and thus deprives the muscles of oxygen delivered with the blood, then the restoration of CRF will not occur.How more consumption of phosphagens per. operating time, the more O2 is required to restore them (to restore 1 mole of ATP, 3.45 liters of O2 are needed). The value of the fast (alactic) fraction of O2-debt is directly related to the degree of decrease in phosphagens in the muscles by the end of work. Therefore, this value indicates the amount of phosphagens consumed during the operation.
At untrained men, the maximum value of the fast fraction of O2-debt reaches 2-3 liters. Particularly large values of this indicator were registered among representatives of speed-strength sports (up to 7 liters in highly qualified athletes). In these sports, the content of phosphagens and the rate of their consumption in the muscles directly determine the maximum and maintained (remote) power of the exercise.
Recovery of glycogen. According to the initial ideas of R. Margaria et al. (1933), glycogen consumed during work is resynthesized from lactic acid within 1-2 hours after work. The oxygen consumed during this recovery period determines the second, slow, or lactate, O2-Debt fraction. However, it is now established that the restoration of glycogen in the muscles can last up to 2-3 days.
WITH The rate of glycogen recovery and the amount of its recoverable reserves in the muscles and liver depend on two main factors: the degree of glycogen consumption during work and the nature of the diet during the recovery period. After a very significant (more than 3/4 of the initial content), up to complete, depletion of glycogen in the working muscles, its recovery in the first hours with normal nutrition is very slow, and it takes up to 2 days to reach the pre-working level. With a diet high in carbohydrates (more than 70% of the daily calorie content), this process accelerates - already in the first 10 hours more than half of the glycogen is restored in the working muscles, by the end of the day it is completely restored, and in the liver the glycogen content is much higher than usual. In the future, the amount of glycogen in the working muscles and in the liver continues to increase, and 2-3 days after the "exhausting" load, it can exceed the pre-working 1.5-3 times - the phenomenon of supercompensation (see Fig. 21, curve 2).
At daily intense and long training sessions, the glycogen content in the working muscles and liver is significantly reduced from day to day, since with a normal diet, even a daily break between workouts is not enough to fully restore glycogen. Increasing the content of carbohydrates in the athlete's diet can ensure a complete restoration of the body's carbohydrate resources by the next training session (Fig. 26). At elimination of lactic acid. During the recovery period, lactic acid is eliminated from the working muscles, blood and tissue fluid, and the faster, the less lactic acid was formed during work. Post-work mode also plays an important role. So, after a maximum load, it takes 60-90 minutes to completely eliminate the accumulated lactic acid in conditions of complete rest - sitting or lying down (passive recovery). However, if light work (active recovery) is performed after such a load, then the elimination of lactic acid occurs much faster. In untrained people, the optimal intensity of the "restoring" load is approximately 30-45% of the IPC (for example, jogging), as well. in well-trained athletes - 50-60% of the IPC, with a total duration of approximately 20 minutes (Fig. 27).WITH There are four main ways to eliminate lactic acid: 1) oxidation to CO2 and SO (this eliminates approximately 70% of all accumulated lactic acid); 2) conversion to glycogen (in muscles and liver) and glucose (in the liver) - about 20%; 3) conversion to proteins (less than 10%); 4) removal with urine and sweat (1-2%). With active recovery, the proportion of lactic acid eliminated aerobically increases. Although lactic acid oxidation can occur in a variety of organs and tissues (skeletal muscles, heart muscle, liver, kidneys, etc.), most of it is oxidized in skeletal muscles (especially their slow fibers). This makes it clear why light work (which involves mainly slow muscle fibers) contributes to faster elimination of lactate after heavy loads.
Z A significant part of the slow (lactate) fraction of O2-debt is associated with the elimination of lactic acid. The more intense the load, the greater this fraction. In untrained people, it reaches a maximum of 5-10 liters, in athletes, especially among representatives of speed-strength sports, it reaches 15-20 liters. Its duration is about an hour. The magnitude and duration of the lactate fraction of O2-debt decrease with active recovery.