How does physical activity affect the heart and blood vessels? The Special Athlete's Heart: Changes and Recovery After Stopping Training Changes in cardiac performance during exercise.

Question 1 Phases of the cardiac cycle and their changes during exercise. 3

Question 2 Motility and secretion of the large intestine. Absorption in the large intestine, the influence of muscle work on the processes of digestion. 7

Question 3 The concept of the respiratory center. Mechanisms of regulation of respiration. 9

Question 4 Age features of the development of the motor apparatus in children and adolescents 11

List of used literature.. 13

Question 1 Phases of the cardiac cycle and their changes during exercise

In the vascular system, blood moves due to a pressure gradient: from high to low. Blood pressure is determined by the force with which the blood in the vessel (cavity of the heart) presses in all directions, including on the walls of this vessel. The ventricles are the structure that creates this gradient.

The cyclically repeated change in states of relaxation (diastole) and contraction (systole) of the heart is called the cardiac cycle. With a heart rate of 75 per minute, the duration of the entire cycle is about 0.8 s.

It is more convenient to consider the cardiac cycle, starting from the end of the total diastole of the atria and ventricles. In this case, the heart departments are in the following state: the semilunar valves are closed, and the atrioventricular valves are open. Blood from the veins enters freely and completely fills the cavities of the atria and ventricles. The blood pressure in them is the same as in the nearby veins, about 0 mm Hg. Art.

The excitation that originated in the sinus node first of all goes to the atrial myocardium, since its transmission to the ventricles in the upper part of the atrioventricular node is delayed. Therefore, atrial systole occurs first (0.1 s). At the same time, the contraction of muscle fibers located around the mouths of the veins overlaps them. A closed atrioventricular cavity is formed. With the contraction of the atrial myocardium, the pressure in them rises to 3-8 mm Hg. Art. As a result, part of the blood from the atria through the open atrioventricular openings passes into the ventricles, bringing the blood volume in them to 110-140 ml (end-diastolic ventricular volume - EDV). At the same time, due to the incoming additional portion of blood, the cavity of the ventricles is somewhat stretched, which is especially pronounced in their longitudinal direction. After this, ventricular systole begins, and at the atria - diastole.

After an atrioventricular delay (about 0.1 s), excitation along the fibers of the conducting system spreads to ventricular cardiomyocytes, and ventricular systole begins, lasting about 0.33 s. The systole of the ventricles is divided into two periods, and each of them - into phases.

The first period - the period of tension - continues until the semilunar valves open. To open them, the blood pressure in the ventricles must be raised to a level greater than in the corresponding arterial trunks. At the same time, the pressure, which is recorded at the end of ventricular diastole and is called diastolic pressure, in the aorta is about 70-80 mm Hg. Art., and in the pulmonary artery - 10-15 mm Hg. Art. The voltage period lasts about 0.08 s.

It begins with an asynchronous contraction phase (0.05 s), since not all ventricular fibers begin to contract at the same time. The cardiomyocytes located near the fibers of the conducting system are the first to contract. This is followed by the isometric contraction phase (0.03 s), which is characterized by the involvement of the entire ventricular myocardium in the contraction.

The onset of ventricular contraction leads to the fact that, with the semilunar valves still closed, blood rushes to the area of ​​\u200b\u200blowest pressure - back towards the atria. The atrioventricular valves in its path are closed by the blood flow. Tendon threads keep them from dislocation into the atria, and contracting papillary muscles create even more emphasis. As a result, for some time there are closed cavities of the ventricles. And until the contraction of the ventricles raises the blood pressure in them above the level necessary for the opening of the semilunar valves, a significant shortening of the length of the fibers does not occur. Only their inner tension increases.

The second period - the period of expulsion of blood - begins with the opening of the valves of the aorta and pulmonary artery. It lasts 0.25 s and consists of phases of fast (0.1 s) and slow (0.13 s) expulsion of blood. The aortic valves open at a pressure of about 80 mm Hg. Art., and pulmonary - 10 mm Hg. Art. The relatively narrow openings of the arteries are not able to immediately pass the entire volume of ejected blood (70 ml), and therefore the developing contraction of the myocardium leads to a further increase in blood pressure in the ventricles. In the left, it rises to 120-130 mm Hg. Art., and in the right - up to 20-25 mm Hg. Art. The resulting high pressure gradient between the ventricle and the aorta (pulmonary artery) contributes to the rapid ejection of part of the blood into the vessel.

However, the relatively small capacity of the vessels, in which there was blood before, leads to their overflow. Now the pressure is rising already in the vessels. The pressure gradient between the ventricles and vessels gradually decreases, as the rate of blood ejection slows down.

Due to the lower diastolic pressure in the pulmonary artery, the opening of the valves and the expulsion of blood from the right ventricle begin somewhat earlier than from the left. And a lower gradient leads to the fact that the expulsion of blood ends a little later. Therefore, the systole of the right ventricle is 10-30 ms longer than the systole of the left.

Finally, when the pressure in the vessels rises to the level of pressure in the cavity of the ventricles, the expulsion of blood ends. By this time, the contraction of the ventricles stops. Their diastole begins, lasting about 0.47 s. Usually, by the end of systole, about 40-60 ml of blood remains in the ventricles (end-systolic volume - ESC). The cessation of expulsion leads to the fact that the blood in the vessels slams the semilunar valves with a reverse current. This state is called the proto-diastolic interval (0.04 s). Then there is a drop in tension - an isometric period of relaxation (0.08 s).

By this time, the atria are already completely filled with blood. Atrial diastole lasts about 0.7 s. The atria are filled mainly with passively flowing blood through the veins. But it is possible to single out an "active" component, which manifests itself in connection with the partial coincidence of their diastole with the ventricular systole. With the contraction of the latter, the plane of the atrioventricular septum shifts towards the apex of the heart, which creates a suction effect.

When the tension in the ventricular walls decreases and the pressure in them drops to 0, the atrioventricular valves open with blood flow. The blood filling the ventricles gradually straightens them. The period of filling the ventricles with blood can be divided into phases of fast and slow filling. Before the start of a new cycle (atrial systole), the ventricles, like the atria, have time to completely fill with blood. Therefore, due to the flow of blood during atrial systole, the intraventricular volume increases by about 20-30%. But this contribution increases significantly with the intensification of the work of the heart, when the total diastole is shortened, and the blood does not have time to fill the ventricles sufficiently.

During physical work, the activity of the cardiovascular system is activated and, thus, the increased need of working muscles for oxygen is more fully satisfied, and the heat generated with the blood flow is removed from the working muscle to those parts of the body where it is returned. 3-6 minutes after the start of light work, a stationary (sustained) increase in the heart rate occurs, which is due to the irradiation of excitation from the motor cortex to the cardiovascular center of the medulla oblongata and the flow of activating impulses to this center from the chemoreceptors of the working muscles. Activation of the muscular apparatus enhances blood supply in the working muscles, which reaches a maximum within 60-90 seconds after the start of work. With light work, a correspondence is formed between blood flow and the metabolic needs of the muscle. In the course of light dynamic work, the aerobic pathway of ATP resynthesis begins to dominate, using glucose, fatty acids and glycerol as energy substrates. In heavy dynamic work, the heart rate increases to a maximum as fatigue develops. Blood flow in working muscles increases 20-40 times. However, the delivery of O 3 to the muscles lags behind the needs of muscle metabolism, and part of the energy is generated due to anaerobic processes.

Question 2 Motility and secretion of the large intestine. Absorption in the large intestine, the effect of muscle work on digestion

The motor activity of the large intestine has features that ensure the accumulation of chyme, its thickening due to the absorption of water, the formation of feces and their removal from the body during defecation.

The temporal characteristics of the process of movement of contents through the sections of the gastrointestinal tract are judged by the movement of an X-ray contrast agent (for example, barium sulphate). After taking it, it begins to enter the caecum after 3-3.5 hours. Within 24 hours, the colon is filled, which is released from the contrast mass after 48-72 hours.

The initial sections of the colon are characterized by very slow small pendulum contractions. With their help, the chyme is mixed, which accelerates the absorption of water. In the transverse colon and sigmoid colon, large pendulum contractions are observed, caused by the excitation of a large number of longitudinal and circular muscle bundles. The slow movement of the contents of the colon in the distal direction is carried out due to rare peristaltic waves. The retention of chyme in the large intestine is promoted by anti-peristaltic contractions, which move the contents in a retrograde direction and thereby promote the absorption of water. Condensed dehydrated chyme accumulates in the distal colon. This segment of the intestine is separated from the overlying, filled with liquid chyme, constriction caused by contraction of circular muscle fibers, which is an expression of segmentation.

When the transverse colon is filled with condensed dense contents, irritation of the mechanoreceptors of its mucous membrane increases over a large area, which contributes to the emergence of powerful reflex propulsive contractions that move a large amount of contents into the sigmoid and rectum. Therefore, such reductions are called mass reductions. Eating accelerates the occurrence of propulsive contractions due to the implementation of the gastrocolic reflex.

The listed phase contractions of the large intestine are carried out against the background of tonic contractions, which normally last from 15 s to 5 min.

The basis of the motility of the large intestine, as well as the small intestine, is the ability of the membrane of smooth muscle elements to spontaneous depolarization. The nature of contractions and their coordination depend on the influence of efferent neurons of the intraorgan nervous system and the autonomic part of the central nervous system.

Absorption of nutrients in the large intestine under normal physiological conditions is insignificant, since most of the nutrients have already been absorbed in the small intestine. The size of water absorption in the large intestine is large, which is essential in the formation of feces.

Small amounts of glucose, amino acids, and some other easily absorbed substances can be absorbed in the large intestine.

Juice secretion in the large intestine is mainly a reaction in response to local mechanical irritation of the mucous membrane by chyme. Colon juice consists of dense and liquid components. The dense component includes mucous lumps, consisting of desquamated epitheliocytes, lymphoid cells and mucus. The liquid component has a pH of 8.5-9.0. Juice enzymes are contained mainly in desquamated epitheliocytes, during the decay of which their enzymes (pentidases, amylase, lipase, nuclease, cathepsins, alkaline phosphatase) enter the liquid component. The content of enzymes in the juice of the colon and their activity is much lower than in the juice of the small intestine. But the available enzymes are sufficient to complete the hydrolysis in the proximal colon of the remnants of undigested nutrients.

The regulation of juice secretion of the mucous membrane of the large intestine is carried out mainly due to enteral local nervous mechanisms.

Similar information.

Biochemical processes

During muscle activity, there is an increase and increase in heart rate, which requires more energy compared to the resting state. However, the energy supply of the heart muscle is carried out mainly due to aerobic ATP resynthesis. Anaerobic ATP resynthesis pathways are activated only during very intensive work.

Great opportunities for aerobic energy supply in the myocardium are due to the peculiarity of the structure of this muscle. Unlike skeletal muscles, the cardiac muscle has a more developed, dense network of capillaries, which makes it possible to extract more oxygen and oxidation substrates from the flowing blood. In addition, myocardial cells have more mitochondria containing tissue respiration enzymes. As energy sources, the myocardium uses various substances delivered by the blood: glucose, fatty acids, ketone bodies, glycerol. Own reserves of glycogen are practically not used; they are necessary for the energy supply of the myocardium during exhausting loads.

During intensive 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. The use of lactate as an energy source makes it possible 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 for oxidation. Oxidation of lactate in the heart muscle also contributes to the normalization of the acid-base balance, since the concentration of this acid in the blood decreases.

Decreased peripheral resistance

At the same time, a significant change in the cardiovascular system during dynamic exercise is a significant decrease in total peripheral resistance caused by the accumulation of metabolic vasodilators and a decrease in vascular resistance in actively working skeletal muscles. The decrease in total peripheral resistance is a pressure reducing factor that stimulates an increase in sympathetic activity through the arterial baroreceptor reflex.

Although the mean arterial pressure during exercise is higher than normal, however, a decrease in total peripheral resistance leads to its fall below this elevated level, at which it would have to be regulated as a result of only actions on the vasomotor center aimed at raising the set point. The arterial baroreceptor arch reacts to this circumstance by increasing sympathetic activity. Thus, the arterial baroreceptor reflex largely determines the increase in sympathetic activity during exercise, despite the seemingly contradictory fact of an increase in blood pressure compared to the norm. In fact, were it not for the arterial baroreceptor reflex, the decrease in total peripheral resistance that occurs during exercise would cause mean arterial pressure to drop substantially below normal.

Skin blood flow may increase with exercise despite an overall increase in sympathetic vasoconstrictor nerve tone, since thermal reflexes can suppress pressor reflexes in regulating skin blood flow under certain conditions. Temperature reflexes are usually, of course, activated during strenuous physical activity to eliminate the excess heat that occurs during active skeletal muscle work. Often skin blood flow decreases at the onset of exercise (as part of an overall increase in arteriolar tone as a result of increased activity of sympathetic vasoconstrictor nerves) and then increases as exercise continues as heat production and body temperature increase.

In addition to increasing blood flow in the skeletal muscles and skin, coronary blood flow also increases significantly during heavy physical exertion. This is primarily due to local metabolic vasodilation of the coronary arterioles, due to increased cardiac work and increased oxygen consumption by the myocardium.

There are two important mechanisms involved in the response of the cardiovascular system to dynamic exercise. The first is the skeletal muscle pump, which we discussed in connection with the vertical position of the body. The skeletal muscle pump is a very important factor in enhancing venous return during exercise and thus prevents an excessive decrease in central venous pressure due to an increase in heart rate and myocardial contractility. The second factor is the respiratory pump, which also promotes venous return during exercise. Strengthening of respiratory movements during exercise leads to an increase in the efficiency of the respiratory pump and, thereby, contributes to an increase in venous return and filling of the heart.

The average value of the central venous pressure with a significant dynamic physical load changes insignificantly, or does not change at all. This is because both the minute volume and venous return curves shift upward with exercise. Thus, minute volume and venous return increase without significant changes in central venous pressure.

In general, significant adaptive changes in the activity of the cardiovascular system during dynamic physical activity occur automatically, due to the work of normal regulatory mechanisms! activities of the cardiovascular system. The colossal increase in blood flow in the skeletal muscles is mainly due to an increase in cardiac output, but in part it is also due to a decrease in blood flow in the kidneys and abdominal organs.

During static (i.e. isometric) physical activity, changes occur in the cardiovascular system that are different from changes during dynamic exercise. As discussed in the previous section, dynamic loading leads to a significant decrease in total peripheral resistance due to local metabolic vasodilation in the working muscles. Static stress, even of moderate intensity, causes compression of blood vessels in contracting muscles and a decrease in volumetric blood flow in them. Thus, total peripheral resistance usually does not decrease during static exercise and may even increase significantly if some large muscles are involved in the work. The primary changes in cardiovascular activity during static exercise are setpoint-raising impulse flows to the vasomotor center of the medulla oblongata from the cerebral cortex (central command) and from chemoreceptors in contracting muscles.

The impact on the cardiovascular system of a static load leads to an increase in heart rate, minute volume and blood pressure - all this is the result of increased activity of the sympathetic centers. At the same time, static exercise leads to a smaller increase in heart rate and minute volume and a greater increase in diastolic, systolic and mean arterial pressure than occurs with dynamic exercise.



Currently, this circumstance is not assessed so unequivocally, modern achievements in sports cardiology allow a deeper understanding of changes in the heart and blood vessels in athletes under the influence of physical activity.

The heart works on average with a frequency of 80 beats per minute, in children - a little more often, in the elderly and the elderly - less often. In one hour, the heart performs 80 x 60 \u003d 4800 contractions, in a day 4800 x 24 \u003d contractions, in a year this number reaches 365 \u003d. With an average life expectancy of 70 years, the number of heartbeats - a kind of engine cycles - will be about 3 billion.

Let's compare this figure with those of the machine cycles. The motor allows the car to pass 120 thousand km without major repairs - these are three trips around the world. At a speed of 60 km / h, which provides the most favorable mode of operation of the engine, its service life will be only 2 thousand hours (120,000). During this time, he will make 480 million engine cycles.

This number is already closer to the number of heart contractions, but the comparison is clearly not in favor of the engine. The number of contractions of the heart and, accordingly, the number of revolutions of the crankshaft is expressed by a ratio of 6:1.

The duration of the heart's service life exceeds that of the engine by more than 300 times. Note that in our comparison, the highest indicators are taken for a car, and average indicators for a person. If we take the age of centenarians for calculation, then the advantage of the human heart over the engine will increase in the number of work cycles at once, and in terms of service life - at once. Is this not evidence of a high level of biological organization of the heart!

The heart has enormous adaptive capabilities, which are most clearly manifested during muscular work. At the same time, the stroke volume of the heart almost doubles, that is, the amount of blood ejected into the vessels with each contraction. Since this triples the frequency of the heart, the volume of blood ejected per minute (minute volume of the heart) increases by 4-5 times. Of course, the heart at the same time expends much more effort. The work of the main - left - ventricle increases 6-8 times. It is especially important that under these conditions the efficiency of the heart increases, measured by the ratio of the mechanical work of the heart muscle to all the energy expended by it. Under the influence of physical activity, the efficiency of the heart increases by 2.5-3 times compared to the level of motor rest. This is the qualitative difference between the heart and the engine of a car; with an increase in load, the heart muscle switches to an economical mode of operation, while the engine, on the contrary, loses its efficiency.

The above calculations characterize the adaptive capabilities of a healthy but untrained heart. A much wider range of changes in his work is acquired under the influence of systematic training.

Physical training reliably increases the vitality of a person. Its mechanism is reduced to the regulation of the relationship between the processes of fatigue and recovery. Whether a single muscle or several groups are being trained, a nerve cell or a salivary gland, the heart, lungs or liver, the basic patterns of training each of them, like organ systems, are fundamentally similar. Under the influence of the load, which is specific for each organ, its vital activity intensifies and fatigue soon develops. It is well known that fatigue reduces the performance of an organ; less well known is its ability to stimulate the recovery process in a working organ, which significantly changes the prevailing idea of ​​fatigue. This process is useful, and one should not get rid of it as something harmful, but, on the contrary, strive for it in order to stimulate recovery processes!

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Physical stress on the heart

People involved in sports, performing various physical exercises often wonder if physical activity affects the heart. Let's take a look and find out the answer to this question.

Like any good pump, the heart was designed to vary its load as needed. So, for example, in a calm state, the heart contracts (beats) once a minute. During this time, the heart pumps approximately 4 liters. blood. This indicator is called minute volume or cardiac output. And in the case of training (physical activity), the heart can pump 5-10 times more. Such a trained heart will wear out less, it will be much more powerful than an untrained one and will remain in better condition.

Heart health can be compared to a good car engine. As in a car, the heart is able to work hard, it can work without any disturbance and at a fast pace. But it also requires a period of recovery and rest of the heart. In the course of the aging of the human body, the need for all this grows, but this need does not increase as much as many people think. As with a good car engine, judicious and proper use enables the heart to function as if it were a new engine.

In our time, an increase in the size of the heart is perceived as a completely natural physiological adaptation to serious physical exertion. And there is no proven evidence that intense exercise and endurance exercise can adversely affect an athlete's heart health. Moreover, now a certain load of endurance is used in the treatment of blockage of the arteries (coronary arteries).

Also, it has been proven for a long time that a person with a trained heart (an athlete who is able to perform serious physical activities) can perform a much greater amount of work than an untrained person before his heart reaches its highest beat rate.

For an average person, the amount of blood pumped by the heart every 60 seconds (cardiac output) increases from 4 liters during exercise. up to 20 l. In well-trained people (athletes), this figure can increase to 40 liters.

This increase is due to an increase in the amount of blood that is ejected with each contraction of the heart (stroke volume), the same as from heart rate (heart rate). As the heart rate increases, the stroke volume of the heart also increases. But if the pulse increases to such an extent that the heart begins to lack time for adequate filling, then the cardiac stroke volume falls. If a person goes in for sports, if he is well trained and copes with high physical loads, then much more time will pass before this limit is reached.

An increase in stroke volume of the heart is determined by increased diastolic volume and increased filling of the heart. As fitness increases, heart rate decreases. These changes indicate that the load on the cardiovascular system is decreasing. And also, it means that the body has already adapted to such work.

How does exercise affect the heart?

The heart is the central organ in the human body. He is more than others subject to emotional and physical stress. In order for stress to go to the heart in favor, and not to harm, you need to know a few simple “rules of operation” and be guided by them.

Sport

Sports can affect the heart muscle in different ways. On the one hand, it can serve as exercises for training the heart, on the other hand, it can cause malfunctions in its work and even illness. Therefore, you need to choose the right type and intensity of physical activity. If you have already had heart problems or you are sometimes worried about chest pains, in no case should you start training without consulting a cardiologist.

Professional athletes often develop heart problems due to heavy physical exertion and frequent training. Regular training is a good help for training the heart: the heart rate decreases, which indicates an improvement in its work. But, having adapted to new loads, this body will painfully endure a sharp cessation of training (or irregular training), as a result of which hypertrophy of the heart muscles, atherosclerosis of blood vessels, and a decrease in blood pressure may occur.

Profession vs heart

Increased anxiety, lack of normal rest, stress and risks adversely affect the condition of the heart muscle. There are peculiar ratings of professions that are harmful to the heart. The honorable first place is occupied by professional athletes, followed by politicians and responsible leaders whose life is connected with making difficult decisions. An honorable third place was given to the teacher.

Also, the top includes rescuers, military, stuntmen and journalists, who are more than other specialists not included in the list, subject to stress and psychological stress.

The danger of working in the office is inactivity, which can lead to a decrease in the level of enzymes responsible for burning fat, insulin sensitivity also suffers. Sedentary work with increased responsibility (for example, bus drivers) is fraught with the development of hypertension. From the point of view of doctors, work with a shift schedule is also “harmful”: the natural rhythms of the body go astray, lack of sleep, smoking can greatly spoil health.

Professions that affect the state of the heart can be divided into two groups. In the first - professions with low physical activity, increased responsibility, night shifts. In the second - specialties associated with emotional and physical overstrain.

In order to minimize the effect of stress on the heart, you need to follow a few simple rules:

1. Leave work at work. When you come home - do not worry about unfinished business: you have many more working days ahead of you.
2. Take more walks in the fresh air - from work, to work or during your lunch break.
3. If you feel stressed, chatting with a friend about something distracting will help you relax.
4. Eat more protein foods - lean meat, cottage cheese, foods with vitamin B, magnesium, potassium and phosphorus.
5. You need to sleep at least 8 hours. Remember that the most productive sleep is around midnight, so go to bed no later than 22.
6. Go in for light sports (aerobics, swimming) and exercises that improve the condition of the heart and blood vessels.

heart and sex

Stress during lovemaking does not always have a positive effect on the body. A surge of hormones, emotional and physical stress in the complex have a positive effect on a healthy person, but the cores need to be more careful.

If you have been diagnosed with heart failure or have recently had a heart attack, having sex can lead to painful attacks. Heart medication should be taken before intimacy.

A consultation with a cardiologist will help you choose the “right” medications that support the heart and do not reduce potency (beta-blockers).

Make love in positions that cause less tension, try to make the process smoother. Increase the duration of foreplay, take your time and do not worry. If the load is increased gradually, soon you will return to a full life.

Exercises to strengthen the heart

Useful exercises for strengthening the heart are any work at home or in the country, because the main enemy of our heart is inactivity. Cleaning the house, working in the garden, picking mushrooms perfectly train your heart, increasing blood conductivity and elasticity. If before that you had no physical activity for a long time, do even simple work without fanaticism, otherwise your blood pressure may rise.

If you do not have a dacha, go in for walking, yoga under the supervision of a trainer, he will help you choose the right simple exercises to strengthen your heart.

Exercises for the heart and blood vessels are necessary if you have been diagnosed with obesity due to poor blood circulation. In this case, cardio training should be combined with dietary nutrition, the correct daily routine and the use of vitamin preparations.

The effect of physical activity on the human heart.

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MUNICIPAL BUDGET GENERAL EDUCATIONAL INSTITUTION

SECONDARY EDUCATIONAL SCHOOL № 1

WITH IN-DEPTH LEARNING OF ENGLISH

Topic: The effect of physical activity on the human heart.

Completed by: Makarova Polina

Student 3 "b" class

Head: Vyushina T.I.

Physical education teacher

The fact that our ancestors needed strength is understandable. With stone axes and sticks, they went to mammoths, thus obtaining the necessary food for themselves, protecting their lives, fought, almost unarmed, with wild animals. Strong muscles, great physical strength were also needed by a person at a later time: in war they had to fight hand-to-hand, in peacetime they worked the fields, and harvested.

XXI Century…! This is the age of new grandiose technical discoveries. We can no longer imagine our life without various technology that replaces people everywhere. We move less and less, spend hours in front of the computer and TV. Our muscles become weak and flabby.

I noticed that after physical education lessons, my heart starts to beat faster. In the second quarter of the third grade, studying the topic "Man and the World around", I learned that the heart is a muscle, only a special one, which has to work all my life. Then I had a question: “Does physical activity affect a person’s heart?”. And since I strive to protect my health, I believe that the chosen research topic is relevant.

The purpose of the work: To find out whether physical activity affects the functioning of the human heart.

1. Study the literature on the topic "Human Heart".

2. Conduct the experiment "Measuring the pulse at rest and under load."

3. Compare the results of heart rate measurements at rest and during exercise.

4. Draw conclusions.

5. Conduct a study of the knowledge of my classmates on the topic of this work.

Object of research: Human heart.

Subject of study: The effect of physical activity on the human heart.

Research Hypothesis: I hypothesize that physical activity affects the human heart.

The human heart knows no limits

the human mind is limited.

Antoine de Rivarol

In the course of the study, I studied in detail the literature on the topic “The Human Heart”. I learned that many, many years ago, in order to understand whether a person is alive or dead, first of all, they checked: is his heart beating or not? If the heart does not beat, then it has stopped, therefore, the person has died.

The heart is a very important organ!

The heart refers to such internal organs, without which a person cannot exist. The heart and blood vessels are the circulatory organs.

The heart is located in the chest and is located behind the sternum, between the lungs (closer to the left). The human heart is small. Its size depends on the size of the human body. You can find out the size of your heart like this: clench your fist - your heart is equal to its size. This is a tight muscular bag. The heart is divided into two parts - into the right and left halves, between which there is a muscular septum. She keeps the blood from mixing. The left and right halves are divided into two chambers. At the top of the heart are the atria. In the lower part - the ventricles. And this bag is constantly compressing and unclenching, without stopping for a minute. It works without rest throughout a person's life, other organs, such as the eyes, sleep, legs and arms rest, and the heart has no time to rest, it always beats.

Why is it trying so hard?

The heart performs a very important job, it, like a mighty pump, distills blood through the blood vessels. If you look at the back of the hand, we will see bluish lines, like rivers and streams, somewhere wider, somewhere narrower. These are blood vessels that extend from the heart throughout the human body and through which blood flows continuously. When the heart makes one beat, it contracts and pushes the blood out of itself, and the blood begins to run through our body, supplying it with oxygen and nutrients. Blood makes a whole journey through our body. Blood enters the right half of the heart after it collects unnecessary substances in the body that it needs to get rid of. This does not pass to her in vain, she acquires a dark cherry color. Such blood is called venous. It returns to the heart through the veins. Collecting venous blood from all cells of the body, the veins become thicker and two wide tubes enter the heart. Expanding, the heart sucks out the waste blood from them. Such blood must be cleansed. It is enriched with oxygen in the lungs. Carbon dioxide is released from the blood into the lungs, and oxygen is taken from the lungs into the blood. The heart and lungs are neighbors, which is why the path of blood from the right side of the heart to the lungs and from the lungs to the left side of the heart is called the pulmonary circulation. The oxygen-rich blood is bright scarlet, returns to the left half of the heart through the pulmonary veins, from there the heart will force it through the aorta into the blood vessels-arteries and it will run throughout the body. This path is long. The path of blood from the heart to the whole body and back is called the systemic circulation. All veins and arteries branch, divide into thinner ones. The thinnest are called capillaries. They are so thin that if you add 40 capillaries, they will be thinner than a hair. There are a lot of them, if you add one chain of them, then the globe can be wrapped 2.5 times. All vessels are intertwined with each other, like the roots of trees, herbs, shrubs. Summarizing all of the above, we can say that the function of the heart is to pump blood through the vessels, providing the tissues of the body with oxygen and nutrients.

1. Heart rate measurement at rest and during exercise

Under the pressure of blood, the elastic walls of the artery oscillate. These vibrations are called the pulse. The pulse can be felt in the area of ​​the wrist (radial artery), the lateral surface of the neck (carotid artery), putting your hand in the area of ​​the heart. Each beat of the pulse corresponds to one heartbeat. The pulse rate is measured by applying two or three fingers (except the little finger and thumb) to the passage of the artery (usually on the wrist) and counting the number of beats in 30 seconds, then the result is multiplied by two. You can also measure the pulse on the neck, on the carotid plexus. A healthy heart contracts rhythmically, in adults in a calm state, beats per minute, and in children. With physical activity, the number of strokes increases.

In order to find out whether physical activity affects the human heart, I conducted the experiment "Measuring the pulse at rest and during exercise."

At the first stage, I measured the pulse of classmates in a calm state, and entered the measurement results into a comparative table. Then I asked the guys to sit down 10 times and measure the pulse again, I entered the results in the table. After the pulse returned to normal, I gave the task: run for 3 minutes. And only after the run we measured the pulse for the third time, and the results were again entered into the table.

Comparing the measurement results, I saw that the pulse of students in different states is not the same. The resting heart rate is much lower than after exercise. And the more physical activity, the greater the pulse. On this basis, we can conclude that physical activity affects the functioning of the human heart.

Having proved that physical activity affects the functioning of the heart, I asked myself: What is this effect? Does it benefit or harm a person?

1. The effect of physical activity on the human heart.

The heart and blood vessels play a very important role - they provide the transfer of oxygen and nutrients to the organs. When performing physical activity, the work of the heart changes significantly: the purity of heart contractions increases and the volume of blood pushed out by the heart in one contraction increases. With intense physical exertion, for example, while running, the pulse quickens from 60 beats to 150 beats per minute, the amount of blood ejected by the heart in 1 minute increases from 5 to 20 liters. When playing sports, the muscles of the heart thicken a little and become more resilient. In trained people, the resting heart rate slows down. This is due to the fact that a trained heart pumps more blood. Lack of movement is harmful to human health. The heart is a muscle, and muscles, without training, remain weak and flabby. Therefore, with a lack of movement, the work of the heart is disturbed, resistance to diseases decreases, and obesity develops.

An excellent workout for the heart is physical labor in the fresh air, physical education, in winter - skating and skiing, in summer - swimming and swimming. Morning exercises and walking strengthen the heart well.

Beware of heart overload! You can not work or run to the point of exhaustion: this can weaken the heart. It is necessary to alternate work with rest.

Restful sleep is one of the necessary conditions for the proper functioning of the heart. During sleep, the body is at rest, at this time the work of the heart also weakens - it rests.

The human heart works continuously, day and night, throughout life. The work of the heart depends on the work of other organs, the whole organism. Therefore, it must be strong, healthy, that is, trained.

At rest, the child's pulse is beats per minute. The results of my research prove that physical activity affects the human heart. And since the heart needs to be trained, it means that physical activity is necessary for the development of its endurance.

I want to highlight the basic rules for training the heart:

1. Outdoor games.
2. Outdoor work.
3. Physical education.
4. Skating and skiing.
5. Bathing and swimming.
6. Morning exercises and walking.
7. Peaceful sleep.
8. It is necessary to increase the load on the heart gradually.
9. Perform exercises systematically and daily.
10. Training should take place under the supervision of a doctor or an adult.
11. Watch your heart rate.

We now know that the human heart does not always work in the same way. During exercise, the heart rate increases.

In order to study the knowledge of classmates on this topic, I conducted a survey. 21 people of the 3rd grade took part in the survey. They were asked to answer the following questions:

1. Do you know how the heart works?
2. Do you think physical activity affects the functioning of the human heart?
3. Do you want to know?

We entered the results of the survey in a table, which shows that only 8 of our classmates do not know how the heart works, and 15 do.

To the second question of the questionnaire, “Do you think physical activity affects the work of a person’s heart?” 16 students answered "yes" and 7 answered "no".

To the question "Do you want to know?" 18 children gave a positive answer, 5 - negative.

Therefore, I can help my classmates find out how physical activity affects the human heart, as I have studied this issue well.

The scope of my knowledge: to make a report on the "Influence of physical activity on the work of the human heart" at a physical education lesson.

In the process of doing educational and research work, I learned that the heart is the central organ of the circulatory system in the form of a muscle bag. The heart works continuously, day and night, throughout life. The work of the heart depends on the work of other organs, the whole organism. In fact, the blood will bring nutrients and air to all organs on time and in the right amount if the heart is doing its job.

Both scientists and simply inquisitive people are amazed by the enormous working capacity of the heart. In 1 minute, the heart overtakes 4 - 5 liters of blood. It is easy to calculate how much the heart will overtake blood per day. It will turn out a lot of 7200 liters. And it's only the size of a fist. That's how trained the heart should be. Therefore, doing physical education and sports, doing physical labor, we strengthen all the muscles of our body, including the heart. But it should be remembered that physical activity has not only a positive effect on the heart. With improper distribution of loads, overloads occur that harm the heart!

SAVE YOUR HEART!

Table for measuring the pulse of students in grade 3 "b"

Physical activity and its effect on the heart

Physical activity has a pronounced effect on the human body, causing changes in the activity of the musculoskeletal system, metabolism, internal organs and the nervous system. The degree of impact of physical activity is determined by its magnitude, intensity and duration. Adaptation of the body to physical activity is largely determined by an increase in the activity of the cardiovascular system, which manifests itself in an increase in heart rate, an increase in myocardial contractility, an increase in stroke and minute blood volume (Karpman, Lyubina, 1982; Kots, 1986; Amosov, Bendet, 1989) .

The amount of blood ejected from the ventricle of the heart in one heartbeat is called the stroke volume (SV). At rest, the value of the stroke volume in an adult is ml and depends on body weight, the volume of the chambers of the heart and the force of contraction of the heart muscle. The reserve volume is the part of the blood that remains in the ventricle at rest after contraction, but is ejected from the ventricle during physical exertion and in stressful situations. It is the value of the reserve blood volume that largely contributes to an increase in the stroke volume of the blood during exercise. The increase in SV during physical exertion is also facilitated by an increase in venous return of blood to the heart. During the transition from rest to exercise, the stroke volume of blood increases. The increase in the value of SV goes until its maximum is reached, which is determined by the volume of the ventricle. With a very intense load, the stroke volume of blood may decrease, because due to a sharp shortening of the duration of diastole, the ventricles of the heart do not have time to completely fill with blood.

The minute volume of blood (MBV) measures how much blood is ejected from the ventricles of the heart in one minute. The value of the minute volume of blood is calculated according to the following formula:

Minute volume of blood (MOV) \u003d VV x HR.

Since in healthy adults the stroke volume at rest is 5090 ml, and the heart rate is in the range of beats / min, the value of the minute volume of blood at rest is in the range of 3.5-5 l / min. In athletes, the value of the minute volume of blood at rest is the same, since the value of the stroke volume is slightly higher (ml), and the heart rate is lower (45-65 beats / min). When performing physical activity, the minute volume of blood increases due to an increase in the magnitude of the stroke volume of the blood and the heart rate. As the magnitude of the exercise performed increases, the stroke volume of the blood reaches its maximum and then remains at this level with a further increase in the load. The increase in the minute volume of blood in such conditions occurs due to a further increase in the heart rate. After the cessation of physical activity, the values ​​of central hemodynamic parameters (MBC, VR and HR) begin to decrease and after a certain time reach the initial level.

In healthy untrained people, the value of the minute volume of blood during exercise may increase in dollars / min. The same value of the IOC during physical activity is observed in athletes who develop coordination, strength or speed. For representatives of team sports (football, basketball, hockey, etc.) and martial arts (wrestling, boxing, fencing, etc.), the MOC value reaches the development of endurance; reaches maximum values ​​(35-38 l / min) due to the large magnitude of stroke volume (ml) and high heart rate (bpm).

Adaptation of the body of healthy people to physical activity occurs in an optimal way, by increasing the value of both stroke volume and heart rate. Athletes use the most optimal variant of adaptation to the load, since due to the presence of a large reserve volume of blood during exercise, a more significant increase in stroke volume occurs. In cardiac patients, when adapting to physical activity, a non-optimal variant is noted, because due to the lack of a reserve blood volume, adaptation occurs only by increasing the heart rate, which causes the appearance of clinical symptoms: palpitations, shortness of breath, pain in the heart, etc.

To assess the adaptive capacity of the myocardium in functional diagnostics, the functional reserve index (FR) is used. The indicator of myocardial functional reserve indicates how many times the minute volume of blood during exercise exceeds the level of rest.

If the patient has the highest minute blood volume during exercise is 28 l / min, and at rest it is 4 l / min, then his myocardial functional reserve is seven. This value of the functional reserve of the myocardium indicates that when performing physical activity, the myocardium of the subject is able to increase its performance by 7 times.

Long-term sports contribute to an increase in the functional reserve of the myocardium. The greatest functional reserve of the myocardium is observed in representatives of sports for the development of endurance (8-10 times). Somewhat less (6-8 times) the functional reserve of the myocardium in athletes of team sports and martial arts representatives. In athletes developing strength and speed, the functional reserve of the myocardium (4-6 times) differs little from that in healthy untrained individuals. A decrease in myocardial functional reserve less than four times indicates a decrease in the pumping function of the heart during exercise, which may indicate the development of overload, overtraining, or heart disease. In cardiac patients, a decrease in the functional reserve of the myocardium is due to the lack of a reserve blood volume, which does not allow an increase in stroke volume during exercise, and a decrease in myocardial contractility, which limits the pumping function of the heart.

Echocardiography (EchoCG) and rheocardiography (RKG) methods are used in practice to determine the values ​​of stroke, minute blood volume and calculate the functional reserve of the myocardium. The data obtained using these methods make it possible to identify in athletes the features of changes in stroke, minute blood volume and myocardial functional reserve under the influence of physical activity and use them in dynamic observations and in the diagnosis of heart diseases.

"Influence of physical activity on the human heart".

This research work is devoted to studying the problem of the influence of physical activity on the human heart.

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Our ancestors needed strength. With stone axes and sticks they went to mammoths, thus obtaining the necessary food for themselves, protecting their lives, fought, almost unarmed, with wild animals. Strong muscles, great physical strength were also needed by a person at a later time: in war they had to fight hand-to-hand, in peacetime they worked the fields, and harvested. Modern man no longer has to deal with such problems. Since the new century has given us many technical discoveries. We can't imagine our life without them. We move less and less, spend hours in front of the computer and TV. Our muscles become weak and flabby. Relatively recently, people again began to think about how to give the human body the missing physical activity. To do this, people began to go to gyms more, go in for running, outdoor training, skiing and other sports, for many these hobbies have grown into professional ones. Of course, people involved in sports, performing various physical exercises often ask themselves the question: does physical activity affect the human heart? This question formed the basis of our study and was designated as a topic.

To study this topic, we got acquainted with the sources of Internet resources, studied reference medical literature, literature on physical culture of such authors as: Amosov N.M., Muravov I.V., Balsevich V.K., Rashchupkin G.V. and others.

The relevance of this study lies in the fact that each person must learn how to choose the right physical activity for himself, depending on his level of health, fitness of the body, everyday psychophysical state.

The purpose of the research work is to find out whether physical activity affects the human heart.

The subject of the research work is the effect of physical activity on the human heart.

The object of the research work is the human heart.

The hypothesis of the research work is that if physical activity affects the human heart, then the heart muscle is strengthened.

Based on the purpose and hypothesis of the research work, we set the following tasks:

1. To study various sources of information related to the problem of the influence of physical activity on the human heart.
2. Organize 2 age groups for the study.
3. Prepare general questions for test groups.
4. Carry out tests: determination of the state of the cardiovascular system using pulsometry; test with squats or jumps; CCC response to physical activity; assessment of anti-infective immunity.
5. Summarize the test results for each group.
6. Draw conclusions.

Research methods: theoretical (analysis of literature, documents, work with Internet resources, generalization of data), practical (work in social networks, measurement, testing).

CHAPTER I. PHYSICAL LOADS AND THE HUMAN HEART.

“The heart is the main center of the circulatory system, working on the principle of a pump, due to which blood moves in the body. As a result of physical training, the size and mass of the heart increases due to the thickening of the walls of the heart muscle and an increase in its volume, which increases the power and performance of the heart muscle. Blood in the human body performs the following functions: transport, regulatory, protective, heat exchange. (1)

“With regular physical exercise: the number of red blood cells and the amount of hemoglobin increase, resulting in an increase in the oxygen capacity of the blood; they increase the body's resistance to colds and infectious diseases, due to the increased activity of leukocytes; recovery processes after a significant loss of blood are accelerated. (1)

“An important indicator of the health of the heart is the systolic blood volume (CO) - the amount of blood pushed out by one ventricle of the heart into the vascular bed with one contraction. Another informative indicator of the health of the heart is the number of heartbeats (HR) - arterial pulse. In the process of sports training, heart rate at rest becomes less frequent over time due to an increase in the power of each heartbeat. (1)

The heart of an untrained person, in order to provide the necessary minute volume of blood (the amount of blood ejected by one ventricle of the heart during a minute), is forced to contract with a greater frequency, since it has a lower systolic volume. The heart of a trained person is more often penetrated by blood vessels, in such a heart muscle tissue is better nourished, and the heart's performance has time to recover during pauses in the cardiac cycle.

Let us pay attention to the fact that the heart has enormous adaptive capabilities, which are most clearly manifested during muscular work. “At the same time, the stroke volume of the heart almost doubles, that is, the amount of blood ejected into the vessels with each contraction. Since this triples the frequency of the heart, the volume of blood ejected per minute (minute volume of the heart) increases by 4-5 times. At the same time, the heart expends much more effort. The work of the main - left - ventricle increases 6-8 times. It is especially important that under these conditions the efficiency of the heart increases, measured by the ratio of the mechanical work of the heart muscle to all the energy expended by it. Under the influence of physical loads, the efficiency of the heart increases by 2.5-3 times compared to the level of motor rest. (2)

The above conclusions characterize the adaptive capabilities of a healthy but untrained heart. A much wider range of changes in his work is acquired under the influence of systematic physical training.

Physical training reliably increases the vitality of a person. “Its mechanism is reduced to the regulation of the relationship between the processes of fatigue and recovery. Whether a single muscle or several groups are being trained, a nerve cell or a salivary gland, the heart, lungs or liver, the basic patterns of training each of them, like organ systems, are fundamentally similar. Under the influence of the load, which is specific for each organ, its vital activity intensifies and fatigue soon develops. It is known that fatigue reduces the performance of an organ; less well known is its ability to stimulate the recovery process in a working organ, which significantly changes the prevailing idea of ​​fatigue. This process is useful for stimulating recovery processes.” (2)

Thus, we can conclude that physical activity in the form of sports training has a positive effect on the heart. The walls of the heart muscle thicken, and its volume increases, which increases the power and efficiency of the heart muscle, thereby reducing the number of heart contractions. And also a trained heart is able to stimulate the processes of fatigue and recovery during intense training.

CHAPTER II. TRAINING RULES IN TERMS OF IMPACT

In order for physical education to have only a positive impact on a person, a number of methodological requirements must be observed.

The first rule of training is the gradual increase in intensity and duration of loads. “The healing effect for different organs is not achieved simultaneously. Much depends on the loads that are difficult to take into account for some organs, so you need to focus on those organs and functions that react the slowest. The most vulnerable organ during training is the heart, therefore, almost all healthy people should be guided by its capabilities with increasing loads. If a person has damaged any organ, then his reaction to the load should be taken into account on a par with the heart, and even in the first place. In most untrained people, only the heart is exposed to danger during physical exertion. But if the most elementary rules are followed, this risk is minimal if a person does not yet suffer from diseases of the cardiovascular system. Therefore, one should not catch up as soon as possible and urgently become healthy. Such impatience is dangerous for the heart.” (3)

The second rule that should be followed when starting a health training is the variety of means used. “For a qualitative variety of physical activity, only 7-12 exercises are enough, but they differ significantly from each other. This will allow you to train different aspects of the functional abilities of the heart and the whole body. If one or two exercises are used, and besides, if they involve small muscle groups in the activity, then highly specialized training effects occur. So, many gymnastic exercises do not improve the overall reactivity of the heart at all. But running, which includes a large number of muscles, is an excellent means of versatile training. Skiing, swimming, rowing, rhythmic gymnastics have the same effect. The value of physical exercises is determined not only by their own health-improving possibilities, but also by the conditions on which the convenience of their use depends. Also important: the emotionality of the exercises, interest in them, or, on the contrary, hostility and boredom during performance. (3)

The third rule, the observance of which provides an active counteraction to premature aging, is the primary training of the motor function. “The opinion that by strengthening weakened motor abilities, we train only the muscles, is a delusion. At the same time, we train the heart, and precisely those of its abilities that, due to untrainedness, turn out to be the most vulnerable. More recently, for middle-aged and elderly people, such exercises as torso torso, running, jumping, strength exercises, etc. were considered contraindicated. Walking was only partially replaced by running, breathing exercises, simple and slowly performed movements of the arms, legs and torso, borrowed from generally accepted morning hygienic gymnastics - that's practically everything that was recommended to the population. Moreover, not for people with diseases of the cardiovascular system, but for everyone over 40 years old. Modern doctors believe that with dosed use, "contraindicated" exercises, the greatest effect for recovery occurs. The more the body becomes unaccustomed to a particular movement, the more valuable it is as a means of training. After all, a training exercise in this case makes up for the missing influence. (3)

The fourth rule of training is the systematic training. Physical education should be a constant factor in the regimen. “Those who want to get the maximum benefit from exercise should, after the first, preparatory period of training, train daily. The options here can be different - classes in fitness groups, independent daily workouts are possible ”(3) and more.

An important role in training is played by the intensity of physical activity. Since the impact of physical exercises on a person is associated with a load on his body, causing an active reaction of functional systems. To determine the degree of tension of these systems under load, intensity indicators are used that characterize the reaction of the body to the work performed. There are many such indicators: change in motor reaction time, respiratory rate, minute volume of oxygen consumption, etc. Meanwhile, the most convenient and informative indicator of the intensity of loads, especially in cyclic sports, is the heart rate (HR). Individual zones of intensity of loads are determined with a focus on the heart rate, which can be measured using conventional pulsometry.

Thus, we have identified a few simple rules that should guide a person starting training.

CHAPTER III. DETERMINATION OF THE FUNCTIONAL STATE

We divided the practical part of the research work into several stages. At the first stage, we organized two age groups. The first age group consisted of 8 people, the average age was from 30 to 50 years. The second age group also consisted of 8 people, the average age was from 10 to 18 years. We asked all participants in the study 7 identical questions: 1. “What is your age?”; 2. “What kind of sport do you (did) do?”; 3. "Do you have chronic diseases associated with the cardiovascular system?"; 4. "What exercises do you do to maintain the heart muscle?"; 5. "Do you do morning exercises?"; 6. “Do you know your pulse? pressure?"; 7. "Do you have bad habits?"

After the survey, we compiled a table in which we entered all the data. The numbers in the top row of the table correspond to the numbers of the questions given above.

Physical activity that requires more energy than is produced at rest is physical load. During physical activity, the internal environment of the body changes, as a result of which homeostasis is disturbed. Muscles' need for energy is provided by a complex of adaptive processes in various tissues of the body. The chapter discusses physiological parameters that change under the influence of a sharp physical load, as well as cellular and systemic mechanisms of adaptation that underlie repeated or chronic muscle activity.

ASSESSMENT OF MUSCLE ACTIVITY

A single episode of muscular work or "acute load" causes responses of the body that are different from those that occur during chronic exercise, in other words during workout. Forms of muscular work can also vary. The amount of muscle mass involved in the work, the intensity of efforts, their duration and the type of muscle contractions (isometric, rhythmic) affect the responses of the body and the characteristics of adaptive reactions. The main changes that occur in the body during exercise are associated with increased energy consumption by skeletal muscles, which can increase from 1.2 to 30 kcal/min, i.e. 25 times. Since it is impossible to directly measure ATP consumption during physical activity (it occurs at the subcellular level), an indirect estimate of energy costs is used - measurement oxygen taken in during respiration. On fig. Figure 29-1 shows the oxygen consumption before, during and after light steady work.

Rice. 29-1. Oxygen consumption before, during and after light exercise.

Oxygen uptake and hence ATP production increase until a steady state is reached in which ATP production is adequate to its consumption during muscle work. A constant level of oxygen consumption (ATP formation) is maintained until the intensity of work changes. Between the start of work and the increase in oxygen consumption to some constant level, there is a delay called oxygen debt or deficiency. oxygen deficiency- the period of time between the start of muscular work and the increase in oxygen consumption to a sufficient level. In the first minutes after the contraction, there is an excess of oxygen uptake, the so-called oxygen debt(See Fig. 29-1). The "excess" of oxygen consumption in the recovery period is the result of many physiological processes. During dynamic work, each person has his own limit of maximum muscle load, at which oxygen uptake does not increase. This limit is called maximum oxygen uptake (VO 2ma J. It is 20 times the oxygen consumption at rest and cannot be higher, but with proper training it can be increased. Maximum oxygen uptake, ceteris paribus, decreases with age, bed rest, and obesity.

Responses of the cardiovascular system to physical activity

With an increase in energy costs during physical work, more energy production is required. Oxidation of nutrients produces this energy, and the cardiovascular system delivers oxygen to working muscles.

Cardiovascular system under dynamic load conditions

Local control of blood flow ensures that only working muscles with increased metabolic demands receive more blood and oxygen. If only the lower extremities work, the muscles of the legs receive an increased amount of blood, while the blood flow to the muscles of the upper extremities remains unchanged or reduced. At rest, skeletal muscle receives only a small fraction of cardiac output. At dynamic load both total cardiac output and relative and absolute blood flow to the working skeletal muscles are greatly enhanced (Table 29-1).

Table 29-1.Distribution of blood flow at rest and under dynamic load in an athlete

Region	Rest, ml/min	%	%
Internal organs
kidneys
coronary vessels
Skeletal muscles	1200		22,0
Leather
Brain
Other organs
Total cardiac output			25,65

During dynamic muscle work, systemic regulation (cardiovascular centers in the brain, with their autonomic effector nerves to the heart and resistive vessels) is involved in the control of the cardiovascular system along with local regulation. Already before the start of muscle activity, her

the program is formed in the brain. First of all, the motor cortex is activated: the overall activity of the nervous system is approximately proportional to the muscle mass and its working intensity. Under the influence of signals from the motor cortex, the vasomotor centers reduce the tonic effect of the vagus nerve on the heart (as a result, the heart rate increases) and switch arterial baroreceptors to a higher level. In actively working muscles, lactic acid is formed, which stimulates the muscle afferent nerves. Afferent signals enter the vasomotor centers, which increase the influence of the sympathetic system on the heart and systemic resistive vessels. Simultaneously muscle chemoreflex activity inside the working muscles lowers Po 2, increases the content of nitric oxide and vasodilating prostaglandins. As a result, a complex of local factors dilates arterioles, despite an increase in sympathetic vasoconstrictor tone. Activation of the sympathetic system increases cardiac output, and local factors in the coronary vessels ensure their expansion. High sympathetic vasoconstrictor tone limits blood flow to the kidneys, visceral vessels, and inactive muscles. Blood flow in inactive areas can drop by up to 75% under heavy work conditions. An increase in vascular resistance and a decrease in blood volume help maintain blood pressure during dynamic exercise. In contrast to reduced blood flow in visceral organs and inactive muscles, the self-regulatory mechanisms of the brain keep blood flow at a constant level, regardless of the load. Skin vessels remain constricted only until there is a need for thermoregulation. During overexertion, sympathetic activity can limit vasodilation in working muscles. Prolonged work at high temperatures is associated with increased blood flow in the skin and intense sweating, leading to a decrease in plasma volume, which can cause hyperthermia and hypotension.

Responses of the cardiovascular system to isometric exercise

Isometric exercise (static muscle activity) causes slightly different cardiovascular responses. Blood-

muscle current and cardiac output increase relative to rest, but high mean intramuscular pressure limits the increase in blood flow relative to rhythmic work. In a statically contracted muscle, intermediate metabolic products appear very quickly under conditions of too little oxygen supply. Under conditions of anaerobic metabolism, lactic acid production increases, the ADP/ATP ratio increases, and fatigue develops. Maintaining only 50% of the maximum oxygen consumption is already difficult after the 1st minute and cannot continue for more than 2 minutes. A long-term stable voltage level can be maintained at 20% of the maximum. Factors of anaerobic metabolism under conditions of isometric load trigger muscle chemoreflex responses. Blood pressure rises significantly, and cardiac output and heart rate are lower than during dynamic work.

Reactions of the heart and blood vessels to one-time and constant muscle loads

A single intense muscular work activates the sympathetic nervous system, which increases the frequency and contractility of the heart in proportion to the effort expended. Increased venous return also contributes to the performance of the heart in dynamic work. This includes the "muscle pump" that compresses the veins during rhythmic muscle contractions, and the "respiratory pump" that increases intrathoracic pressure oscillations from breath to breath. The maximum dynamic load causes the maximum heart rate: even blockade of the vagus nerve can no longer increase the heart rate. Stroke volume reaches its ceiling during moderate work and does not change when moving to the maximum level of work. An increase in blood pressure, an increase in the frequency of contractions, stroke volume and myocardial contractility that occur during work increase myocardial oxygen demand. The linear increase in coronary blood flow during work can reach a value that is 5 times higher than the initial level. Local metabolic factors (nitric oxide, adenosine, and activation of ATP-sensitive K-channels) act vasodilator on coronary

stem vessels. Oxygen uptake in the coronary vessels at rest is high; it increases during operation and reaches 80% of the delivered oxygen.

Adaptation of the heart to chronic muscle overload largely depends on whether the work performed carries the risk of pathological conditions. Examples are left ventricular volume expansion when work requires high blood flow and left ventricular hypertrophy is created by high systemic blood pressure (high afterload). Consequently, in people adapted to prolonged, rhythmic physical activity, which is accompanied by relatively low blood pressure, the left ventricle of the heart has a large volume with a normal thickness of its walls. People accustomed to prolonged isometric contractions have increased left ventricular wall thickness at normal volume and elevated pressure. A large volume of the left ventricle in people engaged in constant dynamic work causes a decrease in the rhythm and an increase in cardiac output. At the same time, the tone of the vagus nerve increases and decreasesβ -adrenergic sensitivity. Endurance training partially alters myocardial oxygen consumption, thus affecting coronary blood flow. Oxygen uptake by the myocardium is approximately proportional to the ratio "heart rate times mean arterial pressure", and since training decreases heart rate, coronary blood flow under the conditions of a standard fixed submaximal load decreases in parallel. Exercise, however, increases peak coronary blood flow by thickening myocardial capillaries and increases capillary exchange capacity. Training also improves endothelial-mediated regulation, optimizes responses to adenosine and control of intracellular free calcium in coronary SMCs. Preservation of endothelial vasodilating function is the most important factor that determines the positive effect of chronic physical activity on coronary circulation.

The effect of exercise on blood lipids

Constant dynamic muscle work is associated with an increase in the level of circulating high-density lipoproteins.

(HDL) and a decrease in low-density lipoprotein (LDL). As a result, the ratio of HDL to total cholesterol increases. Such changes in cholesterol fractions are observed at any age, provided that physical activity is regular. Body weight decreases and insulin sensitivity increases, which is typical for sedentary people who have begun regular exercise. In people who are at risk of coronary heart disease due to very high lipoprotein levels, exercise is a necessary addition to dietary restrictions and a means of losing weight, which helps to reduce LDL. Regular exercise improves fat metabolism and increases cellular metabolic capacity, favoringβ -oxidation of free fatty acids, and also improves lipoprotease function in muscle and adipose tissue. Changes in lipoprotein lipase activity, together with an increase in lecithin-cholesterol acyltransferase activity and apolipoprotein A-I synthesis, increase circulation

HDL.

Regular physical activity in the prevention and treatment of certain cardiovascular diseases

Changes in the ratio of HDL to total cholesterol that occur with regular physical activity reduce the risk of atherosclerosis and coronary artery disease in active people compared to sedentary people. It has been established that the cessation of active physical activity is a risk factor for coronary artery disease, which is as significant as hypercholesterolemia, high blood pressure and smoking. The risk is reduced, as noted earlier, due to a change in the nature of lipid metabolism, a decrease in the need for insulin and an increase in insulin sensitivity, as well as due to a decrease inβ -adrenergic reactivity and increased vagal tone. Regular exercise often (but not always) reduces resting BP. It has been established that a decrease in blood pressure is associated with a decrease in the tone of the sympathetic system and a drop in systemic vascular resistance.

Increased breathing is an obvious physiological response to exercise.

Rice. 29-2 shows that minute ventilation at the beginning of work increases linearly with increasing work intensity and then, after reaching some point near the maximum, becomes super-linear. Due to the load, it increases the absorption of oxygen and the production of carbon dioxide by working muscles. Adaptation of the respiratory system consists in extremely accurate maintenance of the homeostasis of these gases in the arterial blood. During light to moderate work, arterial Po 2 (and hence oxygen content), Pco 2 and pH remain unchanged at rest. The respiratory muscles involved in increasing ventilation and, above all, in increasing the tidal volume, do not create a feeling of shortness of breath. With a more intense load, already halfway from rest to maximum dynamic work, lactic acid, which is formed in working muscles, begins to appear in the blood. This is observed when lactic acid is formed faster than it is (removed) metabolized-

Rice. 29-2. Dependence of minute ventilation on the intensity of physical activity.

sya. This point, which depends on the type of work and the state of training of the subject, is called anaerobic or lactic threshold. The lactate threshold for a particular person doing a particular job is relatively constant. The higher the lactate threshold, the higher the intensity of continuous work. The concentration of lactic acid gradually increases with the intensity of work. At the same time, more and more muscle fibers switch to anaerobic metabolism. Almost completely dissociated lactic acid causes metabolic acidosis. During work, healthy lungs respond to acidosis by further increasing ventilation, lowering arterial Pco 2 levels, and maintaining arterial blood pH at normal levels. This response to acidosis, which promotes non-linear lung ventilation, can occur during strenuous work (see Fig. 29-2). Within certain operating limits, the respiratory system fully compensates for the decrease in pH caused by lactic acid. However, during the hardest work, the ventilation compensation becomes only partial. In this case, both pH and arterial Pco 2 may fall below baseline. The inspiratory volume continues to increase until the stretch receptors limit it.

The control mechanisms of pulmonary ventilation that ensure muscle work include neurogenic and humoral influences. The rate and depth of breathing are controlled by the respiratory center of the medulla oblongata, which receives signals from central and peripheral receptors that respond to changes in pH, arterial Po 2 and Pto 2 . In addition to signals from chemoreceptors, the respiratory center receives afferent impulses from peripheral receptors, including muscle spindles, Golgi stretch receptors, and pressure receptors located in the joints. Central chemoreceptors perceive an increase in alkalinity with the intensification of muscle work, which indicates the permeability of the blood-brain barrier for CO 2 , but not for hydrogen ions.

Training does not change the magnitude of the functions of the respiratory system

The impact of training on the respiratory system is minimal. Diffusion capacity of the lungs, their mechanics and even pulmonary

volumes change very little during training. The widely held assumption that exercise improves vital capacity is incorrect: even loads designed specifically to increase respiratory muscle strength only increase vital capacity by 3%. One of the mechanisms of adaptation of the respiratory muscles to physical activity is a decrease in their sensitivity to shortness of breath during exercise. However, the primary respiratory changes during exercise are secondary to reduced lactic acid production, which reduces the need for ventilation during heavy work.

Muscle and bone responses to exercise

The processes that occur during the work of the skeletal muscle are the primary factor in its fatigue. The same processes, repeated during training, promote adaptation, which increases the amount of work and delays the development of fatigue during such work. Skeletal muscle contractions also increase the stress effect on the bones, causing specific bone adaptation.

Muscle fatigue does not depend on lactic acid

Historically, it has been thought that an increase in intracellular H+ (decrease in cellular pH) played a major role in muscle fatigue by directly inhibiting actinmyosin bridges and thereby leading to a decrease in contractile force. Although very hard work can reduce the pH value< 6,8 (pH артериальной крови может падать до 7,2), имеющиеся данные свидетельствуют, что повышенное содержание H+ хотя и является значительным фактором в снижении мышечной силы, но не служит исключительной причиной утомления. У здоровых людей утомление коррелирует с накоплением АДФ на фоне нормального или слегка редуцированного содержания АТФ. В этом случае соотношение АДФ/АТФ бывает высоким. Поскольку полное окисление глюкозы, гликогена или свободных жирных кислот до CO 2 и H 2 O является основным источником энергии при продолжительной работе, у людей с нарушениями гликолиза или электронного транспорта снижена способность к продолжительной

work. Potential factors in the development of fatigue may occur centrally (pain signals from a tired muscle are fed back to the brain and reduce motivation and possibly reduce impulses from the motor cortex) or at the level of a motor neuron or neuromuscular junction.

Endurance training increases the oxygen capacity of the muscles

Skeletal muscle adaptation to training is specific to the form of muscle contraction. Regular exercise under conditions of low load contributes to an increase in oxidative metabolic capacity without muscle hypertrophy. Strength training causes muscle hypertrophy. Increased activity without overload increases the density of capillaries and mitochondria, the concentration of myoglobin and the entire enzymatic apparatus for energy production. Coordination of the energy-producing and energy-using systems in muscle is maintained even after atrophy when the remaining contractile proteins are adequately maintained metabolically. Local adaptation of the skeletal muscle to perform long-term work reduces dependence on carbohydrates as an energy fuel and allows greater use of fat metabolism, prolongs endurance and reduces the accumulation of lactic acid. The decrease in the content of lactic acid in the blood, in turn, reduces the ventilation dependence on the severity of work. As a result of the slower accumulation of metabolites inside the trained muscle, the chemosensory impulse flow in the feedback system in the CNS decreases with increasing load. This weakens the activation of the sympathetic system of the heart and blood vessels and reduces myocardial oxygen demand at a fixed level of work.

Muscle hypertrophy in response to stretch

Common forms of physical activity involve a combination of muscle contractions with shortening (concentric contraction), with muscle lengthening (eccentric contraction) and without changing its length (isometric contraction). Under the action of external forces that stretch the muscle, a smaller amount of ATP is required for the development of force, since part of the motor units

out of work. However, since the forces exerted on individual motor units are greater during eccentric work, eccentric contractions can easily cause muscle damage. This is manifested in muscle weakness (occurs on the first day), soreness, swelling (lasts 1-3 days) and an increase in the level of intramuscular enzymes in plasma (2-6 days). Histological evidence of damage may persist for up to 2 weeks. The injury is followed by an acute phase response that includes complement activation, an increase in circulating cytokines, and the mobilization of neurotrophils and monocytes. If adaptation to training with stretching elements is sufficient, then soreness after repeated training is minimal or absent altogether. Stretch training injury and its response complex is likely to be the most important stimulus for muscle hypertrophy. The immediate changes in actin and myosin synthesis that cause hypertrophy are mediated at the post-translational level; a week after exercise, messenger RNA for these proteins changes. Although their exact role remains unclear, the activity of S6 protein kinase, which is closely associated with long-term changes in muscle mass, is increased. Cellular mechanisms of hypertrophy include the induction of insulin-like growth factor I and other proteins that are members of the fibroblast growth factor family.

The contraction of skeletal muscles through the tendons has an effect on the bones. Because bone architecture changes under the influence of osteoblast and osteoclast activation induced by loading or unloading, physical activity has a significant specific effect on bone mineral density and geometry. Repetitive physical activity can create unusually high tension, leading to insufficient bone restructuring and bone fracture; on the other hand, low activity causes osteoclast dominance and bone loss. The forces acting on the bone during exercise depend on the mass of the bone and the strength of the muscles. Therefore, bone density is most directly related to the forces of gravity and the strength of the muscles involved. This assumes that the load for the purpose

prevent or mitigate osteoporosis must take into account the mass and strength of the applied activity. Because exercise can improve gait, balance, coordination, proprioception, and reaction time, even in the elderly and frail, staying active reduces the risk of falls and osteoporosis. Indeed, hip fractures are reduced by about 50% when older people exercise regularly. However, even when physical activity is optimal, the genetic role of bone mass is much more important than the role of exercise. Perhaps 75% of population statistics are related to genetics and 25% are the result of various levels of activity. Physical activity also plays a role in treatment osteoarthritis. Controlled clinical trials have shown that appropriate regular exercise reduces joint pain and disability.

Dynamic strenuous work (requiring more than 70% of the maximum O 2 intake) slows down the emptying of the liquid contents of the stomach. The nature of this effect has not been elucidated. However, a single load of varying intensity does not change the secretory function of the stomach, and there is no evidence of the effect of the load on the factors contributing to the development of peptic ulcers. It is known that intense dynamic work can cause gastroesophageal reflux, which impairs esophageal motility. Chronic physical activity increases the rate of gastric emptying and the movement of food masses through the small intestine. These adaptive responses constantly increase energy expenditure, promote faster food processing, and increase appetite. Experiments on animals with a model of hyperphagia show a specific adaptation in the small intestine (increase in the surface of the mucosa, the severity of microvilli, a greater content of enzymes and transporters). The intestinal blood flow slows down in proportion to the intensity of the load, and the sympathetic vasoconstrictor tone increases. In parallel, the absorption of water, electrolytes and glucose slows down. However, these effects are transient and the syndrome of reduced absorption as a consequence of acute or chronic loading is not observed in healthy people. Physical activity is recommended for faster recovery

formation after surgery on the ileum, with constipation and irritable bowel syndrome. Constant dynamic loading significantly reduces the risk of colon cancer, possibly because the amount and frequency of food consumed increases and, consequently, the movement of feces through the colon is accelerated.

Exercise improves insulin sensitivity

Muscular work suppresses insulin secretion due to the increased sympathetic effect on the pancreatic islet apparatus. During work, despite a sharp decrease in the level of insulin in the blood, there is an increased consumption of glucose by the muscles, both insulin-dependent and non-insulin-dependent. Muscle activity mobilizes glucose transporters from intracellular storage sites to the plasma membrane of working muscles. Because muscle exercise increases insulin sensitivity in people with type 1 (insulin-dependent) diabetes, less insulin is required when their muscle activity increases. However, this positive result can be insidious, as work accelerates the development of hypoglycemia and increases the risk of hypoglycemic coma. Regular muscle activity reduces the need for insulin by increasing the sensitivity of insulin receptors. This result is achieved by regularly adapting to smaller loads, and not just by repeating episodic loads. The effect is quite pronounced after 2-3 days of regular physical training, and it can be lost just as quickly. Consequently, healthy people who lead a physically active lifestyle have significantly higher insulin sensitivity than their sedentary counterparts. Increased sensitivity of insulin receptors and less release of insulin after regular physical activity serve as an adequate therapy for type 2 diabetes (non-insulin dependent) - a disease characterized by high secretion of insulin and low sensitivity to insulin receptors. In people with type 2 diabetes, even a single episode of physical activity significantly affects the movement of glucose transporters to the plasma membrane in skeletal muscle.

Chapter summary

Physical activity is an activity that involves muscle contractions, flexion and extension movements of the joints and has an exceptional effect on various body systems.

The quantitative assessment of the dynamic load is determined by the amount of oxygen absorbed during operation.

Excess oxygen consumption in the first minutes of recovery after work is called oxygen debt.

During muscle exercise, blood flow is predominantly directed towards the working muscles.

During work, blood pressure, heart rate, stroke volume, heart contractility are increased.

In people accustomed to prolonged rhythmic work, the heart, with normal blood pressure and normal left ventricular wall thickness, ejects large volumes of blood from the left ventricle.

Long-term dynamic work is associated with an increase in high-density lipoproteins in the blood and a decrease in low-density lipoproteins. In this regard, the ratio of high-density lipoproteins and total cholesterol increases.

Muscle loading plays a role in the prevention and recovery from certain cardiovascular diseases.

Pulmonary ventilation increases during work in proportion to the need for oxygen and removal of carbon dioxide.

Muscle fatigue is a process caused by the performance of a load, leading to a decrease in its maximum strength and independent of lactic acid.

Regular muscle activity at low loads (endurance training) increases muscle oxygen capacity without muscle hypertrophy. Increased activity at high loads causes muscle hypertrophy.

Physical loads cause restructuring of various body functions, the features and degree of which depend on the power, the nature of motor activity, the level of health and fitness. The effect of physical activity on a person can only be judged on the basis of a comprehensive consideration of the totality of reactions of the whole organism, including the reaction from the central nervous system (CNS), cardiovascular system (CVS), respiratory system, metabolism, etc. It should be emphasized that the severity changes in body functions in response to physical activity depends, first of all, on the individual characteristics of a person and his level of fitness. At the heart of the development of fitness, in turn, is the process of adaptation of the body to physical stress. Adaptation is a set of physiological reactions that underlies the body's adaptations to changing environmental conditions and is aimed at maintaining the relative constancy of its internal environment - homeostasis.

The concepts of “adaptation, adaptability”, on the one hand, and “training, fitness”, on the other hand, have many common features, the main of which is the achievement of a new level of performance. Adaptation of the body to physical stress consists in the mobilization and use of the functional reserves of the body, the improvement of the existing physiological mechanisms of regulation. No new functional phenomena and mechanisms are observed in the process of adaptation, just the existing mechanisms begin to work more perfectly, more intensively and more economically (decrease in heart rate, deepening of breathing, etc.).

The adaptation process is associated with changes in the activity of the entire complex of functional systems of the body (cardiovascular, respiratory, nervous, endocrine, digestive, sensorimotor, and other systems). Different types of physical exercises impose different requirements on individual organs and systems of the body. A properly organized process of performing physical exercises creates conditions for improving the mechanisms that maintain homeostasis. As a result, the shifts that occur in the internal environment of the body are compensated faster, cells and tissues become less sensitive to the accumulation of metabolic products.

Among the physiological factors that determine the degree of adaptation to physical activity, indicators of the state of systems that provide oxygen transport, namely, the blood system and the respiratory system, are of great importance.

Blood and circulatory system

The body of an adult contains 5-6 liters of blood. At rest, 40-50% of it does not circulate, being in the so-called "depot" (spleen, skin, liver). During muscular work, the amount of circulating blood increases (due to the exit from the “depot”). It is redistributed in the body: most of the blood rushes to actively working organs: skeletal muscles, heart, lungs. Changes in the composition of the blood are aimed at meeting the increased need for oxygen in the body. As a result of an increase in the number of red blood cells and hemoglobin, the oxygen capacity of the blood increases, i.e., the amount of oxygen carried in 100 ml of blood increases. When playing sports, the mass of blood increases, the amount of hemoglobin increases (by 1–3%), the number of erythrocytes increases (by 0.5–1 million in cubic mm), the number of leukocytes and their activity increase, which increases the body's resistance to colds and infectious diseases. diseases. As a result of muscle activity, the blood coagulation system is activated. This is one of the manifestations of the urgent adaptation of the body to the effects of physical exertion and possible injuries, followed by bleeding. By programming such a situation “in advance”, the body increases the protective function of the blood coagulation system.

Motor activity has a significant impact on the development and condition of the entire circulatory system. First of all, the heart itself changes: the mass of the heart muscle and the size of the heart increase. In trained people, the mass of the heart is on average 500 g, in untrained people - 300.

The human heart is extremely easy to train and needs it like no other organ. Active muscular activity contributes to the hypertrophy of the heart muscle and an increase in its cavities. Athletes have 30% more heart volume than non-athletes. An increase in the volume of the heart, especially its left ventricle, is accompanied by an increase in its contractility, an increase in systolic and minute volumes.

Physical activity contributes to a change in the activity of not only the heart, but also blood vessels. Active motor activity causes the expansion of blood vessels, a decrease in the tone of their walls, and an increase in their elasticity. During physical exertion, the microscopic capillary network is almost completely opened, which at rest is only 30-40% active. All this allows you to significantly accelerate blood flow and, consequently, increase the supply of nutrients and oxygen to all cells and tissues of the body.

The work of the heart is characterized by a continuous change of contractions and relaxations of its muscle fibers. Contraction of the heart is called systole, relaxation is called diastole. The number of heartbeats in one minute is the heart rate (HR). At rest, in healthy untrained people, the heart rate is in the range of 60-80 beats / min, in athletes - 45-55 beats / min and below. Decrease in heart rate as a result of systematic exercise is called bradycardia. Bradycardia prevents “wear and tear of the myocardium and is of great health importance. During the day, during which there were no trainings and competitions, the sum of the daily pulse in athletes is 15–20% less than in people of the same sex and age who do not go in for sports.

Muscular activity causes an increase in heart rate. With intense muscular work, the heart rate can reach 180-215 beats / min. It should be noted that the increase in heart rate is directly proportional to the power of muscle work. The greater the power of work, the higher the heart rate. However, with the same power of muscular work, the heart rate in less trained individuals is much higher. In addition, during the performance of any motor activity, the heart rate changes depending on gender, age, well-being, training conditions (temperature, air humidity, time of day, etc.).

With each contraction of the heart, blood is ejected into the arteries at high pressure. As a result of the resistance of the blood vessels, its movement in them is created by pressure, called blood pressure. The greatest pressure in the arteries is called systolic or maximum, the smallest - diastolic or minimum. At rest, systolic pressure in adults is 100–130 mm Hg. Art., diastolic - 60-80 mm Hg. Art. According to the World Health Organization, blood pressure up to 140/90 mm Hg. Art. is normotonic, above these values ​​- hypertonic, and below 100-60 mm Hg. Art. - hypotonic. During exercise, as well as after exercise, blood pressure usually rises. The degree of its increase depends on the power of the performed physical activity and the level of fitness of the person. Diastolic pressure changes less pronounced than systolic. After a long and very strenuous activity (for example, participating in a marathon), diastolic pressure (in some cases, systolic) may be less than before muscle work. This is due to the expansion of blood vessels in the working muscles.

Important indicators of the performance of the heart are systolic and minute volume. Systolic volume of blood (stroke volume) is the amount of blood ejected by the right and left ventricles with each contraction of the heart. Systolic volume at rest in trained - 70-80 ml, in untrained - 50-70 ml. The greatest systolic volume is observed at a heart rate of 130–180 beats/min. With a heart rate over 180 beats / min, it is greatly reduced. Therefore, the best opportunities for training the heart have physical activity in the mode of 130-180 beats / min. Minute blood volume - the amount of blood ejected by the heart in one minute, depends on the heart rate and systolic blood volume. At rest, the minute volume of blood (MBC) averages 5-6 liters, with light muscular work it increases to 10-15 liters, with strenuous physical work in athletes it can reach 42 liters or more. An increase in the IOC during muscle activity provides an increased need for blood supply to organs and tissues.

Respiratory system

Changes in the parameters of the respiratory system during the performance of muscle activity are assessed by respiratory rate, lung capacity, oxygen consumption, oxygen debt and other more complex laboratory studies. Respiratory rate (change of inhalation and exhalation and respiratory pause) - the number of breaths per minute. The respiratory rate is determined by the spirogram or by the movement of the chest. The average frequency in healthy individuals is 16-18 per minute, in athletes - 8-12. During exercise, the respiratory rate increases by an average of 2–4 times and amounts to 40–60 respiratory cycles per minute. As breathing increases, its depth inevitably decreases. The depth of breathing is the volume of air in a quiet breath or exhalation during one respiratory cycle. The depth of breathing depends on the height, weight, size of the chest, the level of development of the respiratory muscles, the functional state and the degree of fitness of the person. Vital capacity (VC) is the largest volume of air that can be exhaled after a maximum inhalation. In women, VC averages 2.5-4 liters, in men - 3.5-5 liters. Under the influence of training, VC increases, in well-trained athletes it reaches 8 liters. The minute volume of respiration (MOD) characterizes the function of external respiration, is determined by the product of the respiratory rate and the tidal volume. At rest, the MOD is 5–6 l, with strenuous physical activity it increases to 120–150 l/min or more. During muscle work, tissues, especially skeletal muscles, require significantly more oxygen than at rest, and produce more carbon dioxide. This leads to an increase in MOD, both due to increased respiration and due to an increase in tidal volume. The harder the work, the relatively more MOD (Table 2.2).

Table 2.2

Mean indicators of cardiovascular response

and respiratory systems for physical activity

Options		With intense physical activity
Heart rate	50–75 bpm	160–210 bpm
systolic blood pressure	100–130 mmHg Art.	200–250 mmHg Art.
Systolic blood volume		150–170 ml and above
Minute blood volume (MBV)		30–35 l/min and above
Breathing rate	14 times/min	60–70 times/min
Alveolar ventilation (effective volume)		120 l/min and more
Minute breathing volume		120–150 l/min

Maximum oxygen consumption(MIC) is the main indicator of the productivity of both the respiratory and cardiovascular (in general - cardio-respiratory) systems. MPC is the maximum amount of oxygen that a person is able to consume within one minute per 1 kg of weight. MIC is measured in milliliters per minute per 1 kg of body weight (ml/min/kg). MPC is an indicator of the body's aerobic capacity, i.e., the ability to perform intense muscular work, providing energy costs due to oxygen absorbed directly during work. The value of the IPC can be determined by mathematical calculation using special nomograms; it is possible in laboratory conditions when working on a bicycle ergometer or climbing a step. BMD depends on age, state of the cardiovascular system, body weight. To maintain health, it is necessary to have the ability to consume oxygen by at least 1 kg - for women at least 42 ml / min, for men - at least 50 ml / min. When less oxygen enters the tissue cells than is necessary to fully meet the energy needs, oxygen starvation, or hypoxia, occurs.

oxygen debt- this is the amount of oxygen that is required for the oxidation of metabolic products formed during physical work. With intense physical exertion, as a rule, metabolic acidosis of varying severity is observed. Its cause is the “acidification” of the blood, i.e., the accumulation of metabolic metabolites in the blood (lactic, pyruvic acids, etc.). To eliminate these metabolic products, oxygen is needed - an oxygen demand is created. When the oxygen demand is higher than the current oxygen consumption, an oxygen debt is formed. Untrained people are able to continue working with an oxygen debt of 6–10 liters, athletes can perform such a load, after which an oxygen debt of 16–18 liters or more arises. Oxygen debt is liquidated after the end of work. The time of its elimination depends on the duration and intensity of the previous work (from several minutes to 1.5 hours).

Digestive system

Systematically performed physical activity increases metabolism and energy, increases the body's need for nutrients that stimulate the release of digestive juices, activates intestinal motility, and increases the efficiency of digestion processes.

However, with intense muscular activity, inhibitory processes can develop in the digestive centers, which reduce the blood supply to various parts of the gastrointestinal tract and digestive glands due to the fact that it is necessary to provide blood to the hard-working muscles. At the same time, the very process of active digestion of abundant food within 2-3 hours after its intake reduces the efficiency of muscle activity, since the digestive organs in this situation appear to be more in need of increased blood circulation. In addition, a full stomach raises the diaphragm, thereby complicating the activity of the respiratory and circulatory organs. That is why the physiological pattern requires taking food 2.5-3.5 hours before the start of the workout, and 30-60 minutes after it.

excretory system

During muscular activity, the role of the excretory organs, which perform the function of preserving the internal environment of the body, is significant. The gastrointestinal tract removes the remnants of digested food; gaseous metabolic products are removed through the lungs; sebaceous glands, releasing sebum, form a protective, softening layer on the surface of the body; the lacrimal glands provide moisture that wets the mucous membrane of the eyeball. However, the main role in the release of the body from the end products of metabolism belongs to the kidneys, sweat glands and lungs.

The kidneys maintain the necessary concentration of water, salts and other substances in the body; remove the end products of protein metabolism; produce the hormone renin, which affects the tone of blood vessels. With great physical exertion, the sweat glands and lungs, by increasing the activity of the excretory function, significantly help the kidneys in removing decay products from the body, which are formed during intensive metabolic processes.

Nervous system in movement control

When controlling movements, the central nervous system performs a very complex activity. To perform clear targeted movements, it is necessary to continuously receive signals to the central nervous system about the functional state of the muscles, about the degree of their contraction and relaxation, about the posture of the body, about the position of the joints and the angle of bend in them. All this information is transmitted from the receptors of the sensory systems, and especially from the receptors of the motor sensory system, located in muscle tissue, tendons, and articular bags. From these receptors, according to the principle of feedback and the mechanism of the CNS reflex, complete information is received about the performance of a motor action and about its comparison with a given program. With repeated repetition of a motor action, the impulses from the receptors reach the motor centers of the CNS, which accordingly change their impulses going to the muscles in order to improve the learned movement to the level of a motor skill.

motor skill- a form of motor activity developed by the mechanism of a conditioned reflex as a result of systematic exercises. The process of forming a motor skill goes through three phases: generalization, concentration, automation.

Phase generalization characterized by the expansion and intensification of excitation processes, as a result of which extra muscle groups are involved in the work, and the tension of the working muscles turns out to be unreasonably large. In this phase, movements are constrained, uneconomical, inaccurate and poorly coordinated.

Phase concentration characterized by a decrease in excitation processes due to differentiated inhibition, concentrating in the desired areas of the brain. Excessive intensity of movements disappears, they become accurate, economical, performed freely, without tension, stably.

In phase automation the skill is refined and consolidated, the performance of individual movements becomes as if automatic and does not require consciousness control, which can be switched to the environment, the search for solutions, etc. An automated skill is distinguished by high accuracy and stability of all its constituent movements.