Pavlov studied the performance and fatigue of muscles. Physical performance and physical fatigue. What will we do with the received material?
The main indicators characterizing muscle activity are their strength and performance.
Muscle strength. Force is a measure of the mechanical impact on a muscle from other bodies, which is expressed in newtons or kg-force. With isotonic contraction in the experiment, strength is determined by the mass of the maximum load that the muscle can lift (dynamic strength), with isometric contraction - by the maximum tension that it can develop (static strength).
A single muscle fiber develops a tension of 100-200 kgf during contraction.
The degree of muscle shortening during contraction depends on the strength of the stimulus, morphological properties and physiological state. Long muscles are reduced by a greater amount than short ones.
A slight stretch of the muscle, when the elastic components are tense, is an additional irritant and increases muscle contraction, and with a strong stretch, the force of muscle contraction decreases.
The tension that myofibrils can develop is determined by the number of cross-bridges of myosin filaments interacting with actin filaments, since the bridges serve as the site of interaction and development of force between the two types of filaments. In the resting state, a fairly significant part of the cross bridges interacts with actin filaments. When the muscle is strongly stretched, the actin and myosin filaments almost cease to overlap and minor cross-links are formed between them.
The magnitude of the contraction also decreases when the muscle becomes tired.
An isometrically contracting muscle develops the maximum possible tension for it as a result of the activation of all muscle fibers. This muscle tension is called maximum strength. The maximum strength of a muscle depends on the number of muscle fibers that make up the muscle and their thickness. They form the anatomical diameter of the muscle, which is defined as the area of the cross-section of the muscle drawn perpendicular to its length. The ratio of the maximum strength of a muscle to its anatomical diameter is called relative muscle strength, measured in kg/cm2.
Physiological diameter of the muscle- the length of the cross section of the muscle, perpendicular to the course of its fibers.
In muscles with parallel fibers, the physiological diameter coincides with the anatomical one. In muscles with oblique fibers it will be larger than anatomical. Therefore, the strength of muscles with oblique fibers is always greater than that of muscles of the same thickness but with longitudinal fibers. Most muscles of domestic animals and especially birds have oblique fibers of a feathery structure. Such muscles have a larger physiological diameter and have greater strength (Fig. 83).
Rice. 83. Anatomical (a-a) and physiological (b-b) diameters of muscles with different fiber arrangements:
A - parallel-fiber type; B - single-pinnate; B - bipinnate; G - multipinnate.
The strongest are the multipennate muscles, followed by the unipennate, bipennate, semi-pennate, fusiform and longitudinal fibrous muscles.
Many, one, and bipennate muscles have great strength and endurance (they get tired little), but have a limited ability to shorten, and other types of muscles shorten well, but get tired quickly.
A comparative indicator of the strength of different muscles is absolute muscle strength - the ratio of the maximum muscle strength to its physiological diameter, i.e. the maximum load that a muscle can lift divided by the total area of all muscle fibers. It is determined by tetanic stimulation and optimal initial muscle stretch. In farm animals absolute power skeletal muscles range from 5 to 15 kg-force, on average 6-8 kg-force per 1 cm2 of physiological diameter. In the process of muscle work, the diameter of the muscle increases and, consequently, the strength of this muscle increases.
Muscle work. During isometric and isotonic contraction, the muscle performs work.
When assessing the activity of muscles, usually only the external work they produce is taken into account.
The work of a muscle during which the load and bones move in the joints is called dynamic.
Work (W) can be defined as the product of the mass of the load (P) and the lifting height (h)
W= P h J (kg/m, g/cm)
It has been established that the amount of work depends on the magnitude of the load. The dependence of work on the magnitude of the load is expressed by the law of average loads: the greatest work is performed by the muscle under moderate (average) loads.
Maximum muscle work is performed even with an average contraction rhythm (law of average speeds).
Muscle power is defined as the amount of work per unit time. It reaches a maximum in all types of muscles also at medium loads and at an average contraction rhythm. Highest power in fast muscles.
Muscle fatigue . Fatigue- a temporary decrease or loss of performance of an individual cell, tissue, organ or organism as a whole, occurring after loads (activities). Muscle fatigue occurs during prolonged contraction (work) and has a certain biological significance, signaling the (partial) depletion of energy resources.
When fatigued, the functional properties of the muscle decrease: excitability, lability and contractility. The height of muscle contraction gradually decreases as fatigue develops. This decrease can lead to the complete disappearance of contractions. As they decrease, the contractions become more and more extended, especially due to the lengthening of the relaxation period: after the end of the contraction, the muscle does not return to its original length for a long time, being in a state contractures(extremely slow muscle relaxation). Skeletal muscles get tired earlier than smooth ones. In skeletal muscles, white fibers fatigue first, followed by red fibers.
Of the various ideas about the mechanism of fatigue, one of the earliest theories explaining fatigue was attrition theory proposed by K. Schiff. According to this theory, the cause of fatigue is the disappearance of energy substances in the muscle, in particular glycogen. However, detailed study showed that in muscles that are tired to the limit, the glycogen content is still significant. Subsequently, E. Pfluger was nominated theory of organ clogging with products of working decay (theory poisoning). According to this theory, fatigue is explained by the accumulation of large amounts of lactic and phosphoric acids and a lack of oxygen, as well as other metabolic products that disrupt the metabolism in the working organ and its activity stops.
Both of these theories are formulated on the basis of data obtained in experiments on isolated skeletal muscle and explain fatigue in a one-sided and simplified way.
Further study of fatigue under conditions of the whole organism revealed that metabolic products appear in a tired muscle, and the content of glycogen, ATP, and creatine phosphate decreases. Changes occur in the contractile proteins of the muscle. The binding or reduction of sulfhydryl groups of actomyosin occurs, as a result of which the process of ATP synthesis and breakdown is disrupted. Disturbances in the chemical composition of muscle located in the whole organism are less pronounced than in muscle isolated due to the transport function of blood.
Research by N.E. Vvedensky found that fatigue primarily develops in the neuromuscular synapse due to its low lability.
Rapid fatigue of synapses is caused by several factors.
Firstly, with prolonged irritation in the nerve endings, the supply of mediator decreases, and its synthesis does not keep up with consumption.
Secondly, the accumulated metabolic products in the muscle reduce the sensitivity of the postsynaptic membrane to acetylcholine, as a result of which the magnitude of the postsynaptic potential decreases. When it drops to a critical level, no excitation occurs in the muscle fiber.
I.M. Sechenov (1903) -, studying the performance of muscles when lifting a load on the ergograph he designed for two hands, established that the performance of a tired right hand recovers more fully and quickly after active rest, i.e. rest accompanied by the work of the left hand. A similar effect on the performance of a tired hand is exerted by irritation combined with rest by the inductive current of the sensitive (afferent) nerve fibers of the hand of the other hand, as well as footwork associated with lifting weights, and motor activity in general.
Thus, leisure, accompanied by moderate work of other muscle groups, turns out to be more effective means combating fatigue of the musculoskeletal system than simple rest.
Sechenov rightly associated the reason for the most effective restoration of the performance of the musculoskeletal system in conditions of active rest with the effect on the central nervous system of afferent impulses from muscle and tendon receptors of working muscles.
In the body, in various parts of the reflex arc, fatigue primarily occurs in the nerve centers, especially in the cells of the cerebral cortex.
It has now been established that the functional state of muscles is influenced by the central nervous system and primarily the cerebral cortex. This influence is exerted through the somatic nerves, the autonomic nervous system and the endocrine glands.
Impulses from the spinal cord and brain enter the muscle along the motor nerves, causing its excitation and contraction, accompanied by changes in the physicochemical properties and functional state of the muscle.
Impulses entering the muscle through sympathetic fibers enhance metabolic processes, blood supply and muscle performance. The same effect is exerted by the mediators of the sympathetic system - adrenaline and norepinephrine.
However, there is still no single theory explaining the causes of fatigue, the essence of fatigue, because V natural conditions Fatigue of the body's musculoskeletal system is a multifactorial process.
The onset of muscle fatigue can be delayed with training. It develops and improves the functionality of all body systems: nervous, respiratory, circulatory, excretory, etc.
When training, muscle volume increases as a result of growth and thickening of muscle fibers, and muscle endurance increases. The content of glycogen, ATP and creatine phosphate in the muscle increases, and the processes of breakdown and restoration of substances involved in metabolism are accelerated. As a result of training, the coefficient of oxygen use during muscle work increases, recovery processes intensify due to the activation of all enzymatic systems, and energy consumption decreases. During training, the regulatory function of the central nervous system, and first of all, the cerebral cortex, is improved.
Foreign scientists, seeing that fatigue cannot be explained by humoral theories alone, began to study the fatigue of nerve conductors. They argued that under the influence of prolonged passage of excitation impulses (for example, when irritated by electric current), the nerve conductors become tired.
The Russian physiologist N. E. Vvedensky, having criticized a number of errors in the experiments of Western scientists, proved with facts that nerve conductors are practically tireless and that in the nerves the physiological conduction of excitation occurs with minimal waste of energy. Consequently, the cause of fatigue lay not in the muscle or in the nerve conductor. Naturally, the thoughts of scientists turned to studying the performance nerve cells.
One of the first who, through a vivid and interesting experiment, was able to show where the threads of fatigue stretch was I.M. Sechenov. Intensified study of issues of labor physiology in our country began precisely with his brilliant works. The excellent studies of I.M. Sechenov “Participation of the nervous system in human working movements” and “Essay on human working movements” to this day serve as desktop guides for researchers studying the physiology of labor. While dealing with issues of fatigue, I.M. Sechenov looked not only for the causes of fatigue, but also sought to find rational measures to combat this condition.
Let us imagine Ivan Mikhailovich Sechenov sitting at a simple device somewhat reminiscent of the ergograph described above. Only on the Sechenov ergograph it was no longer just one finger that worked, but the whole hand, the movements of which were similar to those made when sawing wood. The weight rises and falls in a certain rhythm with each swing of the arm. 4 hours pass, the hand has already made 4800 movements, the height of lifting the load is decreasing more and more, fatigue is approaching. The inquisitive mind of the scientist decides to fight this inevitable phenomenon; he is looking for that “healing medicine” that could eliminate fatigue.
The scientist finds that short-term use of the left hand relieves fatigue of the right hand much faster than long rest.
I.M. Sechenov explained this in the following way: short-term work with the left (non-working) hand generates excitation impulses in the sensory nerves of the muscles, rushing to the central nervous system, where they seem to rebuild the work of the nervous system, stimulating and refreshing it, setting it up for a new fruitful working rhythm. If this is so, I.M. Sechenov reasoned, then light electrical stimulation of the left hand should also relieve fatigue. In fact, this turned out to be the case: just as external beneficial stimuli that give us a good and pleasant mood (song and music, competition and interest in work), causing excitement of the analyzers, * increase the performance of the nervous system and our brain, so does minor work of the unoccupied left hand or weak electrical stimulation reduces fatigue. Thus, I.M. Sechenov showed that the essence of fatigue is rooted in the processes occurring in the central nervous system.
Many Soviet physiologists have been and are studying the phenomenon discovered by I.M. Sechenov (N.K. Vereshchagin, S.I. Krapiventseva, M.E. Marshak, G.V. Popov, A.D. Slonim, etc.) . Recently, for example, the Soviet scientist Sh. A. Chakhnashvili showed that restoration of the performance of a tired hand occurs not only with active rest associated with the activity of the other hand, but also with short-term work performed during rest lower limbs, muscles of the trunk and neck, chewing muscles. It turned out that contraction of the neck muscles (while moving the head) during a 10-second rest increases the recovery of the tired arm by 61-75% compared to “passive” rest of the same duration.
* The analyzer is a complex formation that includes a receptor, a sensory nerve and a nerve center in the cerebral cortex. Receptors (from the Latin word recipio - I perceive) are sensitive nerve endings in a muscle or other organ (eye, ear). The perception of external and internal stimuli is carried out not by receptors as such, but by the entire analyzer system as a whole. The doctrine of analyzers was first introduced into physiological science.
Fatigue is understood as a decrease in performance caused by performing a certain job.
The study of the causes of fatigue began to be studied at the end of the 19th century. A number of theories of fatigue have been created, which are still supported by some foreign physiologists.
One of the first to appear was the theory of depletion of energy reserves in muscles - carbohydrates and lipoids. This theory has no justification, since it has been shown that in an animal brought to the point of fatigue resulting in death due to intense work, a sufficient supply of glycogen remains in the liver. During very intense work, fatigue can set in quickly, within 2-3 minutes, and it is difficult to imagine that glycogen and lipoid reserves will disappear from the body during this time.
Theories also appeared of “poisoning” the body either by breakdown products of proteins and carbohydrates (Pfluger), or by special toxins - kenotoxins (Weichardt). This theory was justified by the fact that the blood of a tired animal, injected into a normal animal, caused a state similar to fatigue. It was not difficult to prove that in this case there is no reason to talk about fatigue, since the blood of a non-tired animal administered to another animal causes a similar condition, which is a reaction to the introduction of a foreign protein. This theory is not only incorrect, but also harmful, since it tries to interpret labor as a negative factor in human life. Meanwhile, it is well known that labor stimulates life processes; it has been established that decay processes cause active restoration processes.
Finally, the theory of clogging the body with decay products, in particular lactic acid, was created (Hill). Indeed, the accumulation of lactic acid can accompany fatigue; The more intense the work, the more lactic acid can accumulate. However, lactic acid is not the cause of fatigue. This was shown by direct experiments: the accumulation of lactic acid not only did not stop the work, but, on the contrary, stimulated it; cessation of work due to fatigue coincided with a decrease in lactic acid content.
All these theories of fatigue turned out to be physiologically unfounded, since they were based on the results of a study of an isolated muscle without connection with the rest of the functions of the whole organism, and, consequently, with the regulatory role of the central nervous system. The authors of these theories accepted particular changes as general ones in the whole organism.
I.M. Sechenov also expressed the opinion that the feeling of fatigue cannot be associated with the state of working muscles, that the source of the feeling of fatigue is in the central nervous system. The fact that the central nervous system, namely the cerebral cortex, limits work has been proven by many facts. In an animal whose cerebral cortex has been removed, motor activity not only does not decrease, but, on the contrary, increases. A person under the influence of suggestion can perform heavy physical work with little energy expenditure, without the onset of fatigue for a long time.
Based on the teachings of N. E. Vvedensky, A. A. Ukhtomsky and especially I. P. Pavlov, it became possible to prove the connection between cessation of work due to fatigue and the state of the central nervous system, to understand the mechanism of this phenomenon and to create a physiologically based theory of fatigue.
The normal activity of the central nervous system depends on its functional state. It is determined by a number of conditions, the consistency of which creates a functional unity that ensures central nervous coordinating action. Violation of the coordinating regulatory function leads to a decrease in performance or cessation of the functions of the entire system, i.e., fatigue.
A distinction is made (M.I. Vinogradov) between rapidly developing fatigue as a result of unusual or excessive work and slowly developing fatigue (secondary) with mildly pronounced changes in the body as a result of habitual, but too long work.
Rapidly developing fatigue may occur as a result of significant physical effort or unusual, very strenuous work. Fatigue in this case occurs due to a violation of central coordination of functions and the emergence of emergency foci of inhibition as a result of a discrepancy between the work task and the functional capabilities of the body. Indeed, at the beginning of physical stress, conditioned reflex activity increases (increased excitation) - the magnitude of conditioned reflexes increases, the latent period shortens, but at the same time, already at the beginning of work, differentiation is disinhibited, phase states appear, more clearly expressed by the end of work (development of inhibitory processes).
The restoration of the initial state occurs quite quickly and goes through the stage of exaltation - increased excitation, which is characterized by an increase in the intensity of the reflex and a shortening of the latent period.
Accordingly, the electrical activity of the cerebral cortex (biocurrents) changes: the normal frequency of the rhythm (excitation) is disorganized and subsequently completely disappears, the β-rhythm intensifies, and with the development of inhibition, long waves appear - the Δ-rhythm. Restoration occurs in reverse order. Changes in the electrical activity of muscles are of the same nature: at the maximum increase in the amplitude of action potentials (inhibition), further work becomes impossible.
Characteristic feature rapidly developing fatigue is also the rapid restoration of function after work to its original state. Moreover, the greater the static tension, the faster fatigue develops, the faster recovery occurs.
In this case, the question arises: is it possible to identify fatigue and inhibition? This question must be answered in the negative. According to I.P. Pavlov, inhibition is a measure of protecting the cell from functional “exhaustion”, “destruction”. The period of inhibition is a period of cell recovery. This is shown by research metabolic processes cerebral cortex in a state of excitation and inhibition. Excitation is characterized by an increase in metabolic processes in the cerebral cortex - an increase in glycolytic processes, a decrease in the content of ATP and creatine phosphate, an increase in the amount of ammonia, etc.; inhibition under normal physiological conditions is characterized by the restoration of disturbed metabolic processes.
Thus, inhibition is not a depletion of the energy capabilities of the cell, but a state of restoration of function and a measure to prevent its functional exhaustion. This condition apparently allows the cell not to respond to impulses coming to it, as a result of which active activity ceases. The connection between fatigue and inhibition lies in the fact that protective inhibition is one of the important components of a much more complex process - fatigue of a working person (S. A. Kosilov).
The rate of development of inhibition is greatly influenced by cell nutrition through the circulatory system. L. A. Orbeli and his colleagues showed that such a trophic (adaptation-trophic) mechanism for all tissues is the sympathetic nervous system (sometimes parasympathetic), which increases the intensity of chemical processes in the body, increases the level of physiological excitability, and has a positive influence on physiological lability - mobility of the nervous apparatus.
When the sympathetic nerves are irritated, the functional capacity of the tired muscle increases.
Slowly developing fatigue characterized by a gradual decrease in performance as a result of habitual, but excessively long or monotonous work.
Rapidly developing fatigue, as already indicated, most often occurs before the acquisition of work skills; subsequently, as a result of training, a dynamic working stereotype is formed, which makes it possible to perform work for a long time with high performance.
Rapidly developing fatigue can, apparently, be considered to arise already against the background of habitual work.
With primary fatigue, work capacity quickly drops due to developing inhibition; with secondary fatigue, performance decreases gradually as a result of a slow decrease in lability, characterized by prolongation of physiological intervals. In other words, functional activity decreases, expressed in a general decrease in the reactivity of the physiological system.
During primary fatigue, inhibition develops quickly and quickly disappears after stopping work; it is clearly defined, concentrated in certain areas.
With secondary fatigue, inhibition develops slowly, it is unstable, shallow and gradually acquires the character of a kind of stagnant inhibition.
When tired, the magnitude of conditioned motor reflexes fluctuates in waves, reaching a level below the initial level. Receptive functions are sharply weakened: the lability of the visual and auditory analyzers is reduced, the muscular balance of the eyes, coordination of movements, their accuracy, and body balance when standing are disrupted.
The dynamics of lability during the working day changes parallel to the change in performance. A decrease in lability indicates the onset of fatigue, which in production conditions can be expressed in a drop in hourly productivity, an increase in scrap and the duration of individual operations due to micro-pauses.
Secondary fatigue can accumulate from day to day and develop into overwork, which is already a pathological condition. Overwork can lead to increased morbidity.
A person’s ability to perform physical (muscular) work for a long time is called physical performance. The amount of physical performance of a person depends on age, gender, fitness, environmental factors (temperature, time of day, oxygen content in the air, etc.) and the functional state of the body. To compare the physical performance of different people, calculate the total amount of work performed in 1 minute, divide it by body weight (kg) and obtain relative physical performance (kg * m / min per 1 kg of body weight). On average, the level of physical performance of a 20-year-old boy is 15.5 kg*m/min per 1 kg of body weight, and for a young athlete of the same age it reaches 25. In last years determining the level of physical performance is widely used to assess the general physical development and health status of children and adolescents.
Prolonged and intense physical activity leads to a temporary decrease in the physical performance of the body. It's physiological the condition is called fatigue. It is currently shown that the process of fatigue primarily affects the central nervous system, then the neuromuscular junction and, in last but not least, the muscle. For the first time, the importance of the nervous system in the development of fatigue processes in the body was noted by I.M. Sechenov. Proof of the validity of this conclusion can be considered the fact that interesting work does not cause fatigue for a long time, and uninteresting work very quickly, although muscle loads in the first case may even exceed the work performed by the same person in the second case.
Fatigue is a normal physiological process developed evolutionarily to protect the body's systems from systematic overwork, which is a pathological process and is characterized by a disorder of the nervous system and other physiological systems of the body.
7.2.5. Age-related characteristics of muscle systems
The muscular system undergoes significant structural and functional changes during ontogenesis. Formation of muscle cells and muscle development as structural units of the muscular system occurs heterochronically, i.e. are first formed those skeletal ones muscles that are necessary for the normal functioning of the child’s body at this age stage. The process of “rough” muscle formation ends by 7-8 weeks of prenatal development. After birth, the process of formation of the muscular system continues. In particular, intensive growth of muscle fibers is observed up to 7 years and during puberty. By the age of 14-16 years, the microstructure of the skeletal muscle tissue almost fully matured but the thickening of the muscle fibers (improvement of their contractile apparatus) can last up to 30-35 years.
Muscle development upper limbs advances the development of the muscles of the lower extremities. A one year old baby has muscles shoulder girdle and arms are developed much better than the muscles of the pelvis and legs. Larger muscles are always formed before smaller ones. For example, the muscles of the forearm are formed before the small muscles of the hand. The muscles of the arms develop especially intensively at 6-7 years of age. The total muscle mass increases very quickly during puberty: for boys - at 13-14 years old, and for girls - at 11-12 years old. Below are data characterizing the mass of skeletal muscles in the process of postnatal ontogenesis.
Much The functional properties of muscles also change during ontogenesis. Increases excitability and lability muscle tissue. Changes muscle tone. The newborn has increased muscle tone, and the flexor muscles of the limbs predominate over the extensor muscles. As a result, the arms and legs of infants are often in a bent state. They have a poorly expressed ability of muscles to relax (some stiffness in the movements of children is associated with this), which improves with age. Only after 13 - 15 years of age do movements become more flexible. It was at this age The formation of all sections of the motor analyzer ends.
In the process of development of the musculoskeletal system, the motor qualities of muscles change: speed, strength, agility and endurance. Their development occurs unevenly. First of all, speed and agility are developed.
Speed (speed) of movements characterized by the number of movements that a child is able to produce per unit of time. It is determined by three indicators:
1) the speed of a single movement,
2) time of motor reaction and
3) frequency of movements.
Single movement speed increases significantly in children from 4-5 years of age and reaches adult levels by 13-15 years. By the same age, the adult level also reaches simple motor reaction time, which is determined by the speed of physiological processes in the neuromuscular system. Maximum voluntary frequency of movements increases from 7 to 13 years, and in boys at 7-10 years it is higher than in girls, and from 13-14 years the frequency of movements in girls exceeds this figure in boys. Finally, the maximum frequency of movements in a given rhythm also increases sharply at 7–9 years. In general, the speed of movement develops to its maximum by the age of 16-17 years.
Until the age of 13-14 years, most development is completed dexterity, which is associated with the ability of children and adolescents to carry out precise, coordinated movements. Therefore, dexterity is related to:
1) with spatial accuracy of movements,
2) with temporal accuracy of movements,
3) with the speed of solving complex motor problems.
The preschool and primary school periods are the most important for the development of dexterity. The greatest increase in movement accuracy observed from 4 - 5 to 7 - 8 years. Interestingly, sports training has a beneficial effect on the development of agility and in 15 - 16 summer athletes the accuracy of movements is two times higher than that of untrained adolescents of the same age. Thus, until the age of 6 - 7 years, children are not able to make subtle, precise movements in an extremely short time. Then spatial precision of movements gradually develops, A behind it is a temporary one. Finally, Lastly, the ability to quickly solve motor problems improves in various situations. Agility continues to improve until age 17-18.
Largest strength gain observed in middle and high school age, strength increases especially intensively from 10 - 12 years to 16 -17 years. In girls, the increase in strength is activated somewhat earlier, from 10 to 12 years, and in boys, from 13 to 14 years. However, according to this indicator, boys in all age groups superior to girls.
Later than others motor qualities endurance develops, characterized by the time during which a sufficient level of performance of the body is maintained. There are age, gender And individual differences in endurance. The endurance of preschool children is low, especially static work. An intensive increase in endurance for dynamic work is observed from 11 to 12 years old. So, if we take the volume of dynamic work of 7-year-old children as 100%, then for 10-year-olds it will be 150%, and for 14-15-year-olds it will be more than 400%. Just as intensively, from the age of 11-12, children develop endurance to static loads. In general, by the age of 17-19, endurance is about 85% of the adult level. It reaches its maximum level by 25 - 30 years.
Development of movements and mechanisms of their coordination It is most intense in the first years of life and adolescence. In a newborn, the coordination of movements is very imperfect, and the movements themselves have only a conditional-reflex basis. Of particular interest is the swimming reflex, the maximum manifestation of which is observed approximately 40 days after birth. At this age, the child is able to make swimming movements in the water and stay on it until 1 5 minutes. Naturally, the child's head must be supported, since his own neck muscles are still very weak. Subsequently, the swimming reflex and other unconditioned reflexes gradually fade away, and motor skills are formed to replace them. All basic natural movements characteristic of a person (walking, climbing, running, jumping, etc.) and their coordination are formed in a child mainly before 3 - 5 years. Moreover, the first weeks of life are of great importance for the normal development of movements. Naturally, even before school age coordination mechanisms are still very imperfect. Despite this, children are able to master relatively complex movements. In particular, it is V At this age they learn tool movements, i.e. motor skills and skills to use tools (hammer, wrench, scissors). From 6 to 7 years old, children master writing and other movements that require fine coordination. By the beginning of adolescence, the formation of coordination mechanisms is generally completed, and all types of movements become available to adolescents. Of course, improving movements and their coordination with systematic exercises is also possible in adulthood (for example, athletes, musicians, etc.).
Improving movements is always closely related to the development of the child’s nervous system. In adolescence, coordination of movements is very often somewhat disrupted due to hormonal changes. Usually by 15 - ] 6 years this temporary deterioration disappears without a trace. The general formation of coordination mechanisms ends at the end of adolescence, and by the age of 18–25 they fully reach the level of an adult. The age of 18-30 is considered “golden” in the development of human motor skills. This is the age at which his motor abilities flourish.
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Ministry of Education and Science of the Russian Federation
Federal State Budgetary Educational Institution of Higher Professional Education
"MATI - RUSSIAN STATE TECHNOLOGICAL UNIVERSITY named after. K.E. TSIOLKOVSKY"
Department of Natural and Technogenic Safety and Risk Management
in the discipline "Medical and biological foundations of safety"
“Efficiency. Fatigue"
Student: Nesterova A.A.
Head: Kukin P.P.
MOSCOW 2013
Introduction
1. Performance and age
2. Factors affecting performance
3. Performance assessment
4. The main stages of performance during physical education classes
5. Dynamics of performance. Performance and fatigue
6. Causes of fatigue and factors contributing to its development
7. Fatigue and its types
8. Definition of overwork and combating it
9. Theories of fatigue
Conclusion
Bibliography
Introduction
The increasing role of the human factor in the era of accelerating scientific and technological progress determines the need to increase attention to solving a number of theoretical and applied problems of physiological support for high human performance and the preservation of his professional health. One of the central places among these problems is the problem of fatigue. A century and a half of intensive research into this problem in the field of labor and sports physiology, solving some questions, puts forward others. The problem still contains a number of controversial issues today, and some established positions deserve discussion in the light of new facts and ideas. performance health fatigue person
From the point of view of the very essence of the concept under consideration, fatigue is a functional state of the body, a process of decreased performance under the influence of work or a state of reduced performance. Performance depends not only on the functional state of the body (in particular, fatigue), but also on the level of professional preparedness, motivation, interest in work and other factors not related to the content of the workload. From here it is necessary to understand the relationship between the concepts of fatigue and performance. If we understand fatigue as the functional state of the body, then its definition should apparently include both internal (state of functions) and external (efficiency and quality of work) manifestations of it.
When defining the concept of fatigue, we consider it in two aspects: as a functional state of a certain category of specialists and as a state that develops under the influence of a specific type of activity, if it does not determine the specific causes and signs of its development.
The question of the forms and stages of development of fatigue (overwork) and the principles of classification of this condition are debatable.
In the field of studying the mechanisms of fatigue, judgments about the role of regulatory and energy processes and, in particular, about the peculiarities of the dynamics of these processes in the central cortical apparatus and peripheral parts of the working organs.
With regard to the causes of fatigue, we should dwell on the question of what role in the development of this condition, in addition to workload, other external and internal factors of a person’s activity and condition.
In terms of symptoms and diagnosis of fatigue, questions about the content of its specific and nonspecific signs in relation to various forms of fatigue and different types labor and sports activities, on the differential diagnosis of fatigue and other functional conditions of the body (hypoxia, monotony, desynchronosis, etc.), on the discordination of body functions during the development of fatigue and the sequence of violations of various professional and functional indicators
1. Performance and age
Efficiency is a person’s ability to work. In science there is such a concept as working age. It does not depend on our calendar (chronological) age, i.e. what is indicated in our passport or birth certificate. It has no restrictions on the time scale either up or down and depends only on the personal capabilities of each person. It begins when a person becomes capable of work, and ends when such ability is lost.
For example, the performance and working age of the youngest movie actors, like McCaulay Culkin, who played main role in the popular films “Home Alone 1” and “Home Alone 2”, and becoming a millionaire long before receiving an ID card, occurs when they are not yet 10 years old.
And for many outstanding scientists and artists, it ends when they are well over 80, and in fact simultaneously with their lives. This is how physiologist I.P. worked until the last days of his life. Pavlov (died at the age of 87), chemist N.D. Zelinsky (on the 93rd), microbiologist N.F. Gamaleya (at 91st), biologist I.V. Michurin (on the 80th). Michelangelo created at the age of 90, Titian at 99, Aivazovsky painted brilliant paintings at the age of 80-82, I.E. Repin created his best paintings at the age of 80-85. Verdi composed his last opera at the age of 80, Leo Tolstoy, Voltaire, Goethe, Hugo, Bernard Shaw created their masterpieces at the age of 80-90, and Sophocles wrote his brilliant tragedy “Oedipus” in the hundredth year of his life. This list can be continued indefinitely.
In the press and on television today we often see the faces and names of people aged 100 and even 130-150 years old who feel normal and have not lost their ability to work and have clarity of mind.
Just 25 years ago in our country, only 16.7% of people continued to work after retirement, today - every fourth (i.e. 25%). Because the feeling of being needed by society has a positive effect on human health. Statistics say that if we compare how people of the same age feel, then among workers there are 2 times more of those who feel good and 1.5 times less of those who feel bad. In addition, a working person feels more confident and calm in our difficult times.
I would like to give a few facts about record performance in terms of age, in particular in sports.
The youngest world champion in the history of the sport, Gertrude Caroline Ederls, set a world record in 880-yard freestyle swimming in 1919 at the age of 12 years 10 months.
The youngest Olympic gold medalist was American team, who won the 1952 Olympics in Helsinki relay race 4x100m Barbara Pearl Jones. She was only 15 years and 4 months old.
The oldest conqueror of Everest was a Japanese pensioner who climbed at the age of 63. Two years later, at 65, she climbed the 8,516-meter Lotse peak in the Himalayas. And her compatriot Juichiro Miura climbed Everest when he was already 70 years old.
Another elderly Japanese athlete, 95-year-old Kozo Haraguchi from Miyazaki, set a record among sprinters aged 95 to 99 years. He ran the 100 m in 22.04 seconds, improving his own performance by 2 seconds. And 5 years ago he ran the same 100 m in 18.08 seconds. Interestingly, he only started running at the age of 65.
Englishwoman Gertie Edwards Land proved that the idea of a recession physical activity and performance (mental and physical) do not apply to her, having passed her driver’s license in 1988, when she was already 90 years and 7 months old.
But, unfortunately, today there are many other facts when young or middle-aged people become unable to work due to various reasons and circumstances (illness, injury and, as a result, disability). Cardiovascular, endocrine, oncological and some other types of diseases have become significantly younger.
2 . Factors affecting performance
Performance and well-being, like a mirror, reflect the general state of our health.
Human performance is not strictly constant; it changes under the influence of many reasons. It is influenced by health status, nutritional conditions, work and household factors, mood and much more.
It depends quite strongly on the duration and nature of sleep, during which a person rests and recuperates. A healthy and moderately tired person usually falls asleep quickly and sleeps deeply until the morning; by morning, his sleep becomes less deep and more superficial. With the right regimen, the need for sleep occurs after equal periods of wakefulness (after about 16 hours).
It is generally accepted that a person needs about 8 hours a day to sleep. The most acceptable time for sleep is from 11-12 pm to 7-8 am. University of Chicago Medical Center professor Eva Van Braun argues that modern people not only sleep less than they did 100 years ago, but also no longer adjust their sleep to seasonal variations in the length of day and night. Now the correlation between the number of conceptions and the time of year, clearly expressed even before the First World War (1914-1918) and associated with the length of winter nights, has practically disappeared.
Sleep is passive rest, it eliminates fatigue and prevents the depletion of nerve cells, helps restore the body's performance, because During sleep, a person’s breathing not only slows down, the pulse becomes less frequent, the muscles relax, the activity of the kidneys and gastrointestinal tract decreases, but the functioning of the central nervous system also changes dramatically. It begins to slow down. Sleep is essential for human survival.
Modern people like to boast about their productivity, declaring that they can get by with just a few hours of sleep. But scientists have discovered that chronic sleep deprivation can pose a serious threat to human health and life.
People lived on the planet for thousands of years without artificial lighting, and circadian biorhythms were established in their bodies. Having dispelled the darkness with the help of artificial lighting just some 200-250 years ago, man began to live as if every night was short, like in the height of summer. He doesn’t care that his cells store the memory of the existing biorhythms, he strives to stay up as long as possible, ignoring the onset of bio-night, and then he is surprised that after 50-55 years he is tormented by insomnia. After all, for the previous 30-35 years all he did was to steal from sleep extra hour to stay awake, upsetting your biological clock. Those who suffer the most are those with flexible work schedules and those who work at night. Among them, the level of gastrointestinal, cardiovascular diseases, as well as infertility and chronic fatigue.
Good nutrition plays an important role in overcoming fatigue. Nutrition should replenish the body's energy reserves and increase its performance. That is, the diet of a person involved in sports or heavy physical work should be high-calorie, small in volume so as not to overload the digestive system, and easily digestible. For example, honey is an excellent, easily digestible product; it is also useful during the recovery period, when it is necessary to improve the nutrition of the heart muscle and increase its performance. Being a high-calorie product (100 g contains 315-335 kcal), it allows you to quickly replenish the energy expended by the body, for example, during exercise physical culture and sports.
A person’s mental and physical performance depends on factors such as time of day, day, week, season, state of health and biological rhythms.
All phenomena occurring in the Universe (the rotation of the earth around the Sun and its own axis, the alternation of seasons, sea ebbs and flows, the change of day and night, and many others) occur rhythmically. Daily and seasonal fluctuations in illumination, temperature, air humidity, and atmospheric pressure are eternal. All living things are born and exist with them. They are associated with the rotation of the Earth around its axis and around the Sun, with the processes occurring on the luminary itself. Back at the beginning of the 20th century. scientist A.L., who later perished in Stalin’s camps. Chizhevsky wrote: “Life is to a much greater extent a cosmic phenomenon than an earthly one.” And all living organisms, incl. humans, in the process of evolution, have developed the finest mechanisms with the help of which they adapt the activities of their systems, organs, cells and intracellular structures to this changing external environment. Simple examples of the existence of physiological rhythms include the rhythm of wakefulness and sleep, the annual rhythm of hibernation in animals, the rhythm of breathing, and heart contractions.
Currently, scientists have established that humans have more than 100 different physiological functions, which are characterized by rhythm.
Research has found that a person's body temperature rises in the evening and becomes lower in the morning. The pulse rate, blood flow in tissues, arterial and intraocular pressure change. It is no coincidence that it has been noticed that some diseases, in particular cardiovascular diseases, worsen in the evening and night hours. The number of red blood cells and white blood cells in the blood decreases at night. The content of chemical substances in it also changes in a known sequence. The acidity of gastric juice is highest in the morning. A person's muscle strength is maximum during the day, and in the morning and at night it decreases. The heart, lungs, and digestive organs, endocrine glands. The rhythmicity of the nervous system determines the performance of the body as a whole.
Research has found that throughout the day a person reacts differently to physical activity; endurance, muscle strength, speed change in waves, obeying the general rhythmic processes occurring in the body. A person is weakest in terms of his functional capabilities from 3 to 5 o'clock and from 12 to 16 o'clock. The first period of decline is well known to everyone who has at least once experienced insomnia and predawn hopelessness. From 12 o'clock in the afternoon, most people become drowsy, consciousness becomes dull, and the number of accidents in production and transport increases noticeably. Most people, during these hours, fall ill, become depressed due to troubles or accumulated chronic fatigue, and die.
Researchers have long noticed that most people's performance is highest in the morning from 8 to 12 o'clock and in the evening from 16 to 18 o'clock.
In addition, each organ in the human body has its own “critical hours” when they are least efficient.
Daily, multi-day and annual rhythms are of great importance on the influence of a person’s performance, therefore, at the beginning of the work week, a person’s performance is good, in the middle of the work week, a person’s performance is maximum, and at the end of the week it declines.
Scientists have also long ago noticed a decline in the ability to work in some people in the spring and autumn. The alternation of light and darkness is the main “spring” of the biological clock. If a person follows an established lifestyle, he almost very rarely experiences a feeling of discomfort and gets tired during these periods, since the human body is well adapted to the rhythm of natural phenomena. But when disturbances occur in a person’s lifestyle or the body’s adaptive capabilities are exhausted, a person’s performance decreases, he often gets tired, weakens, and even gets sick.
Over the past 25 years, our country has adopted transitions to “summer” and “winter” time, which are expressed in changing the clocks. Many people tolerate this very poorly, and the older the person, the worse. I have repeatedly heard from practically healthy and able-bodied people of 40-45 years of age that in the fall, after changing the clocks, they wake up an hour earlier for 1-1.5 months and because of this they actually do not get enough sleep and feel uncomfortable. Over time, their body adapts to the new rhythm.
But, if a person has health problems, then this process takes longer for him, it is also delayed in children, because their body is not yet ready enough for such changes.
As economists have found out, the economic profits that the state receives from changing the hands of the clock are small, but the losses in a person’s working capacity and the damage to his health are quite noticeable.
For some time now, the attention of scientists has been drawn to the effect of the Sun on the biological rhythms of people. Its “perturbations” associated with the intensification of thermonuclear reactions also, as it turned out, are strictly periodic - occurring on average once every 9-11 years. At this time, the electrification of the air and the state of the Earth’s magnetic field change, X-ray radiation, and the intensity of ultraviolet and infrared radiation increase. During years of increased solar activity, blood clotting ability changes, the body's reactions to signals slow down, the number of cardiovascular diseases increases, and outbreaks of influenza and some other epidemic diseases occur more often.
But people born in years of solar activity are more resistant to adverse weather and climatic conditions. They tolerate stress more easily, get sick less often, and are more active and productive. This applies to those born in 1917-1918, 1928-1929, 1937-1939, 1947-1949, 1956-1959, 1968-1970, 1978-1981, 1989-1990, 2001-2002, now also experiencing strong solar flares and the peak of its activity. Children born today may have the above properties, but, of course, provided that their mothers were not ill during pregnancy.
In addition, researchers claim that in healthy people during periods of solar activity, geophysical disturbances stimulate an increase in physical and mental performance. So, hurry up to create, wisely adhering to a rational lifestyle!
By the way, A.L. Chizhevsky, mentioned above, concluded that during years of solar activity, natural disasters and social upheavals occur more often on Earth
If after labor, educational activities If you play sports, you feel good, have an appetite, sleep, and continue to have a desire to work, study, and play sports, then these are positive factors that indicate that the body is successfully coping with the loads and they can be gradually increased.
3. Performance assessment
Physical performance is assessed using a range of tests. One of them provides for the characteristics of physical performance based on the duration of work at a given power. Others - by the value of the frequency of maximum oxygen consumption (MOC), others - by the value of the heart rate (HR) when performing a load of a certain power or by the value of the work power that is necessary to increase the heart rate to a certain level (for example, to 130, 150 or 170 beats/min).
The most accurate are the so-called “maximum” tests, for example MIC. However, the methodology for carrying them out is complex and requires specially trained personnel and is associated with the need to perform maximum physical activity, which is sometimes undesirable even for an athlete, because can negatively affect his athletic performance, and for middle-aged and elderly people it can even be hazardous to health.
In this regard, “submaximal” tests, which use relatively moderate muscle loads, are most widespread.
Among them, the most widespread is the Harvard step test, 12- minute test Cooper, test PWC170 (which means: physical performance at a pulse of 170 beats/min) and some others.
4 . The main stages of performance during physical education classes
Let's consider several stages of changes in performance during physical education and sports. The following stages are distinguished: starting state, warm-up, warm-up, “dead point” and “second wind”, steady state.
The starting state is a state when physiological changes occur in the body, similar to those caused by muscular work, since the physiological changes necessary for intense physical activity already begin in a person’s body in advance. It is based on a conditioned reflex to the upcoming training or competition. The conditioned stimuli here are the environment (the view of the gym, playground, swimming pool, rivals, comrades, coach’s fans, etc.). The very thought of training or competition is also a conditioned stimulus. The unconditioned stimulus, on the basis of which conditioned reflexes arise, is the muscular work itself.
Developing is a stage associated with the establishment of conditioned reflex connections. Plays an important role in the process of the body’s gradual entry into physical activity. The increase in performance at the beginning of physical activity depends on a number of physiological processes occurring in the body. The circulatory apparatus gradually comes into operation, most of the capillaries of the muscles are closed at rest, but now they open, supplying the muscles with blood. Muscle resistance to blood flow decreases, heart function becomes easier, breathing becomes faster and deeper. Performance depends on the degree of excitability of the nervous system, which is relatively low at rest, but begins to increase with load. The main indicator of the performance of nerve centers is lability (an indicator expressed in the maximum frequency of nerve impulses).
Warm-up is based on all the above processes and allows you to regulate the work-in, bringing it at a certain moment to the point (for example, during the start) so that the body reaches the required high level of performance.
"Dead point" or "second wind". “Dead spot” is a condition when an athlete’s performance drops sharply, movements are stiff, breathing is difficult, heart rate increases, and the frequency and strength of movements decreases. This condition may be associated with a lack of adaptability of the body, when, due to the high intensity of movements, excessive inhibition occurs in the motor nerve centers. The onset of a “dead point” forces you to either reduce the pace or stop exercising.
If an athlete, through an effort of will, continues a competition or activity, slowing down the pace, after a while a “second wind” comes. The body gradually improves coordination between breathing, blood circulation and the intensity of movements and its performance increases again.
Thus, the “dead point” is the result of inhibition that followed strong excitation, and the “second wind” is excitation that replaced inhibition.
Steady state is a period when the working-in process has ended, the activity of all organs and systems of the body has reached a certain constant level, allowing long-term performance of the load in a given mode. This condition is observed in runners during stayer and marathon distances, among participants in cross-country skiing, cycling races, etc.
5 . Dynamics of performance. Performance and fatigue
In general, the dynamics of any person’s performance includes the following phases:
1) mobilization, i.e. preparation for activities;
2) the primary reaction, reflecting the process of quantitative balancing;
3) overcompensation, i.e. searching for an optimal solution when performance is adequate to the requirements of the activity;
4) subcompensation, gradual depletion of the body’s strength;
Excessive and prolonged load that exceeds the body's performance limits (overload) often leads to a decrease in both physical and mental performance. A person begins to make a large number of mistakes, the pace of his work slows down, coordination of movements and the accuracy of operations are impaired, absent-mindedness appears, and sometimes headaches and insomnia. This state is called fatigue - subjective (i.e., characteristic of a particular person, subject) fatigue.
Time of onset of fatigue (subjective fatigue) different people during physical activity they manifest themselves differently. Fatigue is an indicator that the body cannot work at full capacity.
Signs of fatigue during static work, for example, can be identified by conducting simple laboratory work. It is necessary to take a load (3-4 kg) in your hand and pull it to the side strictly horizontally, having previously noted the level at which your hand is on the wall.
6 . Causes of fatigue and factors contributing to its development
The main cause of muscle fatigue may be the accumulation of large amounts of unoxidized lactic acid. This makes it difficult for the further breakdown of energy substances and reduces muscle performance.
It may be associated with changes in the function of the endocrine glands (for example, a change in the ratio between the work of the glands, partial depletion of some glands, etc.).
Fatigue can occur due to insufficient performance of the cardiovascular and respiratory systems. Due to a lack of oxygen and excess carbon dioxide, the acidity of the blood changes and the sugar level in it drops.
But the central nervous system plays a leading role in the development of fatigue. Nerve cells are very sensitive to changes in the composition of the tissue fluids that wash them. Skeletal muscles can still maintain their performance, but in nerve cells it is already decreasing, lability decreases, the excitability of nerve cells decreases, the normal process of correlation between the processes of excitation and inhibition is disrupted, and extreme inhibition develops.
Fatigue is a set of changes in the physical and mental state of a person that develop as a result of activity and lead to a temporary decrease in efficiency.
Fatigue is a process that occurs during work and limits its duration. It is characteristic of all phases of performance, starting with subcompensation, when a significant decrease in physiological reserves occurs and the body switches to energetically less favorable types of reactions, for example, maintaining minute blood flow by increasing the heart rate instead of the more beneficial reaction of increasing stroke volume. Or, for example, the implementation of motor reactions is carried out by a large number of functional muscle units when the force of contraction of individual muscle fibers is weakened, i.e. violation of the alternation of periods of work and rest of muscle groups involved in contraction. In the initial stages of fatigue, a person’s performance efficiency decreases, i.e. the amount of physiological and psychological costs required for the same labor act, action increases, and only then labor productivity and activity efficiency decrease.
When tired, first of all, the stability of vegetative functions, strength and speed are disrupted. muscle contraction, regulation of functions, development and inhibition of conditioned reflexes deteriorate. As a result, as mentioned above, the pace of activity slows down, the rhythm, accuracy and coordination of movements are disrupted, and it turns out that the same activity requires large energy expenditures. The thresholds of sensory (sensitive) systems increase, ready-made stereotypical decisions dominate in decision-making processes during mental activity, a person’s attention is weakened and switches with difficulty. Fatigue is characterized by an increase in the number of errors and a change in their structure, so in the initial phases of fatigue quantitative errors dominate, and in subsequent phases qualitative errors also appear.
The development of the pattern of fatigue can be generally characterized as a violation of the body’s adequate (correct) response to the requirements imposed by the nature of the activity. In this case, all 3 basic requirements of adequacy are violated:
Optimality of private reactions underlying the activity;
And their coordination with each other;
Qualitative and quantitative compliance of the body’s response with the requirements of the task and minimization of the consumption of physiological reserves.
With severe fatigue, a complete cessation of work is observed.
Fatigue in humans, like animals, is associated with a number of mechanisms associated with biochemical changes at the cellular level and disruption of conditioned reflex activity. But the dynamics and a number of structural mechanisms of fatigue in a person are also regulated by the motives of activity, its goals, and character. Therefore, fatigue in animals and humans has a number of fundamental differences. In particular, in animals there is no strict development of phases of fatigue; it is more typical to simply sequential quantitative indicators and the change in the structure of activity is less pronounced. Their fatigue is practically not suppressed by volitional effort.
The dynamics of fatigue are influenced by the nature of the activity, primarily its intensity and tempo. There is an optimal intensity of activity at which fatigue occurs later. Increasing or decreasing this intensity accelerates the onset of fatigue.
For example, everyone is well aware that fatigue develops most quickly during monotonous, static work and sensory (sensually) impoverished activity. If a person performs the same operation for a long time, physical exercise, requiring a limited range of movements, his attention decreases quickly, and positive motives for activity fade away. This usually happens during highly specialized work on a conveyor belt, when assembling any mechanisms, manufacturing parts (monotonous work).
A person doing work in a static position (knitting, embroidery, typing, working at a computer, etc.) gets tired quickly.
Fatigue is also influenced by external stimuli received by a person, for example, sound and light signals containing information about the conditions of activity. For example, a driver has traveled 500 km in daylight and good weather conditions, he feels tired. But the same driver, who drove the same route in bad weather conditions (fog, night, heavy rain), will definitely get even more tired. A high level of noise tires a person, but complete silence can also cause irritation and fatigue in a person. Therefore, in production, great attention should be paid to the microclimate of the working environment: air temperature, humidity, composition, the presence of chemical impurities in it, noise, vibration, illumination, etc.
The rate of occurrence and development of fatigue also depends on a number of psychological characteristics of the individual - the level of anxiety, volitional qualities, including perseverance and other activation parameters, i.e. such functional properties of a person that provide the degree of realization of his potential capabilities in a specific activity. For example, attention, as an activation parameter, provides greater opportunities for memorization. And a high level of volitional personality traits allows you to maintain the necessary high level of activity even with a pronounced feeling of fatigue.
The development of fatigue depends on the state of a person’s health and his physical training, which not only provide large physiological reserves, but also contribute to faster and more sustainable mobilization and formation of functional systems. For example, a physically strong and healthy person, if necessary, can walk 5-10 km a day and still feel great, although he has not experienced such physical activity for a long time. A sick person may simply not be able to do this, or he will be extremely tired, and may even be unable to work for a long time. Or another example, an experienced driver does not feel tired, although he has spent many hours on the road, but a novice driver who has traveled from one settlement to another (even if it is only a few tens of kilometers) may feel very tired.
7 . Fatigue and its types
Depending on the type of work performed, mental and physical fatigue are distinguished.
With changes that appear as a result of intensive processes of reproductive activity associated with processing information according to a rigid scheme or rules (for example, counting or distributing information simultaneously into many categories), mental fatigue is formed. It also arises during productive activities, including processes of information transformation, the formation of judgments, concepts, and conclusions. This type of fatigue is also typical for heuristic (search) activity, or creative activity carried out according to individual, implicit algorithms.
In case of physical fatigue, deviations in energy metabolic parameters are taken into account, for example, changes in body temperature and bioelectric potentials.
Due to the fact that the fundamental commonality of these two types of fatigue has been discovered, a classification based on the predominant localization of fatigue in the parts of the nervous system that ensures human activity is becoming increasingly widespread.
This is how they distinguish between sensory fatigue and its types (perceptual and informational) and effector fatigue.
In addition, general fatigue is noted.
Sensory fatigue develops as a result of prolonged or intense exposure to a stimulus (strong noise, light), in which primary changes occur in the sensory systems, starting from the receptor and ending with the cortical end of the analyzer.
Perceptual fatigue, localized primarily in the cortical end of the analyzer, is associated with the difficulty of detecting a signal (for example, with large interference, with its low intensity, difficulty in differentiation).
Information fatigue develops as a result of insufficient information or information overload, when the greatest load falls on the dynamics of intercentral relations, which consists in closing temporary connections between various structures in the central nervous system and reviving associative connections that allow one to correctly reflect an objective picture of the environment in the mind. For example, a person quickly gets tired if he is forced to constantly listen due to noise, to look closely due to poor visibility and lighting, or because information changes quickly, flashes, or is simply very voluminous.
Effector fatigue occurs when changes are localized primarily in the parts of the central nervous system that form the motor act.
The initial phases of fatigue have a beneficial effect on the stability of the body, subsequently contribute to a faster and more perfect mobilization of reserves and compensatory functions, they accelerate the acquisition of skills and contribute to their consolidation.
But pronounced fatigue negatively affects the body, reducing labor productivity and human performance as a whole. And even leads to a pre-pathological phase of breakdown.
At the same time, fatigue has not only a negative side, but also a positive one. The feeling of fatigue protects the human body from overstrain and prevents exhaustion of the nervous system.
8 . Definition of overwork and combating it
After each mental and physical activity, training session, the body rests and gradually becomes functional again. Moreover, the more intense the mental or physical activity, the longer the recovery process will take.
Alternating work with rest is important in a person’s life. Rest is considered complete when the teacher, always gathered in a classroom where there are a lot of people making noise, manages to sit quietly and be silent. When the salesman, who had spent the day standing behind the counter, managed to lie down, he managed to lie down and listen to quiet music. And students, graduate students, scientists who sit for hours at a table in the classroom, library, laboratory, managed to escape to a picnic, where everyone is having fun, singing, dancing, singing, and playing ball.
Active recreation is the most favorable. It can be daily, weekly or annual.
Each person, if desired, can allocate 0.5-1.5 hours during the day for a walk on fresh air(walk a few stops if the house is far from work, or even walk if it’s nearby) or dancing. The latter have a very beneficial effect on the human body, relieve irritability and moodiness, normalize blood pressure, dilate and fill the vessels that nourish the muscles.
It is very important to plan active holidays on weekends. A walk in the forest or at least to a park, work in a summer cottage, a visit gym, sports ground or swimming pool, sports and physical education, dancing are simply necessary for those who have been busy with mainly mental work all week. Picking mushrooms or hunting, fishing, and being in the fresh air increase overall performance and are important components of successful preparation for the new week.
For those who have spent the entire week primarily engaged in physical labor or sports, on the contrary, other types of recreation are more suitable: visiting a museum or exhibition, etc. They could use an extra hour or two of quiet, deep sleep during the day, preferably during those hours when our body is weakest (between one o'clock in the afternoon and four o'clock in the afternoon). In general, sleep does not bother anyone.
An annual vacation is not just a vacation and, at best, a multi-day trip to the sea, where a person will eat, sleep and lie on the beach for hours. This, of course, is also rest, but passive. This is time that can be used more rationally and with greater benefit for the body. To have a good rest, you need to switch gears, go somewhere you haven’t been before, do something opposite to everyday life. Walking, water, mountain tourism, cycling, hunting, fishing, in various combinations, in combination with housework (repairs, general cleaning) or at the dacha, with an excursion trip will give a greater effect. These options are good for those who lead a sedentary lifestyle throughout the year and for those who work a lot physically. Being outdoors among nature at different times of the day and year, a person is exposed to changes in different temperatures, solar insolation, air movement, etc. all these factors harden the body, strengthen its health and performance.
Irrational rest also leads to the development of a pathological state of overwork. One day it may happen that performance decreases and recovery requires longer rest than usual. This is how overwork or illness usually makes itself felt. It may be accompanied by neuroses and vascular diseases.
In popular science and medical literature, the concept of “spring fatigue” syndrome appears quite often. One of the reasons for this syndrome is improper organization of work, educational activities or sports training. Secondly, a person encounters it because in the spring our body undergoes a kind of seasonal adaptation, as mentioned above. To smooth out this adaptation process, it is necessary to avoid excessive physical and mental stress, rush jobs at work and school, and establish a daily routine. It means the correct alternation of periods of work and rest, their duration, rational distribution in time during not only the day, but also the week and month. It is necessary to devote sufficient time to rest and get enough sleep. Good immunity not only resists diseases, but also increases a person’s performance; taking multivitamins will help support it in the spring.
For quick recovery strength and prevention of fatigue and overwork, a person should include physically active and informative-cognitive types of recreation, which were mentioned above, in his daily routine.
It is not so easy to determine the causes of overwork, which is why it is necessary to consult a doctor.
It is advisable to recognize the symptoms of overwork as early as possible, so for those who are seriously involved in sports, coaches often advise keeping a diary in which the athlete learns to control his condition.
Subjective signs of a person’s physical fatigue are unpleasant sensations in working muscles and joints; in a static posture, pain and a feeling of numbness in the muscles of the back, abdomen and neck, the appearance of pain in the forehead and back of the head; the latter symptoms are also characteristic of mental fatigue. Both types of fatigue are characterized by impaired concentration, easy distractibility, initially a slight increase and then a sharp limitation of contacts with others, an unconscious desire to take breaks from work more often and for longer.
It should be taken into account that isolated cases of poor sleep and insomnia can sometimes occur under very heavy loads or on the eve of any important events (competitions, tests, tests, exams, etc.), but constant bad dream indicates overwork. Lack of sleep (insomnia), appetite and sudden weight loss are warning signs indicating overwork.
Fatigue can become chronic and develop into overwork. In this case, doctors talk about “chronic fatigue” syndrome. And more and more often such a familiar word is heard - depression, which characterizes general fatigue, emphasizing the most pronounced disorders in the central nervous system.
In this case, a person, and especially an athlete, should consult a doctor. Chronic fatigue can be the result of heavy loads at the same time, not only training, but also educational process or at work, if they are combined. Often, as noted above, this is due to an incorrect lifestyle.
Symptoms of “chronic fatigue” are:
Persistent sleep disturbance (insomnia or vice versa drowsiness);
A sharp disturbance of appetite (its loss or, conversely, a sharp increase);
Intestinal dysfunction (constipation);
Increased fatigue during normal physical and intellectual activity, constant weakness, dizziness;
Pain and various discomforts in the body (for example, in the heart, stomach, muscles);
Decreased libido (sexual desire).
Methods to combat fatigue began to be developed almost simultaneously with theories of fatigue.
The fight against fatigue is carried out at work, in educational institutions and at home.
In production, this is carried out by introducing rational work and rest regimes, ergonomic recommendations for organizing the workplace, panels and control panels, rational distribution of functions between man and machine (this is the so-called scientific organization of labor - NOT). In addition, industrial gymnast complexes have been developed for various categories of workers (See the list of references, No. 12-16). At first glance this is incredible and fantastic, but simple exercises can affect a person’s performance and health.
In educational activities, in particular at school, this is carried out through the introduction of various pedagogical technologies into the educational and pedagogical process (health-saving, personality-oriented, etc.). A powerful means of combating fatigue in educational activities in general and sports in particular is training, which involves the formation of optimal functional systems that ensure minimal consumption of physiological reserves at a given intensity, strengthening of skills, and the correct distribution of micropauses and breaks in work. For example, breaks between lessons, training sessions should not be less than 10 minutes, because this is the minimum time that the human body needs to adjust from one type of activity to another. During the school day, it is preferable to give students two long breaks (20 minutes each) rather than one (30-40 minutes). To avoid overloading students and, as a consequence, their fatigue and overwork, when drawing up a schedule, the complexity of the subject being studied, its position in the daily and weekly schedule, and the number of lessons per day and week are also taken into account. So, the most productive school days, from the point of view of psychologists and physiologists, are Wednesday and Thursday, and the hours are 2-3 lessons.
In everyday life, the problem of overwork is intended to be solved by improving living conditions. For example, it is undesirable for a person to travel to or from work by transport for more than 45 minutes, since after this time the so-called “transport fatigue” begins to develop. A person should not spend more than 1.5-2 hours every day on shopping and other consumer services while getting home from work. At home, each person solves the problem of overcoming fatigue on his own, buying various household appliances that make work easier and save our time. But, by the way, if a person does not engage in physical labor at home and at work he is primarily engaged in mental activity, he is in danger of physical inactivity. It is associated with weight gain and an increase in cardiovascular diseases. Thus, there should be a “golden mean” in the amount of physical and mental stress.
The emotional and motivational content of activity is of great importance in the fight against overwork. The more significant the motives for work, the later fatigue sets in, especially if these are motives of high social significance or they are of a competitive nature. They determine interest in work and a creative attitude towards it. Positive emotions ensure rapid inclusion in the rhythm of work activity, contribute to the preservation of optimal performance, and more complete mobilization of the body’s physiological reserves.
Physical education and sports, a correct measured lifestyle and nutrition, mental balance - these are the components of longevity, preservation of health and performance. Planning and organization will allow you to achieve the highest performance and avoid fatigue. Famous academician N.E. Vvedensky, the author of one of the theories of fatigue, wrote: “Every young organism under normal conditions carries within itself a huge reserve of strength and energy.”
9 . Theories of fatigue
Theories of fatigue began to emerge. Of the numerous theories of fatigue, the theory of “poisoning” by the German scientist E. Pfluger (1872), “exhaustion” by M. Schiff (1868, Switzerland), the “exchange theory” of the English researcher A. Hill (1929) and others are of only historical interest. E. Pfluger assumed that muscle fatigue occurs due to poisoning or contamination with toxic products. M. Schiff assumed that the muscle is depleted from a lack of nutrients. However, all these theories did not explain the causes of fatigue. As a result, the assumption arose that the cause of fatigue did not lie in the muscle. Nerve fatigue was hypothesized. However, I.M. Sechenov and N.E. Vvedensky proved that nerve conductors are practically indefatigable. The path to solving the mystery of fatigue was opened by I.M. Sechenov.
Today, 2 groups of theories are recognized, on the basis of which changes in the nerve centers are considered primary.
According to one of them, the basis of fatigue is hypoxic, i.e., associated with insufficient oxygen supply, disturbances in the nervous structures that regulate homeostasis processes, especially changes in mediator metabolism and chemical processes in the generation and transmission of excitations.
Proponents of the second group of theories deny a single mechanism for the occurrence of fatigue. In their opinion, the appearance of fatigue can be caused by a number of factors or their combinations, starting with circulatory failure with local muscle fatigue and ending with a change in the structure of homeostatic regulation from the higher parts of the central nervous system (protective inhibition) with general fatigue.
A major role in the development of modern theories of fatigue was played, as noted above, by the famous physiologist I.M. Sechenov, Academy N.E. Vvedensky, as well as Nobel laureate 1904 physiologist I.P. Pavlov, A.A. Ukhtomsky and L.A. Orbeli. The latter, by the way, considered fatigue as a violation of adaptive-trophic regulation on the part of the autonomic nervous system.
The problem of fatigue was also studied by physiologists of the Soviet period G.V. Folbort, S.A. Kosilov and others.
Modern research has revealed a number of subtle mechanisms of fatigue associated with impaired metabolism of high-energy compounds, decreased activity of oxidative enzymes, and changes in the nature of endocrine regulation by the hypothalamus. For example, a decrease in adrenal function and inhibition of the production of adrenocorticotropic hormone by the pituitary gland have been recorded. It has been established that at the beginning of fatigue, the activity of the insular apparatus of the pancreas increases and then decreases. This leads to an increase in under-oxidized products in the human body and to hyperglycemia. As a consequence of these processes, a person experiences secondary changes in afferent impulses, which further worsens the state of homeostasis and leads to a disruption in the coordination of autonomic and motor working reactions.
Also I.M. Sechenov found that the right hand, after prolonged work, quickly restored its functionality if it worked during the period of rest. left hand. The nerve centers of the left hand seemed to infect the tired nerve centers of the right hand. It turned out that fatigue is relieved faster when the rest of some organs is combined with the work of others. With his experiments I.M. Sechenov outlined ways to relieve fatigue and ways to rationally organize rest, which were mentioned above.
Conclusion
In practical terms, questions about methodological techniques for diagnosing fatigue are important for discussion. There is increasing attention to methods for assessing the functional reserves of the body, their qualitative and quantitative characteristics, as indicators of the rate of development of fatigue, the adequacy and information content of professional and functional stress tests. The possibilities of new methodological directions, such as, for example, assessing changes in the level of functional asymmetry of paired organs, are also interesting.
Some subjective and objective methods have been developed: a test for determining the localization of various sensations of fatigue, a test for subjective scaling of fatigue in different regions of the body, a method for measuring the perimeters of human limbs.
The test for determining the localization of sensations of fatigue consists of a diagram of dividing the surface of the human body into 100 regions and a small questionnaire. When subjectively scaling fatigue, those localizations are studied where it has been established in advance that signs of fatigue are especially pronounced; 5 to 11 scales are used. To determine the perimeters of the limb, special measurement kits are used, consisting of measuring tapes with a width of 1 to 3 mm and calibrated rulers with divisions from 0.1 to 0.2 mm.
Laboratory studies have shown the promise of the developed methods. Thus, the correlation coefficient between the obtained data on subjective scaling of fatigue and objective measurement of decreased performance was 0.8 0.9, and between the same subjective indicators and an increase in limb perimeters up to 0.75.
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