Efficiency is the ability of a person to perform the assigned work with the proper quantity and quality. How to determine the ability to perform the job of this or that employee? It is necessary to understand that performance indicators are an indirect characteristic of this physiological and psychological personality trait.

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BASHKIR STATE MEDICAL UNIVERSITY

Department of Clinical Toxicology and Occupational Pathology with IPO course

	I approve:
	_____________________
	Head of the Department, Professor
	Z.S. Teregulova
	"____" __________ 200_

METHODOLOGICAL DEVELOPMENT OF LECTURE No. 4

01. TOPIC: Performance and fatigue

02. Medical-prophylactic faculty, 4th year

03. Section: Fundamentals of physiology and psychology of labor

04. Lecture course 9 semester

05. Duration: 2 hours (90 min.)

06. Contingent: 4th year students of the medical-preventive faculty

07. GENERAL PURPOSE OF THE LECTURE: To consider and discuss modern concepts of working capacity, fatigue and measures to prevent overwork and overstrain of the human body

PRIVATE DIDACTIC OBJECTIVES (OBJECTIVES):

1. Conduct an analysis of modern data on theory, process and state

fatigue and consider regular changes in performance

2. Determine the state of overwork and overstrain; to discuss

the reasons for their occurrence and distinctive features

3. Measures to prevent premature development

fatigue, overwork and overexertion

08. Equipment:

Graph: Phases of human performance

Graph: Daily change in human performance

Table: Impact of short breaks on labor productivity during product assembly (AC relay)

Table: Labor productivity and energy consumption of a trolley hauler, depending on the modes of work and rest

Table: Theories of Fatigue

Table: Directions of rationalization of labor processes

Diagram of the formation of a dynamic working stereotype and signs of training in movement

Table: Features of the ratio of the influence of the working environment and labor activity, all other things being equal, on the functional state of the employee

09. New information (absent in previous training): regular changes in human performance

10. PLAN OF THE LECTURE:

1 hour: Performance and fatigue	45 minutes
The concept of working capacity
Natural changes in a person's ability to work
Fatigue and fatigue theories
2 hours: Overwork and overstrain	45 minutes
Overwork and overstrain concepts
Overexertion diseases
Measures to prevent fatigue and ensure high
labor productivity

11. Control of the assimilation of the material: an active survey at the end of the lecture.

Questions:

1. Name the phases of performance

2. Determine the content of the concepts: performance and fatigue

3. Is fatigue a process or a condition?

4. The theory of depletion of energy reserves in explaining the development of fatigue

5. The theory of poisoning in explaining the development of fatigue

6. The theory of clogging the body in explaining the development of fatigue

7. The role of the central nervous system in the regulation of performance

8. The regulating value of fatigue

9. Theory (concept) of active rest I.М. Sechenov. The works of P.A. Konopasevich and V.O. Boguslavsky (1891-92)

10. Types of fatigue according to M. Vinogradov

11. Is it possible to identify fatigue of an organism (organ) and inhibition in the corresponding cells of the brain?

12. What are the main directions of physiological rationalization of labor processes

13. Signs of a trained movement

14. The essence and significance of the quantification of labor movements for the rationalization of production processes

15. The role of rhythm and monotony in the optimization of human labor activity

12. LIST OF REFERENCES:

1. Alekseev S.V., Usenko V.R. Occupational hygiene. M., Med., 1988, 576s.
2. Belozerova L.M. Age working capacity of persons of mental and physical labor // Physiological and medical issues of non-traditional forms of human production activity: 2 hours - Tyumen. - 1991. - Part 2. - S. 179 - 182.
3. N.P. Benevolenskaya Ergonomics studies. - Novosibirsk: Science, 1977.
4. Buguslavsky V.O. Muscle fatigue curve under different conditions. Dis. - JV b. - 1891.
5. Bykov K.M., Vladimirov G.E., Delov V.E., Konradi G.P., Slonim A.D. Physiology textbook. M., 1975
6. Vinogradov M. The problem of fatigue. M., 1978 - 298 p.
7. Occupational hygiene. Hygienic criteria for assessing working conditions in terms of hazard and hazard indicators of the working environment, the severity and intensity of the labor process: Manual (R 2.2.755 - 99) / State system of sanitary and epidemiological regulation of the Russian Federation. Official edition. - Moscow, Ministry of Health in Russia, 1999 - 150 p.
8. Gorshkov S.I., Zolina Z.M., Moikin Yu.V. Research methods in labor physiology. M .: Medicine, 1974 .-- 311 p.
9. GOST 12.2.032-78. SSBT. Workplace when performing work while sitting. General ergonomic requirements.
10. GOST 12.2.033-78. SSBT. Workplace when performing work while standing. General ergonomic requirements.
11. Gritsevsky M.A. Physiological and hygienic principles of the rational organization of labor of managers in chemical production: Author's abstract. dis ... d.m.s. - M., 1981.
12. Evstafiev V.N. Physical performance and ergonomic indicators of the functional state of the cardiovascular system in the ship crew // Gig. labor. - 1989. - No. 7. - 22 - 25.
13. Konopasevich P.A. Further material on the physiology of muscle fatigue. Dis. - JV b. - 1892.
14. Konradi G.P., Slonim A.D., Farfel V.S. General foundations of labor physiology. - M.; L., Biomedgiz, 1934 .-- 672 p.
15. Krasovsky V.O. On some restrictions for the application of the phenomenon of I.M. Sechenov in the prevention of overwork and overstrain // Ecological and hygienic problems of the Ural region: Mat. report 2nd Russian scientific and practical. conf. - Ufa, 1997.- S. 7 - 14
16. Krasovsky V.O. On the applicability of "active rest" for the prevention of fatigue in unfavorable working conditions // Valeological questions of the interaction of somatosensory and autonomic functions in the process of work: Sat. Scientific tr. - Tver, Tver State University. - 1999 .-- S. 42 - 48.
17. Krasovsky V.O. On the properties of multifactorial industrial impact // Hygienic and occupational pathological problems of Siberia regions / Ed. V.D. Surzhikov. - Novokuznetsk, 1998 .-- P. 116 - 124.
18. Kulak A.I., Guripovich L.A., Vasilievskaya K.V. et al. Physiological assessment of the severity and intensity of labor of workers and employees of different ages // Gerontology and geriatrics: Yearbook (Social environment, lifestyle and aging). Kiev, 1970 .-- P. 106 - 111.
19. Kulak I.A. Physiology of fatigue during mental and physical work of a person. Minsk: Belarus, 1968 .-- 272 p.
20. V.L. Marishchuk Functional state and performance // Research methodology in engineering psychology and labor psychology. - L., 1974 .-- S. 81-95
21. Moikin Yu.V., Kikolov A.I., Tkhorevsky V.I. Psychophysiological foundations of overvoltage prevention - M .: Medicine, 1987, 256 p.: Ill.
22. Rosenblat V.V. The problem of fatigue. M .: Medicine, 1975 - 240 p.
23. Guide to practical training in occupational health / Ed. prof. A.M. Shevchenko. - Kiev, 1986.- 336 p.
24. Manual on the physiology of labor / Ed. Z.M. Zolina, N.F. Izmerova. - M .: Medicine, 1983 .-- 528 p., Ill.
25. Sapov I.A., Solodkov A.S. The state of the body's functions and the efficiency of sailors. L .: Medicine, Leningradskoe. department, 1980. - 192 p .: ill.

LECTURE TEXT

Efficiency is the ability of a person to perform the assigned work with the proper quantity and quality. How to determine the ability to perform the job of this or that employee? It is necessary to understand that an indirect characteristic of this physiological and psychological personality trait are indicators of labor productivity (production), time-based operational data, product quality assessments, etc.

It is necessary to distinguish between two categories of performance: potential (opportunity) and kinetic (at the end of the work). The ability to perform a particular job is determined by age, experience, special training, as well as medical indications and contraindications. Kinetic performance is determined by the energy consumption after the work performed.

Human labor activity is carried out in the order of the joint functioning of various systems of the body under the wise guidance of the central nervous system. The presence of a dynamic stereotype and dominants establishes a certain level of the body's working capacity, the maintenance time of which depends to a large extent on the severity and intensity of work activity, as well as on the existing working conditions, work and rest regimes.

O. Graf back in 1934 proposed a physiological curve, which reflects the period of the lowest level of working capacity, unfavorable for work. This time is between 1 - 3 am.

Studies of the state of physiological functions of a person and the dynamics of working capacity in terms of production and other indicators (all other things being equal) in the process of labor activity make it possible to identify a certain pattern, which is characterized by the phasing of physiological shifts. This pattern boils down to the recognition that there are always four phases in work of any duration:workability, stable and unstable working capacity and its decline.

Phase one corresponds to the initial period of work, when the working dynamic stereotype is improved and reinforced by the correct options for coordinated actions. An important point in this process is the formation of a dominant, which ensures the normal flow of the work performed.

Note that the more periods of work-in (for example, after distractions for a smoke break), the lower the labor productivity and the lower the kinetic efficiency.

Second phase - sustainable performance is a characteristic combination of high indicators of labor results with relative stability and even a slight decrease in the intensity of physiological functions.

Third phase sometimes incorrectly referred to as "the final rush". During this period, bursts of working capacity are possible, but the general tendency towards a decrease in its performance (production) is increasing more and more.

Fourth phase - the decline in working capacity is characterized by increasing fatigue. However, this phase was not seen in their practical research in production. Such a state, close to overwork, was observed in workers who came to work after labor in the garden plots.

The nature of the performance curve depends on the rate of onset and the depth of fatigue that occurs in the unstable phase and depends on the characteristics of working conditions and the work itself. Therefore, in practice, there are deviations from the typical classical performance curve, which are manifested in a more or less pronounced phase, sometimes with a complete absence of any of them. It must be remembered thatthe presence of sharp fluctuations in working capacity and the short duration of its stable phase is a sign of increased labor severity.

Fatigue is the reciprocal of performance.Fatigue is understood as a decrease in the ability to work due to the performance of a certain job. It is necessary to distinguish: the state of fatigue (after work or during work) and the process of developing fatigue.

The study of the causes of the development of fatigue began to be dealt with at the end XIX centuries. A number of theories of fatigue were created, which are still supported by some foreign physiologists.

One of the first to appear was the theory of muscle depletion of energy reserves - carbohydrates and lipids. Such a theory has no scientific substantiation, since it has been shown that an animal brought to fatigue that ends in death as a result of intensive work has a sufficient supply of glycogen in the liver. With very intense work, fatigue can come quickly, after 2 - 3 minutes, and it is difficult to assume that during this time the reserves of glycogen and lipoids have disappeared from the body.

There were also theories of "poisoning" of the organism either by the decay products of proteins and carbohydrates (Pfluger), or by special toxins - kenotoxins (Weichardt). This theory was based on the fact that the blood of a tired animal, injected into a normal animal, caused him a state similar to fatigue. But, at the same time, one should not forget about the compatibility of blood and the 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, fatigue stimulates life processes, it has been established that decay processes cause active recovery processes.

Finally, there was the theory of the clogging of the body with decay products, in particular lactic acid (Hill). Indeed, the accumulation of lactic acid can accompany fatigue: the more intense the work, the more lactic acid accumulates. 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 work, but, on the contrary, stimulated it. Termination of work due to fatigue coincided with a decrease in the lactic acid content.

This theory of fatigue turned out to be physiologically unfounded, since it was based on the results of the study of an isolated muscle without connection with the rest of the functions of the whole organism. Consequently, with the regulatory role of the central nervous system. The authors of these theories took particular changes for general changes in the whole organism.

In practice, the theory of clogging the body in explaining the processes of fatigue is an opportunistic interpretation of the dialectics of the particular and the general.

Even I.M.Sechenov 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 the work, is 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 low energy costs, without fatigue for a long time.

On the basis of the teachings of N.E. Vvedensky, A.A.Ukhtomsky, and especially I.P. Pavlov, it became possible to prove the connection between the termination 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 grounded theory of fatigue.

The normal functioning 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 provides a central nervous coordinating action. Violation of the coordinating and regulatory function of the cerebral cortex leads to a decrease in working capacity or, the cessation of the functions of the entire system, that is, to fatigue.

Distinguish (M. Vinogradov) rapidly developing fatigue as a result of unusual or excessive work and - slowly developing fatigue (secondary) with mild changes in the body as a result of albeit habitual, but too long work.

Rapidly developing fatigue can occur as a result of significant physical effort or unusual, very strenuous work. Fatigue occurs as a result of a violation of the 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 exertion, conditioned reflex activity (increased arousal) increases. The strength of conditioned reflexes increases, the latent period is shortened, but at the same time, at the beginning of work, differentiation is disinhibited, phase states appear, which are more clearly expressed by the end of work (development of inhibitory processes).

The restoration of the initial state occurs rather quickly and passes the stage of exaltation - increased excitement, which is characterized by an increase in the intensity of the reflex, a shortening of the latent period.

Accordingly, the electrical activity of the cerebral cortex (biocurrents) changes: the normal rhythm (excitation) frequency is disorganized and subsequently completely disappears, increases -rhythm, and with the development of inhibition, long waves appear - -rhythm. Recovery takes place in the 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.

A characteristic feature of rapidly developing fatigue is the rapid recovery of function after work to its original state. The more static stress, the faster fatigue develops, the faster recovery occurs. We can assume that fatigue occurs as a result of inhibition in the motor center of the cerebral cortex.

In this case, the question arises: is it possible to identify fatigue and inhibition? This question should be answered in the negative. According to IP Pavlov, inhibition is a measure of cell protection from functional "exhaustion", "destruction".

The period of inhibition in the brain cell is the period of cell recovery.

This is proved by the study of metabolic processes in the cerebral cortex in a state of excitement and inhibition. Excitation is characterized by an increase in metabolic processes in the cerebral cortex. In particular, glycolytic processes are enhanced, the content of ATP and creatine phosphate decreases, the amount of ammonia increases, etc.

Inhibition under normal physiological conditions is characterized by the restoration of disturbed metabolic processes.

Thus, inhibition is not a depletion of the cell's energy capabilities, but a state of restoration of function and a measure of preventing its functional depletion. This state, apparently, allows the cell not to respond to impulses arriving at it, as a result of which vigorous activity stops. 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 the nutrition of the cell, carried out through the circulatory system. L.A. Orbeli and his colleagues showed that such a trophic (adaptive-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 effect on physiological lability - mobility of nervous processes. When the sympathetic nerves are irritated, the functional capacity of the tired muscle increases.

Slow onset fatigue is characterized by a gradual decline in performance as a result of habitual but excessively prolonged 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.

With primary fatigue, working capacity falls faster due to rapidly developing inhibition. With secondary fatigue, the efficiency gradually decreases as a result of a slow decrease in the lability of the nerve centers, which is characterized by prolongation of physiological intervals. In other words, functional activity decreases, which is expressed in general, a decrease in the reactivity of the physiological system.

With primary fatigue, inhibition develops rapidly and quickly disappears after stopping work - it is clearly delineated, concentrated in certain foci. With secondary fatigue, inhibition develops slowly, it is unstable, shallow and gradually takes on the character of a kind of stagnant inhibition.

With any fatigue, the value of conditioned motor reflexes fluctuates in waves, reaching a level below the initial one. The receptor functions are sharply weakened: the lability of the visual and auditory analyzers decreases, the muscular balance of the eyes, the coordination of movements, their accuracy, and body balance when standing are disturbed. The dynamics of lability during the working day changes in parallel with the change in working capacity. A decrease in lability indicates incipient fatigue, which in production conditions can be expressed in a drop in hourly labor productivity, an increase in rejects and an increase in the duration of individual operations due to micropauses.

The processes that determine primary fatigue do not create conditions for the cumulation of functional or organic changes, both in the central nervous system and in peripheral organs and systems. This is not only due to the fact that the primary fatigue arises from a new job no more than two or three times, since then the elements of the system of a dynamic working stereotype and dominants are created. Previously unaccustomed work becomes habitual, and therefore such work that causes the appearance of secondary fatigue.

Changes during secondary fatigue can accumulate from day to day and turn into overwork or overstrain, which is already a pathological condition. These conditions lead to an increased nonspecific morbidity of workers. On the other hand, they can cause so-called “overexertion diseases”. Callousness of the skin of the hands in persons of physical labor is a sign of overstrain of the skin function in the process of labor. Shoulder scapular periarthrosis in painters, plasterers, glue of large products are caused by repetitive movements of the upper limbs during labor. Tenosynovitis, muscle neuralgia, etc. Masons also have a consequence of overstrain of the neuromuscular apparatus.

When working with personal electronic computers, the danger is not low-power electromagnetic fields (up to 5 W, leakage currents), but a prolonged sitting posture and eye strain. The first manifests itself in men in the development of prostate adenomas, in women - in miscarriages, adnexitis, etc. We, from our experience with a computer, distinguish transient computer myopia, characterized by a rapid restoration of visual acuity after sufficient rest.

Varicose veins of the lower extremities in teachers, surgeons, weavers (Ryzhov A.Ya.) and other workers, in whose work a working standing posture prevails, are largely due to work and are the result of overstrain of the leg muscles.

By definition, overwork and / or overstrain are conditions in which signs of fatigue that have not passed during a regulated rest are detected. Not all functional indicators have reached the initial background, performance is lower than in the previous period, etc.

The second differential sign of fatigue and overwork, as already mentioned, is the change in the indicators of various functions in comparison with the beginning of work. If they do not go beyond the confidence limits of the original indices, then we are talking about fatigue. If they do, then this is a clear symptom of overwork and / or overexertion.

Moving on to the discussion of measures to improve performance and prevent overwork, we should recall the works of F. Taylor. It was he who, organizing work on the Ford conveyors, made sure that:

1. The speed of the conveyor should be determined by the state of the weakest and least trained worker or the most difficult and lengthy labor operation,

2. There should be breaks, rest periods,

3. The best labor productivity is determined during the daytime (10.00-11.00 hours), on Wednesday,

Fatigue is not only a physiological and hygienic problem, but also a social problem. Scientific and technological progress is aimed at increasing labor productivity and thereby making it easier. In developed countries, in order to increase labor productivity and prevent fatigue, mechanization of labor-intensive work, automation of production processes, rationalization of machine tools and equipment, and radio and television control are carried out on a large scale.

All this, undoubtedly, greatly facilitates and improves working conditions, contributes to an increase in its productivity and an improvement in the health of workers.

Along with this, extremely great importance is attached to the physiological optimization of work processes. The main directions in it are:

1) Rational organization of the labor process;

2) Creation of conditions for quick mastering of labor skills;

3) Rational organization of the regime of work and rest.

The rational organization of the labor process includes a set of very important measures and, above all, measures to build labor movements.

Rational movement should be based on the physiologically beneficial use of active and passive forces.

A skilled worker, for example, moves at first with a high speed, and towards the end with a low speed.

A worker with insufficient experience strives to maintain a constant speed throughout the movement. The latter is physiologically unreasonable, since in this case the excitement persists throughout the entire movement, it is diffuse, and not concentrated, active muscle tension lasts much longer, passive forces are not used.

The movement should be smooth, without a sudden change in pace and direction. This movement is accompanied by less strenuous work of the cerebral cortex.

The elliptical shape of the trajectory of movement is many times more expedient than the rectilinear one, since it corresponds to the anatomical structure of the joints.

Full swing movements are unreasonable: increased energy expenditure and additional proprioceptive impulses appear, leading to a more rapid onset of fatigue.

With the combined work of both hands, the productivity of not only the general, but also of each hand individually increases. By combining the work of the flexors of one arm and the extensors of the other, performance increases.

Excessive movements should be eliminated. This is usually achieved by quantifying (dividing) a complex labor process, movements into separate elements.

At the same time, on the one hand, it is necessary to keep in mind the uniformity of physical activity, on the other, not to strive too much, to dismember the labor process, since repeated performance of elementary operations creates conditions of monotony and contributes to faster fatigue. When rationalizing working movements, the principle of saving muscle mass should be observed. Heavy work should involve the large proximal muscles, and light work should involve the small distal muscles.

Computer programs have long been developed that make it possible to sort out the variants of movements and find the most reasonable ones. So, for machine operators, thanks to the quantification of movements for different machine operators, programs have long been created in the USA that offer up to 200 variants of various control movements, which significantly optimizes the workload.

Motor activity arises and is continuously corrected with the active participation of mainly the visual and motor analyzers. Analyzers operate in combination, but in each case, the predominance of the activity of one or another analyzer is possible. So, when driving a car, vision determines the correct direction of movement, hearing determines the state of the engine. Based on the study of the work of car drivers and other workers who operate machines by ear, the concept of “information component of industrial noise” was created (Kolganov L.K. et al.).

Rhythm plays an important role in the rationalization of the labor process. The rhythm is expressed in the repeated reproduction of a complex of individual techniques, which is a complete cycle. The repeatability of the cycle has a strictly temporal and spatial characteristic. The concepts of rhythm and tempo (speed) are often distinguished.

In practice, these two concepts are inseparable, and rhythm as a broader concept includes tempo (speed) as a particular concept.

Rhythmic work activity contributes to the formation of temporary connections that are fixed in a dynamic stereotype. The efficiency of rhythmic work is due to the fact that thanks to the strengthened mutual connections, the automatism of working movements and the maximum use of the passive forces of the muscular apparatus - inertia and elasticity - are acquired. With the learned rhythm, the highest efficiency is achieved, the lowest energy costs, low lactic acid content, and slightly increased stable blood sugar levels are noted.

The individual rhythm can be accelerated, and the new learned rhythm becomes optimal; while biochemical and physiological processes proceed at the level of the previous rhythm.

In the light of what has been said, the mechanistic concept of some physiologists, who believe that for each person there is his own constant optimal rhythm, should be rejected. The theory of “three biorhythms” comes from such ideas. Its essence is that a person's life proceeds according to three main rhythms: emotional (28 days), intellectual (24 days) and physical (21 days), which are established from the moment of birth. We have verified this concept by calculation. It turned out that the error in calculations taking into account the millisecond of the moment of birth of a person after 40 years of life reaches 30-40 days, that is, it twice overlaps the duration of these cycles. On the other hand, there are some statistics when the intersection of the curves of these cycles was marked by some unfavorable situations. However, familiarity with these statistics did not convince us of the validity of the concept.

On the other hand, conducting research in this direction at the Orenburg helium plant in 1989-90, we found that the totality of these cycles among shift team workers depends on the overall performance indicator in the daytime and does not depend on at night.

Rhythmic work, along with positive aspects, has negative properties. Long-term rhythmic, monotonous in nature, activity acquires monotony, which in turn leads to a drop in working capacity and fatigue due to developing inhibition in the cerebral cortex.

Note that according to M.A. Gritsevsky, two types of monotony of labor should be distinguished: a) Monotony of movement (the work of a car driver), b) Monotony of rest (the work of a chemical production operator is active expectation).

It is generally accepted that static stress in the labor process, in general, is an unfavorable factor that quickly leads to fatigue. Meanwhile, in some cases, static stress turns out to be a favorable factor that increases the efficiency of dynamic muscle work. It has been proven that preliminary static stress, for example, the flexors of the forearm, not only does not reduce the subsequent dynamic work, but, on the contrary, increases it. This circumstance explains the need for static stress before the start, for example, in running competitions, cycling, as well as in the complexes of physical exercises of some eastern systems.

As you know, with prolonged static work, fatigue is associated with the development of central inhibition due to prolonged and frequent repetition of impulses coming from the working muscles, that is, unfavorable (pessimal, according to N.E. Vvedensky) conditions of innervation. When, during the transition to dynamic work, the conditions of innervation become favorable (optimal), situations of increased excitability and increased performance are created. However, it does not come immediately, but after the second phase contraction (trace changes, according to N. Ye. Vvedensky). An example is the following experience: after static work to failure, the first test of dynamic work does not cause an increase in muscle strength, and after the second test of dynamic work, a sharp increase in muscle effort occurs.

It turns out that with a combination and appropriate ratios of static and dynamic work in one cycle, energy is consumed more economically both during operation and during the recovery period.

The foregoing indicates that static stress under certain conditions serves as a stimulator of dynamic work. A prerequisite is the alternation of static and dynamic forces. This condition must be put into. the basis for the rationalization of labor processes.

But, if the static component has a significant proportion and duration in the labor process, it must be limited as much as possible - in some cases by mechanizing labor processes.

From a physiological point of view, muscle tension to maintain the so-called "posture states", that is, the posture of a person during work, can be attributed to typical static work.

The "standing" posture, to which he has adapted in the process of evolution, is specific for a person. However, with prolonged standing, disorders of physiological functions are possible up to pathological changes: venous stasis, varicose veins, edema, flat feet, etc. In a sitting position, tetanic muscle tension is replaced by tonic, the activity of the heart and other organs improves.

The choice of posture should be consistent with the nature of the work, to ensure stable performance. When choosing a posture, the magnitude of the applied efforts is of great importance: with an effort of 5 kg, it is beneficial to work while sitting, with an effort of more than 10 kg, the effect is the same both sitting and standing, and with an effort of 20 kg, it is beneficial to work while standing.

In a sitting position, it is necessary to provide for the conditions for a correct fit without a forced body position. This does not mean, of course, that you should always sit with your body erect. It is sometimes beneficial to sit with a slight forward bend and a slight bend in the lumbar spine. From a physiological point of view, the correct choice of posture is to create conditions for a periodic change in posture from slightly bent to erect, from a sitting posture to a standing posture.

This possibility can be provided, in particular, by a rational design of a working chair. The following requirements are imposed on the design of the chair:

Comfortable back support, easy to move vertically and from front to back;

Seat surface conforming to the anatomical shape of the buttocks; a screw barrel that allows you to move the seat vertically;

Folding seat so that, if the worker wishes, it is possible to work while standing.

Additionally, in accordance with the nature of the work, the following requirements may be presented:

a cutout in the seat for a leg, if necessary, press the pedal,

armrests for hand support,

castors if necessary to move, shock absorbers in the presence of vibration, footrest.

Exercise and training are important conditions for the rapid development of work skills. In the process of exercise, which lies at the basis of the formation of any motor act, the whole body takes part, an exact interaction is established between the central nervous system, receptors, motor apparatus and the respiratory, cardiovascular and all other systems. This is due to the formation of conditioned reflexes to a complex of external and internal stimuli. The performance curve during training (according to M.I.Vinogradov) appears to be three-phase.

Phase one - performance is constantly falling and quickly reaches the level that characterizes the impossibility of work.

Second phase - elimination of unnecessary movements; movements lose their initial stiffness, become precise, light, automated.

Third phase - bringing the movement to automatism does not mean inhibition in the nerve centers, but a certain decrease in excitability, which makes it possible to perform automatically conditioned reflex movements. For example, training recruits for such an element as “approach, report to the boss”. In the process of training, some may fall ... Or practicing the "drill step" ... In the future, when consolidating such skills to automatism, the soldier performs them without hesitation ...

Thus, exercise (training) is a powerful factor in preventing fatigue.

The organization of a rational regime of work and rest, that is, a rational alternation of work and breaks, is of great importance in the complex of measures to increase efficiency and prevent fatigue.

In the organization of the work and rest regime, the following main tasks arise:

1) Determination of the time for granting rest breaks during the working day,

2) Establishing the duration of the breaks.

The first problem is solved relatively simply - by accounting, if possible, the hourly productivity of labor during the day.

Note that productivity growth is recorded at the beginning of the working day up to a certain level (the working phase). Then the indicator falls by the time of the lunch break. In the second half of the working day, the character of the curve is repeated.

With tiring work, labor productivity (working capacity) may decrease long before lunch break or the end of the working day. Rest breaks should be provided in such a way as to ensure sustainable productivity throughout the working day. For this purpose, it is better to record productivity for short periods commensurate with the nature, content, rhythm and pace of labor.

In the event that performance is not amenable to hourly counting, other criteria can be used to determine when a rest break is granted. Parameters such as an increase in the time spent on labor operations and a reduction in the time of micropauses between operations, an increase in indicators of energy expenditures or functional shifts of one or another system, tension of attention, etc. can be informative.

The second task is to determine the duration of rest breaks, as a rule, it is solved experimentally by comparing two or three options for work and rest.

During the working day, one long lunch break is necessarily provided, and it is rational to take such a break in the middle of the working day. In addition to this long break, it is necessary, based on hourly performance or other criteria, to provide short breaks during the working day. The usefulness of such short rest breaks has been proven by numerous researchers in the field of occupational physiology. For illustration, we present the following table.

Table 1

Impact of short breaks on labor productivity

when assembling the relay

Duration experiences (weeks)	Mode labor	Average performance in hour
	Work without short breaks	49,8
	Two 5-minute pauses	52,4
	Two 10-minute pauses	55,4
	Six 5-minute breaks	55,5

It can be seen from the table that, despite a longer general rest (30 minutes), a mode with six-5-minute pauses gives higher labor productivity than other modes.

Thus, the hourly productivity of weavers with a 7-hour working day with a 10-minute rest in addition to a 30-minute lunch break increased by 3.45% (A.A. Balazhkova). Obviously, it is rational to provide short breaks of unequal duration for rest, increasing them as you continue to work. In light of this, the data in the following table 2 are of interest.

In two non-regulated modes, the breaks were set by the worker himself (trolley truck). In the other two regimes, rest breaks were regulated in this manner.

I option: after every 5th trolley rest 2 minutes, after every 15th trolley - 5 minutes, after every 45th trolley - 15 minutes;

II Option: after every 10th trolley, rest 2 minutes, after every 20th trolley - 5 minutes, after every 50th trolley - 15 minutes.

The second variant of the mode of work and rest, despite the shorter total duration of rest during the working day, turned out to be the most effective in terms of labor productivity and energy consumption.

table 2

Labor productivity and energy consumption of the trolley hauler

depending on the mode of work and rest

Mode work and rest	Working day, in hours hours	Total length tel- ness re- jerks, in minutes	Labor productivity on number of trolleys	Energy consumption kcal / min	Ener- hetic cost- bridge I trolleys, kcal.
Not regulated
Not regulated					29,9
Option 1, rest is regulated					24,8
Option 2, rest is regulated					22,9

How can you explain from a physiological point of view the benefits of short breaks - 5 and 2 minutes?

It has been proven that in such a short period of time there is no recovery of functional changes. The study of the period of resumption of work at different intervals after the previous work showed that in the post-work period there is a kind of alternation of pessimal and optimal states of the body according to N.E. Vvedensky.

The resumption of work in the phase of increased excitability (optimum) after the working period is advisable because in this phase the working attitude has not yet been lost, and the dynamic stereotype is easily reproduced.

The ratio of the elements of work and rest, that is, the presence and duration of micropauses between muscle contractions, is of great importance in organizing the regime of work and rest at the same intensity. When the ratio of work elements and pauses is 1: 1, the efficiency and labor productivity are the highest. The duration of micropauses is of great importance for the recovery processes, since they occur in the muscle during the period of its relaxation. With an inadequate duration of micropauses, decay products accumulate, functional lability and efficiency decrease.

Currently, as a rule, the mode of work and rest is established experimentally for a specific type of labor process and its conditions. It is quite obvious that in this way it is impossible to scientifically substantiate the mode of work and rest for all work processes. Therefore, one should try to classify all types of labor processes and, according to this classification, establish standard schemes of the regime of work and rest.

In addition to the mode of work and rest during the working day, it is also necessary to regulate weekly and annual rest with a duration of 12, 24, 48 working days. It is advisable to divide the annual rest of 48 working days into two periods.

A special place is occupied by the question of the mode of work and rest in the conveyor system of work. Its main feature is monotony, leading to rapid fatigue.

From a physiological point of view, the conveyor system for organizing labor is deeply contradictory. On the one hand, the rhythm inherent in this system allows the development of automatism and greatly facilitates the work. On the other hand, prolonged, repeated exposure to a monotonous stimulus on the same area of ​​the cerebral cortex causes inhibition and rapidly developing fatigue.

A number of researches (S.A. At the same time, there is an increase in the latent period of motor reflexes, a decrease in the lability of the visual and auditory analyzers, a lengthening of the working operation due to the shortening of micropauses, which leads to a decrease in the time for rest, a decrease in labor productivity and the quality of work. By the end of the working day, pronounced fatigue may occur with the development of inhibitory processes in the cerebral cortex.

To prevent fatigue when working on a conveyor belt, it was no longer enough to introduce only short breaks for rest during the working day. Switching from one operation to another proved to be effective, the physiological basis of which is based on intercentral relations (KS Tochilov). Avoid oversimplification of working operations by bringing them to elementary monotonous movements. In some cases, elementary operations can be combined into more complex and diverse in content. It is recommended to reduce the speed of the conveyor in case of an imminent drop in performance. The introduction of short (5-10 minutes) rest breaks every hour, using them for physical exercise, also has a beneficial effect. The introduction of stimuli such as music can be beneficial. The effectiveness of all these measures has been confirmed in practice.

The rational organization of the work and rest regime also includes the so-called active rest. IN. Buguslavsky and P.A. Konopasevich, students of I.M. Sechenov, in their Ph.D. theses (1891-92), they were the first to raise the question of the possibility of relieving muscle fatigue by alternately including individual muscle groups in the work and thereby laid the experimental foundations of the theory of "active rest".

A holistic, generalized physiological substantiation of the feasibility of this theory was given by I.M.Sechenov, who proved the effectiveness of changing working muscles to increase working capacity. The “Sechenov Phenomenon” was the basis for organizing active recreation.

According to IP Pavlov, during inhibition, recovery processes occur in the cells of the cerebral cortex, preparing them for new activity. During the rest of the tired right hand, the excitement that occurs when the left hand is turned on, according to the law of induction, will deepen inhibition in cells in which inhibition has already developed. the result of tedious work. As a result, recovery processes are enhanced, and a faster recovery of working capacity occurs than with passive rest.

The Sechenov phenomenon in industrial conditions is used in. the form of including a specially developed set of physical exercises in labor processes. They help to improve the activity of the centers of the cerebral cortex, activate the functional processes of the whole organism, increase the emotional tone and efficiency, and, consequently, labor productivity.

Introductory gymnastics (preferably with elements of static tension) creates a state of readiness for work, enhances the processes of excitation and inhibition, which is of great importance for the formation of a dynamic stereotype, and accelerates the process of working out. When compiling a set of introductory gymnastic exercises, the movements and rhythm typical for the upcoming labor process should be taken into account.

Physical training pauses during work are applied one to three times during the day during regular breaks and at the beginning of the lunch break. The distribution of physical training breaks is made depending on the performance and functional state of a person. The content of the complex of physical exercises is determined by the nature of the nervous and muscular activity in the labor process. With light monotonous work, during which inhibition develops rapidly, the set of exercises should be varied, aimed at involving muscle groups inactive in the process of work. With hard physical work and a variety of movements, movements should be used that contribute to the acceleration of the processes of restoration of functions. This can be achieved by applying relaxation and stretching of the muscular apparatus in combination with periods of complete rest.

The set of physical exercises should be periodically diversified, otherwise it will become an integral part of the working stereotype and lose the properties of a new stimulus.

Our studies have found a limitation for the application of the phenomenon at work: if physical culture pauses, physical exercises are carried out in a polluted atmosphere, the effectiveness of rest decreases.

Physical exercise during work and, especially during the lunch break, does not exclude passive rest, that is, a state of rest. In this case, it is necessary to strive to create such conditions under which the human body would be in the most natural to a comfortable position - sitting or lying down.

Thus, you and I have examined the peculiarities of modern ideas about the working capacity and fatigue of a working person. Let me emphasize that the physiological capabilities of a person, which determine these functions, are primarily regulated and depend on the central nervous system. This is another manifestation of the principle of nervousism, substantiated by the works of not only I.P. Pavlov, but also by the works of a number of Russian physiologists.

Compiled by: V.O. Krasovsky,

09.08.2004

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The ability of a person to perform physical (muscle) work for a long time is called physical performance. The amount of physical performance of a person depends on age, sex, fitness, environmental factors (temperature, time of day, oxygen content in the air, etc.) and the functional state of the body. For a comparative characteristic of the physical performance of different people, the total amount of work performed in 1 minute is calculated, divided by body weight (kg), and the relative physical performance (kg * m / min per 1 kg of body weight) is obtained. On average, the level of physical working capacity of a 20-year-old boy is 15.5 kg * m / min per 1 kg of body weight, and in a young man-athlete of the same age it reaches 25. In recent years, the definition of the level of physical work is widely used to assess the general physical development and state health of children and adolescents.

Long-term and intense physical activity leads to a temporary decrease in the physical performance of the body. This is physiological the condition is called fatigue. It has now been shown that the process of fatigue affects primarily the central nervous system, then the neuromuscular synapse and, in the last thing is 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. The proof of the validity of this conclusion can be considered the circumstance 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 fatigue, which is a pathological process and is characterized by a disorder in the activity of the nervous system and other physiological systems of the body.

7.2.5. Age features of the muscular systems

The muscular system undergoes significant structural and functional changes during ontogenesis. The formation of muscle cells and about muscle building as structural units of the muscular system occurs heterochronously, i.e. first formed those skeletal 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 formation of the muscular system continues. In particular, intensive growth of muscle fibers is observed up to 7 years of age and during puberty. By the age of 14-16, the microstructure of skeletal muscle tissue almost completely matures, but the thickening of muscle fibers (improvement of their contractile apparatus) can last up to 30 -35 years.

The development of the muscles of the upper extremities is ahead of the development of the muscles of the lower extremities. In a one-year-old child, the muscles of the shoulder girdle and arms are much better developed than the muscles of the pelvis and legs. Larger muscles are always formed before small 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 the age of 6-7 years. The total muscle mass builds up very quickly during puberty: for boys - at 13-14 years old, and for girls - at 11-12 years old. Below are the data characterizing the mass of skeletal muscles in the process of postnatal ontogenesis.

Much the functional properties of muscles also change in the process of ontogenesis. Is increasing 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 more often bent. They have a poorly expressed ability of muscles to relax (this is associated with some stiffness in the movements of children), which improves with age. Only after 13 - 15 years do the movements become more plastic. It was at this age the formation of all parts of the motor analyzer ends.

In the process of development of the musculoskeletal system, the motor qualities of the muscles change: speed, strength, agility and endurance. Their development is uneven. First of all, quickness and dexterity are developed.

The speed (speed) of movements characterized by the number of movements that the child is able to perform per unit of time. It is determined by three indicators:

1) the speed of a single movement,

2) the time of the motor reaction and

3) the frequency of movements.

Single movement speed increases significantly in children from 4-5 years old and reaches the adult level by 13-15 years. By the same age, the level of an adult reaches and time of a simple motor reaction, which is due to the speed of physiological processes in the neuromuscular apparatus. Maximum arbitrary frequency of movements increases from 7 to 13 years old, and in boys at 7-10 years old it is higher than in girls, and from 13-14 years old, the frequency of movements of girls exceeds this indicator for boys. Finally, the maximum frequency of movements in a given rhythm also increases sharply at the age of 7-9 years. In general, the speed of movements develops at its maximum by the age of 16-17.

Until the age of 13-14, mainly development is completed agility, which is associated with the ability of children and adolescents to carry out accurate, coordinated movements. Hence, agility is related to:

1) with spatial accuracy of movements,

2) with temporal precision of movements,

3) with the speed of solving complex motor problems.

The preschool and primary school period is most important for the development of dexterity. Greatest gain in movement accuracy observed from 4 - 5 to 7 - 8 years. It is interesting that sports training has a beneficial effect on the development of agility and in 15-16 year old athletes the accuracy of movements is twice as high as in untrained adolescents of the same age. Thus, up to 6 - 7 years old, children are not able to make fine precise movements in an extremely short time. Then the spatial accuracy of movements gradually develops, a behind it and temporary. Finally, last of all, the ability to quickly solve motor problems is improved in different situations. Agility continues to improve until the age of 17-18.

The greatest gain in strength observed in middle and senior school age, especially intensively the strength increases from 10-12 years to 16-17 years. In girls, the increase in strength is activated a little earlier, from 10 to 12 years old, and in boys - from 13 to 14 years old. Nevertheless, boys are superior to girls in this indicator in all age groups.

Endurance develops later than other motor qualities, characterized by the time during which a sufficient level of the body's performance is maintained. There are age, sex and individual differences in endurance. The endurance of preschool children is low, especially for static work. An intensive increase in endurance to dynamic work is observed from 11 - 12 years old. So, if we take the volume of dynamic work of 7-year-old children as 100%, then it will be 150% for 10-year-olds, and more than 400% for 14-15-year-olds. Just as intensively from 11-12 years of age, children increase their endurance to static loads. In general, by the age of 17-19, endurance is about 85% of an adult's level. It reaches its maximum level by the age of 25-30.

Development of movements and mechanisms of their coordination most intensively occurs in the first years of life and in adolescence. In a newborn, the coordination of movements is very imperfect, and the movements themselves have only a basal-reflex basis. Of particular interest is the swimming reflex, the maximum manifestation of which is observed at about 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 as his own neck muscles are still very weak. In the future, the swimming reflex and other unconditioned reflexes gradually fade away, and motor skills are formed to replace them. All basic natural movements inherent in humans (walking, climbing, running, jumping, etc.) and their coordination are formed in a child mainly up to 3 - 5 years old. At the same time, the first weeks of life are of great importance for the normal development of movements. Naturally, in preschool age, coordination mechanisms are still very imperfect. Despite this, children are able to master relatively complex movements. In particular, namely v at this age they learn to move with tools, i.e. motor skills and skills to use a tool (hammer, wrench, scissors). From 6 to 7 years old, children master writing and other movements that require fine coordination. By the beginning of the adolescent period, the formation of coordination mechanisms as a whole is completed, and all types of movements become available for adolescents. Of course, the improvement of movements and their coordination with systematic exercises is also possible in adulthood (for example, among 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 impaired 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 years is considered "golden" in the development of human motor skills. This is the heyday of his motor abilities.

1.1. Fatigue in an isolated neuromuscular apparatus. Theories of the development of fatigue.

Fatigue is a complex phenomenon that develops throughout the body. The fatigue of an isolated muscle developing in the experiment due to its long-term work is expressed in a gradual decrease in the amplitude of contractions, lengthening the relaxation phase, and also in the fact that relaxation gradually becomes less and less complete - contracture develops. Special studies have found that in a tired muscle, excitability decreases (the threshold of irritation rises), the latent period lengthens (the time interval from the moment of muscle irritation to the start of contraction), and viscosity increases. It should be noted that these signs also take place during motor activity in the muscles of the whole organism.

A neuromuscular preparation contains three elements: muscle fiber, neuromuscular synapse, and nerve fiber. Experience shows that with fatigue of a neuromuscular drug, a change in functional properties occurs, first of all, in the neuromuscular synapses, and secondly, directly in the muscle fibers. As for the nerve conductors, they, as N. Ye. Vvedensky first showed, are practically "indefatigable." A change in the functional properties of neuromuscular synapses is expressed in a violation of the process of transfer of excitation from nerve fibers to muscle ones.

There are several theories for the development of fatigue. All of them were developed under conditions of an isolated muscle, on a neuromuscular preparation.

One of the earliest theories to explain the origin of fatigue was the "exhaustion" theory. Since the implementation of any activity is associated with energy transformations, it was assumed that fatigue of a muscle during its work is a consequence of the expenditure of energy substances, that is, the result of the depletion of the known reserves of these substances available in it. However, experiments have shown that significant fatigue of an isolated muscle occurs before it actually depletes its carbohydrate reserves. If the experiment is carried out under conditions when the muscle is not separated from the body and normal blood circulation is maintained in it, then the carbohydrate content in the tired muscle generally differs little from the initial data. Further, it turned out to be possible to restore the working capacity of the tired isolated muscle by washing it with saline, which in itself does not replenish the expenditure of energy substances. Thus, the theory of "exhaustion" does not provide a proper explanation for the fatigue of an isolated muscle, the more it is unacceptable for explaining fatigue during muscular activity of the whole organism.

The essence of the "strangulation" theory is reduced to the assumption that muscle fatigue during work is caused by an increasing lack of oxygen supply. However, studies have shown that a muscle can perform its work without any access of oxygen from the outside at all, for example, when an isolated muscle is in a chamber filled with nitrogen. Muscle contraction without external oxygen access occurs due to the anaerobic processes of the breakdown of adenosine triphosphate and creatine phosphate and the breakdown of glycogen to lactic acid. Muscle fatigue in an oxygen-free environment nevertheless occurs much faster than under normal conditions.

The theory of "clogging" is based on the fact that muscular work is associated with increased breakdown of energetic substances, which leads to a certain accumulation of intermediate products of this decay. The authors of the theory of "clogging" attached exceptional importance to this circumstance, and the role of the main "clogging" substance was attributed to lactic acid. But in the twenties of the present century, it was first established that a muscle can contract even if the carbohydrate metabolism in it is completely turned off and, therefore, lactic acid is not formed at all. At the same time, muscle fatigue occurs faster than with undisturbed carbohydrate metabolism. Undoubtedly, in some types of work, the accumulation of under-oxidized products of muscle metabolism in the body takes place and plays a role in the development of fatigue, but this does not exhaust the causes of fatigue.

The theory of "poisoning" is of historical interest. In 1912, a German scientist announced his discovery of the "fatigue poisons" allegedly formed in the muscles during work. It was pointed out that it was possible to induce fatigue in animals by injecting them with certain doses of blood taken from a tired animal. The discovery of the "fatigue poisons" opened up the fundamental possibility of developing antidotes against fatigue using methods well known in microbiology. However, all the experiments that served as the basis for the proclamation of the theory of "poisoning" turned out to be deeply erroneous and untenable.

The listed theories concern only individual links in the complex and multifaceted process of fatigue.

Fatigue of the body as a result of changes in the functional state of the central nervous system. Muscle work is a holistic activity of the whole organism. The functioning of the organism as a whole and its interaction with the outside world is carried out by means of the nervous system, with the leading role of its higher section - the cerebral cortex. Fatigue of the body due to muscular work is primarily the result of shifts in the functional state of the central nervous system. IM Sechenov wrote: "The source of the feeling of fatigue is usually placed in the working muscles: I place it ... exclusively in the central nervous system" (IM Sechenov, 1935). Research by domestic physiologists - I.M.Sechenov, I.P. Pavlov, N.E. Vvedensky, A.A. Ukhtomsky, L.A. Orbeli, G.V. the nervous system plays a leading role in the onset and development of fatigue.

Fatigue of the body during muscular work is primarily associated with fatigue of the central nervous system, since intense muscular activity is at the same time an intense activity of the nerve centers. The latter is disrupted as a result of prolonged hard work. The expression of this violation is a change in the normal relationship between the processes of excitation and inhibition, and the inhibitory process begins to prevail. As a result, the normal course of reflex processes is upset, the regulation of autonomic functions and coordination of movements are disturbed, the motor apparatus gradually comes to an inactive state (Pavlov S.E., 1999; Pavlov S.E. et al., 2001; Selye G., 1960; Surkina I.D. et al., 1991; Khmeleva S.N. et al., 1997).

The nervous system is most sensitive to changes in the internal environment. Fatigue factors such as the accumulation of cellular products in the blood, a decrease in blood sugar, a lack of oxygen in the blood under certain conditions, reduce the body's performance not directly, but mainly indirectly - through the central nervous system (Fig. 1).

These capabilities of the cerebral cortex and other parts of the brain, carried out through the intracentral pathways and autonomic nerves, are realized with the help of regulatory influences on all organs and tissues, including also on the central nervous system. In the activation of these influences, the leading role belongs to conditioned reflex reactions arising under the action of a wide variety of signal stimuli.

Among conditioned stimuli for humans, a verbal stimulus is of great importance, exerting its influence through the second signaling system of the cerebral cortex, interacting with the first signaling system. The mechanism of the influence of various emotional factors on the body's performance during fatigue should be considered in the light of the interaction of two signaling systems. Various speech influences (verbal encouragements, calls, etc.) can significantly affect the course of the phenomena of fatigue.

Interesting experiments with hypnotic verbal suggestion of various motor representations during work performance should be pointed out. The subject in a state of hypnosis lifted a light or heavy load, and when lifting a light load, he was inspired that he was lifting a heavy one, and when lifting a heavy one, it was suggested that he was lifting a light one.

In the first case - when performing light work against the background of a suggested idea of ​​hard work - physiological changes were higher and fatigue set in much faster than in control experiments with performing the same work outside hypnosis. In the second case, when doing hard work against the background of an instilled notion of light work, the opposite phenomenon was observed.

Experiments with the performance of work against the background of certain suggested motor representations convincingly show that fatigue and fatigue depend on the state of the central nervous system and, above all, on processes in the cerebral cortex, which can change by conditioned reflex, in particular through the second signal system. ...

In physiology, it is customary to distinguish between the concepts of fatigue and fatigue. Fatigue is a state of the body that arises as a result of work and is objectively characterized by a decrease in working capacity, fatigue is the subjective side of the manifestation of fatigue, a mental experience associated with fatigue, a feeling of fatigue.

The degree of fatigue largely corresponds to the degree of actual decline in performance, which in turn is related to the quantity and quality of the work done. However, there are often cases when fatigue and other signs of fatigue in their severity do not correspond to each other, for example, when fatigue is felt great, and there is no objective data for a sharp decrease in working capacity, since the work done is insignificant. This is observed if the work is done without interest and desire, without a clear idea of ​​the purpose of this work or its immediate results. There may be other cases when all the data for pronounced fatigue are available, since the work has been done a lot, but fatigue is nevertheless not felt. This happens when the performance of the work is accompanied by an emotional uplift, conditioned by the interest in the work, the consciousness of a high goal, etc.

The conditions in which the tedious work was performed (environmental factors, environment, team, time of day, etc.) can acquire a signal value through the mechanisms of temporary connections, contributing to the further development of fatigue and fatigue. These conditions can also become signals that counteract the development of fatigue and fatigue, if the work itself was not tiring at first. The value of conditioned reflex mechanisms in the development of fatigue is extremely high (Vasilyeva V.V. et al., 1977; Volkov V.M., 1976; Zhbankov O.V. et al., 1999; Sashenkov S.L. et al., 1995) ...

Trophic influences of the central nervous system through the autonomic nerves are essential for the development of fatigue phenomena. The sympathetic and parasympathetic nerves, as Pavlov first showed using the example of the heart muscle, carry out part of the trophic influences of the central nervous system on organs. When sympathetic nerves are irritated, functional properties change and the performance of tired skeletal muscles increases. Subsequent studies revealed the peripheral mechanisms by which the adaptive-trophic influences of the nervous system on the muscle during fatigue are realized. It has been shown that irritation of sympathetic nerves intensifies oxidative processes, increases the formation of adenosine triphosphoric acid, increases the buffering (alkaline reserve) of the tissue, increases the electrical conductivity of the muscle and its elastic-viscous properties. Impulses along the sympathetic nerve also affect the function of the neuromuscular synapse, improving the transmission of excitation from the nerve to the muscle, which is disturbed during fatigue. Trophic influences of the central nervous system (i.e., influences on metabolic processes) are universal in the body. The essence of these influences can be expressed in a change in the functional state of various organs. The stimulating trophic effects of the central nervous system on all organs and tissues, which arise unconditionally and conditioned reflex, play an important role in the muscular activity of a person during industrial work and sports activity. These influences, depending on their intensity, can, to a greater or lesser extent, counteract the oncoming fatigue or, to a certain extent, “remove” the already onset fatigue (Karpman V.L. et al., 1988; Kulikov V.P. et al., 1998 ; Ozolin N.N. et al., 1993; Suzdalnitsky R.S. et al., 2000).

7 people each. The age of the subjects was 15-16 years old. All the trainees had the second sports category. The planning of the training process of skiers-racers of these groups was aimed at solving the main problems of developing special endurance. During the study period, the groups performed approximately the same amount of cyclical work. There were 4-6 training sessions per week, each session was ...

Experimental work on the development of quickness and dexterity in older preschool children. Purpose: To select, develop and test a set of outdoor games that promote the development of speed and dexterity in older preschool children. In the course of the experimental work with children, outdoor games were carried out to promote the development of speed and dexterity. Work with children was carried out ...

Games with lightweight rules, massage. The described physical therapy exercises for myocardial infarction can be used for other diseases of the cardiovascular system, but the transition time to higher loads is shorter. 2. Exercise therapy for ischemic heart disease Ischemic heart disease is a common disease that manifests itself as angina pectoris - pain in the area ...

Information, churches, etc. Education in the pedagogical sense is a specially organized and controlled process that contributes to the development of the individual. This paper deals with family education. The family also acts as a social unit of society and, at the same time, as the most important factor in the formation of personality. The family, from the standpoint of sociologists, is a small social group, ...

Working capacity is a human property for a long time and with a certain efficiency to perform the maximum amount of physical or mental work. Throughout the work shift, working capacity varies widely. This is due to the fact that it is influenced by both external factors in relation to a person (nature of work, environmental conditions, work and rest regimes, working posture, organization of the work process from the point of view of ergonomics), and internal (motivation, degree of perfection labor skills, functional reserves of a person).

In an industrial setting, working capacity changes throughout the work shift and is conventionally divided into four phases. First phase - activation phase , during which the activity of the central nervous system increases, the level of metabolic processes in the body of the worker increases, the activity of the cardiovascular and respiratory systems increases. The duration of this phase depends on the type of activity. It is always shorter in physical labor than in mental labor. Moreover, the physically harder the work, the faster the training takes place.

The second phase is the phase of relatively stable performance , characterized by the optimal, from the point of view of achieving a useful result, the level of functioning of the systems of the body that ensure the work, maximum labor efficiency. The duration of the period of stable working capacity depends on the physical severity and nervous tension of labor (the harder the work, the shorter the period of stable working capacity), on the psychophysiological state of a person, on the hygienic working conditions.

The third phase is the phase of decreasing efficiency , associated with the development of fatigue. The fourth phase is the phase of the secondary increase in efficiency at the end of the working day. It is based on a conditioned reflex mechanism associated with the upcoming end of work and subsequent rest. The professional performance of a person also changes during the working week in a similar way.

Fatigue is the cause of decreased performance during the working day, week or year. During work, fatigue manifests itself in a decrease in muscle strength and endurance, a deterioration in coordination of movements, in an increase in energy consumption when performing the same work, in a slowdown in the speed of information processing, memory impairment, difficulty in concentrating and switching attention from one type of activity to another. Subjectively, fatigue manifests itself as a feeling of fatigue, which makes you want to stop working or reduce the load.

During dynamic work with an intensity below the limit of fatigue, the recovery of high-energy phosphates used in muscle contraction occurs during the work itself, during muscle relaxation (micropauses ). If the duration of muscle relaxation corresponds to the time required for the synthesis of ATP and the removal of metabolic products from them, then such work is not fatiguing . With dynamic work of high intensity, there is no possibility of continuous recovery of ATP during the work itself. This is due to the fact that the duration of periods of muscle relaxation is shorter than the time required for the current restoration of its energy potential. The restoration of energy reserves and the removal of lactic acid from the muscles are incomplete.

The physiological mechanisms of neuropsychic fatigue are not exactly known. Typical symptoms of such fatigue are a slowdown in the transmission and comprehension of information, a decrease in the efficiency of mental activity in general, and a weakening of sensory and sensorimotor functions. Such fatigue not only reduces performance, but sometimes leads to a decrease in a person's social activity, irritability, emotional instability, causeless anxiety and even depression.

Neuropsychic fatigue occurs in the following situations:

1) with prolonged and intense mental work, requiring increased concentration of attention, solving complex production problems in conditions of lack of time;

2) with hard physical labor;

3) with monotonous monotonous work;

4) when working in conditions of low light, high temperature, noise and vibration;

5) with frequent conflict situations in the team, lack of interest in work, inconsistency of the psychophysiological capabilities of a person with the nature of his work activity.

Unlike muscle fatigue, fatigue of a central origin (neuropsychic) ​​can quickly disappear. This happens, for example, in situations where one type of activity is replaced by another; a person finds himself in stressful situations that threaten his life; if there is new information that increases interest in the work. Since fatigue in the neuropsychic sphere can pass so quickly, this indicates that its root cause is neither a decrease in energy substrates in the nervous structures, nor the accumulation of metabolic products in them, nor an insufficient blood supply to the brain.

Any type of work will not lead to the development of overwork and overstrain and, on the contrary, will have a positive effect on the performance and health of a person, if you adhere to the physiological principles of its rational organization.

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Physiology of excitable tissues

The importance of studying the section .. Section Physiology of excitable tissues is studied first in the course of normal physiology. Excitable tissues play an important ..

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General physiology of excitable tissues
Irritability is the ability of living matter to actively change the nature of its life activity under the action of an irritant. The reactions of individual cells, tissues to the action of an irritant m

Structural and functional organization of the cell membrane
According to Robertson's definition, the cell can be considered as a triphase system, which consists of a nucleocytoplasmic matrix, a membrane phase and an external phase. The membranes account for about 2/3

Ionic channels
Ionic channels are formed by proteins, they are very diverse in structure and mechanism of their action. More than 50 types of canals are known, each nerve cell has more than 5 types of canals. Asset status

Electrical phenomena in tissues
1.2.1. Discovery of "animal electricity" At the end of the XVIII century. (1786) professor of anatomy at the University of Bologna, Luigi Galvani, conducted a series of experiments that laid the foundation for the goal

Local potential (local response)
When excitable tissue is irritated, PD does not always occur. In particular, if the strength of the stimulus is small, depolarization will not reach a critical level, naturally, there will be no impulse propagation.

The laws of irritation of excitable tissues
The response of the excitable tissue to the action of the stimulus depends on two groups of factors: the excitability of the excitable tissue and the characteristics of the stimulus. Cell excitability changes

1. Will the value of the resting potential change if the concentration of K + ions is artificially increased by 30% inside the nerve cell? A. resting potential will decrease to 0

Physiology of nerve fibers and nerves
2.1.1. The structure of the nerve fiber Nerve fibers are the processes of neurons, with the help of which communication between neurons is carried out, as well as

High lability
2.1.7. Axonal transport The presence of processes in a neuron, the length of which can reach 1 m (for example, axons innervating the muscles of the limbs), creates

Functional role of axonal transport
- Antegrade and retrograde transport of proteins and other substances is necessary to maintain the structure and function of the axon and its presynaptic endings, as well as for processes such as axo

Synaptic transmission of excitation
A synapse (Greek synapsis - connection) is a specialized structure that ensures the transmission of excitatory or inhibitory influences between two excitable cells. Through the synapse nar

Level 1-2 tests for self-control of knowledge

Fatigue means temporary decrease in performance cell, organ or organism, which arises as a result of work and disappears after rest.

Muscle fatigue... If a single rhythmic stimulation is applied to an isolated muscle with an induction current at a frequency of 1-2 times per second and its contractions are recorded on the drum of a kymograph ( myogram), the following phenomena can be noted. In the first period of the experiment, an increase in the magnitude of muscle contractions is observed. An increase in muscle performance is the result of an increase in metabolic processes, excitability and lability. Then a constant amplitude of muscle contractions is observed for a long time. In the future, there is a gradual decrease in the contractile effect of the muscle up to the absence of its response, which indicates the development of fatigue (Fig. 68).

Analysis of myograms shows that as fatigue develops, the duration of a single muscle contraction increases, mainly due to delayed muscle relaxation. In the future, the latent period of contraction and the threshold of irritation increase. With the development of fatigue, muscle chronaxia increases significantly. The causes of fatigue in the muscle are the accumulation of metabolic products (lactic, phosphoric acid, etc.), a decrease in the supply of oxygen and depletion of energy resources.

Neuromuscular fatigue... Sufficiently strong (or frequent) irritations are applied to the nerve, and the muscle contraction curve is recorded on the drum of the kymograph. With prolonged irritation of the nerve, there is a gradual decrease in the amplitude of contractions and even the absence of a muscle response (see Fig. 68). The weakening of the strength of the applied stimulation or a decrease in its frequency is also not accompanied by a muscle response, which indicates the development of fatigue in the neuromuscular preparation (see Fig. 68, B).

In order to answer the question in which structure of the neuromuscular preparation fatigue develops in the first place, let us turn to direct stimulation of the muscle with stimuli of the initial strength or frequency. In this case, the restoration of the mechanical reaction of the muscle is observed. It is logical to assume that fatigue developed either in the nerve or in the myoneural synapse. The works of N.E. Vvedensky established that the nerve is practically indefatigable. Consequently, fatigue primarily develops in the area of ​​the myoneural synapse of the frog's neuromuscular preparation, which is associated with the depletion of the transmitter stores in the nerve fiber terminals. In addition, if we compare the lability of various formations of a neuromuscular preparation, it turns out that the functional mobility of the myoneural synapse is the lowest (Fig. 69). In this regard, fatigue sets in faster in the synapse, as in a structure with lower lability.

Domestic physiologists I.M.Sechenov, I.P. Pavlov, A.A. In an organism, the unity of which is ensured by the joint activity of the central and peripheral nervous mechanisms, fatigue develops first of all in the nerve centers.

The speed of the onset of fatigue during prolonged performance of physical or mental work is influenced by the person's mode of life, the conditions of his nutrition, sleep, the state of the central nervous system, the degree of fitness, etc.

At the end of the last century, physiologists began to study individual manifestations of fatigue. Italian scientist Mosso suggested ergographic method studies in humans of the process of fatigue that occurs during muscular work. Using the device ergograph the influence of the rhythm of the work performed and the size of the lifted load on the rate of onset of fatigue was studied. The essence of the ergographic method consists in the fact that the examinee is offered, by extending and bending the finger of the upper limb, fixed in the device, to raise and lower a certain amount of weight in the rhythm of the metronome beats. Finger movements are recorded on the drum of the kymograph. The curve of muscle contractions recorded with an ergograph is called an ergogram (Fig. 70). It was found that the development of fatigue is primarily influenced by the rhythm of the work performed.

I.M.Sechenov studied fatigue, registering muscle contraction when lifting a load on an ergograph, designed by him. I.M.Sechenov found that the working capacity of a tired hand during its rest is restored more fully and better if the other hand is doing the work during this period. The same effect on the performance of a tired hand is exerted by irritation by the induction current of the afferent nerves of the other hand, as well as leg work associated with lifting weights, and physical activity in general.

An analysis of the established facts allowed I.M.Sechenov to come to the conclusion that rest, accompanied by moderate work of muscle groups, is a more effective means of combating fatigue of the motor apparatus than rest - passive rest... The concept appeared in physiology leisure.

An increase in efficiency after active rest is due to an increase in the excitability of neurons in the central nervous system under the influence of nerve impulses coming from proprioceptors, as well as the adaptive trophic effect of the sympathetic nervous system on tired muscle groups (I.M.Sechenov, L.A. Orbeli).

Thus, the best way to combat fatigue is to change the form of work, change one type of activity to another.