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Lecture notes, cheat sheets
Life safety. Physiological foundations of labor (lecture notes)
Directory / Lecture notes, cheat sheets Table of contents (expand) Lecture No. 17. Physiological foundations of labor Labor is necessary for the optimal flow of biological processes in the body, therefore, it has a great impact on health. Physical labor is characterized by severity and is associated with the performance of static and dynamic work, while mental labor is associated with tension against the background of static stress. Physical and mental labor are based on the same central mechanisms. Physical labor is characterized by high energy consumption, oxygen consumption, rapid development of fatigue and relatively low productivity. Static work is more tedious than dynamic work. During dynamic work, due to the alternation of the processes of contraction and relaxation of the muscles, the latter rest. Contracting skeletal muscles simultaneously act as micropumps, facilitating blood circulation and performing the function of a "peripheral heart". During static work, muscle tension lasts continuously, the vessels in them are constantly compressed, and normal blood circulation is difficult. This leads to stagnation of blood, accumulation in the muscles and in the body of products of incomplete oxidation. Mental work is one of the most laborious and stressful. First of all, a clear and precise work of the brain is necessary: attention and memory, which most people consider the main guarantee of success in mental work. Attention has wave-like fluctuations due to natural physiological reasons - a periodic increase in the excitability of the brain is replaced by a decrease in its activity and is associated with the appearance and maintenance of a persistent focus of excitation in one (or several) well-defined centers of the brain. Memory is associated with the preservation of persistent traces of excitation (or internal inhibition) in various centers of the cerebral cortex of the cerebral hemispheres. With an increase in the severity of physical labor and the intensity of mental labor, oxygen consumption increases. There is a limit to the maximum amount of oxygen that a person can consume - the so-called oxygen ceiling. Usually it does not exceed 3-4 l / min. During the performance of very hard work, the supply of oxygen to the body reaches its limit, but the need for it becomes even greater and is not satisfied in the process of work. At this moment, a state of oxygen deficiency occurs in the body - hypoxia, which becomes a damaging factor. Intracellular oxidative processes are disturbed and toxic substances are formed - oxygen free radicals that poison the body. If hard physical and mental work continues for a very long time or a person is not accustomed to great physical or mental stress, then his respiratory and cardiovascular systems poorly provide the work of muscles and brain cells. There are mechanisms in the body that prevent the development of such a dangerous condition. There is a decrease in efficiency, fatigue develops. However, if the working capacity does not have time to recover by the beginning of the next working day, overwork develops, accompanied by chronic hypoxia, impaired nervous activity, diseases of the cardiovascular and other systems. Fatigue Prevention Fatigue - This is a physiological state of the body that occurs as a result of excessive activity and manifests itself in a decrease in efficiency. Fatigue can occur during any kind of activity - both mental and physical work. Mental fatigue is characterized by a decrease in the productivity of intellectual work, impaired attention, slow thinking, and sleep disturbance. Physical fatigue is manifested by a violation of muscle function: a decrease in strength, speed, accuracy, consistency and rhythm of movements. Efficiency can be reduced not only as a result of the work done, but also due to illness or unusual working conditions. In these cases, a decrease in efficiency is a consequence of a violation of the functional state of the body. The speed of fatigue depends on the specifics of labor: it occurs much sooner when performing work, accompanied by a monotonous posture, muscle tension; less tiring rhythmic movements. Many people in a period of emotional stress for a long time do not have signs of fatigue and a feeling of fatigue. Fatigue is associated with a decrease in performance, which is restored as a result of proper rest. A tired person works less accurately, making first small, and then serious mistakes. Insufficient rest or excessive workload for a long time often leads to chronic fatigue or overwork, which can cause neuroses and diseases of the cardiovascular system. To prevent overwork, it is necessary to take into account two phases of working capacity: I - excitatory, associated with motor restlessness, absent-mindedness; II - inhibitory, when there is lethargy, a decrease in vitality. The efficiency and quality of work during the excitatory phase of fatigue can remain high, but this is achieved through volitional effort and mental stress. A subjective feeling of fatigue appears, but work should be continued until the onset of phase II of fatigue. When signs of inhibition of the central brain structures appear, attempts to overcome it and continue to work can cause overwork, so the onset of the inhibitory phase dictates the need for rest. An important means of combating overwork is a rational regime of work and rest or the organization of short-term breaks at a strictly defined time of the working day, which are arranged taking into account the nature of the labor process. A good rest does not consist in idleness, but should alternate with physical activity and a change of activity. One of the effective means of long-term preservation of efficiency during the working day is a clear rhythm of labor activity. Work performed rhythmically is about 20% less tiring than non-rhythmic work of the same severity. When carrying out measures to prevent fatigue, an important place should be given to the elimination of unnecessary movements, the rational organization of the workplace, which allows not only to save movement, but also to work in a normal posture that excludes static muscle tension. Authors: Alekseev V.S., Zhidkova O.I., Tkachenko I.V. << Back: Classification of the main forms of activity >> Forward: Physiological effects of meteorological conditions on humans
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