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Physiology of muscular activity


Biochemistry and physiology of muscle activity when performing physical work can be described as follows. We show through simulation how the

physiological processes in the muscle when performing a speed test.

Assume that the muscle (e.g., quadriceps femoris) has the IIM 50 %, the amplitude of the step — 5 % maximum alactate power, the value of which is taken as 100 %, duration — 1 min. On the first rung in connection with a small external resistance are recruited, according to “rule of size” Hanneman, low DE (MV). They have a high oxidative capabilities, the substrate they are fatty acids. However, the first 10 of 20 from the power supply goes at the expense of ATP and KRF active in MV. Already within one step (1 min.) is the recruitment of new muscle fibers, this helps to maintain the set power on the step. It is caused by the decrease in the concentration of phosphoenol active in MV, force (power) to reduce these MV, increased the activating influence of the Central nervous system, and this leads to the involvement of new DE (MV). A gradual stepwise increase of external load (capacity) is accompanied by a proportional change of some indicators: increases in heart rate, oxygen consumption, pulmonary ventilation, does not change the concentration of lactic acid and hydrogen ions.

When reaching the external power some value there comes a time when we are involving all the IIM and beginning to intermediate recruited muscle fibers (CEM). Intermediate muscle fibers are those in which the mass of mitochondria is not sufficient to ensure the balance between the formation of pyruvate and the oxidation in the mitochondria. In CEM after reducing the concentration of phosphoenol activates glycolysis, part of the pyruvate begins to transform into lactic acid (more precisely, to lactate and hydrogen ions), which goes into the blood, penetrates into the IIM. Getting into IIM (GVM) of lactate leads to inhibition of fat oxidation, substrate oxidation becomes more of glycogen. Therefore, a symptom of recruitment of all the IIM (GVM) is the increase in the blood concentration of lactate and increased pulmonary ventilation. Pulmonary ventilation increases, in connection with the formation and accumulation in CEM hydrogen ions, which upon release into the blood interact with the buffer systems of the blood and cause the formation of excess (ametabolism) of carbon dioxide. Increasing the concentration of carbon dioxide in the blood leads to increased respiration (human Physiology, 1998).

Thus, when performing a speed test is the phenomenon, which is called the aerobic threshold (AET). The emergence of AEDs indicates the leisure studies the design of all OMV. The value of external resistance can be judged on the strength of OMV, which they can show for the resynthesis of ATP and KRF by oxidative fosfory of stimulation (Seluyanov V. N. with Soave. 1991).

Further increase in power requires the recruitment of more vysokoporogovymi DE (SMOA) in which mitochondria are very few. It strengthens the processes of anaerobic glycolysis, more out lactate and ions in the blood. If you get lactate in OMV it is converted back to pyruvate by the enzyme lactate dehydrogenase (LDH) N (Karlsson, 1971,1982). However, the capacity mitochondrial system OMV has a limit. So first comes the ultimate dynamic equilibrium between the formation of lactate and its consumption in OMV and PMA, and then the balance is disturbed, and uncompensated metabolites — lactate, N, 2 — cause sharp intensification of physiological functions. Breathing is one of the most sensitive processes, respond quickly. Blood when passing light depending on the phase of the respiratory cycle should have a different partial tension WITH 2 . “Portion” of arterial blood with high CO 2 content reaches chemoreceptor and modular directly homocysteine structures of the Central nervous system, which causes intensification of breathing. In the end, WITH 2 starts to clean up from the blood so that the average concentration of carbon dioxide in the blood begins to decline. When reaching the speed assigned to the ANP, the rate of release of lactate from working glycolytic MV is compared to the rate of its oxidation in OMV. At this point, substrate oxidation in OMV become only carbohydrates (lactate inhibits fat oxidation), part of them is glycogen IIM, another part — the lactate formed in the glycolytic MV. The use of carbohydrates as substrates oxidation provides the maximum rate of formation of energy (ATP) in the mitochondria of OMV. Consequently, oxygen consumption and / or power at anaerobic threshold (At) is characterized by the maximal oxidative capacity (power) OMV (Seluyanov V. N. with Soave. 1991).

Further increase of the external power makes it necessary to introduce more vysokoporogovymi DE innervating glycolytic MV. Dynamic equilibrium is disturbed, the production of N, lactate begins to exceed the rate of their elimination. This is accompanied by a further increase in pulmonary ventilation, heart rate and oxygen consumption. After ANP oxygen consumption is mainly due to the work of respiratory muscles and myocardium. When the maximum values of pulmonary ventilation and heart rate or during local muscle fatigue oxygen consumption stabilizes, and then begins to decrease. At this point, fix the IPC.

Thus, IPC is the sum of the values of oxygen consumption, oxidative MV (MMV), the respiratory muscles and the myocardium.