Adenosine triphosphoric acid ATP is the source of muscle energy. Restoration of phosphagens (ATP and KrP). Spiritual and cultural origins of color revolutions
Anaerobic pathways ATP resynthesis These are additional paths. There are two such pathways: the creatine phosphate pathway and the lactate pathway.
The creatine phosphate pathway is associated with the substance creatine phosphate. Creatine phosphate consists of the substance creatine, which binds to the phosphate group via a high-energy bond. Creatine phosphate in muscle cells is contained at rest at 15 – 20 mmol/kg.
Creatine phosphate has a large energy reserve and high affinity for ADP. Therefore, it easily interacts with ADP molecules that appear in muscle cells during physical work as a result of the ATP hydrolysis reaction. During this reaction, a phosphoric acid residue with a reserve of energy is transferred from creatine phosphate to an ADP molecule with the formation of creatine and ATP.
Creatine phosphate + ADP → creatine + ATP.
This reaction is catalyzed by the enzyme creatine kinase. This ATP resynthesis pathway is sometimes called creatikinase.
The creatine kinase reaction is reversible, but is biased toward ATP production. Therefore, it begins to take place as soon as the first ADP molecules appear in the muscles.
Creatine phosphate is a fragile substance. The formation of creatine from it occurs without the participation of enzymes. Creatine not used by the body is excreted from the body in urine. Creatine phosphate synthesis occurs during rest from excess ATP. During moderate muscular work, creatine phosphate reserves can be partially restored. The stores of ATP and creatine phosphate in muscles are also called phosphagens.
The maximum power of this pathway is 900-1100 cal/min-kg, which is three times higher than the corresponding indicator of the aerobic pathway.
Deployment time is only 1 – 2 seconds.
Operating time from maximum speed only 8 - 10 seconds.
The main advantage of the creatine phosphate pathway for ATP formation is
· short deployment time,
· high power.
This reaction is the main source of energy for maximal power exercises: running short distances, throwing jumps, lifting the barbell. This reaction can be triggered repeatedly during execution physical exercise, which makes it possible to quickly increase the power of the work performed.
Biochemical assessment of the state of this ATP resynthesis pathway is usually carried out by two indicators: creatine ratio and alactic debt.
Creatine ratio is the excretion of creatine per day. This indicator characterizes the reserves of creatine phosphate in the body.
Alactate oxygen debt is an increase in oxygen consumption in the next 4 to 5 minutes after performing a short-term exercise of maximum power. This excess oxygen is required to ensure a high rate of tissue respiration immediately after the end of the load to create an increased concentration of ATP in muscle cells. In highly qualified athletes, the value of alactic debt after performing maximum power loads is 8–10 liters.
The glycolytic pathway of ATP resynthesis, like creatine phosphate, is an anaerobic pathway. The source of energy necessary for the resynthesis of ATP in in this case is muscle glycogen. During the anaerobic breakdown of glycogen, the terminal glucose residues in the form of glucose-1-phosphate are alternately cleaved from its molecule under the action of the enzyme phosphorylase. Next, the glucose-1-phosphate molecules, after a series of sequential reactions, are converted into lactic acid. This process is called glycolysis. As a result of glycolysis, intermediate products are formed containing phosphate groups connected by high-energy bonds. This bond is easily transferred to ADP to form ATP. At rest, glycolysis reactions proceed slowly, but with muscular work, its speed can increase 2000 times, and already in the pre-start state.
The maximum power is 750 – 850 cal/min-kg, which is two times higher than with tissue respiration. This high power is explained by the presence of a large supply of glycogen in the cells and the presence of a mechanism for activating key enzymes.
Deployment time is 20-30 seconds.
Operating time at maximum power is 2-3 minutes.
The glycolytic method of ATP formation has a number of advantages over the aerobic way:
· it reaches maximum power faster,
· has a higher maximum power,
· does not require the participation of mitochondria and oxygen.
However, this path also has its drawbacks:
- the process is not economical,
- the accumulation of lactic acid in the muscles significantly disrupts their normal functioning and contributes to muscle fatigue.
To assess glycolysis, two biochemical methods are used - measuring the concentration of lactate in the blood, measuring the blood pH and determining the alkaline reserve of the blood.
The lactate content in urine is also determined. This provides information about the total contribution of glycolysis to providing energy for the exercises performed during training.
Another important indicator is lactate oxygen debt. Lactate oxygen debt is an increased oxygen consumption in the next 1 - 1.5 hours after the end of muscle work. This excess oxygen is necessary to eliminate lactic acid formed during muscle work. Well-trained athletes have an oxygen debt of 20–22 liters. The size of the lactic debt is used to judge the possibilities of this athlete at submaximal power loads.
Boost ATP Levels for Fast Recovery and Growth
ATP is a source of intracellular energy that controls almost all muscle functions and determines the level of strength and endurance. It also regulates the anabolic response to training, as well as the influence of most hormones at the cellular level. It is quite possible to assume that the more ATP contained in the muscles, the larger and more powerful they will be.
The fact is that intense training as a bodybuilder depletes the ATP stores in the muscles. And this state of emptiness can last for several days, preventing muscle growth. In particular, overtraining is the result of the body being in a state of ATP depletion for a long time. In order to restore ATP levels in your muscles, you must learn how to effectively use various ATP boosters.
ATP levels during exercise
Muscle contractions use the energy of ATP contained in muscle cells. However, with intensive cuts, the supply of this “fuel” is quickly exhausted. It is for this reason that you cannot continue to produce the same force forever. The harder you train, the more ATP you need. But the heavier the burden becomes, the more your cells lose the ability to recreate ATP. As a result, a heavy load will quickly knock you down, causing enormous frustration as it robs you of the ability to complete your last, most productive reps. That's when you start to feel muscle contractions, feel every fiber, but they all stop working due to lack of ATP.
In fact, ATP levels are one of the most limiting factors in training. It reduces the number of growth-promoting reps in each set. To make up for the lack of intensity at the end of a set, you perform more sets, resulting in a significant amount of ineffective low-intensity work.
Contrary to popular belief, ATP levels after performing a set are not at all zero. In fact, it is very far from zero. Medical research shows that muscle ATP levels decrease by 25% after 10 seconds of maximal muscle contraction (1). After 30 seconds of such effort, the ATP level is at around 50%. Therefore, you are still far from completely depleting your ATP reserves. But even a slight decrease in its level is enough to prevent your muscles from contracting as powerfully as you would like. Of course, ATP stores become increasingly depleted as you perform more than one set. Research has shown that 4 minutes of rest was not enough to fully restore ATP levels in type 2 fibers after 30 seconds of muscle contraction (2). Consequently, when you start the second set, the ATP reserve in the muscles is not optimal. As you perform more and more sets, ATP levels become less and less.
What happens to ATP after exercise?
After training is completed, ATP reserves may be significantly reduced. When you rest, you might expect your muscles to have a chance to recover. After all, the need for ATP at this time decreases, and production increases. However, remember that at the beginning of the recovery period, ATP levels are low, so it will take some time for them to return to normal. Which? Surprisingly, it will take 24 to 72 hours for ATP to be fully replenished.
If you are in a state of overtraining, your ATP levels will not return to normal, baseline levels. Although, unfortunately, ATP levels are somewhat reduced after exercise, they are still quite high. There are several reasons for this, including the following:
1) When you exercise, sodium accumulates in muscle cells. They must then get rid of sodium using a mechanism called the Na-K-ATPase pump. As the name suggests, this mechanism uses ATP as an energy source.
2) If your muscles hurt, it means a large amount of calcium has accumulated in them. They will try to return the calcium they contain to its natural stores, but this also requires a certain supply of ATP.
3) Another interesting aspect concerns the formation of glutamine. After training, the body's need for glutamine increases greatly. To cope with the increased need for glutamine, the body begins to produce more glutamine from other amino acids, such as amino acids branched chains. A state of “tug of war” arises. As the use of glutamine increases, the body's efforts to produce new glutamine also increase. The production of glutamine is very expensive from an energy point of view - meaning ATP. It occurs mainly in the muscles, but the level of ATP in the muscles after exercise is reduced, which interferes with the production of glutamine. After a certain period of time, its production no longer covers the increased need, which leads to a significant reduction in glutamine levels after training. On the other hand, to make this reduction minimal, the body tries to increase the rate of glutamine synthesis, using even more ATP. Consequently, muscle ATP consumption remains high for a long period of time after exercise and this causes muscle recovery to take too long.
ATP and diet
The process of training and muscle development is quite difficult even when you eat normally. But bodybuilders have to follow a low-carb diet from time to time. You can imagine how reducing food intake affects the energy levels in the cell. During a long-term restrictive diet, the energy balance in the muscles is disrupted, which makes it even more difficult to maintain normal ATP levels. This leads to decreased strength during training and prolonged recovery after training.
Functions of ATP
In addition to its primary function of providing energy for muscle contraction and controlling electrolyte levels in muscles, ATP performs many other functions in muscles. For example, it controls the rate of protein synthesis. Just as the construction of a building requires the availability of raw materials and a certain expenditure of energy, so does the construction of muscle tissue. The material is amino acids, and the energy source is ATP. Anabolism is one of the most energy-consuming processes that occurs within muscles.
It consumes so much ATP that when this substance is reduced by 30%, most of the anabolic reactions stop. Thus, fluctuations in ATP levels greatly affect the anabolic process.
This explains the fact that muscles do not grow during training. When a person exercises, their ATP levels are too low. And if you triggered the anabolic process at this point, it would further deplete your ATP supply, reducing your ability to contract muscles. The sooner ATP levels return to normal, the sooner the process of protein synthesis will begin. So while it's important to increase your ATP levels during a workout, it's even more important to do so post-workout for muscle growth. ATP is also necessary for anabolic hormones to work their magic. Both testosterone and insulin require ATP to function properly.
Paradoxically, the level of ATP also controls the rate of catabolism. Major proteolytic pathways require energy to break down muscle tissue. While you might assume that a post-workout reduction in ATP levels would save muscles from catabolism, unfortunately, this is not the case. When muscle ATP levels reach a lower threshold, other catabolic mechanisms that are independent of ATP are activated. The calcium contained in the cells begins to be removed from the cells, causing major disorders. A more advantageous option would be to enhance both the anabolic and catabolic processes than a strong catabolic process and a weak anabolic one. Therefore, the more ATP, the better.
How to Increase ATP Levels
As a bodybuilder, you have a huge arsenal of powerful tools to increase your ATP levels. In this article I will talk about the use of creatine, prohormones and ribose. I will not dwell on carbohydrates, since too much has already been written about them as a source of energy. Glutamine and branched chain amino acids also have a small effect on ATP production, but I won't go into detail about them at this time. It is important that you understand that all of these stimulants are characterized by different timing of operation, therefore they are only auxiliary.
The fastest-acting stimulant is D-ribose. The ATP molecule is created by the interaction of one adenine molecule, three phosphate groups and one ribose molecule. Thus, ribose is a necessary raw material for ATP synthesis. Ribose also controls the activity of the enzyme 5-phosphoribosyl-1-pyrophosphate, which is necessary for ATP resynthesis.
I recommend consuming at least 4 grams of ribose 45 minutes before your workout. Not only will your strength levels improve immediately, but ribose also prevents performance-impacting nerve fatigue as you add reps to your heaviest sets.
However, ribose acts not only as a stimulator of ATP production. Research has shown that it is effective in increasing ATP levels and increasing levels of uridine triphosphate, another, albeit lesser known, source of cellular energy. Uridine triphosphate is most important for slow-twitch fibers. Research shows that it has a strong anabolic effect on muscles. It also helps them get rid of sodium infestations by helping potassium move inside the muscle cells, which in turn spares ATP stores.
I consider creatine to be a moderate ATP stimulator, and the longest acting ATP stimulants are prohormones. I doubt that creatine can have a stimulating effect on ATP production in those who lead a sedentary lifestyle. However, as discussed above, intense exercise stress reduces ATP levels for a long time. In this case, creatine can provide the necessary starting material for ATP resynthesis, thanks to its transformation into phosphocreatine within the muscles. An experiment conducted by European scientists showed that with additional consumption by athletes high level After training with creatine for five days in the amount of 21 g per day, together with the consumption of 252 g of carbohydrates, the level of ATP in the muscles increased by as much as 9%, and when consuming the ATP precursor phosphocreatine - by 11% (3).
Regarding prohormones, animal studies have shown that the level of male hormones greatly influences the level of ATP in the muscles. When rats were castrated, the level of ATP in their muscles was reduced (4). When the rats were given testosterone, ATP levels were restored to normal levels. The results of this study proved the importance of taking testosterone stimulants, especially in the post-workout period, when testosterone levels are reduced even by simply consuming carbohydrates. You can use an intracrine testosterone stimulant such as androstenedione and endocrine stimulants such as nandrolone precursors. Thus, you can naturally regulate declining testosterone levels in the blood by replacing it with nandrolone, while also increasing testosterone levels in the muscles with androstenedione.
Ribose, creatine and prohormones are effective stimulators of ATP production. Taking them in combination will increase your strength level during resistance training, while improving muscle recovery and growth after training. Because their influence is distributed differently over time and they have different modes of action, they produce optimal results by working in synergy.
The ATP molecule consists of adenine, ribose and three phosphates. Energy is released when one of the three phosphates is separated from the molecule and ATP is converted to ADP (adenosine diphosphate). Can be separated if necessary more one phosphorus residue to produce AMP (adenosine monophosphate) and re-release of energy.
The most important quality is that ADP can quickly be restored to a fully charged ATP, which is explained by the low stability of bonds - for example, the life of an ATP molecule is on average less than one minute, and up to 3000 recharge cycles can occur with this molecule per day.
The energy released by ATP is large and therefore refers to MACROERGIC compounds. Naturally, when recovering, her body will be forced to expend the same amount of energy.
The total volume of ATP is stable and usually does not exceed 0.5% of muscle mass. The volume itself cannot be increased, but it can be improved recovery rate molecules, which will directly affect the endurance and strength of the athlete.
ATP restoration occurs in several ways - first physical activity a large amount of resources is consumed for recharging, but the rate of ATP recovery is very high, then the body switches to more and more economical methods of resynthesis; ultimately, the muscular system is able to function for a long time with moderate ATP synthesis.
ATP synthesis
First of all, it should be said that high-quality and rapid synthesis of ATP is possible only by maintaining high levels of testosterone, since male hormones are the main stimulators of biological processes aimed at increasing strength and endurance. Read how to increase testosteronethis article.
More about ATP synthesis
When creatine phosphate reserves drop, so-called ANAEROBIC endurance is activated. ATP synthesis uses a lot of energy, which the body receives from glycogen reserves; ATP restoration occurs more slowly, but the process actively continues for more than 2 minutes. Positive side – no oxygen required, negative– a lot of lactic acid is produced.
Anaerobic metabolism is the basis of strength endurance.
When glycogen reserves are noticeably depleted, AEROBIC metabolism intensifies, which ensures slow but rather long-term production of ATP with very economical consumption of glucose. This process is fully started after three minutes of intense exercise. Providing energy in this case requires the participation of oxygen. To produce ATP, carbohydrates are used first, followed by fats. Fats can also be used earlier together with carbohydrates - in stressful conditions - see. cortisol. When natural energy reserves come to an end, the body also turns on muscle proteins (primarily those that can be quickly restored).
The greatest yield of ATP molecules occurs during the breakdown of fatty acids.
ATF in BODYBUILDING
The body usually carefully consumes ATP, so the athlete cannot spend the entire energy reserve in one intense approach. If the body gets a short break, ATP reserves will be partially restored and energy can be expended again; repeating the approaches many times can achieve a significant load on the muscles, but also noticeably deplete ATP.
Complete restoration of ATP requires long-term time, therefore, in the process of exercising from one exercise to another, the overall energy level constantly decreases. According to modern research, severe fatigue comes after hour intense training, which causes a rapid increase in cortisol (the fatigue hormone) in the blood and exercise from this point on does more harm than good.
Post-workout body continues expend ATP to restore chemical balance and other processes, including the cost of muscle growth. Only after all recovery processes are completed will the body be able to replenish a sufficient level of ATP. Depending on the intensity of training, nutrition, testosterone levels, psychological state and genetic characteristics, complete restoration of ATP levels can take from 1 to 4 days, so the standard 3 workouts per week is more likely averaged calculation. Individually, the frequency of exercise should be selected based on your general well-being (not to be confused with laziness).
Continuous insufficient restoration of ATP levels over time clearly leads to a state of overtraining, requiring long-term and serious treatment. Read how to keep ATP levels high
Reduction of phosphagens (ATP and KrP)
Phosphagens, especially ATP, are restored very quickly (Fig. 25). Already within 30 s after stopping work, up to 70% of the consumed phosphagens are restored, and their complete replenishment ends in a few minutes, almost exclusively due to the energy of aerobic metabolism, i.e., due to the oxygen consumed in the fast phase of O2 debt. Indeed, if immediately after work you tourniquet the working limb and thus deprive the muscles of oxygen delivered through the blood, then restoration of KrF will not occur.
How The greater the consumption of phosphagens during operation, the more O2 is required to restore them (to restore 1 mole of ATP, 3.45 liters of O2 are required). The magnitude of the fast (alactate) fraction of O2 debt is directly related to the degree of decrease in phosphagens in the muscles at the end of work. Therefore, this value indicates the amount of phosphagens consumed during the work process.
U In untrained men, the maximum value of the fast fraction of O2 debt reaches 2-3 liters. Particularly large values of this indicator were recorded among representatives of speed-strength sports (up to 7 liters among highly qualified athletes). In these sports, the content of phosphagens and the rate of their consumption in the muscles directly determine the maximum and maintained (remote) power of the exercise.
Glycogen restoration. According to the initial ideas of R. Margaria et al. (1933), glycogen consumed during work is resynthesized from lactic acid within 1-2 hours after work. The oxygen consumed during this recovery period determines the second, slow, or lactate, fraction of O2-Debt. However, it has now been established that the restoration of glycogen in muscles can last up to 2-3 days
Speed glycogen restoration and the amount of its restored reserves in the muscles and liver depend on two main factors: the degree of glycogen consumption during work and the nature of the diet during the recovery period. After a very significant (more than 3/4 of the initial content), up to complete, depletion of glycogen in the working muscles, its restoration in the first hours with normal nutrition is very slow, and it takes up to 2 days to reach the pre-working level. With a diet high in carbohydrates (more than 70% of daily calories), this process accelerates - already in the first 10 hours more than half of the glycogen is restored in the working muscles, by the end of the day it is completely restored, and in the liver the glycogen content is significantly higher than usual. Subsequently, the amount of glycogen in the working muscles and liver continues to increase and 2-3 days after the “depleting” load it can exceed the pre-working load by 1.5-3 times - the phenomenon of supercompensation.
At daily intensive and long-term training sessions The glycogen content in working muscles and liver decreases significantly from day to day, since with a normal diet, even a daily break between workouts is not enough to completely restore glycogen. Increasing the carbohydrate content in an athlete’s diet can ensure complete restoration of the body’s carbohydrate resources by the next training session.
Elimination lactic acid. During the recovery period, lactic acid is eliminated from working muscles, blood and tissue fluid, and the faster, the less lactic acid is formed during work. The after-work regime also plays an important role. So, after maximum exercise, it takes 60-90 minutes to completely eliminate accumulated lactic acid under conditions of complete rest - sitting or lying down (passive recovery). However, if after such a load light work is performed (active recovery), then the elimination of lactic acid occurs much faster. For untrained people, the optimal intensity of the “recovery” load is approximately 30-45% of the VO2max (for example, jogging), a. in well-trained athletes - 50-60% of MOC, for a total duration of approximately 20 minutes.
Exists four main ways to eliminate lactic acid:
- 1) oxidation to CO2 and SHO (this eliminates approximately 70% of all accumulated lactic acid);
- 2) conversion to glycogen (in muscles and liver) and glucose (in liver) about 20%;
- 3) conversion to proteins (less than 10%); 4) removal with urine and sweat (1-2%). With active reduction, the proportion of lactic acid eliminated aerobically increases. Although the oxidation of lactic acid can occur in a variety of organs and tissues (skeletal muscles, heart muscle, liver, kidneys, etc.), the largest part of it is oxidized in skeletal muscles (especially their slow fibers). This makes it clear why light work (mostly slow-twitch muscle fibers) helps clear lactate more quickly after heavy exercise.
Significant part of the slow (lactate) fraction of O2 debt is associated with the elimination of lactic acid. How more intense load, the larger this faction. In untrained people it reaches a maximum of 5-10 liters, in athletes, especially among representatives of speed-strength sports, 15-20 liters. Its duration is about an hour. The magnitude and duration of the lactate fraction of the O2 debt decrease with active reduction.
ATP energy is used during skeletal muscle activity for 3 processes:
■ operation of a K + -Na + pump, ensuring a constant concentration gradient of K + and Na + ions on both sides of the membrane;
■ the process of sliding of actin and myosin filaments, leading to shortening of myofibrils;
■ the work of the calcium pump necessary to relax the fiber.
When muscles work, chemical energy is converted into mechanical energy, i.e. muscle is a chemical engine, not a thermal one. The processes of muscle contraction and relaxation require ATP energy. The cleavage of ATP with the detachment of one phosphate molecule and the formation of adenosine diphosphate (ADP) is accompanied by the release of 10 kcal of energy per 1 mole: ATP = ADP + P + En. However, ATP reserves in muscles are small (about 5 mmol/l). There are only enough of them for 1 - 2 s work. The amount of ATP in muscles cannot change, because in the absence of ATP, contracture develops in the muscles (the calcium pump does not work and the muscles are unable to relax), and in the absence of ATP, elasticity is lost.
To continue working constant replenishment of ATP reserves is required. ATP recovery occurs under anaerobic conditions- due to the breakdown of creatine phosphate (CrP) and glucose (glycolysis reaction), under aerobic conditions- due to the oxidation reactions of fats and carbohydrates.
Rapid ATP recovery occurs in thousandths of a second due to the decay of KrF: ADP + KrF = ATP + Kr. This energy generation path achieves the greatest efficiency by 5 - 6 seconds work, but then the reserves of the KrF are exhausted, because there are also few of them (about 30 mmol/l).
The slow recovery of ATP under anaerobic conditions is provided by the energy of the breakdown of glucose (released from glycogen) - the reaction of glycolysis with the eventual formation of lactic acid (lactate) and the reduction of two ATP molecules. This reaction reaches its greatest power towards the end 1- th minutes of work. This path of energy generation is of particular importance at high power work, which continues from 20 From to 1 – 2 min (for example, when running at medium distances), as well as with a sharp increase in the power of longer and less powerful work (finishing accelerations when running at long distances) and with a lack of oxygen during static work . Limiting the use of carbohydrates is not associated with a decrease in glycogen (glucose) reserves in the muscles and liver, but with inhibition of the glycolysis reaction by excess lactic acid accumulated in the muscles.
Oxidation reactions provide energy for muscle work under conditions of sufficient oxygen supply to the body, i.e. during aerobic work lasting more than 2 – 3 min . Oxygen delivery reaches the required level after sufficient deployment of the functions of the body’s oxygen transport systems (respiratory, cardiovascular and blood systems). An important indicator of the power of aerobic processes is the maximum amount of oxygen entering the body in 1 minute - maximum oxygen consumption ( IPC ). This value depends on the individual capabilities of each person. In untrained individuals, about 2.5–3 liters of O2 are delivered to the working muscles per minute, and in highly qualified athletes (skiers, swimmers, runners, stayers, etc.) it reaches 5–6 liters and even 7 liters per minute.
With significant work power and a huge need for oxygen, the main oxidation substrate in most sports exercises are carbohydrates , because their oxidation requires much less oxygen than the oxidation of fats. When using one molecule of glucose (C 6 H 12 O 6), obtained from glycogen, 38 molecules of ATP are formed, i.e. The aerobic pathway of energy production provides many times more ATP production for the same carbohydrate consumption than the anaerobic pathway. Lactic acid does not accumulate in these reactions, and the intermediate product - pyruvic acid - is immediately oxidized to the final metabolic products - CO 2 and H 2 O.
Fats are used as a source of energy in a state of motor rest, during any work of relatively low power (requiring up to 50% of the maximum capacity) and during very long endurance work (requiring about 70 - 80% of the maximum capacity). Among all energy sources, fats have the greatest energy capacity : when 1 mole of ATP is consumed, about 10 kcal of energy is released, 1 mole of CrP - about 10.5 kcal, 1 mole of glucose during anaerobic breakdown - about 50 kcal, and when 1 mole of glucose is oxidized under aerobic conditions - about 700 kcal, during oxidation 1 mole of fat – 2,400 kcal. However, the use of fats during high-power work is limited by the difficulty of delivering oxygen to working tissues.
Muscle work is accompanied by the release of heat. Heat generation occurs at the moment of muscle contraction - initial heat generation (it is only one thousandth of all energy expenditure) and during the recovery period - delayed heat generation.
Under normal conditions, when muscles work, heat losses account for about 80% of all energy expenditure. To assess the efficiency of mechanical work of a muscle, the coefficient of performance (efficiency) is calculated. The efficiency value shows what part of the expended energy is used to perform the mechanical work of the muscle. It is calculated using the formula
efficiency = [A: (E - e)] 100%,
where A is the energy spent on useful work;
E – total energy consumption;
e – energy consumption at rest for a time equal to the duration of work.
For an untrained person, the efficiency is approximately 20%, for an athlete - 30 - 35%, i.e. the muscle uses 20–35% of chemical energy for movement, the rest in the form of heat is transferred by the blood to other tissues and evenly warms the body. That is why in the cold a person tries to move more - he warms himself up with muscle energy. Small involuntary muscle contractions cause trembling - the body increases heat production.
When walking, the greatest efficiency is observed at a speed of 3.6 - 4.8 km/h, when pedaling on a bicycle ergometer - with a cycle duration of about 1 second. With an increase in work power and the inclusion of “unnecessary” muscles, efficiency decreases. During static work, since A = 0, work efficiency is assessed by the duration of maintained muscle tension.
Outer thigh
Soleus
| 84 % |
67 % -
Rice. 24. Compound muscle fibers V different muscles :
slow; ,.*>%" - fast
V<>-
Self-study materials
Questions for the colloquium and for self-control
1. What types of muscles do you know in vertebrates and humans?
2. Name the functions of skeletal muscles.
3. List the neurons that innervate skeletal muscles.
4. What is the functional unit of muscle?
5. What is included in the motor unit (MU)?
6. What is called the motoneuron pool?
7. Characterize large and small DUs.
8. What is Henneman's rule?
9. Describe the structure of muscle fiber.
10. How are myofibrils structured?
11. What is a sarcomere?
12. How can you explain that at rest the muscle has a striated appearance in a light microscope?
13. Describe the structure of actin and myosin filaments.
14. What is the role of the action potential in the occurrence of muscle contraction?
15. Describe the mechanism of contraction and relaxation of muscle fiber.
16. Who discovered the enzymatic activity of myosin?
17. Indicate the sequence of events leading to contraction and then relaxation of the muscle fiber.
18. What is it? role of ATP in the mechanisms of muscle contraction?
19. List the phases of a single muscle contraction.
20. In what cases does the summation of abbreviations occur? What is tetanus?
21. What forms of tetanus do you know?
22. What does the contraction of a whole muscle depend on?
23. What is the electromyography method?
24. What factors does the EMG amplitude depend on?
25. What is muscle strength and what morphological and physiological factors does it depend on?
26. List the types of muscle fibers. Give their characteristics.
27. Name the modes of muscle function.
28. Describe the energetics of muscle contraction.
