The concept of a motor unit. Law of strength for skeletal muscles

A comparison of the increase in energy costs with an increase in the severity of work shows that the amount of energy expended minus the basal metabolism is always greater than the “useful” mechanical work performed by a person. The reason for this discrepancy lies primarily in the fact that when the chemical energy of nutrients is converted into work, a significant part of the energy is lost in the form of heat without being converted into mechanical energy. Some of the energy is spent on maintaining static stresses, which are only partially taken into account when calculating the mechanical work done by a person. Each human movement requires both static and dynamic stresses, and the ratio of both at various works different. Thus, lifting a load from a height of 1 m to a height of 1.5 m with a straightened body requires less energy than lifting the same load from a height of 0.5 m to a height of 1 m with an inclined position of the body, since keeping the latter in an inclined state requires more significant static tension of the back muscles.

A certain part of the energy generated during chemical reactions, is spent on overcoming resistance to movement from the antagonist muscles stretched during movement and elastic tissues in the joints, on overcoming the viscous resistance of muscle deformation and on overcoming the inertia of the moving parts of the body with changes in the direction of movement. The ratio of the amount of mechanical work performed by a person, expressed in calories, to the amount of energy expended, also in calories, is called the energy efficiency.

The value of the efficiency depends on the way of work, its pace and the state of fitness and fatigue of a person. Sometimes the value of the efficiency factor is used to evaluate the quality of working methods. So, when studying the movements of metal filing, it was found that 0.023 kcal is expended for each kilogram-force-meter of work, which corresponds to an efficiency factor 1/ = 10.2
This relatively low efficiency is due to the significant static work during filing, which requires tension in the muscles of the trunk and legs to maintain the working posture. For other types of work, the efficiency may be greater or less than the value found for metal filing. Below are the efficiency values ​​for some jobs:
Weight lifting ........................8.4
File work ............................... 10.2
Vertical lever operation (pushing) 14.0
Handle rotation .................20.0
Cycling .....................30.0
The highest value that the efficiency of the human body can reach is 30%. This value is achieved when performing well-mastered, familiar work with the participation of the muscles of the legs and torso.

The value of the efficiency of work in some cases allows you to establish more rational conditions for the performance of physical work, in particular, to determine the optimal speed (rate), load, work productivity. For the most part, the value of energy expenditure per unit of production is the smallest, and the reciprocal of the efficiency factor is the largest at medium degrees of speed and load in the middle of the period of work, if it continues to fatigue.

The change in the efficiency in individual cases, in particular, when homogeneous jobs are compared that differ only in the way they are performed, can serve as one of the criteria for assessing the rationality of certain specific aspects of labor. However, this criterion for a working person does not in any way have the defining and universal significance that it has in evaluating the operation of a machine. While in a steam engine only external mechanical work is the main useful effect transformations of energy, and the rest of the energy extracted from the fuel is rightly considered to be uselessly lost, the part of the energy consumed is useful for the human body, which goes not to external mechanical work, but to increase the vital activity of cells during work and to restore temporarily decreasing efficiency.

A more accurate and universal criterion for the physiological assessment of the rationality of specific working methods and individual movements is the duration of maintenance high level efficiency, which is manifested in an increase in labor productivity and in such an adaptation of physiological functions, which leads to further development physical and spiritual abilities of a person.

Walk around the equator

It is estimated that during the day a person takes up to 30 thousand steps, that is, about 20 kilometers. For every 5.5 years, he imperceptibly makes a path equal to the circumference of the equator.

How much does a human skeleton weigh?

The mass of the human skeleton is about 11 kilograms.

When is a person taller: in the morning or in the evening?

Due to the flattening of the intervertebral cartilages, a person’s height decreases by about 1.5 cm by the evening. A person’s height by the age of 80 decreases by 5–7 cm compared to the age of forty.

How many bones are in the skull?

The human skull is made up of 23 bones. Only two bones of the skull - the mandibular and hyoid - are movable, the rest are firmly connected by sutures.

Stronger than brick and granite

Bone material is 30 times stronger than brick and 2.5 times stronger than granite. A large femur can withstand a vertical load of one and a half tons.

It can withstand a load of 350 kilograms

The strongest ligament in the human body is the Bertinian ligament, which strengthens hip joint, - withstands a load of 350 kilograms.

How many muscles in a person?

The amount of muscle a person has is not the same for all people. Within the normal range, it ranges from 400 to 680 muscles. If all these muscles were tensed, they would cause a pressure of approximately 25 tons. A grasshopper has about 900 muscles, and some species of caterpillars even have about 4,000. The total weight of all muscles is 40% of the total body weight in men, and 30% in women.

Which organ loses the most heat?

The efficiency of human muscles is 20%. The remaining 80% is spent on heat losses.

Where are the strongest muscles located?

The strongest are those that are located on both sides of the mouth and are responsible for compressing the jaws. They are capable of developing a force of about 70 kilograms.

Who loses energy more: a crying or a daring person?

According to studies by French neurologists, a crying person uses 43 facial muscles, while a laughing person has only 17. Thus, laughing is more energetically beneficial than crying.

When is the peak time for muscle activity?

It is noted that the most effective muscles work at 13:00. 30 minutes.

Oxygen consuming organ. Who is he?

Up to 60% of oxygen entering the body is consumed by muscles.

Rhythm is your guide

Rhythm is an important element of work, and everyone should learn from his heart in this respect: if you work rhythmically, then the work will be productive and you will have the strength to work for a long time.

When the biological clock breaks

Frequent violations of the physiological cycle "day-night" can lead to a painful disorder of the internal "biological clock" of a person.

Breath

How much air can you breathe?

Lung ventilation (the number of breaths multiplied by the volume of air inhaled) in a healthy person reaches 5–9 liters per minute. At rest, a person takes an average of 16 breaths per minute. This is about 23,000 per day. At the same time, about 7,000 liters of air pass through the lungs. The minute volume of a person's breathing (the amount of air passed through the lungs in one minute) is 5-8 liters per minute at rest, and during physical work it can reach more than 100 liters per minute.

Breathe easy

A person at rest consumes 400-500 liters of oxygen per day, making 12-20 breaths and exhalations per minute. The respiratory rate of a horse is 12 breaths per minute, rats - 60, canaries - 108.

Who invigorates us?

Negatively charged ions of air gases are friends of health; they make a person cheerful, efficient.

Biovacuum cleaner

Ciliated epithelium respiratory tract a person takes out of them up to 20–30 g of dust per day.

Circulation

Blood plasma... and ancient seas

The composition of blood plasma resembles the composition of the water of ancient earthly seas, in which life originated.

twice the length of the equator

total length blood capillaries in the human body are approximately 100,000 kilometers. This is 2.5 times the length of the earth's equator, and the total internal area is 2,400 m 2.

A pump that lasts a lifetime

For 60 years of a normal, not very stressful life, the human heart makes more than 2,000,000,000 contractions. The same work would be done by a tractor if it lifted a boulder weighing 65 tons from sea level to a height of 5,500 meters.

When is there more cholesterol?

100 ml of blood of a healthy person contains 20–250 mg of cholesterol in autumn and winter, and only 170–180 mg in summer and spring.

Heart "shirt"

The heart has a shirt - a layer of connective tissue; between the heart and the "shirt" there is a small amount of fluid. The pericardial sac ("heart shirt") protects the working heart muscle.

Flattened red balls

Red blood cells, or erythrocytes, whose total surface is 3,400 m 2. Every day, about 2,000,000,000 of them die in the body, which is 0.01% of their total number. Total area the surface of all erythrocytes is 3,400 m 2. In each mm3 of blood there are 5,000,000 erythrocytes, and in all five liters contained in the body of an adult, there are 25,000,000,000,000. If you put all these erythrocytes in a row, the resulting chain will stretch for 200,000 kilometers, encircling the globe five times along the equator.

"Sprints" within us

Almost all cells of the human body have nuclei that control all physiological processes in the cell itself and are involved in the process of cell division. The only exception is erythrocytes. They are born with a nucleus, but already on early stages development, lose it, thereby losing the ability to reproduce. New red blood cells are formed in the red bone marrow from stem cells. Every second, about 2,500,000 red blood cells are formed and about the same number die. In one day, an erythrocyte travels about 15 kilometers in the blood vessels, supplying tissues with oxygen and taking carbon dioxide from them. During the existence of one erythrocyte, on average, it travels a distance of 1,800 kilometers.

They live to die

Blood cells are constantly dying and being replaced by new ones. The life of erythrocytes (red blood cells) lasts 90-125 days, leukocytes (white blood cells) - from several hours to several months, depending on the type of leukocytes. About a billion red blood cells and five billion white blood cells die every hour in an adult's blood. They will be replaced by new blood cells. During the day, 25 grams of blood undergoes complete regeneration.

thinner hair

Blood capillaries are 10 times thinner than hair.

That's the speed!

Within one minute, the heart ejects about 4 liters of blood into the aorta. The speed of movement in the aorta is 0.5 m / s, and through the capillaries, blood flows at a speed of 0.5 mm / s. A complete circulation of blood through both circles of blood circulation is completed in 21-22 seconds.

special blood substance

Each red blood cell contains 265,000,000 hemoglobin molecules. The assembly of its molecule takes only 90 seconds. Every second, 6.5∙1014 hemoglobin molecules are synthesized in the human body. 100 ml of human blood contains 13–16 g of hemoglobin. One gram of hemoglobin can bind up to 1.34 ml of oxygen. At rest, about 4 l / min flows through the human heart, which ensures that the tissues receive about 400 ml of oxygen.

Ah, those "thin tubes"!

The wall thickness of the arteries is 0.8–0.9 mm. The diameter of various human arteries is 0.4–2.5 cm. The average diameter of human capillaries is about 7 microns, which is slightly less than the diameter of an erythrocyte. In the arteries, the volume of blood is on average 950 ml.

"Sugar Queen"

This is what the ancient Tibetan doctors called the liver. She stores nutritional reserves and, if a person is hungry, she turns them into sugar, thereby feeding him. At rest, up to 50% of the blood in a person can be in the "blood depot" - the liver and spleen, from where, if necessary, it is released into the bloodstream. The blood flow in the kidneys is 420 ml / min, in the heart - 84, in the liver - 5.7, in the brain - 53, in the striated muscles - only 2.7 ml / min. The liver consumes 10 times more oxygen than an equal muscle, and generates more heat. It is a powerful protective barrier on the way of blood flow from the digestive organs to other organs. The liver breaks down alcohol most efficiently between 6 and 8 pm. 1.5 liters of blood flows through the liver in one minute, and up to 2,000 liters per day.

Women beat more often

The heart of an adult pumps about 10,000 liters of blood per day. A normal resting heart rate for a man is 60-80 beats per minute. A woman's heart beats 6-8 beats faster. Heavy physical activity increases the heart rate to 200 beats per minute. The pulse rate of an elephant is 20, that of a bull and a frog is 25, that of a rabbit is 200, that of a mouse is 500.

Digestion

Even the saber is blunt

The tip of a saber blunts when it hits tooth enamel. The hardness of enamel can be compared with quartz.

How many, two or four?

Milk teeth are replaced by permanent ones. The last molar usually erupts by the age of 18–20, and sometimes even later, when a person “acquires wisdom through teaching,” Hippocrates thought so. This tooth he called the wisdom tooth. Half of humanity has only two, not four wisdom teeth.

The naked part of our skeleton

The specific gravity of tooth enamel is 2.9–3.05 g/cm2. The dentin of the tooth has specific gravity only 2.2 g/cm 2 . The dentin of an adult tooth contains about 65% mineral salts, 28% organic matter and 8% water. The composition of dental cement includes about 30% organic matter, more than 55% calcium phosphate, about 8% calcium carbonate, as well as calcium and magnesium fluorides.

Can't stand it!

The most painful place in the human body is the teeth. There are usually no more than 200 pain receptors per square centimeter of skin, and from 15,000 to 30,000 receptors per square centimeter of tooth dentin. There are even more of them on the border of enamel and dentin - up to 75,000 receptors.

"Acorn" or "stomach"?

The word "stomach" is derived from the word "acorn" (in the old days, "small acorns were called stomachs"). There are one hundred gastric glands per 1 cm2 of the gastric mucosa. They are located closely. Unlike other digestive juices, bile contains almost no enzymes.

"Toothed" enzymes

During the day, a person secretes about 1 liter of saliva, 3 liters of gastric juice, 2 liters of pancreatic juice, 3.5 intestinal juice, 2 one liter of bile. A person produces an average of one liter of saliva per day.

What does the hour of the day mean for the stomach?

Most of the gastric juice is formed at 13 o'clock, even if the person has not eaten anything.

And is it all in us?

The length of the intestine in humans exceeds the length of the body by 3-4 times. The total surface area of ​​the villi of the jejunum is 37 m 2 , duodenal - 1.3 m 2 , ileum - 5.3 m 2 .

Do we still have gases?

In the process of fermentation of food gruel in the right (ascending) section of the large intestine, hydrogen and carbon dioxide are formed, and in the process of putrefaction in the left (descending) section, methane and hydrogen sulfide are formed. All this mixes with the air that enters the intestines in the process of eating along with food. When digesting lunch, about 15 liters of gases are formed.

Here are the villi!

On one cm 2 of the inner surface of the intestine there are 3,000–4,000 villi. Each is covered with 3,000 cells, which in turn have 100 suction tubes. The suction surface in the small intestines is about 5 m2, i.e. three times the body surface.

Short "life"

Every day, about 70,000,000,000 cells of the intestinal epithelium die, each of which lives only 1-2 days.

She needs to breathe, move, think

At rest and on an empty stomach, the human body produces so much energy per day that it would be enough to heat 20 liters of water from 10ºС to boiling. The heat generated by a woodcutter working for eight hours is enough to heat 100 liters of water to a boil.

Who is afraid of intestinal bacteria?

There is a lot of benzoic acid in lingonberries and cranberries. It kills putrefactive bacteria in the intestines.

What are we "made" of?

All from cells

The human body is made up of 100,000 billion cells. For comparison: the body of an elephant consists of 6,500,000 billion cells.

Water, water...

Water makes up 80% of a child's body weight and 70% of an adult's body weight. Human brain cells contain 80%, muscles - 76%, bones - about 25% of water. A sip of water is 20 milliliters of liquid for men, and 14 for a woman. The richest tissue of the human body is the vitreous body of the eye, in which it is 99%, and the poorest is tooth enamel. It contains only 0.2%.

Is water really that important?

Loss of moisture in the amount of 6–8% of body weight causes a fainting state in a person, 10% causes hallucinations and a violation of the swallowing reflex. The loss of 12% of the fluid entails cardiac arrest.

Are there gases too?

Over 96% of the human body weight is made up of four chemical element. Oxygen accounts for about 60% of the mass, carbon for about 20%. They are followed by hydrogen - 10% and nitrogen - 4%.

Not only there, but also from there!

A person per day can allocate 0.5–12 liters of sweat, which contains 9899% water, 0.1% urea, urinary, lactic, pyruvic, citric acid, ammonia, creatinine, serine, fats, volatile fatty acids, cholesterol, aromatic hydroxy acids, acetone, mineral salts.

Skin formations

Non-removable "clothes"

Skin is the heaviest organ of the human body. She weighs an average of 2.7 kg. The skin does not pass water, microbes, dirt. Protects us from blows, injections, bites. About 2% of the oxygen consumed by a person enters the body through the skin. A person of average height loses about 800,000 microparticles of skin every hour, and an average of 675 grams per year. By the age of seventy, the total skin loss is a little more than 47 kg, that is, 70% of the average human weight. The human body excretes about 0.5 liters of water per day through the skin. Solids stand out about 10 grams.

Who's to say if we're cold or hot?

The entire skin surface of the human body contains about 250,000 "cold" receptors and only 30,000 "heat" ones. The temperature of the skin is different in different parts of the body. So, in the armpit it is 36.6ºС, then on the stomach - 34ºС, and on the face - 25ºС. Blood and internal organs have a temperature of 37.2–38.5ºС.

Is it better to be clean or dirty?

On one cm 2 of dirty skin, there are about 40,000 microbes.

Transmitting "SOS!"

Hidden in our skin are 250,000 nerve endings that respond to cold, 30,000 to heat, and about 1,000,000 to pain.

skin and time

The skin is least sensitive to injections at 9 am and most permeable to cosmetics between 6 and 8 pm.

Space "antennas"

A human hair is 500 times thicker than the walls of a soap bubble, 5 times thicker than a capillary, 12 times thicker than the walls of the alveoli, and 20 times thicker than cobwebs. Hair grows in newborns at a rate of 0.2 mm per day, later - up to 0.3-0.5 mm per day. Eyebrow, eyelash and axillary hair live 3-4 months, head hair - 4-6 years. In a month, hair grows by one centimeter. About 100 hairs die on the head every day. Dead hair may not fall out immediately, so sometimes up to 20% of dead hair accumulates on the head.

Spit - not only girlish beauty

The most long braid one Japanese woman has 3 meters, she grew it for 20 years. Most long hair worn by Swami Pandarasannadi, head of the Indian monastery Tirudathurai. In 1949, the length of his hair was 7 meters 92 centimeters.

And beard and mustache

The longest beard belonged to Hans Langseth - 5 meters 33 centimeters, and the longest mustache was from the Swede Birger Pellas - 2 meters 90 centimeters.

Heritage of primates

The tips of all twenty fingers on our limbs bear dense flat horny formations - nails. Nails are the property of primates. The nail grows from the epithelium of the nail bed. Nails protect especially sensitive fingertips. The nail on the hand grows at a rate of a hundredth of a millimeter per day, and on the leg - five hundredths. For a year on the finger, the nail lengthens in total by three centimeters. Longest nail on hand thumb left hand) reaches a length of 101.6 centimeters. It belonged to the Indian Sridhar Chillar. The total length of the nails on the finger of his left hand, when measured in March 1990, was 4.40 meters. He hasn't cut his nails since 1952.

Selection

Why are we crying?

Children cry to get attention, to express their emotions: fear, anger or joy. And also to leave the body with tears harmful substances, which are produced from pain and suffering. In addition, when we blink, tears wash over the eyeball, cleaning it of dust and germs. Healthy human body produces approximately 0.5 liters of lacrimal fluid per year. Even the most severe man sheds daily from 1-3 milliliters of tears.

Blood filters

The total length of the renal tubules is 120 kilometers. In both kidneys, a person has about 2,000,000 nephrons. During the day, the kidneys pass through themselves 2,000 liters of blood, and this is a whole tank. An adult excretes 1,200–1,600 ml of urine per day and 15–45 mg of oxalic acid should be excreted in the urine.

What are uroliths?

The chemical composition of uroliths - kidney stones - can be different. 40% of uroliths are oxalates (salts of oxalic acid), 27% are phosphates (salts of phosphoric acid), 12–15% are urates (salts of uric acid), 2% are cystine, xanthine and protein stones, and 20–30% are mixed stones. type.

Vision

Sophisticated optical device

Up to 14 months in newborn girls and up to 16 months in boys, there is a period of complete non-perception of colors. Then comes the perception of red, then green, and even later of blue color. The formation of color perception ends at 7.5 years for girls and by 8 years for boys. The eye is able to distinguish between 130–250 pure colors and 5–10,000,000,000 mixed shades.

After an hour in the dark

After one hour in the dark, the light sensitivity of the eye increases 200 times.

Rods and cones

The human retina contains 125,000,000 rods and 6,500,000 cones, and taken together, they are so sensitive that a person could theoretically see a candle flame at a distance of 200 kilometers.

Hearing, smell, touch

"Hello, I can't hear you!"

The human middle ear contains 2,500 cells that respond to sounds. The upper limit of the frequencies we perceive reaches 16–20 million hertz. As the years go by, the sensitivity of the ear, especially to high-pitched sounds, decreases.

Delicious when +24ºС

There are about 9,000 nerve endings on the surface of the tongue that respond to taste. They function best at 24°C.

Mal, yes daring

The surface of the olfactory zone of the nose is only 5 cm 2, but about 1,000,000 nerve endings are located on it. The sensation of smell occurs when at least 40 nerve endings are excited.

That's why he's dying!

The coldest part of the human body is the nose. The temperature of its tip usually does not exceed +22ºС.

Nervous system

A gigantic amount and ... one percent

The human nervous system consists of 10,000,000,000 neurons and 70,000,000,000 support cells. Of this gigantic number, only one percent fulfills independent work, that is, it receives signals and controls the work of muscles; the remaining 99% are intermediary cells.

The center of all centers or the main organ of the mind

At three years old, the human brain is already 80% developed. It reaches its highest development by about 20 years. In the future, there is a decrease in its mass. The cerebral cortex makes up approximately 44% of the volume of the brain. The surface of the crust as a whole is 1468–1670 cm2.

We are in third place

Man is in third place in terms of brain mass (1,400 g) in wildlife after an elephant (5 kg) and a whale (2.5 kg).

Those are the squares!

The total area of ​​the cerebral cortex in humans averages 83,591 mm 2, chimpanzees - 24,353 mm 2, dogs - 6,523 mm 2, rabbits - 843 mm 2, rats - 254 mm 2.

Nature is not fair

Starting from the age of thirty in a person, 30,000 to 50,000 nerve cells of the brain die daily.

Water and nerve cell

A nerve cell - a neuron - contains 65–68% water and 32–35% solids, among which 68–70% are proteins. 20–25% are lipids, 2–5% are nucleic acids, and 1–2% are carbohydrates.

With him, the vessels are in good shape

Nitric oxide (II) can be formed in the human body. It provides communication between neurons and maintains vascular tone.

The bigger, the better

The larger the diameter of the nerve fiber, the faster the excitation spreads through it. In warm-blooded animals, the excitation speed is 0.5–120 m / s.

"Nervous" Helpers

No human action can be carried out without the participation nervous system. To transfer the body from a horizontal to a vertical position, the human brain sends hundreds of nerve impulses - signals through the nerves to the muscles.

All for sight

As part of the cranial nerves, 2,600,000 nerve fibers enter the brain, and 140,000 exit. About half of the outgoing fibers carry orders to the muscles of the eyeball, controlling fast and complex eye movements. The remaining nerves control facial expressions, chewing, swallowing, and the activity of internal organs. Of the incoming nerve fibers, 2,000,000 are visual.

Men and women

"Strong Sex"

• The male brain weighs 200 g more than the female.
• A boy aged 15–24 falls 6 times more often than girls of the same age.
• There are 12 times more men than women among outstanding mathematicians.
• Deviations from the norm of color vision are much more common in men (8%) than in women (0.5%).
• Men have 20% more lung capacity than women.
• 48% of men and only 22% of women snore in their sleep.
• Boys are more likely than girls to be left-handed and generally fluent in their left hand, which is explained by the leading role of the right hemisphere of the male brain.
• 80% of all people who stutter are men.
• The volume of blood averages 5.2 liters in men and 3.9 liters in women.
• The mass of the heart of a man is on average 330 g of a woman - 250 g.

"Weaker sex"

• Girls start talking earlier than boys.
• A woman's sense of smell is 20% better than a man's.
• Mental depression is twice as common in women as in men.
• Musical ear in women is better than in men: for 6 women who are not out of tune, there is 1 man.
• Three quarters of all migraines occur in women.
• Women are twice as sensitive to alcohol as men.
• Women prefer sweet foods, while men prefer salty ones.
• In women, the right eye sees more sharply and hears better in the right ear, while in men it is vice versa.
• Adipose tissue makes up 11% of a man's weight and 23% of a woman's weight.
• Women, more often men, suffer from dental caries.
• 42% of men and 62% of women complain of insomnia.

The energy source of muscle contraction is the energy of ATP hydrolytic cleavage with the help of the enzyme myosin-ATP-phase to ADP and inorganic phosphate (3 ATP molecules per 1 “stroke”). The splitting of 1 mole of ATP provides about 48 kJ. 50-60% of this energy is converted into heat and only 40-50% goes to muscle work, and only 20-30% is converted into mechanical energy, the rest goes to work ion pumps and oxidative reduction of ATP.

ATP recovery systems

Recovery of ATP is carried out immediately after its splitting to ADP. This process is carried out with the participation of 3 energy systems.

1) phosphogenic system where the energy of creatine phosphate is used (ATP-CrF system). This system has the highest speed of action, power, but insignificant capacity, therefore it is used at the very beginning of work or when working at maximum power (but not more than 5 s). This is an anaerobic process, i.e. it proceeds without the participation of oxygen.

2)system oxidative phosphorylation unfolds as the operating time lengthens (after 2-3 minutes). If the intensity of muscle work is not maximum, then their oxygen needs are fully satisfied. Therefore, work can be performed for many hours. The energy required for ATP resynthesis comes from the oxidation of fats and carbohydrates, and the greater the intensity, the smaller the contribution of fats. This is an aerobic process.

3) glycolytic system , where ATP recovery is due to the energy of anaerobic breakdown of carbohydrates (glycogen, glucose) to lactic acid. During this reaction, the rate of ATP formation is 2-3 times higher, and the mechanical work is 2-3 times greater than during long-term aerobic work. However, the capacity of the glycolytic system is thousands of times less than the oxidative one (although it is 2.5 times greater than the phosphogenic one. Therefore, such a system can provide work for a period of 20 s to 1-2 minutes and ends with a significant accumulation of lactic acid.

Efficiency

It should be noted that both the chemomechanical reaction in the system of actomyosin bridges and all subsequent processes proceed with loss of energy in the form of warmth. Coefficient of performance (COP) of the muscle as a mechanical machine (here it must be noted that the muscle is not only a mechanical machine, but also the main heater of the body, so its thermal output is not useless) can be calculated by the formula:

where A is the work done, and Q is the thermal output of the muscle.

Thermal output of the muscle

Thermal output of the muscle ( Q ) complicated. Firstly, there is a release of heat during isometric muscle tension, with a delay in its contraction by a stopper. This exit is called heat of activation . If, against the background of this state, the muscle with the load is released from the stopper and, contracting, lifts the load, then it releases additional heat. -heat of shortening , proportional to mechanical work (fenn effect ). Apparently, the movement of the filaments with the connection to the work of more and more new (charged with energy) bridges contributes to the release of additional energy (both mechanical and thermal).

Under conditions of free lifting of the load, the activation heat (corresponding to the phase of tendon tension) and the shortening heat merge, forming the so-called initial heat generation . After contraction (single or short tetanus) in the muscle occurs delayed heat generation , which is associated with the processes that ensure the resynthesis of ATP, it lasts seconds and minutes. If we calculate the efficiency of the muscle according to the initial heat generation, then it will be approximately 50-60% (for optimal conditions of stimulation and load). If we calculate the efficiency based on the types of heat production associated with a given mechanical work, then the efficiency will be approximately 20-30% (the efficiency of the muscles of mammals decreases when adapting to cold, which contributes to an increase in heat production in the body).

Muscle tissues called tissues that are different in structure and origin, but similar in ability to pronounced contractions. They provide movement in the space of the body as a whole, its parts and the movement of organs inside the body and consist of muscle fibers.

A muscle fiber is an elongated cell. The composition of the fiber includes its shell - sarcolemma, liquid contents - sarcoplasm, nucleus, mitochondria, ribosomes, contractile elements - myofibrils, and also containing Ca 2+ ions - the sarcoplasmic reticulum. The surface membrane of the cell forms transverse tubes at regular intervals, through which the action potential penetrates into the cell when it is excited.

The functional unit of a muscle fiber is the myofibril. The repeating structure in a myofibril is called a sarcomere. Myofibrils contain 2 types of contractile proteins: thin filaments of actin and twice as thick filaments of myosin. The contraction of the muscle fiber occurs due to the sliding of myosin filaments over actin filaments. In this case, the overlap of the filaments increases and the sarcomere shortens.

Main function muscle fiber- ensuring muscle contraction.

Energy conversion during muscle contraction. For muscle contraction, the energy released during the hydrolysis of ATP by actomyosin is used, and the process of hydrolysis is closely associated with the contractile process. By the amount of heat released by the muscle, one can evaluate the efficiency of energy conversion during contraction. When the muscle is shortened, the rate of hydrolysis increases in accordance with the increase in the work performed. the energy released during hydrolysis is sufficient to provide only the work done, but not the full energy production of the muscle.

Efficiency(efficiency) of muscle work ( r) is the ratio of the magnitude of external mechanical work ( W) to the total amount released in the form of heat ( E) energy:

The highest value of the efficiency of an isolated muscle is observed with an external load that is about 50% of the maximum value of the external load. Work performance ( R) in a person is determined by the amount of oxygen consumption during the period of work and recovery according to the formula:

where 0.49 is the coefficient of proportionality between the volume of oxygen consumed and the mechanical work performed, i.e. at 100% efficiency to perform work equal to 1 kgf․m (9,81 J), you need 0.49 ml oxygen.

Motor action / efficiency

Walking/23-33%; Running at an average speed / 22-30%; Cycling/22-28%; Rowing/15-30%;

Shot put/27%; Throwing/24%; Lifting the bar / 8-14%; Swimming / 3%.

4. Isotonic mode of muscle work. Static muscle work.

Isotonic regimen(constant muscle tone mode) is observed when there is no load on the muscle, when the muscle is fixed at one end and freely contracts. The voltage in it does not change. Since under these conditions the load value P = 0, the mechanical work of the muscle is also zero (A = 0). In this mode, only one muscle works in the human body - the muscle of the tongue.

Static work does not involve strong tension, however, in some cases, the static work of the muscles can be very intense, for example, when holding a barbell, with some exercises on rings or parallel bars. Such work requires the simultaneous contraction of all or almost all muscle fibers and can last only a very short time. During dynamic work, various muscle groups alternately contract, and some muscles work either dynamically, producing movement in the joint, or statically, ensuring the immobility of the bones of the same joint for some time. The degree of muscle tension can be different.

Static work tires the skeletal muscles more than dynamic work.

5. general characteristics circulatory systems. The speed of blood movement in the vessels. Stroke volume of blood. Work and power of the heart.

The circulatory system includes the heart and blood vessels - blood and lymph .. The heart of mammals is four-chambered. Blood moves through two circles of blood circulation.

functions of all elements of the cardiovascular system: 1) trophic - tissue supply nutrients; 2) respiratory - supply of tissues with oxygen; 3) excretory - removal of metabolic products from tissues; 4) regulatory - the transfer of hormones, the production of biologically active substances, the regulation of blood supply, participation in inflammatory reactions.

When blood moves through the vessels, a distinction is made between linear and volumetric blood flow velocity.

Linear blood flow velocity determined by the total cross section of the vascular system. It is maximal in the aorta - up to 50 cm/sec and minimal in the capillaries - about zero. In the venous part of the vascular system, the linear velocity increases again. The linear velocity in the vena cava is two times less than in the aorta and is approximately 25 cm/min.

Volumetric blood flow velocity- this is the amount of blood flowing through the total section of the vascular system per unit time. It is the same in all parts of the vascular system of the blood.

The time of complete circulation of blood is the time during which blood passes through the systemic and pulmonary circulations. At 70-80 heart beats per minute, a complete blood circulation occurs in approximately 20-23 seconds.

The movement of blood in the body: aorta - 500-600 mm / s, arteries - 150-200 mm / s, arterioles - 5 mm / s, capillaries - 0.5 mm / s, middle veins - 60-140 mm / s, hollow veins - 200 mm/s. Hypertension - elevated blood pressure. Hypotension - low blood pressure.

Systolic blood volume. The volume of blood pumped by each ventricle into the main vessel (aorta or pulmonary artery) during one contraction of the heart is referred to as the systolic, or shock, volume of blood.

Work done by the heart, is spent on overcoming resistance and the message of blood kinetic energy.

Calculate the work done with a single contraction of the left ventricle.

V y - stroke volume of blood in the form of a cylinder. We can assume that the heart supplies this volume through the aorta with a cross section S to a distance I at an average pressure p. The work done is equal to:

A1 = FI = pSI = pV y .

The work expended on the communication of kinetic energy to this volume of blood is:

where p is the density of blood; υ is the velocity of blood in the aorta. Thus, the work of the left ventricle of the heart during contraction is:

This formula is valid both for rest and for the active state of the body, but these states differ in different blood flow rates.

6. Poiseuille equation. The concept of the hydraulic resistance of blood vessels and how to influence it.

Poiseuille equation- the law that determines the flow rate of a fluid in a steady flow of a viscous incompressible fluid in a thin cylindrical pipe of circular cross section.

According to the law, the second volumetric flow rate of a liquid is proportional to the pressure drop per unit length of the tube (pressure gradient in the pipe) and the fourth power of the radius (diameter) of the pipe:

Where Q is the volumetric second flow rate of the liquid; R - pipeline radius; p1-p2 - pressure difference on the tube; n-coefficient of friction; L is the length of the tube.

Poiseuille's law works only for laminar flow and provided that the length of the tube exceeds the so-called length of the initial section, which is necessary for the development of laminar flow in the tube.

Hydraulic resistance directly proportional to the length of the vessel and blood viscosity and inversely proportional to the radius of the vessel to the 4th degree, that is, it depends most of all on the lumen of the vessel , as well as the state of the walls of blood vessels and their elasticity.

Since the arterioles have the greatest resistance, the total peripheral vascular resistance (OPVR) depends mainly on their tone. There are central mechanisms for regulating the tone of arterioles ( nervous and hormonal influences) and local ( myogenic, metabolic and endothelial regulation) .

Sympathetic nerves have a constant tonic vasoconstrictive effect on arterioles. The main hormones normally involved in the regulation of arteriole tone are epinephrine and norepinephrine.

Myogenic regulation is reduced to contraction or relaxation of vascular smooth muscles in response to changes in transmural pressure; while the stress in their wall remains constant. This ensures autoregulation of local blood flow - the constancy of blood flow with changing perfusion pressure.

Metabolic regulation ensures vasodilation with an increase in basal metabolism (due to the release of adenosine and prostaglandins) and hypoxia (also due to the release of prostaglandins).

Understanding such quantities as the efficiency of a gasoline or diesel internal combustion engine is practically a matter of honor for every man. The magic numbers of 33% or 40% can be a serious reason for a heated discussion for the whole evening. Understanding the efficiency of your own body is usually not enough time and desire, and, by the way, in vain. The efficiency of our body directly depends on how we take care of it, how well we understand and satisfy its needs.

What is life based on? That's right, energy! Energy is everything! All processes that take place in our body require energy. We get energy from food. Carbohydrates, fats and proteins are broken down during metabolism, supplying the body with building material and energy. The main type of fuel that is quickly and easily utilized by the body is carbohydrates. Along with carbohydrates, the most important source of energy are the constituent components of fats - fatty acids.

Oxidation fatty acids provides almost half the energy needs of the adult body. This important process("beta-oxidation") occurs in the energy factories of cells - in the mitochondria. By the way, note to fans of numbers: the efficiency of mitochondria is 55%! There is reason to wonder how much human inventions still lag behind the "inventions" of nature.

In order for the "energy factories" of the body to work properly and supply a sufficient amount of energy, an uninterrupted supply of fuel, i.e. fatty acids, must be established. L-carnitine is responsible for this important stage. It is a key participant in the transport of fatty acids into the mitochondria.

According to the chemical structure, L-carnitine is an amino acid, a substance related to B vitamins. L-carnitine in its natural form is present in almost all human organs and tissues, and in maximum concentrations where excess energy is needed to maintain the basic functions of the body (muscles, heart, brain, liver, kidneys). The need for L-carnitine is individual for each individual and may vary depending on the load. L-carnitine intake also increases with stress and during physical activity. An insufficient amount of L-carnitine can cause various diseases.

To maintain the required level of L-carnitine or to make up for its deficiency during stressful periods of life, the drug Elkar of the domestic pharmaceutical company PIK-PHARMA will help.
Elcar is water solution L-carnitine for oral use. The uniqueness of the drug lies in the fact that it does not have side effects and is not addictive.

When and to whom should Elcar be used? Elcar is vital if:
work or study is accompanied elevated neuropsychiatric;
the current period of life is filled with stressful situations;
workouts in the gym or fitness center began to bring instead of pleasure
fatigue;
flu, SARS or colds do not want to “hook off” in any way;
weekends and holidays are held under the slogan "Faster, higher, stronger!";
less than 10 years until retirement;
there are symptoms of "energy hunger" of the body.
In all these cases, Elkar will improve the adaptive capabilities of the body, increase immunity, help overcome chronic fatigue syndrome and contribute to
increase in working capacity.