Concentric, eccentric, isometric.
18) Complete the sentence:
Eccentric muscle contraction- this is a type of muscle contraction in which the muscle, while performing work, lengthens
19) What types of muscle fibers do you know:
Fast
Slow
intermediate
20) Place the numbers corresponding to the main function of a particular muscle from the right column to the left column:
| A (5) Rectus abdominis muscle | 1. Hip flexion, shin extension |
| B (1) Quadriceps femoris muscle | 2. Forearm extension |
| B (3) Biceps femoris | 3. Shin flexion |
| G (7) Gastrocnemius muscle | 4. Adduction, extension, medial rotation of the shoulder |
| D (9) Trapezius muscle | 5. Spinal flexion |
| E (10) Deltoid | 6. Horizontal (medial) flexion of the shoulder, adduction, internal rotation |
| F (4) Latissimus muscle backs | 7. Plantar flexion of the ankle joint, participation in flexion of the knee joint |
| B (2) Triceps brachii | 8. Hip extension |
| And (8) Gluteus maximus muscle | 9. Movement of the scapula upward and backward |
| K (6) Large pectoral muscle | 10. Abduction, flexion, extension of the shoulder |
21) List the tasks of the preparatory period:
- Studying and practicing exercise techniques
- muscle hypertrophy
- development of strength indicators
- capillarization of muscle tissue
22) What is the main purpose of the warm-up:
- Decrease in heart rate to normal
- Increasing core body temperature, increasing muscle elasticity, stimulating the nervous system
- Increasing heart rate to target value, reducing body fat
- Relieving nervous excitement
In which part of the digestive system does absorption of nutrients occur?
- oral cavity
- stomach
- small intestine
- colon
In which organ or tissue are carbohydrates stored in the form of glycogen?
- kidneys
- liver
- lungs
- muscles
What substances are carbohydrates broken down into in the digestive tract?
- sucrose
- glucose
- starch
- fructose
To what substances are fats broken down in the digestive tract?
1. glycerin
Triglycerides
3. lipoproteins
Fatty acid
27) List the functions of proteins and their sources:
catalytic, structural, regulatory, protective, signaling, transport, reserve, motor. Sources: low fat and low carbohydrate foods (milk, meat, fish, eggs)
28) List the functions of fats and their sources:
Energy, thermal insulation, structural, regulatory, protective. Sources: oil, nuts, fish
29) List the functions of carbohydrates and their sources:
Structural, protective, plastic, energy, storage, osmotic, receptor. Sources: vegetables, fruits, unprocessed grains
30) List what symptoms you should stop doing exercises for:
- sweating
- feeling thirsty
- dizziness
- rapid breathing
What exercises are prohibited for varicose veins?
- sitting exercises
- exercises in a lying position
- standing exercises
- exercises in motion
What type of activity is prohibited if you are obese?
- swimming
- aqua aerobics
- strength training exercises
What types of activities are prohibited for spinal osteochondrosis?
- stretching
- jumping
- swimming
- half-hangs
What types of activities are prohibited if you have kyphosis?
- strengthening back muscles
- strengthening chest muscles
- backstroke
- stretching the abdominal muscles
35) Write Karvonen’s formula:
Heart rate during training = (maximum heart rate - resting heart rate) x intensity (in percent) + resting heart rate.
36) Energy sources for long-term aerobic work are:
- creatine phosphate, carbohydrates
- glucose, proteins
- proteins, carbohydrates
- at carbohydrates, fats
37) List 5 basic exercises for the triceps brachii muscle:
Dips
–French press standing barbells
Seated French barbell press
Extension of arms with a barbell at the elbow joints to a position lying on horizontal bench
Raising and lowering the barbell with straight arms and bending the torso forward
Where in the cell does ATP synthesis occur?
In mitochondria
What filaments does myofibril consist of?
Actin and myosin
Specify the types of muscle tissue?
-smooth
-striated skeletal muscle tissue
-striated cardiac muscle tissue
How many ATP molecules are produced during anaerobic glycolysis?
How many ATP molecules are produced during aerobic glycolysis?
Which gland secretes dopamine?
Adrenal
What hormones does the pancreas produce?
Insulin and glucagon
List methods for developing strength?
-"to failure" method
-maximum effort method
-isometric method
-repeated method
List the means of developing strength?
-ex. with external resistance
-ex. with overcoming weight own body
-ex. in self-resistance
-ex. with combined weights - isometric exercises.
List general training principles?
-principle of gradualism
- principle of repetition
-the principle of feasibility or individualization
-the principle of systematicity and regularity
48) Indicate the build types of men:
Ectomorph (naturally thin)
Mesomorph (muscular and athletic)
Endomorph (prone to gaining fat)
Due to what layer does the bone grow in thickness?
periosteum
What is basal metabolic rate?
This is the energy expenditure of the body in a state of complete rest, ensuring the functions of all organs and systems and maintaining body temperature.
What parts does the autonomic nervous system consist of?
Central and peripheral
What bones form the shoulder joint?
Humerus, scapula
53) Indicate the pathways for ATP resynthesis:
Aerobic and anaerobic mechanisms, and lipid oxidation
What determines bone strength?
55) Universal energy source:
Which endocrine gland is the main one and secretes pathways?
pituitary
57) List the types of power abilities:
-absolute power
-muscle strength
-maximum strength
-explosive force
What is the principle of stepped sets?
This method consists of immediately switching to a lighter weight after a high load with a large weight, but making the load maximum.
At what levels does skeletal muscle adaptation occur?
What exercises are suitable for an ectomorph?
Exercises that require heavy weights:
-deadlift with straight legs
–squats
-bench press with dumbbells or barbell
- chest press with dumbbells or barbell
-bend curls with dumbbells or barbells
What elements transport oxygen in the blood?
red blood cells
Without what is the synthesis of sex hormones impossible?
No cholesterol
What's happened strength abilities?
This is a complex of various manifestations of a person in a certain motor activity, which are based on the concept of “strength”. Strength is a person’s ability to overcome external resistance or resist it through muscle effort (tension).
64) List the basic exercises:
-lifting legs while hanging on the bar
-extension of arms from the upper block
-bend curls with dumbbells while sitting (standing)
-leg bending in a lying machine
- leg extensions in the simulator
-hyperextension
-deadlift with dumbbells
Around which axis does flexion and extension occur?
Around the frontal axis
66) Indicate a person’s strength abilities:
1. Flexibility
2. Maximum strength
3. Dexterity
67) List the disadvantages of simulators:
- massiveness
-high price
-energy dependence
Is it possible to drink water during classes?
How can you increase the intensity of your workout?
Interval and variable (repeated) methods
What symptoms should you stop exercising for?
1. sweating
2. feeling thirsty
3. dizziness
4. rapid breathing
What percentage of weights should be used during work to cause muscle hypertrophy?
85% from 1RM (repetition with maximum weight) to muscle failure or almost there.
72) List the advantages of simulators:
-full body workout
-The best way achieve an athletic figure
What is fatigue?
A temporary decrease in muscle performance caused by their work.
- ballistic
- dynamic
- static
75) Specify the main exercises for the gluteus maximus muscle:
- hip extension in the simulator
- bridge lying on the floor
- leg extensions in the simulator
- hip extension lying on the floor
- 15-30 minutes
- 45-60 minutes
- 60-75 minutes
- 75-90 minutes
77) First aid for bruises and sprains:
- ensure peace
- rub with warming ointment
- apply a pressure bandage
- position the injured area (limb) below waist level.
78) Define the concept:
Flexibility - the absolute range of motion in a joint or series of joints that is achieved with instantaneous force.
Immobilization is
- Lack of structural homeostasis in muscles
- A condition where the joints do not work for any period of time
- The aging process of connective tissue
There are three modes of muscle contraction:
Isotonic;
Isometric;
Mixed (auxometric).
The isotonic mode of muscle contraction is characterized by a predominant change in the length of the muscle fiber, without a significant change in tension. This mode of muscle contraction is observed, for example, when lifting light and medium weight loads.
The isometric mode of muscle contraction is characterized by a predominant change in muscle tension, without a significant change in length. An example is changes in the state of the muscles when a person tries to move a large object (for example, when trying to move a wall in a room).
Mixed (auxometric) type of muscle contraction, the most realistic, most common option. Contains components of the first and second options in different proportions depending on actual environmental conditions.
Types of muscle contraction
There are three types of muscle contraction:
Single muscle contraction;
Tetanic muscle contraction (tetanus);
Tonic muscle contraction.
In addition, tetanic muscle contraction is divided into serrated and smooth tetanus.
A single muscle contraction occurs under conditions of action on the muscle of threshold or suprathreshold electrical stimuli, the interpulse interval of which is equal to or greater than the duration of a single muscle contraction. In a single muscle contraction, three time periods are distinguished: latent period, shortening phase and relaxation phase (see Fig. 3).
Rice. 3 Single muscle contraction and its characteristics.
LP – latent period, FU – shortening phase, FR – relaxation phase
Tetanic muscle contraction (tetanus) occurs under conditions of action on the skeletal muscle of a threshold or suprathreshold electrical stimulus, the interpulse interval of which is less than the duration of a single muscle contraction. Depending on the duration of the interstimulus intervals of the electrical stimulus, either jagged or smooth tetanus may occur when exposed to it. If the interpulse interval of the electrical stimulus is less than the duration of a single muscle contraction, but greater than or equal to the sum of the latent period and the shortening phase, serrated tetanus occurs. This condition is met when the frequency of the pulsed electrical stimulus increases in a certain range.
If the duration of the interpulse interval of the electrical stimulus is less than the sum of the latent period and the shortening phase, smooth tetanus occurs. In this case, the amplitude of smooth tetanus is greater than the amplitude of both single muscle contraction and serrated tetanic contraction. With a further decrease in the interpulse interval of the electrical stimulus, and therefore with an increase in frequency, the amplitude of tetanic contractions increases (see Fig. 4).
Rice. 4 Dependence of the shape and amplitude of tetanic contractions on the frequency of the stimulus. – the beginning of the action of the stimulus, - the end of the action of the stimulus.
However, this pattern is not absolute: at a certain frequency value, instead of the expected increase in the amplitude of smooth thetatnus, the phenomenon of its decrease is observed (see Fig. 5). This phenomenon was first discovered by the Russian scientist N.E. Vvedensky and was called pessimum. According to N.E. Vvedensky, the basis of pessimal phenomena is the mechanism of inhibition.
Rice. 5. Dependence of the amplitude of smooth tetanus on the frequency of the stimulus. The designations are the same as in Figure 5.
− Depending on conditions in which muscle contraction occurs, there are two main types - isotonic and isometric . Contraction of a muscle in which its fibers are shortened but the tension remains constant is called isotonic . Isometric is a contraction in which the muscle cannot shorten if both ends are fixed motionless. In this case, as the contractile process develops, the tension increases, but the length of the muscle fibers remains unchanged.
In natural motor acts, muscle contractions are mixed: even when lifting a constant load, the muscle not only shortens, but also changes its tension due to the actual load. This reduction is called auxotonic.
− Depending on the frequency of stimulation, there are solitary and tetanic abbreviations.
Single cut(tension) occurs when a single electrical or nerve impulse acts on a muscle. The excitation wave occurs at the site of application of the electrodes for direct stimulation of the muscle or in the area of the neuromuscular junction and from here spreads along the entire muscle fiber. In the isotonic mode, a single contraction of the frog gastrocnemius muscle begins after a short hidden (latent) period - up to 0.01 s, followed by a rise phase (shortening phase) - 0.05 s and a decline phase (relaxation phase) - 0.05-0, 06 p. Typically the muscle shortens by 5-10% of its original length. As is known, the duration of the excitation wave (AP) of muscle fibers varies, amounting to a value of the order of 1-10 ms (taking into account the slowdown of the repolarization phase at its end). Thus, the duration of a single contraction of a muscle fiber that follows its excitation is many times greater than the duration of the AP.
The muscle fiber reacts to irritation according to the “all or nothing” rule, i.e. responds to all suprathreshold stimuli with a standard AP and a standard single contraction. However, the contraction of an entire muscle when directly stimulated is highly dependent on the strength of the stimulation. This is due to the different excitability of muscle fibers and their different distances from the stimulating electrodes, which leads to an unequal number of activated muscle fibers. At threshold stimulus strength, muscle contraction is barely noticeable because only a small number of fibers are involved in the response. As the strength of stimulation increases, the number of excited fibers increases until all fibers are contracted, and then maximum muscle contraction is achieved. Further strengthening of the stimuli does not cause an increase in the contraction amplitude.
Under natural conditions, muscle fibers operate in single contraction mode only at a relatively low frequency of motor neuron impulses, when the intervals between successive motor neuron APs exceed the duration of a single contraction of the muscle fibers innervated by them. Even before the next impulse from the motor neurons arrives, the muscle fibers have time to completely relax. A new contraction occurs after the muscle fibers are completely relaxed. This mode of operation causes slight fatigue of muscle fibers. At the same time, they develop relatively little tension.
Tetanic contraction- This is a prolonged continuous contraction of skeletal muscles. It is based on the phenomenon of summation of single muscle contractions. When two rapidly successive stimulations are applied to a muscle fiber or a whole muscle, the resulting contraction will have a greater amplitude. The contractile effects caused by the first and second stimuli seem to add up; a summation, or superposition, of contractions occurs, since the actin and myosin filaments additionally slide relative to each other. In this case, previously non-contracting muscle fibers may be involved in contraction if the first stimulus caused subthreshold depolarization in them, and the second increases it to a critical value. When obtaining summation in a single fiber, it is important that the second stimulation is applied after the disappearance of the AP, i.e. after the refractory period. Naturally, superposition of contractions is also observed during stimulation of the motor nerve, when the interval between stimulation is shorter than the entire duration of the contractile response, as a result of which contractions merge.
At relatively low frequencies there occurs serrated tetanus , at high frequency - smooth tetanus (Fig. 13).
Rice. 13. Contractions of the frog gastrocnemius muscle with increasing frequency of sciatic nerve stimulation. Superposition of contraction waves and the formation of different types of tetanus.
a - single contraction (G = 1 Hz); b, c - jagged tetanus (G = 15-20 Hz); d, e - smooth tetanus and optimum (G = 25-60 Hz); e - pessimum - muscle relaxation during stimulation (G = 120 Hz).
Their amplitude is greater than the maximum single contraction. The tension developed by muscle fibers during smooth tetanus is usually 2-4 times greater than during a single contraction. The mode of tetanic contraction of muscle fibers, in contrast to the mode of single contractions, causes fatigue faster and therefore cannot be maintained for a long time. Due to shortening or complete absence of the relaxation phase, muscle fibers do not have time to restore the energy resources expended in the shortening phase. The contraction of muscle fibers in the tetanic mode, from an energy point of view, occurs “on credit.”
There is still no generally accepted theory to explain why the tension developed during tetanus, or superposition of contractions, is so much greater than during a single contraction. During short-term muscle activation, at the beginning of a single contraction, elastic tension arises in the cross-bridges between actin and myosin filaments. However, it has recently been shown that such activation is not sufficient for the attachment of all bridges. When it is longer, provided by rhythmic stimulation (for example, with tetanus), more of them are attached. The number of cross bridges connecting actin and myosin filaments (and, consequently, the force developed by the muscle), according to the sliding filament theory, depends on the degree of overlap of thick and thin filaments, and therefore on the length of the sarcomere or muscle.
Ca 2+ release during tetanus. If stimuli are delivered at a high frequency (at least 20 Hz), the Ca level 2 + remains high in the intervals between them, because the calcium pump does not have time to return all ions to the longitudinal system of the sarcoplasmic reticulum. Under such conditions, individual contractions almost completely merge. This state of sustained contraction, or tetanus, occurs when the intervals between stimuli (or action potentials in the cell membrane) are less than about 1/3 of the duration of each single contraction. Consequently, the frequency of stimulation required for their fusion is lower, the longer their duration; for this reason it depends on temperature. The minimum time interval between successive effective stimuli during tetanus cannot be less than the refractory period, which approximately corresponds to the duration of the action potential.
As it turned out, the amplitude of smooth tetanus varies widely depending on the frequency of nerve stimulation. At some optimal At a (sufficiently high) stimulation frequency, the amplitude of the smooth tetanus becomes greatest. This smooth tetanus is called optimum . With a further increase in the frequency of nerve stimulation, a block of excitation conduction develops at neuromuscular synapses, leading to muscle relaxation during nerve stimulation - Vvedensky's pessimum. The frequency of nerve stimulation at which pessimism is observed is called pessimal (see Fig. 6.4).
The experiment easily reveals that the amplitude of muscle contraction, reduced during pessimal rhythmic stimulation of the nerve, instantly increases when the frequency of stimulation returns from pessimal to optimal. This observation provides good evidence that pessimal muscle relaxation is not a consequence of fatigue or depletion of energy-intensive compounds, but is a consequence of special relationships that develop at the level of post- and presynaptic structures of the neuromuscular synapse. Vvedensky's pessimum can also be obtained with direct, but more frequent irritation of the muscle (about 200 impulses/s).
Contracture. Contracture is a state of reversible local sustainable contraction. It differs from tetanus in the absence of a spreading action potential. In this case, prolonged local depolarization of the muscle membrane may be observed, for example with potassium contracture, or a membrane potential close to the resting level, in particular with caffeine contracture . Caffeine at non-physiologically high (millimolar) concentrations penetrates muscle fibers and, without causing membrane stimulation, promotes the release of Ca 2+ from the sarcoplasmic reticulum; As a result, contracture develops. With potassium contracture, the degree of persistent depolarization and contractile tension of the fiber depends on the concentration of K + in the external solution.
Hello, my dear readers, admirers and other good and not so good personalities! Today we are waiting for an archivally important and necessary note of a scientific or similar nature. In it we will talk about the types of muscle contractions, what they are, what they are and how to use them in your daily training activities.
So, make yourself comfortable, let's start gesturing.
Types of muscle contractions: what, why and why
If you are not yet aware, the ABC of Bodybuilding project is an educational resource, and therefore unusual in-depth articles periodically appear on it, revealing the essence of various pumping (and related) processes. In particular, the latest such notes include: , and others like them. So, when it comes to changing your own body, it is important not just to mindlessly pump weights and lift heavy weights, it is important to understand what is happening in the muscles at this particular moment, what type of load is applied to them and what this can ultimately result in. In general, today we will invest in our heads, so that later we can pump up our body even better. Actually, let's get closer to the point.
Note:
For better assimilation of the material, all further narration will be divided into subchapters.
Types of muscle contractions: how they happen
Every time you pick up a projectile (for example, a dumbbell) and start doing the exercise (for example, dumbbell biceps curl), the process of contraction of skeletal muscles occurs. We are in previous notes (in particular this one) We have already looked at how the process of muscle contraction itself occurs, therefore, in order not to repeat ourselves, I will give only a general diagram.
...and visual animation (click and launch the application by pressing "play").
The motor center consists of a motor neuron and a certain number of innervated fibers. Muscle contraction is the response of a muscle unit to the action potential of its motor neuron.
Total exists 3 type of graduated muscle responses:
- wave summation – formed by increasing the frequency of the stimulus;
- multi-element summation (multiple motor unit summation)– formed by increasing the strength of the stimulus (increase in the number of motor neurons);
- staircase (treppe) - a reaction with a certain frequency/strength to a constant stimulus.
Speaking about muscles, one cannot fail to mention muscle tone - a phenomenon in which muscles exhibit slight contraction even at rest, maintaining their shape and ability to respond to load at any time. You don’t have to remember all this, it will just help you better understand the essence of the ongoing processes in the muscles during different types of muscle contractions.
What types of muscle contractions are there?
Did you know that to ensure better growth muscles, they need to be given different types of load, but not in the sense of weight or changing one exercise to another, but to influence the characteristics of the muscles differently. This is what we are talking about - static and dynamic contraction of skeletal muscles. Static and dynamic work combine five types of muscle contractions, each of which is divided into two forms of movement: concentric and eccentric.
Let's go through each one in order and start with...
Dynamic contractions (DC)
Occur while driving or using free weights- when an athlete lifts a free weight and resists gravity. The most common type of DS are isotonic - those in which the muscle changes its length when it contracts during movement. Isotonic contractions (IS) allow people (and animals) to carry out their usual activities and move around. There are two types of IS:
- concentric – the most common and often encountered in everyday and sports activities. They imply shortening of a muscle due to its contraction (compression). An example is bending the arm at the elbow joint, resulting in a concentric contraction of the biceps brachii muscle and biceps muscle. This contraction is often called the positive lifting phase of the projectile;
- eccentric is the exact opposite of concentric. Occurs when a muscle lengthens during contraction. It occurs much less frequently in pumping practice and involves control or slowing down of movement at the initiative of an eccentric muscle agonist. An example is when kicking a ball, the quadriceps muscle contracts concentrically and the hamstring muscles contract eccentrically. Lower phase (extension/lowering) dumbbell curls or pull-ups are also examples of ES. This type puts more stress on the muscle, increasing the likelihood of injury. This contraction is often called the negative phase of the projectile's descent.
The features of eccentric contractions include greater force production - i.e. the athlete can reduce (in controlled mode) a weight that significantly exceeds in terms of “tonnage” its working lifting weight. Greater strength is provided by greater inclusion of type II fibers (fast muscle fibers). Thus, the exercise concentrated dumbbell lift for the biceps, or rather its negative phase, allows you to more actively include white fibers in the work. This feature is often used by advanced athletes to improve explosive power, such as in the bench press.
Note:
The muscles become rigid 10% stronger during eccentric movements than during concentric contractions.
Most often, in such cases, a dumbbell is taken that is distant from the usual weight. (let's say 15 kg) on 3-7 kg. The positive phase is carried out by throwing the dumbbell upward with the help of a partner or another hand, and the negative phase takes about 4 sec (against 2 sec rise). Such eccentric training is sometimes very useful because... create extensive damage to muscle fibers, which leads to an increase in protein synthesis, subsequently the phenomenon of supercompensation and better muscle hypertrophy. The downside is the high likelihood of injury. (if you do everything without a head), so it’s better for beginners not to bother.
Static contractions (SS)
The name itself speaks for itself, static, i.e. no movement, no change in lengthening/shortening. Such contractions are called isometric. Example – holding an object in front of you (bags in the store) when the weight is pulled down, but the muscles contract to keep the object on the right level. Also an excellent example of isometric muscle contraction is hovering at some point on the trajectory for an unspecified amount of time. For example, when performing squats in the middle of the trajectory (half up) the quadriceps contract isometrically. The amount of force produced during an isometric contraction depends on the length of the muscle at the point of contraction. Each muscle has an optimal length at which maximum isometric strength is observed. The resulting force of isometric contractions exceeds the force produced by dynamic contractions.
For clarity, I will give examples demonstrating different types of muscle contractions (clickable).
We have looked at the main types of contractions that are most common in training practice, however, if you look at the initial classification, there are several more of them. Let's also look at them so that you at least have an idea about them and can surprise your ignorant colleagues in the hall :).
Isokinetic contractions
In isokinetic contractions (Iso=constant, kinetic=movement) neuromuscular systems can operate at a constant speed at each stage of movement against a given resistance. This allows the working muscles and muscle groups to create a high degree of tension throughout the entire range of motion. This type of contraction is effective for uniform development of muscle strength at any angle of movement. These are dynamic contractions, and they change the length of the muscle. The defining characteristic of IS muscles is that they result in movements at a constant speed.
IN gym a similar type of contraction is used on special isokenetic dynamometer simulators Cybex, Nautilus and others. Swimming and rowing, constant speed activities, are also isokinetic forms of contractions.
The benefits of isokinetic contractions include:
- lead to improved neuromuscular coordination, increasing the number of fibers involved in the work;
- lead to an increase in muscle strength of the entire muscle throughout the entire range of motion;
- control of the speed of movement can significantly reduce the likelihood of injury, which is especially important in the postoperative periods and periods of rehabilitation;
- lead to improved overall endurance and cardiac function.
Oxotonic contractions
This is a dynamic type of increased tension contraction. (increasing tension). When an athlete flexes his arms while holding a barbell, its mass obviously does not change throughout the entire range of motion. The force required to perform this movement is not constant, but depends on the athlete's body type, leverage, limb angle, and speed of movement.
Plyocentric contractions
It is a hybrid (combination), the muscle performs isotonic compression from an extended position. An activity that uses this type of muscle contraction to its fullest is called plyometric training or. This type of activity is good for cumulatively developing the strength and power of the athlete, and is often recommended as a basis for women's training.
So, in order to finally settle all of the above, I will give a combined picture-presentation (which I found in the archives of a foreign sports and medical university) by type of abbreviation. Here, in fact, is it (clickable).
Effect of contraction types on muscle length
The result of isotonic contractions is a change in muscle length (at constant force). Concentric IS - shortens the muscle as the load moves, eccentric - lengthens the muscle as it resists the load. The result of isometric contractions is an increase muscle tension, however, neither lengthening nor shortening of the muscle occurs.
In visual form, all this disgrace looks like this.
Type of muscle contractions during running
We analyzed the types of muscle contractions depending on the activity, but the following question remained unexamined: what type of contractions takes place in running. In general, errands are a universal tool that covers several types of contractions at once, in particular: isotonic, concentric and eccentric. Contractions occur within slow and fast twitch muscle fibers.
During running, hip elevation and knee flexion produce concentric isotonic contractions of the hip flexors and hamstrings. (hamstring muscles). When you straighten your leg to push off the ground and make a forward movement, your hip extensors (hamstrings, gluteus maximus) and knees (quadriceps) perform concentric isotonic contractions.
Eccentric isotonic contractions are especially activated during downhill (downhill) . During normal running, the knee extensors and quadriceps contract to straighten the leg. When running downhill, the quadriceps contract eccentrically. In addition, the tibialis anterior muscle also contracts eccentrically, controlling the downward movement of your leg after your heel strikes the ground. As for the involvement of different types of fibers during running, running errands at a relatively calm pace (jogging) uses mainly slow-twitch fibers for its muscle activity. Increasing speed allows for greater recruitment of fast-twitch muscle fibers.
What do basic exercises give?
In fact, knowledge about the types of muscle contractions should sway athletes even more (especially beginners) towards fulfilling the base, and here's why.
Many skeletal muscles contract isometrically to stabilize and protect active joints during movement. While during execution the quadriceps femoris muscle contracts concentrically (during the ascending phase) and eccentrically (in descending phase), many of the deeper thigh muscles contract isometrically to stabilize the hip joint during movement.
Thus, working with basic exercises, you can drive away at once muscle groups for several types of abbreviations. In fact, this will have a positive effect on their volume-strength characteristics and provide a better incentive for growth.
Well, that’s probably all for today, all the topics have been covered, questions have been addressed, the children have been fed, so it’s time to wrap things up.
Afterword
The next one, who knows what kind, has come to an end :) note, in it we talked about the types of muscle contractions. Someone may say that it is not practical - perhaps, but the theory and understanding of all pumping processes are also very important in building a shaped body, so let's absorb it!
That’s all for now, let me take my leave, until we meet again!
PS. Friends, do you use this information in your training, or did you know nothing about it until now?
P.P.S. Did the project help? Then leave a link to it in your social network status - plus 100 points for karma, guaranteed :) .
With respect and gratitude, Dmitry Protasov.
Physiology of muscles. Classification of muscles according to structural, biochemical and functional criteria
The muscle tissue of the human body includes striated (skeletal and cardiac) and smooth muscles. The first type of muscles ensures the maintenance of posture, position in space and movement of the body and its parts in it. The functions of smooth muscles are to maintain blood pressure, move food masses and remove waste products of metabolism. The heart muscle consists of cross-striated mononuclear muscle cells, but has different properties compared to striated skeletal muscle. Regulation of the tone and contractile activity of smooth muscles is carried out by the sympathetic and parasympathetic nervous systems. Skeletal muscle contractions occur in response to nerve impulses coming from the spinal cord.
There are more than 600 muscles in the human body, their share of the human body weight is approximately 30% (35–45% in men and 28–32% in women).
Basic functional properties of muscles:
1) excitability;
2) conductivity;
3) contractility.
Excitation and contraction of muscles is carried out under the influence of nerve impulses coming from nerve centers. In muscles, chemical energy stored in the form of ATP is converted directly into mechanical and thermal energy.
The muscle consists of a belly (the contractile part, built from striated muscle tissue) and tendons that attach the muscle to the skeleton.
Skeletal muscle groups:
1. According to form– narrow and wide. In narrow (fusiform) muscles (for example, on the limbs) the tendons are narrow and long, in wide (ribbon-shaped, for example, on the anterior abdominal wall) the tendons are wide and are called aponeurosis.
2. According to the location of muscle bundles:
Cirrus - in them, muscle bundles are attached to the tendon on one or both sides, as in a bird’s feather, and diverge on the other side. These muscles are capable of contracting strongly, but over short distances (strong muscles).
Muscles with parallel arrangement of long muscle bundles. These muscles are not very strong, but can shorten up to 50% of their length (dexterous muscles).
3. According to the function performed and the effect on the joints: flexors and extensors, adductors and abductors, compressors (sphincters) and dilators.
Exists two kinds muscle contractions - single and tetanic. Single muscle contraction is the only type of contraction for the heart muscle, and in skeletal muscles it has an artificial etiology and occurs in response to a single electrical signal and the occurrence of an action potential (AP). Such a contraction, lasting » 100 ms, has a waveform (see figure) and includes three phases: 1 – latent period (from 2-3 to 10 ms), lasting from the moment of application of stimulation to the start of contraction, 2 – shortening phase or contraction (40-50 ms) and 3 – relaxation phase (about 50 ms). Under natural conditions, impulses do not arrive singly, but in series of at least 15-50 impulses/s, to which the muscle responds by producing tetanic contraction(tetanus). It is based on the phenomenon of summation of several single contractions. Depending on the frequency of the impulses, serrated and smooth tetanus are distinguished.
Figure 5 – Types of muscle contractions:
A – single contraction phases; B – single and tetanic contractions
Serrated tetanus(incomplete) occurs when each subsequent impulse comes into the muscle relaxation phase.
If the frequency of stimulation is higher, and each subsequent impulse comes in the phase of muscle shortening, then complete summation occurs, and the tetanic contraction is of a continuous nature - smooth tetanus(full).
An increase in the response under the action of submaximal stimuli to a certain (maximal) level occurs due to the involvement of new, previously uninvolved fibers in the excitation process. In the case of a further increase in irritation (supermaximal level), the response no longer increases, and vice versa, with very strong stimuli (5-10 or more thresholds), a pessimal response can be achieved.
In the whole organism, motor neurons send bursts of action potentials to motor units, which respond tetanically. Skeletal muscles are in a state of constant tone due to constant background impulses from the motor areas of the central nervous system.
Muscle work(A) is the product of the load (F) and the distance (h). A = F*h, or A = F*dl, where dl is the amount of muscle shortening.
Relative muscle strength determines the maximum load that a muscle can lift. This value depends much more on the thickness of the muscle than on its length.
The strength of muscle contraction is determined by the number of motor units involved in the contraction process. Absolute Power is the ratio of relative force to the cross-sectional area of the muscle, expressed in cm 2. For example, the absolute strength of the biceps is 11.9 kg∕cm 2, the calf muscle is 5.9 kg∕cm 2.
To assess the functional activity of muscles, we talk about their tone and phasic contractions.
Tone– a state of prolonged continuous tension.
Phasic Muscle contractions are short-term shortening of a muscle followed by its relaxation.
The magnitude of contraction (degree of shortening) of a muscle depends on its morphological properties and physiological state. The greater the thickness of the muscle, the greater the load it can lift during its contraction. Long muscles contract by a greater amount than short ones. Moderate stretching of a muscle increases its contractile effect; with strong stretching, muscle contraction weakens.
Rule of average loads : maximum work muscles is carried out with average , and not the maximum load values, since
At higher loads, fatigue quickly develops.
Muscle contraction modes:
1) isotonic– contraction, in which the muscle fibers shorten, but the same tension remains (for example, when lifting a load);
2) isometric– a contraction in which the length of the muscle fibers does not change, but the tension in it increases (for example, when resisting pressure);
3) auxotonic- a contraction in which both the tension and length of the muscle change.
The strength of muscle contraction is determined by the number of active muscle fibers involved in the contraction, the frequency of nerve impulses and the presence of synchronization of the activity of individual muscle fibers over time. Even at rest, skeletal muscles are rarely completely relaxed. Usually some tension remains in them - tone. Muscle tone increases after heavy physical exercise and during psycho-emotional stress.
With regular physical training, the number of muscle fibers does not change, but their diameter increases due to an increase in the number of myofibrils in the fibers.
Muscular work is associated with significant energy costs and, therefore, requires an increased flow of oxygen. This is achieved by activating the activity of the respiratory and cardiovascular systems. Increased metabolic processes during muscle work leads to the need for increased release of metabolic products, and, accordingly, increased activity of the kidneys and sweat glands. Hence, physical exercise increase the activity of physiological systems, have a stimulating effect on the motor system, lead to the improvement of motor skills, and the development of mental functions. When children are physically inactive, metabolic processes suffer, immunity and performance, including mental performance, decrease.
Muscle fatigue depends on its supply of oxygen and blood. The efficiency of using O2 by the muscle is 20-25%, and with training it can reach 30%.
In each muscle there are many motor units, or motor units - a certain number of muscle cells innervated by one nerve cell, and each myocyte has its own nerve ending.
Among the motor units, they are distinguished: fast, which includes on average about 50, and slow - from several hundred to thousands of muscle cells.
Types of nerve fibers:
1) slow, tireless(red, static, tonic) - these are thin muscles, rich in blood vessels and myoglobin, which exhibit great strength, do not get tired for a long time, but the speed of their contractions is small. For example, they maintain vertical statics, hold individual parts of the body in a certain position, i.e. perform a supporting function. These also include the external muscles of the eyeball. Slow phasic contractions provide muscle tone, and therefore such contractions are called tonic. They are necessary to maintain balance in statics and dynamics. Slow muscle cells make up the bulk of motor units. They contain a lot of myoglobin and myosin, where oxidation occurs. Such muscles are red in color and are less fatigued.
2) fast, easily tired(white, dynamic, phasic): they have thick muscle bundles, fewer blood vessels and myoglobin, their contraction speed is high as well as fatigue. While inferior in strength, they are capable of making a variety of small, quick movements. Fast phasic aerobic muscles are slightly paler because they contain less myoglobin, but a fairly large amount of myosin is still retained, and therefore oxidation processes occur intensively. In such muscles, fatigue develops faster than in those described above. In terms of the number of muscle cells in a motor unit, fast phasic muscles occupy second place after slow ones. Anaerobic muscles provide the fastest contractions. They are low in myoglobin and myosin. The cells that make up fast anaerobic muscles are white. Anaerobic glycolysis occurs in such muscles, therefore, as a result of the accumulation of under-oxidized products (lactic acid), an oxygen debt develops, and as a result, rapid fatigue. Examples of such muscles are the muscles of the fingers and eyes.
3) fast, fatigue resistant(intermediate).
All three types of fibers can be contained in the same muscle, and the ratio of their numbers is determined to a large extent by heredity. For example, in the human quadriceps muscle, the percentage of slow fibers can range from 40 to 98%. The more slow fibers, the more muscle adapted for endurance work. Conversely, people with a high percentage of fast, strong fibers are more capable of work that requires greater strength and speed of muscle contraction.
The strength of muscle contraction is determined by the number of active muscle fibers involved in the contraction, the frequency of nerve impulses and the presence of synchronization of the activity of individual muscle fibers over time. Even at rest, skeletal muscles are rarely completely relaxed. Usually they retain some tension - tone. Muscle tone increases after heavy physical exercise and during psycho-emotional stress.
