Arm muscles and their training. Flexor and extensor muscles: features, structure and examples Flexor and extensor muscles

2. back muscles - movement of the head, neck, spine, maintaining a vertical body position, movement of the scapula, movement of the upper and lower extremities;

3.abdominal muscles- form the abdominal press, participate in bending and turning the body;

4. Respiratory muscles: external and internal intercostal muscles, diaphragm.

The muscles of the trunk perform the function of breathing, support the body in an upright position, and participate in the work of the arms and legs.

III. Muscles of the Limbs:

Arm muscles allow a person to perform very complex and precise movements. Muscles upper limbs provide labor activity.

Leg muscles hold the body, ensure its vertical position, walking, running. Muscles of the lower extremities - provide support and movement of the body.

Muscles of the Torso AndLimbs:

A - front view: 1-deltoid; 2-major pectoralis; 3-biceps brachii; 4-triceps brachii; 5-abdominal muscles;

6-sartorius muscle; 7-quadriceps femur; 8-gastrocnemius; 9-extensors of the hand and fingers;

IN-viewbehind: 1-triceps shoulder; 2-deltoid; 3-trapezoidal; 4-latissimus dorsi;

5-flexors of the hand and fingers; 6-gastrocnemius; 7-biceps femur; 8-gluteal.

Muscle work

Body movement occurs due to muscle contraction.

When muscles contract, they do work. When muscles contract, the bones move closer or further away, moving the body or its parts, lifting or holding a load.

The muscles that provide movement are divided into:

1. Flexors and extensors,

2.Adductors and abductors,

3. Rotating the bone clockwise and counterclockwise.

The same muscle cannot bend and straighten bones in a joint,

and the movement of the bones and, along with them, parts of the body is produced by at least two muscles (in fact, there are much more of them). The muscles are not always located where their force is applied.

Amplitude - range of movements- depends on the length of muscle fibers,

and the strength- on the cross-sectional area of ​​the muscle bundle.

To bend the hand into a fist, the muscles must be of sufficient length. This is why the muscles that flex and extend the fingers are located on the forearm,

muscles that lower and raise the shoulder - on the torso, etc.

Muscles that act in the opposite direction are called antagonists,

and muscles acting in one direction synergists. They work in harmony.

When the flexor muscles contract, the extensor muscles relax.

When the extensors contract, the flexors relax.

The somatic part of the nervous system regulates the work of skeletal muscles.

Both muscle groups can be simultaneously in a relaxed state (arms hang freely along the body). When holding weights with outstretched arms, the flexor and extensor muscles work together to press the bones together. Here they act as synergists.

Any work involves energy consumption.

The source of energy in the body is biological oxidation and breakdown of organic substances. When muscles contract, energy consumption and waste of organic substances, most often glucose, increase.

Why does a person need muscles?

Without muscles, people would be weak. For example, a loader - he would not be able to lift heavy bags

2nd grade student Kolya explains.

Muscle work

When muscles contract or tense, they produce work. It can be expressed in the movement of the body or its parts. This kind of work is done when lifting weights, walking, running. This is a dynamic job. When holding parts of the body in a certain position, holding a load, standing, maintaining a pose, static work is performed. The same muscles can perform both dynamic and static work.

By contracting, the muscles move the bones, acting on them like levers. The bones begin to move around the fulcrum under the influence of the force applied to them.

Movement in any joint is provided by at least two muscles acting in opposite directions. They are called flexor and extensor muscles. For example, when you bend your arm, the biceps brachii muscle contracts, and triceps relaxes. This occurs because stimulation of the biceps muscle through the central nervous system causes the triceps muscle to relax.

Skeletal muscles are attached to both sides of the joint and, when contracted, produce movement in it. Typically, the muscles that perform flexion - flexors - are located in front, and the muscles that perform extension - extensors - are located behind the joint. Only in the knee and ankle joints, the anterior muscles, on the contrary, produce extension, and the posterior muscles - flexion.

Muscles lying outside (lateral) of the joint - abductors- perform the function of abduction, and those lying medially (medially) from it - adductors- cast. Rotation is produced by muscles located obliquely or transversely relative to the vertical axis ( pronators- rotating inward, arch supports- outward). Several muscle groups are usually involved in the movement. Muscles that simultaneously produce movement in one direction in a given joint are called synergists(shoulder, biceps muscle shoulder); muscles performing the opposite function (biceps, triceps brachii) - antagonists. The work of different muscle groups occurs in concert: for example, if the flexor muscles contract, the extensor muscles relax at this time.

The muscles “set off” nerve impulses. One muscle receives an average of 20 impulses per second. In each step, for example, up to 300 muscles take part and many impulses coordinate their work.

The number of nerve endings in different muscles is not the same. There are relatively few of them in the thigh muscles, and oculomotor muscles, making subtle and precise movements all day long, are rich in motor nerve endings. The cerebral cortex is unevenly connected to individual muscle groups. For example, large areas of the cortex are occupied by motor areas that control the muscles of the face, hand, lips, and feet, and relatively small areas by the muscles of the shoulder, thigh, and lower leg. The size of individual zones of the motor cortex is proportional not to the mass of muscle tissue, but to the subtlety and complexity of the movements of the corresponding organs.

Each muscle has a double nerve subordination. One nerve carries impulses from the brain and spinal cord. They cause muscle contraction. Others, moving away from the nodes that lie on the sides of the spinal cord, regulate their nutrition.

The nerve signals that control the movement and nutrition of the muscle are consistent with the nervous regulation of the blood supply to the muscle. This results in a single triple nervous control.

For fine control of muscle activity, regulation of the tension developed by each individual muscle is necessary. This regulation is carried out in one of two ways (or both at the same time):

1. Number may vary muscle fibers, indignant at every given moment. The greater the number of stimulated fibers, the greater the force developed by the muscle, and vice versa. This is usually the case in skeletal muscles.

2. The frequency of nerve impulses coming to muscle fibers may change. Thus, more frequent stimulation will also lead to an increase in the force developed by the muscle.

Muscle contraction in the body occurs smoothly and coordinatedly. This is ensured by asynchronous reduction different groups muscle fibers in antagonist muscles.

Types of movements produced by pairs of antagonist muscles

Anna came to me complaining about a problem with her index finger. right hand– after a minor injury, for some reason he did not regain mobility.

-How long ago did you injure your finger? – I asked.

- About seven weeks ago. The doctor said that there was no fracture or crack, but the joint was very swollen. You see, it’s a different size than the others,” she said, pointing to the metacarpophalangeal joint. – The doctor also said that it is possible to apply a splint, but he does not recommend doing this. He told me to move that finger as much as possible to develop it, which is what I did the whole time. The problem is that he still doesn't move as fully as he used to, and the pain just won't go away.

– How did you get this injury? – I asked.

She was shy, but still told me her story. As it turned out, she, being late for work in the morning, in her haste, hit her finger on the toilet paper holder. I immediately interrupted her story and asked her to demonstrate how her index finger was moving now. I didn’t find any problems with bending, however, straightening the finger was significantly difficult.

“In addition, I feel that this finger has become significantly weaker.” When I try to press something with it, for example, the doorbell button, sometimes I can't even do it. I just realized how often I used my index finger before.

I told her what I was going to do.

– In our case, there are three problem areas - the flexor of the fingers, the extensor of the fingers and the ligaments of the joint itself. I will examine each area until we know what is causing your problem. You easily bend your finger, which means that the extensors, being antagonistic muscles, do not limit its movement, despite the weakness that you talked about. However, the range of finger extension is reduced, which may be caused by either flexor muscle spasm or extensor muscle weakness.

In addition, weakness and decreased range of extension may be explained by a process of arthrokinetic inhibition. This protective mechanism comes into play when a joint is injured, limiting the ability of the muscles to contract.

Muscles recover relatively quickly, but joint injuries can last a lifetime, causing the brain to “sacrifice” the muscle to protect the joint. When a muscle contracts to protect a joint, the pressure exerted by the muscle on the joint increases. This is why, after such an injury, the muscle's ability to contract may be permanently reduced to prevent further damage to the joint.

After the explanation, I proceeded to diagnose the flexor digitorum superficialis, flexor digitorum profundus, and index finger tendons. Despite the full range of motion, I found several areas of increased sensitivity in the body of the muscle.

- So we got to the cause of your problem. The main task of a muscle is to contract. When injured, the muscles cope less well with the implementation of this function - you recognize this as weakness. My work in in this case will not be aimed at increasing mobility, but at strengthening muscle strength. “Do you feel anything here?” I asked, palpating the extensor muscle of the index finger.

“This is where it hurts the most.” What role does this muscle play?

– This muscle extends your finger. The core of the problem is that your index finger extensor is weakened. When a joint is injured, the brain sends a signal to the muscle to contract to avoid further damage. Unfortunately, by the time the danger had passed, the muscle could no longer understand that it was time to relax. Without proper treatment, this problem will haunt you for the rest of your life.

For the next 20 minutes, I worked the extensors and flexors of the index finger, using medium-intensity pressure and unidirectional friction along the muscle fibers. In addition, I applied cross friction at the location of the ligaments of the metacarpophalangeal joint.

When Anna returned a week later, the swelling of the joint had noticeably decreased, and the range of extension of her index finger was almost normal.

“The finger has become much stronger!” she said happily. She was very pleased with the result of the treatment.

Before leaving, I told her to come up with a new story about how she got this injury.

(Douglas Nelson)

Coordinated work of flexor and extensor muscles. When a person performs any movement, two opposite groups take part: acting muscles: flexors and extensors of joints.

Flexion at the joint is accomplished by contracting the flexor muscles and simultaneously relaxing the extensor muscles.

The coordinated activity of the flexor and extensor muscles is possible due to the alternation of excitation and inhibition processes in the spinal cord. For example, contraction of the arm flexor muscles is caused by the stimulation of motor neurons in the spinal cord. At the same time, the extensor muscles relax. This is due to inhibition of motor neurons.

The flexor and extensor muscles of the joint can be in a relaxed state at the same time. Thus, the muscles of the arm hanging freely along the body are in a state of relaxation. When holding a weight or dumbbell in a horizontally extended arm, a simultaneous contraction of the flexor and extensor muscles of the joint is observed.

When contracting, the muscle acts on the bone as a lever and produces mechanical work. Any muscle contraction associated with energy consumption. The sources of this energy are the breakdown and oxidation of organic substances (carbohydrates, fats, nucleic acids). Organic substances in muscle fibers undergo chemical transformations that involve oxygen. As a result, fission products are formed, mainly carbon dioxide and water, and energy is released.

The blood flowing through the muscles constantly supplies them with nutrients and oxygen and removes carbon dioxide and other waste products from them.

Fatigue when muscle work. With prolonged physical work without rest, muscle performance gradually decreases. A temporary decrease in performance that occurs as work is completed is called fatigue. After rest, muscle performance is restored.

When performing rhythmic physical exercise fatigue occurs later, since muscle performance is partially restored in the intervals between contractions.

At the same time, with a large contraction rhythm, fatigue develops more quickly. Muscle performance also depends on the magnitude of the load: the greater the load, the sooner fatigue develops.

Muscle fatigue and the influence of the rhythm of contractions and the magnitude of the load on their performance were studied by the Russian physiologist I.M. Sechenov. He found out that when performing physical work, it is very important to select the average values ​​of the rhythm and load. In this case, productivity will be high, and fatigue will set in later.

It is widely believed that The best way restoration of performance is complete rest. THEM. Sechenov proved the fallacy of this idea. He compared how performance is restored under conditions of complete passive rest and when changing one type of activity to another, i.e. in active recreation conditions. It turned out that fatigue goes away faster and performance is restored earlier with active rest.

Any type of impact on the physical body becomes many times more productive if a person understands which muscles he uses, how they depend on each other and how to properly work them out to the maximum to obtain quick and high results. In this article, we will look at extensor and flexor muscles, their work and features of interaction using simple and easily understandable examples.

What are the muscles that act oppositely called?

Human musculature is designed in such a way that many muscles have “brothers” that perform completely opposite work: at the moment when one muscle tenses, the opposing one relaxes, and vice versa.

These muscles - flexors and extensors, which control the movement of the human body or individual limbs in space, are called antagonists. This is exactly how a person makes movements - thanks to a control system strictly coordinated by the brain and the coordinated work of the muscles that move the skeleton.

How do they work?

The brain sends an impulse to the nerve endings of a muscle, such as the biceps of the arm, and it contracts, bending the arm. The triceps - the extensor of the arm - is relaxed at this moment, since the brain gave the corresponding signal to it.

Flexor and extensor muscles, that is, antagonists, always work harmoniously, mutually replacing each other, but sometimes they can work simultaneously, maintaining a motionless, that is, static position of the body in space. A striking example of such work is the famous plank pose, in which the body hangs motionless above the floor, resting only on the hands and toes. Most of the main flexors and extensors of the muscles in this position do exactly half of the work required for them, as a result, the body maintains this position. If a person does not strain, say, the abdominal muscle, then it becomes difficult for his back, since under the pressure of gravity the lower back begins to sag and sag. Arms lowered down along the body are completely relaxed antagonist muscles, and an outstretched arm in front of you at shoulder level is synchronous work of both muscle groups.

What determines the quality of movement?

The quality of the flexor and extensor muscles depends on several factors:

1. The amplitude of movement mainly depends on the length of muscle fibers and the factors restraining them, for example, muscle spasm or post-traumatic scar greatly reduces the range of movement, and elasticity and good blood flow, on the contrary, significantly add amplitude to muscle work. That is why it is important to warm up the body well with dynamic movements before training in order to saturate the muscles with blood.
2. depends on two aspects: the size of the lever that the muscle uses, and directly the number and thickness of the muscle fibers that make it up. For example, lifting a 10 kg weight using the entire length of your arm is easy (large lever), but lifting it with just your hand will be more difficult. It’s the same with quantity: a muscle that is 5 cm in diameter is several times stronger than one that is only 2 cm thick.
3. All muscle movements are controlled by the somatic nervous system, therefore all body movements, especially the coordinated actions of the flexor and extensor muscles, depend on the speed and quality of its work.

If an athlete knows about the correct functioning of muscles, his training becomes more conscious and therefore correct, the level of efficiency increases significantly with less energy expenditure.

Examples of antagonist muscles

The simplest examples of flexor and extensor muscles:

• The femoral biceps and quadriceps are the flexor and extensor muscles of the leg, or more precisely the hip. The biceps is located at the back, attached to the ischium at the top and bottom, turning into a tendon, adjacent to the femur in the area of ​​the knee joint. And the quadriceps is an extensor, located on the front side of the thigh, attached by a tendon to the knee joint, and the upper part is attached to the pelvic bone.
• The biceps and triceps are the flexor and extensor muscles of the arm, located between the elbow and shoulder joint and attached to them by powerful tendons. They are the main muscles that form the shoulder and control the vast majority of flexion and extension movements of the arm.

You can often notice that if there is an overly active extensor muscle, then, as a result, the flexor muscle will be in a passive state, that is, not sufficiently developed, which creates inadequate body movements with a greater loss of energy than in harmoniously trained people (yogis are an example of this) .

Another example of antagonist muscles

The rectus abdominis and longitudinal muscles along the spine, along with the lumbar muscle, are also prominent representatives of the flexors and extensors of the body, and they are the most global, because thanks to their coordinated and uninterrupted work, the human body takes on various positions in space: from a vertical position of the torso to bending in an arc or, on the contrary, bending back.

And if a person is working to correct his posture: eliminate kyphosis, correct scoliotic curvature, or remove hyperlordosis in the lower back, he needs not only to work on the spinal extensors and psoas muscles, but also actively pump up the abdominal muscles, in particular the longitudinal abdominal muscle.

Pectoral muscles and diamond backs

These two couples also belong to the antagonists, although they are often unfairly classified in other categories. Spasm relationship pectoral muscles and passive rhomboid muscles The back has repeatedly become an area of ​​study for physio- and yoga therapists, kinesiologists and rehabilitation specialists. The pectoralis major and minor muscles are shaped like a fan. They are located on the front chest, originate in one bundle at the collarbones, the lower one - at the upper abdominal wall and are attached to the ridges humerus. Spasm of the pectoral muscles can be determined not only by the person’s stoop, but also by the position of his arms, lowered along the body. His arms from the shoulder and down to the hand will be turned inward, that is, the hands will face back with the palms.

They are located between the shoulder blades, controlling their work together with the trapezius, which, in turn, directly depend on the freedom of the shoulder muscles, in the area of ​​which there is already attachment of the pectoral muscles. As a result, a person works on stooping, loading the back muscles, but in fact he first needs to get rid of hypertonicity of the pectoral muscles, then work the extensor and flexor muscles of the neck, which will give freedom to his posture.