We all move actively: we walk, walk, run, jump, climb and fall. Without a developed muscular system, all these movements will be very difficult. The main part of the work falls on the flexor and extensor muscles.
These are constantly opposing antagonists. Their resistance is inherent in the nerve centers that control their activities. The movement centers located in the brain of the head give out signals. They go to motor neurons, nerve cells located in the brain of the back, and then along the longest processes to the necessary muscles.
The centers that send signals to antagonists are located in radically different states. When the flexor center is excited, the extensor counterpart relaxes.
Flexors and extensors work by straining. They move the entire body or its individual elements, doing work dynamically when running, walking or lifting objects. Static work is performed while maintaining a particular pose and holding an object.
Both activities can be performed by the same muscles.
By contracting, they act like levers on the bones. Every joint moves thanks to muscle mass, fastened on the sides. Which muscle is a flexor and which is an extensor depends on the situation.
When the arm bends, the 2nd head muscle of the shoulder contracts, and the 3rd head muscle relaxes. Typically, extension extensors are located posteriorly and flexor flexors are located in front of the joint. Only in the ankle and knee joint are they attached in the reverse order.
There are also abductors, located outside the joint and abducting one or another part of the body, and adductors, located inside and, conversely, adducting. They rotate muscles that lie transversely or obliquely relative to the vertical (instep supports outward, pronators inward).
Each movement is performed by a separate muscle group. Those of them that move in the same direction are synergists, on the contrary, they are antagonists. All groups work in harmony, contracting and relaxing at the right moments.
Each muscle type is triggered by nerve signals traveling at a speed of two dozen impulses per second. Each of them has its own number of nerve endings. For example, there are a lot of them in the eyes, but few in the thigh. The connections between the cerebral cortex and muscle groups are also uneven. The size of the zones does not depend on the mass of the recipient tissue, but on the complexity and subtlety of the resulting movements.
Each muscle receives brain impulses through some nerves, and nutritional regulation through others.
All this is coordinated with the regulation of its blood supply. The finest control of muscle activity is carried out by adjusting the tension it develops. In this case, either the number of fibers working in the muscle or the frequency of nerve impulses approaching them changes. As a result, the smoothness and consistency of all cuts is ensured.
The structure of the human shoulder
There are two types of muscles in this group:
- actually, the shoulder muscles, running from the deltoid to the elbow;
- muscles of the forearm, starting from the elbow and including all the muscles to the edge of the fingers.
The flexors used by humans are located in the front and include the muscles:
- biceps;
- coracobrachial;
- shoulder;
The extensors are located posteriorly and include:
- elbow;
- triceps
Arm flexors
The arm flexors are divided into zones. They answer:
- shoulder - behind the forearm;
- biceps – behind the shoulder and elbow joints, rotations and turns;
- coracobrachial - for flexion and rotation in the same joints.
The flexors of the hand are located lower.
Arm extensors
The arm extensors include the triceps, also called the triceps brachii muscles and consisting of the heads:
- lateral;
- medial;
- long.
The triceps, extending the arms at the elbow and shoulder, and forearm, also bring them to the body. The elbow muscles help him extend the limb at the elbow. All flexors and extensors of the arm work synchronously.
Muscles and their functions
The functionality of muscle groups is very diverse - especially in the hands that we actively work with. The shoulder joint works due to the muscles that extend to the shoulder from the bones shoulder girdle. The accuracy of finger movements is ensured by the extensor and flexor muscles of the wrist, as well as the metacarpus and forearm. They are connected to the bones by tendons.
The muscles in the legs are larger and stronger, which makes sense since they take heaviest weight. The calf muscles are the most developed. It is located on the back of the shin and works when running and walking:
- bends at the knee;
- raises the heel;
- turns his foot.
The muscles of the buttocks are attached to the bones of the thigh and pelvis and attach hip joint, helping a person maintain a vertical position. This, as well as many other functions, is performed by the muscles of the back. It runs along the spine and is attached to processes that are directed backwards. They also provide backward bending of the body.
The muscle mass that runs from the skull to the bones of the body holds up the head. Pectoral muscles help you breathe and move. Among the many functions of the abdominal muscles are bending and turning the torso in all directions.
The head has muscles for facial expression and chewing. The first group is extremely developed in humans and is responsible for the expression of emotions. The second group controls jaw movements.
The structure of the muscles of the forearm
The muscles in the forearm are divided into posterior and anterior. Each group has layers on the surface and in depth.
Front group
The main muscle group, including the flexors and extensors located in the front, includes several muscles. The flexor carpi ulnaris works in the wrist and elbow. Its radial counterpart works similarly, also penetrating the forearm. The pronator teres is smaller than the previous two, but repeats their functions.
The flexor digitorum superficialis assists in flexion of the elbow, hand, and medial phalanges. In the palm of your hand longus muscle controls this part of the arm and also helps it bend at the elbow.
The deep layer includes:
- on the thumb, bending it, as well as the phalanx of the nail;
- deep digital flexor, working with the extreme phalanges and the hand;
- pronator quadratus – for the forearm.
Back group
In the posterior group, the superficial layer includes:
- wrist extensors (longus, brevis and ulnaris);
- digital extensors;
- brachioradialis muscle.
The latter works in the elbow and forearm.
The deep layer includes:
- extensors, short and;
- abductor longus muscle;
- extensor index finger;
- diverting;
- opposing;
- moving;
- bending;
- extensors.
The hand includes not only the extensor and flexor of the wrist, but also the muscles that work with the fingers:
At the same time, the arms move due to a huge number of muscles that make up a complex complex (and not just flexors and extensors).
Sport is the key to health and visual attractiveness, so nowadays everything more people set aside time to visit the gym. The most attention and concern for beginners is usually upper body training. Every day, attention is paid to exercises that pump up the biceps, triceps and other arm muscles. At the same time, the technology often remains simply terrible. All this comes from ignorance of the anatomical structure of human muscles. A deep understanding of the process and the degree of involvement of a particular muscle in an exercise will allow you to load it as much as possible. target muscle and achieve the best result.
What is included in the concept of “arm muscles”?
Anatomically, the muscles of the human arm can be divided into two main groups:
1. Shoulder muscles - originate from the deltoid and are located up to the elbow muscle.
2. Forearm muscles - start from the elbows and include all the muscles to the fingertips.
The structure of the human shoulder
The shoulder muscles are divided into the following groups:
1. Arm flexors (anterior shoulder muscles), which include the brachialis, coracobrachialis, and biceps muscles.
2. Arm extensors (posterior shoulder muscles), which include the triceps and anconeus muscles.
Arm flexors
Considering in more detail the anatomy and functional purpose of this element, it should be noted that brachialis muscle provides flexion of the forearm. The biceps, also called the biceps brachii muscle, is designed for flexion of the upper limbs at the elbow and shoulder joints, as well as for rotational movements of the forearm. It consists of a short and a long head. The coracobrachialis muscle is directly involved in flexion and rotation of the arm at the elbow and shoulder joints.
Arm extensors
The main extensors are the triceps - the muscles of the arms, which are also called triceps muscles shoulder They consist of long, medial and lateral heads. The main functions of the triceps are extension of the forearm at the shoulder and elbow joints, as well as adduction of the upper limbs to the body. Elbow muscle helps the triceps in extending the arm at the elbow joint.
The structure of the muscles of the forearm
The muscles of the forearm are similar in their division to the shoulder muscles (they are also divided into anterior and posterior), while each of the given subgroups is divided into deep and superficial layers of muscles.
Front group
Let's consider the muscles of the arms of the superficial layer of the anterior group, which include the following elements:
2. Flexor radialis wrists - performs functions adjacent to the ulnar flexor, and also pronates the forearm.
3. Pronator teres - more small muscle, completely repeating the functions of the previous two.
4. Superficial flexor of the fingers - takes part in flexion of the elbow joint and hand, as well as the middle phalanges.
5. Long palmaris muscle- controls the palm and takes part in flexion of the elbow joint.
The deep layer is represented by the following muscles:
1. Long flexor thumb- flexes the thumb and nail phalanx.
2. Flexor digitorum profundus - flexes the hand and extreme phalanges.
3. Pronator quadratus - the main pronator of the forearm.
Back group
Surface layer posterior group consists of the ulnaris, extensor carpi brevis and longus, extensor digitorum, and brachioradialis muscle, which bends the upper limb at the elbow, rotates and pronates the forearm. The deep layer consists of the extensor pollicis longus, extensor brevis and abductor pollicis longus muscles, which abduct and extend the human thumb. The extensor muscles also belong to this layer index finger, the functions of which are clear from its name, and an instep support that controls the hand and forearm.
Carpal muscles
The human hand consists of nine muscles, the main functions of which are flexion and extension of the fingers, as well as providing them with static positions: short flexors of the thumb and little finger, abductors of the thumb and little finger, muscles of the opposable thumb and little finger, muscles that move the thumb, lumbrical and interosseous muscles.
Thus, the human hands contain many different muscles that have a huge number of functions.
Training muscle groups of the upper limbs
How to properly train arm muscles? Human anatomy allows the upper extremities to respond quite well to training. Each muscle has specific movements, and therefore requires specific pumping exercises. So, the biceps is responsible for bending the arm, so it will be effective various exercises for lifting loads (barbells, dumbbells) by bending the arm at the elbow joint from various positions (sitting, standing). The triceps works to straighten the arm. The exercises involve applying effort at the moment when the arm muscles are straightened (push-ups, overhead extensions, and so on). For the forearm muscles, wrist flexion and extension, as well as exercises with an expander (or rubber ball), are best suited.
A pleasant feature of the arm muscles is their ability to rapid recovery after training, which makes pumping more frequent. But in arm training, just like any other muscle group, the main thing is not to overdo it, otherwise you can achieve the opposite result - constant fatigue and even injuries.
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Elbow joint (EL)
The elbow joint (EL) is formed by the humeroulnar, humeroradial and radioulnar joints. When examining a joint, pay attention to the contours of the shoulder, forearm, the direction of the axes, and the extensor and flexion surfaces of the joints with the arm straightened. Rotation of the radius around the ulna at the radioulnar joint allows pronation and supination of the arms. The humeroulnar and humeroradial joints take part in flexion and extension in the LM. When fully flexed, the front surface of the forearm touches the front surface of the shoulder.When extended, the shoulder and forearm most often form a straight line. The measurement of the volume of flexion and extension occurs from the initial position in which the arm hangs freely along the body, the protractor is located in the sagittal plane, its fixed part is parallel humerus, movable follows the movement of the forearm. The normal flexion angle is 150-160°, the extension angle is 0° (Fig. 2.5).
Rice. 2.5. Measuring the angle of flexion at the elbow joint
With supination and pronation in starting position the forearm is bent at a right angle, the hand is in the sagittal plane, the thumb is retracted parallel to the axis of the shoulder. With full supination (outward rotation), the hand is installed in a horizontal plane with the palmar surface facing upward. The volume of supination is 90°. With full pronation (inward rotation), the hand is installed in a horizontal plane with the back surface facing upward. The pronation angle is 90°.
Radiocarpal and intercarpal joints (LZS and MZS)
The wrist and intercarpal joints (LJS and MJS) are in close functional dependence. Inspection of the LZS contours is carried out from above and from the side. Palpation is carried out on the back of the hand (palpation is more accessible). The LZS line is located 1 cm distal to the line connecting both styloid processes.Movements in the LZS are performed in the sagittal plane - flexion and extension, and in the frontal plane - abduction and adduction (radial and ulnar abduction). The amplitude of movements in them is determined with the wrist and hand straightened in relation to the forearm. When measuring the volume of flexion in the LZS, the goniometer is placed in the sagittal plane. The normal flexion angle is 80-90°, and extension is 70°. With full flexion and extension, the hand and forearm form an almost right angle. When determining the ulnar and radial abduction, the protractor is placed in the horizontal plane and normally the angles are 45-60° and 20-30°, respectively.
The most common and important impairment of wrist mobility is loss or limitation of wrist extension.
The carpometacarpal joints (CMJ) are inactive, with the exception of the 1st carpometacarpal joint - flexion, extension, adduction, abduction, medial and lateral rotation are possible in it, which occur at such an angle that the first finger is opposed to the other fingers.
Metacarpophalangeal joints (MCP) of the hand
The metacarpophalangeal joints (MCP) of the hand provide flexibility to the hand. The projection of the PFJ of the II-V fingers is at the level of the distal fold of the bent hand. With atrophy of the interaxial and lumbrical muscles, a so-called “hollow” hand is formed. With flexion contracture and subluxations in the PFJ with hyperextension, the fingers of the hand deviate to the ulnar side and the hand acquires a “walrus fin” deformity. During examination, changes in the contours and volume of the joints are determined, and upon palpation, the presence of synovitis is determined. The following movements are possible in the PFJ: flexion - extension, abduction (spreading the fingers of the entire hand), adduction (moving the fingers towards the third finger). The combination of these movements allows for circular movements.The range of movements in the PFJ of the II-V fingers is determined when the straightened fingers are positioned at an angle of 180° (0°) relative to the wrist. If mobility in these joints is limited, the patient cannot clench his hand into a fist. When measuring the range of motion with an inclinometer, the movable branch is located along the wrist. With full flexion, the wrist and fingers form an angle of 90°, with full extension - up to 30°. The amplitude of abduction and adduction varies from joint to joint and averages 30-40°.
The MCP joint of the thumb is examined from the dorsal and palmar surfaces. Abduction and adduction occur in the metacarpophalangeal joint of the first finger. When abducted, the first finger forms a right angle (90°) with the outer edge of the wrist; when adducted, it forms an acute angle (45°). Palmar flexion or opposition and dorsiflexion occur in the same joint. With full palmar flexion, the tip of the thumb is in contact with the other fingers of the hand. The flexion angle, measured by an inclinometer located in the sagittal plane, is 70°. The dorsal extension of the PFJ is insignificant and amounts to only 10°.
Interphalangeal joints (IPJs) are involved in flexion and extension of the fingers. Examination of these joints reveals deformation and exudative phenomena, as well as Heberden's nodes - in the area of the base of the nail phalanges and Bouchard's nodes - in the area of the proximal interphalangeal joints (PIPJ).
Flexion contracture of the MCP joint in combination with hyperextension of the PIP joint and flexion contracture of the distal interphalangeal joints (DIPJ) is described as a gooseneck deformity. Flexion contracture of the PIPJ in combination with hyperextension of the DMJ is described as a “button loop” deformity. Hyperextension in the PIPJ and flexion contracture of the DIPJ of the II-V fingers leads to a deformation of the hand called “cock paw”.
The approximate amount of flexion in the MFS is determined by the ability to compress the hand into a fist. Normally, the palmar surface of the nail phalanges fits tightly to the palm. The limitation of this movement cannot fully indicate a violation of the flexion of the hand due to the MFS, since the PFJ also takes part in this movement. Full clenching of the fingers into a fist is assessed as 100%. Impossibility of compression - 0%. Between these extreme boundaries intermediate degrees are established. If the fingertips do not reach the surface of the thenar and hypothenar by 2 cm, then the compression of the hand into a fist is 75%, if this distance is 5-6 cm, the compression of the hand into a fist is estimated at 50%, and at a distance of 10-12 cm - 25%.
Flexion and extension are possible in the PIPJ and DIPJ. The angle of flexion in the PIPJ is usually 100-120°, in the DIPJ - 45-90° (in the initial extended position - 0°). The extension angle in the PIPJ does not exceed 10°, in the DIPJ - about 30°. Flexion of the IMF of the first finger is possible by 80-90°, extension - by 20-35°.
V.I. Mazurov
