Briefly everything about human muscles. How do human muscles work? Muscle groups by structural features

The anatomy of human muscles, their structure and development, perhaps, can be called the most pressing topic that arouses maximum public interest in bodybuilding. Needless to say, the structure, work and function of muscles is a topic that a personal trainer should pay special attention to. As in the presentation of other topics, we will begin the introduction to the course with a detailed study of the anatomy of muscles, their structure, classification, work and functions.

Maintaining a healthy lifestyle, proper nutrition and systematic physical activity help develop muscles and reduce body fat levels. The structure and work of human muscles will be understood only by sequentially studying first the human skeleton and only then the muscles. And now that we know from the article that it also functions as a frame for attaching muscles, it’s time to study what main muscle groups form the human body, where they are located, what they look like and what functions they perform.

Above you can see what the human muscle structure looks like in the photo (3D model). First, let's look at the musculature of a man's body with terms applied to bodybuilding, then the musculature of a woman's body. Looking ahead, it is worth noting that the muscle structure of men and women is not fundamentally different; the musculature of the body is almost completely similar.

Human muscle anatomy

Muscles are called organs of the body that are formed by elastic tissue, and the activity of which is regulated by nerve impulses. The functions of muscles include movement and movement in space of parts of the human body. Their full functioning directly affects the physiological activity of many processes in the body. Muscle function is regulated by the nervous system. It promotes their interaction with the brain and spinal cord, and also participates in the process of converting chemical energy into mechanical energy. The human body forms about 640 muscles (various methods of counting differentiated muscle groups determine their number from 639 to 850). Below is the structure of human muscles (diagram) using the example of a male and female body.

Muscle structure of a man, front view: 1 – trapezoid; 2 – serratus anterior muscle; 3 – external oblique abdominal muscles; 4 – rectus abdominis muscle; 5 – sartorius muscle; 6 – pectineus muscle; 7 – long adductor muscle of the thigh; 8 – thin muscle; 9 – tensor fascia lata; 10 – pectoralis major muscle; 11 – pectoralis minor muscle; 12 – anterior head of the humerus; 13 – middle head of the humerus; 14 – brachialis; 15 – pronator; 16 – long head of the biceps; 17 – short head of the biceps; 18 – palmaris longus; 19 – extensor muscle of the wrist; 20 – adductor carpi longus muscle; 21 – long flexor; 22 – flexor carpi radialis; 23 – brachioradialis muscle; 24 – lateral thigh muscle; 25 – medial thigh muscle; 26 – rectus femoris muscle; 27 – long peroneal muscle; 28 – extensor digitorum longus; 29 – tibialis anterior muscle; 30 – soleus muscle; 31 – calf muscle

Muscle structure of a man, rear view: 1 – posterior head of the humerus; 2 – teres minor muscle; 3 – teres major muscle; 4 – infraspinatus muscle; 5 – rhomboid muscle; 6 – extensor muscle of the wrist; 7 – brachioradialis muscle; 8 – flexor carpi ulnaris; 9 – trapezius muscle; 10 – rectus spinalis muscle; 11 – latissimus muscle; 12 – thoracolumbar fascia; 13 – femoral biceps; 14 – adductor magnus muscle of the thigh; 15 – semitendinosus muscle; 16 – thin muscle; 17 – semimembranosus muscle; 18 – calf muscle; 19 – soleus muscle; 20 – long peroneal muscle; 21 – abductor hallucis muscle; 22 – long head of the triceps; 23 – lateral head of the triceps; 24 – medial head of the triceps; 25 – external oblique abdominal muscles; 26 – gluteus medius muscle; 27 – gluteus maximus muscle

The structure of a woman's muscles, front view: 1 – scapular hyoid muscle; 2 – sternohyoid muscle; 3 – sternocleidomastoid muscle; 4 – trapezius muscle; 5 – pectoralis minor muscle (not visible); 6 – pectoralis major muscle; 7 – serratus muscle; 8 – rectus abdominis muscle; 9 – external oblique abdominal muscle; 10 – pectineus muscle; 11 – sartorius muscle; 12 – long adductor muscle of the thigh; 13 – tensor fascia lata; 14 – thin muscle of the thigh; 15 – rectus femoris muscle; 16 – vastus intermedius muscle (not visible); 17 – vastus lateralis muscle; 18 – vastus medialis muscle; 19 – calf muscle; 20 – tibialis anterior muscle; 21 – long extensor of the toes; 22 – long tibialis muscle; 23 – soleus muscle; 24 – anterior bundle of deltas; 25 – middle bundle of deltas; 26 – brachialis muscle; 27 – long biceps bundle; 28 – short biceps bundle; 29 – brachioradialis muscle; 30 – extensor carpi radialis; 31 – pronator teres; 32 – flexor carpi radialis; 33 – palmaris longus; 34 – flexor carpi ulnaris

Muscle structure of a woman, rear view: 1 – posterior bundle of deltas; 2 – long triceps bundle; 3 – lateral triceps bundle; 4 – medial triceps bundle; 5 – extensor carpi ulnaris; 6 – external oblique abdominal muscle; 7 – extensor of the fingers; 8 – fascia lata; 9 – biceps femoris; 10 – semitendinosus muscle; 11 – thin muscle of the thigh; 12 – semimembranosus muscle; 13 – calf muscle; 14 – soleus muscle; 15 – short peroneus muscle; 16 – flexor pollicis longus; 17 – teres minor muscle; 18 – teres major muscle; 19 – infraspinatus muscle; 20 – trapezius muscle; 21 – rhomboid muscle; 22 – latissimus muscle; 23 – spinal extensors; 24 – thoracolumbar fascia; 25 – gluteus minimus; 26 – gluteus maximus muscle

Muscles have quite a variety of shapes. Muscles that share a common tendon but have two or more heads are called biceps (biceps), triceps (triceps), or quadriceps (quadriceps). The functions of the muscles are also quite diverse, these are flexors, extensors, abductors, adductors, rotators (inward and outward), levator, depressor, straightener and others.

Types of muscle tissue

Characteristic structural features allow us to classify human muscles into three types: skeletal, smooth and cardiac.

Types of human muscle tissue: I - skeletal muscles; II - smooth muscles; III - cardiac muscle

• Skeletal muscles. The contraction of this type of muscle is completely controlled by the person. Combined with the human skeleton, they form the musculoskeletal system. This type of muscle is called skeletal precisely because of its attachment to the bones of the skeleton.
• Smooth muscles. This type of tissue is present in the cells of internal organs, skin and blood vessels. The structure of human smooth muscles implies that they are located mostly in the walls of hollow internal organs, such as the esophagus or bladder. They also play an important role in processes that are not controlled by our consciousness, for example in intestinal motility.
• Heart muscle (myocardium). The work of this muscle is controlled by the autonomic nervous system. Its contractions are not controlled by human consciousness.

Since the contraction of smooth and cardiac muscle tissue is not controlled by human consciousness, the emphasis in this article will be focused specifically on skeletal muscles and their detailed description.

Muscle structure

Muscle fiber is a structural element of muscles. Separately, each of them represents not only a cellular, but also a physiological unit that is capable of contracting. The muscle fiber has the appearance of a multinucleated cell; the fiber diameter ranges from 10 to 100 microns. This multinucleated cell is located in a membrane called the sarcolemma, which in turn is filled with sarcoplasm, and within the sarcoplasm there are myofibrils.

Myofibril is a thread-like formation that consists of sarcomeres. The thickness of myofibrils is usually less than 1 micron. Taking into account the number of myofibrils, white (aka fast) and red (aka slow) muscle fibers are usually distinguished. White fibers contain more myofibrils but less sarcoplasm. It is for this reason that they contract faster. Red fibers contain a lot of myoglobin, which is why they got their name.

Internal structure of human muscle: 1 – bone; 2 – tendon; 3 – muscular fascia; 4 – skeletal muscle; 5 – fibrous membrane of skeletal muscle; 6 – connective tissue membrane; 7 – arteries, veins, nerves; 8 – bundle; 9 – connective tissue; 10 – muscle fiber; 11 – myofibril

The work of muscles is characterized by the fact that the ability to contract faster and stronger is characteristic of white fibers. They can develop force and speed of contraction 3-5 times higher than slow fibers. Physical activity of the anaerobic type (working with weights) is performed primarily by fast-twitch muscle fibers. Long-term aerobic physical activity (running, swimming, cycling) is performed primarily by slow-twitch muscle fibers.

Slow fibers are more resistant to fatigue, while fast fibers are not adapted to prolonged physical activity. As for the ratio of fast and slow muscle fibers in human muscles, their number is approximately the same. In most of both sexes, about 45-50% of the muscles of the limbs are slow muscle fibers. There are no significant gender differences in the ratio of different types of muscle fibers in men and women. Their ratio is formed at the beginning of a person’s life cycle, in other words, it is genetically programmed and practically does not change until old age.

Sarcomeres (components of myofibrils) are formed by thick myosin filaments and thin actin filaments. Let's look at them in more detail.

Actin– a protein that is a structural element of the cell cytoskeleton and has the ability to contract. It consists of 375 amino acid residues and makes up about 15% of muscle protein.

Myosin- the main component of myofibrils - contractile muscle fibers, where its content can be about 65%. The molecules are formed by two polypeptide chains, each of which contains about 2000 amino acids. Each of these chains has a so-called head at the end, which includes two small chains consisting of 150-190 amino acids.

Actomyosin– a complex of proteins formed from actin and myosin.

FACT. For the most part, muscles consist of water, proteins and other components: glycogen, lipids, nitrogen-containing substances, salts, etc. Water content ranges from 72-80% of the total muscle mass. Skeletal muscle consists of a large number of fibers, and characteristically, the more fibers there are, the stronger the muscle.

Muscle classification

The human muscular system is characterized by a variety of muscle shapes, which in turn are divided into simple and complex. Simple: spindle-shaped, straight, long, short, wide. Complex muscles include the multicipital muscles. As we have already said, if the muscles have a common tendon, and there are two or more heads, then they are called biceps (biceps), triceps (triceps) or quadriceps (quadriceps), and multitendon and digastric muscles are also multi-headed. The following types of muscles with a certain geometric shape are also complex: quadrate, deltoid, soleus, pyramidal, round, serrated, triangular, rhomboid, soleus.

Main functions muscles are flexion, extension, abduction, adduction, supination, pronation, raising, lowering, straightening and more. The term supination means outward rotation, and the term pronation means inward rotation.

By grain direction muscles are divided into: rectus, transverse, circular, oblique, unipennate, bipennate, multipennate, semitendinosus and semimembranosus.

In relation to the joints, taking into account the number of joints through which they are thrown: single-joint, double-joint and multi-joint.

Muscle work

During contraction, actin filaments penetrate deep into the spaces between myosin filaments, and the length of both structures does not change, but only the total length of the actomyosin complex is reduced - this method of muscle contraction is called sliding. The sliding of actin filaments along myosin filaments requires energy, and the energy required for muscle contraction is released as a result of the interaction of actomyosin with ATP (adenosine triphosphate). In addition to ATP, water plays an important role in muscle contraction, as well as calcium and magnesium ions.

As already mentioned, muscle function is completely controlled by the nervous system. This suggests that their work (contraction and relaxation) can be controlled consciously. For the normal and full functioning of the body and its movement in space, muscles work in groups. Most of the muscle groups in the human body work in pairs and perform opposite functions. It looks like this: when the “agonist” muscle contracts, the “antagonist” muscle stretches. The same is true vice versa.

• Agonist- a muscle that performs a specific movement.
• Antagonist- a muscle that performs the opposite movement.

Muscles have the following properties: elasticity, stretching, contraction. Elasticity and stretching give the muscle the ability to change in size and return to its original state, the third quality makes it possible to create force at its ends and lead to shortening.

Nerve stimulation can cause the following types of muscle contraction: concentric, eccentric and isometric. Concentric contraction occurs in the process of overcoming the load when performing a given movement (lifting up when pulling up on a bar). Eccentric contraction occurs in the process of slowing down movements in the joints (lowering down when pulling up on a bar). Isometric contraction occurs at the moment when the force created by the muscles is equal to the load exerted on them (keeping the body hanging on the bar).

Muscle functions

Knowing the name and location of this or that muscle or group of muscles, we can move on to studying the block - the function of human muscles. Below in the table we will look at the most basic muscles that are trained in the gym. As a rule, six main muscle groups are trained: chest, back, legs, shoulders, arms and abs.

FACT. The largest and strongest muscle group in the human body is the legs. The largest muscle is the gluteus. The strongest is the calf muscle; it can hold weight up to 150 kg.

Conclusion

In this article, we examined such a complex and voluminous topic as the structure and functions of human muscles. When we talk about muscles, we of course also mean muscle fibers, and the involvement of muscle fibers in the work involves the interaction of the nervous system with them, since the execution of muscle activity is preceded by the innervation of motor neurons. It is for this reason that in our next article we will move on to consider the structure and functions of the nervous system.

To each beginner It will be useful for a bodybuilder, and simply curious people, to learn the anatomy of human skeletal muscles in order to navigate security forces training programs, especially when it comes to, and also so that we understand each other when you ask questions about how you can pump up this or that muscle group.

In addition, knowing your muscles will help you better in the future. work through with the help of selected exercises all parts of the body, thanks to the fact that you will no longer have one-sided understanding devices of muscle groups.

For example, many athletes are still in pursuit of spherical shoulders, they don’t know that the deltoids consist of the front, middle and back heads, so in order to pump up your shoulders like a ball, you need to do everything exercises, which develop all three deltoids, and not just the favorite barbell/dumbbell press up with an emphasis on the front and middle deltas.

In total there are more than 600 skeletal muscles, and they all consist of fibers of different lengths (up to 13 cm) and thickness (from 40 to 80 microns), but we will consider only the main groups, since knowledge of the rest does not carry any practical benefits for bodybuilding.

Major human muscle groups

Anatomy and function of the main human skeletal muscles, using the example of a bodybuilder, with colorful drawing and numbering of muscles, for even greater clarity. And at the end there is a single photo with captions of muscle groups bodybuilder.

Neck

Neck connects the head to the body, main function– providing balance and head movement, as well as assistance in swallowing and pronouncing sounds.

• Omohyoid muscle
• Sternohyoid
• Sternocleidomastoid
• Trapezius muscle

Muscles of the human neck (side view and back view)

Breast

Pectoral muscles occupy a large part of the front part of the body, they are attached to the humerus, collarbone, and ribs. Carry out rotating the arms inward, pulling the torso when climbing, pulling the shoulder blade forward and down, and also helps the diaphragm to breathe.

• Pectoralis major muscle
• Pectoralis minor muscle
• Serratus anterior muscle
• Subclavius ​​muscle
• Intercostal muscles

Anatomy of the human pectoral muscles

Deltas

The shape resembles triangle, the Greek letter "delta". They will feel in abduction of the arm to the sides, as well as extension and flexion of the shoulder. The front deltas pull the arm forward, and the rear ones pull the arm back.

• Anterior delta
• Middle delta
• Rear delta

Anatomy of human deltas (shoulders)

Biceps

Muscles biceps consist of a long and a short head, joining together to form abdomen, which is attached to the tuberosity of the radial bone by a tendon.

Anatomy of the biceps (short and long heads)

Function biceps - ensure flexion of the shoulder at the shoulder joint, and the forearm at the elbow.

• Long head (on the outer part of the arm)
• Short head (on the inside of the arm)

Forearm

Muscles forearms- small muscle groups located between the elbow and wrist, they are divided into the posterior anterior group, each of which has its own superficial and deep layers.

Carry out extension and flexion of the hand and fingers, and also perform penetrating and supinating movements of the radius.

• Extensor carpi radialis
• Abductor pollicis longus muscle
• Pronator teres
• Palmaris longus muscle
• Extensor carpi radialis brevis
• Extensor pollicis brevis
• Flexor carpi
• Brachioradialis muscle
• Flexor carpi ulnaris

Anatomy of the forearm (brachialis, radialis, flexors)

Press

Abdominal Press rotates the body to the side (sideways, forward, backward), creates intra-abdominal pressure, protecting internal organs from damage, forms posture, keeps the spine in a straight position.

Human abdominal anatomy

• Rectus abdominis muscle
• External oblique muscle
• Internal oblique muscle
• Transverse abdominis muscle

Thigh muscles

Carry out abduction, extension and rotation of the thigh outward, pulling the thigh towards the body, extension of the lower leg at the knee and its rotation inward, and also keep the body in equilibrium and stretch the fascia lata of the thigh, thereby strengthening the knee joint.

Anterior thigh muscle group

• Tailoring
• Quadriceps (quadriceps)
• Straight
• Lateral wide
• Medial wide
• Intermediate wide

Anatomy of the anterior thigh muscles

Posterior thigh muscles

• Biceps femoris
• Common tendon
• Semitendinosus
• Semimembranosus

Anatomy of the posterior thigh muscles

Medial thigh muscle group

• Thin
• Comb
• Long adductor
• Short adductor
• Adductor magnus

Anatomy of the muscles of the medial thigh

Shin and calves

Shin occupies part of the leg, starting from the knee to the heel, consists of the tibia and fibula. Main function extension of the foot and toes, as well as adduction and rotation of the foot outward.

Calf muscles refers to the two-headed ones, they consist of a medial and lateral head, thanks to them a person takes a stable position in space, maintains body balance, equilibrium, and can rotate ankle joint, raise your heels, bend your feet.

• Peroneus longus muscle
• Medial head of the gastrocnemius muscle
• Tibialis anterior muscle
• Soleus muscle
• Peroneus brevis muscle
• Extensor digitorum longus
• Superior extensor retinaculum
• Tibialis anterior tendon
• Inferior extensor retinaculum

Anatomy of the lower leg muscles (posterior and anterior group)

Back

Back muscles perform a supporting role to fix the spine in a stationary state, by giving a stable position vertebrae, making it possible to perform body turns, flexion, extension and bending, and also support the natural bends (curvature) of the back and perform the role shock absorbers when performing movements that create vibration and shock to the spine.

• Teres minor muscle
• Big round
• Cavity muscle
• Rhomboid muscle
• Trapezius muscle
• Extensor spinae
• Latissimus dorsi muscles
• Thoracolumbar fascia
• External oblique muscles

Human back muscle anatomy

Triceps

Anatomical structure of the human triceps

Triceps has three heads, which is why it is called triceps shoulder muscle, attached to the olecranon process of the ulna using a flat, wide tendon.

Provides extension of the forearm, as well as bringing the arm to the body and moving the arm back.

• Lateral (lateral) head
• Long (back) head
• Middle (medial) head

Buttocks

Quadrangular large gluteal muscles attached symmetrically to the bones of the spine, pelvis and femur. Carry out function hip extension, external rotation of the hip, abduction and adduction of the hip to the center, and also help to straighten the torso while securing the hip and stabilize knee joint (due to the tension of the fascia lata of the thigh).

• Gluteus minimus
• Gluteus medius
• Gluteus maximus muscle

Anatomy of the human gluteal muscles

Proportionally harmonious, beautiful muscles are the goal of any bodybuilder, especially when it comes to competitive level where proportions can decide whether an athlete becomes a champion or not. That is why, below, we want to provide a list effective exercises, for each muscle group, with the help of which you can “carve” yourself the muscle size that you want.

Anatomy of a bodybuilder's body

Exercises to develop skeletal muscles

All development exercises skeletal muscles can be divided into two types, insulating(use one joint), and basic(involve two or more joints). You should first of all focus on training a particular muscle group on the basic ones, because they are most effective raise muscle mass.

Human Skeletal Muscle Anatomy

Isolation exercises are good for separation, muscle relief, that on initial The level of training of a bodybuilder should not worry at all.

Trapeze

Muscles trapezoids refers to the upper back, feel in raising and lowering the shoulders.

The best exercise for training the trapezius is.

Exercises for trapezius muscles

Latissimus dorsi muscles

Attached triangular shape of the back (especially when the waist is narrow), the wider the back, the more lats muscles.

Main function– adduction and extension of the shoulder, internal circular movement (rotation) of the shoulder, and also helps lower the shoulder girdle.

The best exercise for the back is.

Exercise for the latissimus dorsi muscles

Longus dorsi muscle

This muscle group is one of the strongest in the human body, located in the form of two “ pillars", which stretch along the lumbar region.

Main function- holds the muscle corset, and is also responsible for flexion and extension of the torso.

If you have problems with the spine, or just a weak back, then you simply need strengthen these muscles.

The best exercise to strengthen the “pillars” is.

Hyperextension for long back muscles

Pectoral muscles

Breasts the muscles are involved in the process of inhalation, and also pull the scapula forward, down and inward and indirectly contribute to the elevation of the ribs.

Basic exercise for the pectoral muscles

Abdominal Press

Press- one of the most “capricious” muscles in the human body. To have beautiful sculpted abs, it is necessary not only to train him, but also keep an eye on food(a layer of fat can simply hide sculpted abs). For those interested, you can read in detail about how to build beautiful abs.

Main function– stabilization of the abdominal muscles.

One of the most effective and proven exercises– at an angle downward and .

Abdominal exercise in the gym

Delts or shoulders

Deltas are divided into three main bundles: anterior, middle and posterior.

Function in the body - raising, lowering, and rotating the arm.

If you want to have big, pumped up shoulders do barbell lifts sitting/standing behind your head and with free weight, and also use for additional, isolated load on the rear delts.

Basic exercise for deltoids (shoulders)

Biceps

Biceps participates in the flexion of the arm, consists of from a long (external) and short (internal) head.

One of the most effective exercises in the gym to build big and strong arms - (with a straight bar).

Exercise for developing biceps

Triceps

Triceps performs the function of arm extension, consists of 3-ex main bunches: internal, medial and lateral.

The best exercises to pump up the mass (volume) of the triceps - on a horizontal bench and push-ups on the uneven bars.

Basic exercise for developing triceps

Forearms

Forearm is responsible for moving the fingers, rotating the hand and clenching the hand into a fist.

How stronger forearm, the more weight the athlete can lift in a separate exercise, when the load is on the corresponding muscles, for example, in, and also with the help of strong grip you can hang for a long time on the horizontal bar, which will greatly facilitate the process of pull-ups.

The best exercises There is no way to increase forearm strength, since they need to be trained comprehensively, in different directions and at different angles (as they do arm wrestlers), concerning volume forearm, then the leading position is occupied by the exercise and extension of the arms at the wrists.

Exercise to develop powerful triceps

Gluteal muscles

Buttocks- one of the largest muscles in the body, participate in bending and straightening the body, and is also responsible for turning the hip inward and outward.

Consists of the gluteus minimus, medius and maximus muscles.

The best exercise for pumping up elastic buttocks - deep.

Basic exercise for the gluteal muscles

Biceps hamstrings

Biceps hamstrings participates in the rotation and flexion of the lower leg, as well as in the extension of the hip and together with the gluteus maximus muscle of the trunk.

biceps femoris muscle, consists of of two heads - long and short.

Isolated exercises for hamstrings

Quadriceps

Quadriceps comprises 4-ex heads - rectus, vastus medialis, vastus laterally, and vastus intermedius muscles, which is why it is called the quadriceps.

Quadriceps the muscle is involved in extension of the tibia at the knee joint and flexion of the hip.

Everything is the same as with the hamstrings - first you pump up the rough muscle mass of the legs by squatting with a barbell on your shoulders, and then start sharpen her.

The best isolation exercise for pumping up large quadriceps is considered.

An effective exercise for quadriceps relief

Caviar

Calf muscle the most resilient in our body, responsible for flexion and extension of the foot, as well as for stabilizing the body when walking and running.

It is quite difficult to increase its size, because our body made it anatomically hardy. And as you know, endurance muscles are not famous for their volumes, therefore, in order to enlarge the calf muscles, it is necessary to load them with heavy weights, shock them with a load, this is the only way to stimulate muscle growth of the lower leg.

Select the working weight on the machine in the range 15-20 repetitions in 3-4 approaches so that the last repetitions are difficult to complete.

The best exercise for pumping up your calves is on the machine.

Exercise for calf muscles

The given exercises for skeletal muscles are some of the most effective of their kind, so they should definitely be included in your training program on bodybuilding.

The more muscle group, the more time it takes to recovery her after the training. That is why we strongly recommend that you train according to cyclic method, when trying to progress in heavy basic exercises (deadlift, squats with a barbell, bench press), that is, use light, medium and heavy training, or build training according to split system(suitable for advanced athletes).

Quantity repetitions in mass exercises, should be in the range 6-12 , in 3-4 approaches, with break 2-2.5 minutes. If your goal is to increase strength, then reduce the number of repetitions to 2-4 , and increase the rest time between approaches to 3-5 minutes.

Clear vision and understanding training process, will bring you the best results in bodybuilding, your training will be more effective and safe.

Movement is the most important function of the body. It is carried out by the musculoskeletal system, which includes bones that serve as a kind of levers, and muscles that activate these levers. Muscles contract on command from the central nervous system. When a muscle contracts, it shortens, causing the bones to which it is attached to move closer together. This changes the position of the body parts relative to each other and relative to the surface on which the body rests.

There are about 400 skeletal muscles in the human body, which are involved in performing various movements due to their ability to contract. Muscles make up about 35-40% of an adult’s body weight, but in children and the elderly this figure decreases to 25%, and in athletes it reaches 50%. The relief of the human body is determined by the location and degree of muscle development, which is easy to see when comparing the body of an athlete and an ordinary individual.

Structure of skeletal muscle

Skeletal muscle is built from so-called striated muscle tissue. Its main working element is striated muscle fiber, the length of which can range from several millimeters to 10-12 cm with a diameter of 12-100 microns. Muscle fiber contains special formations - myofibrils, which determine its contraction. Myofibrils are built from regularly alternating dark and light disks, which makes the fiber "striped".

Muscle fibers, with the help of connective tissue, are combined into bundles that form the contractile part of the muscle, called the body, or abdomen. For attachment to bones, skeletal muscle has tendons, built from dense connective tissue rich in collagen and characterized by high tensile strength. At the places of attachment of muscle tendons on the bones there are various processes, roughnesses, tubercles and pits, which are more pronounced the larger and stronger the muscle attached to them. On the outside, each skeletal muscle is covered with a dense sheath - muscle fascia.

The nerves that carry commands from the central nervous system to the skeletal muscle are divided into thin branches that reach each muscle fiber. On the muscle fiber they form a motor nerve ending, which serves to transmit a nerve impulse that causes contraction of the fiber. Since there is a motor nerve ending on every muscle fiber, skeletal muscle contraction occurs quickly, strongly, and clearly obeys the will of the person. This consumes a lot of energy, of which only 1/4 is converted into mechanical work, and the remaining 3/4 into heat. It is muscle contraction that serves as the main source of heat formation in the body.

The muscle also receives impulses from the nervous system that regulate its tone, metabolism, growth and development. Information about the state of muscle fibers is perceived by sensitive nerve endings, which constantly signal to the central nervous system about the degree of tonic muscle tension. In small muscles involved in performing fine and precise movements, the number of sensitive nerve endings is much greater than in large ones.

The structure of muscle tissue of internal organs and blood vessels

In addition to skeletal muscles, muscle tissue is found in the walls of internal organs and blood vessels. This tissue has a different structure and is called smooth muscle tissue. The cells of this tissue are spindle-shaped and are located in layers of organs. A specific feature of smooth muscles is their ability to perform automatic (independent of human will) contractions, which are tonic in nature (slowed down and spread to the entire layer of cells). The autonomic (vegetative) nervous system regulates the activity of smooth muscles. Peristaltic movements of the intestines, changes in the lumen of the bronchi, gland ducts, increased vascular tone, etc. are carried out by contraction of smooth muscle tissue in the walls of these organs. Particularly distinguished is the muscular tissue of the heart, which is similar in structure to striated tissue, but contracts automatically and is innervated by the autonomic nervous system.

Classification of skeletal muscles

Classification of skeletal muscles is carried out according to a number of characteristics.

By shape and size
Depending on the shape and size, there are long and short, rhomboid, quadratus, trapezius, etc. muscles. The muscles located on the body usually have a flat shape; they are larger and occupy larger areas. The muscles of the limbs are distinguished by their length, fusiform shape, and often feathery structure, when the bundles of muscle fibers are located at an angle to the longitudinal axis of the muscle (this increases the force developed by the muscles). Muscles with oblique direction of fibers attached to the tendon on one side are called unipennate, on both sides - bipennate.

Differences in muscle shape are closely related to their functional characteristics. Long, thin muscles with a small area of ​​attachment to bones (for example, the muscles that move the fingers) are involved in precise movements with a large amplitude. Short, thick muscles can overcome significant resistance, but their range of motion is small. There are many such muscles in the pelvis and spine.

By grain direction
Based on the direction of the fibers, rectus muscles are distinguished (muscle fibers are located parallel to the longitudinal axis of the body), oblique, transverse and circular. Thus, the anterior and lateral walls of the abdomen are formed by the rectus abdominis muscle, the external and internal oblique muscles, and the transverse abdominal muscle. The circular muscles form sphincters (sphincters) located around natural openings and canals; when they contract, the holes close. These include, for example, the orbicularis oculi muscle and the orbicularis oris muscle.

By function performed
According to function, muscles are divided into flexors and extensors, abductors and adductors, external rotators (supinators) and internal rotators (pronators). By position, they distinguish between superficial and deep, external and internal muscles, etc. An indication of the function and location of the muscle is often included in its name: for example, on the anterior surface of the forearm there are the pronator teres and quadratus muscles, the radial and ulnar flexors of the wrist, the superficial and deep flexors fingers. Some muscles are named according to their external shape (deltoid, rhomboid, quadrate, serratus, etc.), number of heads (biceps, triceps, quadriceps), position (intercostal, popliteal), place of origin and attachment (brachioradialis, sterno -cleidomastoid).

In relation to the joints
In relation to the joints, single-joint, two-joint and multi-joint muscles are distinguished - depending on how many joints they directly act on. Multi-joint muscles are usually longer and more superficial than single-joint muscles. By region of the body, the muscles of the trunk, head, neck, upper and lower extremities are distinguished.

By interaction with other muscles
Since the performance of any movement is the result of the cooperative action of a number of muscles, it is customary to distinguish synergistic and antagonistic muscles: the former jointly perform the same movement in the joint (for example, flex the hand), the latter participate in opposite movements (for example, flex and extend brush). As a rule, synergistic muscles are located on one surface of the limb, and antagonist muscles are located on opposite surfaces (for example, flexors are on the anterior surface of the shoulder and forearm, extensors are on the posterior surface). The concept of synergism and antagonism of muscles refers to their functional characteristics. Thus, muscles that work as synergists in one movement can be antagonists in another movement. Coordination of muscle work is achieved through coordination of their contractions by the nervous system.

Muscle assist devices

To facilitate and increase the efficiency of work, muscles have auxiliary devices: fascia, synovial bursae and muscle blocks.

Fascia is a dense connective tissue membrane that covers individual muscles or their groups in the form of cases. Fascia delimits muscles, promoting their independent contraction. At the same time, they serve as attachment sites for muscle fibers and contribute to the transmission of muscle forces to bone levers. Synovial bursae are closed cavities filled with a special fluid. They are located between muscles and bones in places of greatest mechanical mobility of tissues. These devices serve to facilitate the sliding of muscles during their contraction. There are many synovial bursae in the area of ​​the knee and shoulder joints. In the area of ​​the joints of the hand and foot, synovial membranes surround numerous tendons, facilitating and directing their movements. Blocks form in those places where the muscle tendon changes direction, throwing itself over the bone.

Vessels and nerves in muscle tissue

Vessels and nerves usually penetrate the muscle from the inside, often in one, less often in several places, called the gate of the muscle. In the muscle, the blood vessels branch into tiny capillaries, which entwine each muscle fiber in a dense network. Blood supplies nutrients and oxygen to the muscle. Due to the fact that muscles are abundantly supplied with blood and are easily accessible for action, they are one of the most common routes for introducing drugs into the human body. When administered intramuscularly, the drug quickly enters the bloodstream and spreads throughout the body.

Biomechanical principles of muscle function

The work of muscles is considered from the standpoint of biomechanics. When contracting, a muscle performs mechanical work, defined as the product of the muscle force and the distance the load moves. The strength of a muscle depends on its cross-sectional area and the number of muscle fibers involved in contraction. The larger the diameter of the muscle, the stronger it is. Remember how effectively you can demonstrate trained biceps (that is, the strength of the biceps brachii muscle, from the Latin musculus biceps brachii) by bending your arm at the elbow joint.

To characterize any movement and the muscles involved in it, the principle of leverage is used. In this case, the lever of the first kind is called the balance lever (for example, the balance of the head relative to the spine), and the lever of the second kind is called the force lever (foot during tiptoeing) or the speed lever (movement of the arm in the elbow joint). The muscular system constantly works against the force of gravity. Biomechanically, any movement of the body in space, as well as maintaining its posture, is the result of complex coordination of contraction of individual muscles and coordination of the developed muscle efforts with the gravitational forces acting on the body. Knowledge of the laws of biomechanics is especially important when studying sports and other professional movements.

Under the influence of physical training, the number of muscle fibers increases, which become thick and contain a large number of myofibrils, which indicates the good development of their contractile apparatus. The structure of nerve endings is improved, and the blood supply to the muscles improves. As a result of training, the cross-sectional area of ​​the muscle increases, which causes an increase in its strength. Special exercises using machines allow you to develop certain muscle groups. Thus, a person can change the relief of his body, modeling it at his own request.

When a person moves, he usually does not even suspect that a huge number of mechanical and chemical processes are happening in his body.

Thousands of reactions add up to the contraction of muscle tissue cells, and we go to work or do something more enjoyable.

Actually, even when a person sleeps, the muscles work: the sleeper breathes, his heart beats.

So how do our muscles work?

ATP and ADP

The main thing you need for muscle function is energy. The law of conservation of which no one has canceled.

The only source of energy located directly in the muscles is a substance with a difficult name to pronounce adenosine triphosphoric acid. For the convenience of the uninitiated, chemists call it with three letters - ATP. When ATP is broken down, quite a lot of energy is released and adenosine diphosphoric acid. Or for short - yes, that's right, ADF.

Three more letters

But here's the problem - the ATP reserve in the muscles lasts literally for a split second. A special substance also monitors the supply of ATP in the muscles, creatinine phosphate. It is also called by three letters: KrF. It reduces ADP to ATP and allows you to last for some time. This is an anaerobic process, it occurs without the participation of oxygen.

But KrF does not last long - only 5-6 seconds. But the process of replenishing muscles with energy using KrF the most efficient and fastest. And these seconds are enough for the starting jerk, for the initial movement, until the other processes of supplying energy to the muscles have time to turn on. The greater the muscle mass, the greater the KrF. It’s clear why the “jocks” are so strong - and why they don’t last long.

Glycogen

If we need to work for more than 5-6 seconds (I understand that I’m usually lazy, but we have to), then the next system turns on. It is called glycolytic. Its essence is that the body begins to break down glucose and the reserve carbohydrate glycogen stored mainly in the liver. That is, carbohydrates.

This process also happens without breathing. But it only lasts about three minutes. Therefore, if you are chasing someone, try to catch up with him during this time, otherwise it will be more difficult.

Aerobic oxidation

If we have to work for more than three minutes (this happens in life), then we will have to breathe. For long-term muscle work is ensured by a process called oxidative phosphorylation.

It is only possible with sufficient oxygen supply to muscles. In this process, both carbohydrates and fats are broken down. If our work is intense and powerful, then carbohydrates are burned, and, if the work is low-intensity and long, then fats are burned.

Before plunging into the world of bodybuilding, it is necessary to understand in theory how our muscles work, and then create a bodybuilder’s body in the gym. Of course, you may not know this and achieve good results in bodybuilding, but still, any self-respecting bodybuilder who approaches his occupation professionally must know how his body works.

The article was written in accessible language, nothing superfluous, all the essentials that an athlete should know.

How muscles work

There are three types of muscles in the human body: smooth muscle, skeletal muscle, and cardiac muscle. Smooth muscle covers our internal organs, and we cannot pump it up. Skeletal muscles are the same muscles that bodybuilders pump every day.

Skeletal muscle is made up of fibers, which in turn are made up of muscle cells. Each muscle cell has two nuclei that are responsible for division and repair. The so-called myofibrils (threads), which are contained in muscle cells, are responsible for muscle contraction. The number of myofibrils in a muscle cell can reach up to several thousand. Thus, muscle cells form tissue, which in turn forms muscle.

Our muscles contain fibers, nerve endings, and blood vessels. Muscle contraction occurs with the help of nerve impulses that come from the spinal cord to muscle tissue.

Muscle contraction
To build muscle, you need to do a lot of work in the gym, that is, contract your muscles. Muscle contraction occurs by transmitting a nerve impulse along the path - the brain - the spinal cord - the muscles we need. Now we understand why spinal cord injury is so dangerous.

A person regulates the intensity of muscle contraction using the strength of the impulse supplied along the nerve endings.

Muscle energy
The ATP (adenosine triphosphate) molecule is the main source of energy for muscle contraction. The breakdown of ATP releases energy, which provides the impulse for muscle contraction. During intense work, ATP is consumed, so it is impossible to endlessly load yourself.

There are three main sources of ATP: creotine phosphate, glucose and the oxidation of organic elements.

Creotine phosphate is broken down into creatine and a phosphate group, which in turn attaches to ADP (adenosine phosphate), forming ATP.

Glycolysis is the process of breaking down glycogen contained in muscles. As a result, one molecule of glucose and two molecules of lactic acid are formed. The breakdown of glycogen, as well as the breakdown of creotine phosphate, occurs without the participation of oxygen. The more glycogen our body has accumulated, the more energy we will have during training.

And the last source of ATP is the oxidation of organic substances, which occurs with the active participation of oxygen. Carbohydrates are broken down first, then fats. When working for endurance, this source of energy is used.