BIOMECHANICAL CONTROL. CLINICAL ANALYSIS OF MOVEMENTS. TESTS IN BIOMECHANICS. SURVEY METHODS

The functioning of the human musculoskeletal system is based on the principles of mechanics. To study human biomechanical systems, data from biophysics, physiology, mathematics, etc. are used. It is known that man, as a biomechanical system, obeys the laws of physics and mechanics.

When studying movements in biomechanics, data from anthropometry, anatomy, nervous and physiology are used. muscular systems and etc.; The biomechanics of the musculoskeletal system includes its functional (dynamic) anatomy, etc.

The purpose of biomechanical research is the creation of sports equipment and equipment (bicycles, boats, oars, sports shoes and much more), the development of movement techniques in a particular sport, as well as the prevention and treatment of injuries, etc.

Asymmetry of the sides of the body and limbs, differences in the circumference of segments of one limb compared to the other, in the volume of joints, changes in the physiological curves of the spine and other deviations from the norm should be noted and taken into account in the process biomechanical control(Fig. 16.1).

The axis of the normal lower limb runs from the anterosuperior iliac spine through the middle of the kneecap and the second toe (Fig. 16.2). The long axis of the upper limb passes through the center of the head of the humerus, the head of the radius and the head of the ulna (Fig. 16.3).

The length of the lower limb is measured in a lying position: the limbs are placed strictly symmetrically and two are selected on each of them. symmetrical points(Fig. 16.4). The highest point can be the anterosuperior pelvic spine or the tip of the greater trochanter. The lowest point can be the lower end of the inner or outer ankle (see Fig. 16.4).

The length of the upper limb is measured in the same way. The upper point is the end of the acromial process of the scapula or the greater tubercle of the humerus, the lower point is the styloid process of the radius or to the end of the third finger (Fig. 16.5).

To measure the length of the upper arm or forearm, the intermediate point is usually the tip of the olecranon or the head of the radius.

After measurements of the diseased limb, the data obtained are compared with the measurement data of the healthy limb (Fig. 16.6).

It is necessary to distinguish between anatomical (true) and functional shortening or lengthening of the limb. The anatomical length (shortening or lengthening) is the sum of the length of the thigh and lower leg for the lower limb and the shoulder and forearm for the upper limb.

In the first case, the measurement is made from the top of the greater trochanter to the gap of the knee joint and from the latter to the outer (inner) ankle; in the second case - from the greater tubercle of the humerus to the head of the radius and from the latter to the styloid process of the radius (ulna). These summary data are compared with the same data obtained when measuring a healthy limb. The difference between them is the amount of anatomical shortening (Fig. 16.7).

Functional shortening or lengthening of the limb is determined by the above-mentioned measurement of its individual segments, but the upper point for the lower limb is the anterior superior iliac spine, and for the upper limb - the end of the acromial process of the scapula. Functional shortening

usually depends on the presence of contractures or ankylosis of joints in a vicious position, bone curvatures, dislocations, etc.

Functional shortening can be measured in a standing position (see Fig. 16.7, b). It is equal to the distance from the plantar surface of the foot of the diseased limb to the floor when resting on a healthy limb (see Fig. 16.7, b).

There can be a significant difference between anatomical and functional shortening. So, for example, the length of the thigh and lower leg of the diseased and healthy side can be the same, and yet in the presence of flexion contracture in the knee or hip joints, dislocation, ankylosis of the hip joint in the adducted position, functional shortening can reach 10-15 cm or more (Fig. 16.8).

Determination of range of motion in joints(16.9). The degree and type of movement of a normal joint depends on the shape of the articular surfaces, the limiting action of the ligaments, and the function of the muscles.

There are active and passive restrictions of movement in the joints. The volume of normal range of motion is known in various

joints (Fig. 16.10, see pp. 454-455). However, for practical purposes, much more important data can be obtained by comparing movements in the joints of the diseased side and the healthy one.

Movements in the sagittal plane are called flexion and extension (flexio et extensio), in relation to the hand it is customary to say palmar and dorsal flexion, in relation to the foot - dorsal and plantar flexion.

Movements in the frontal plane are called adduction (adductio) and abduction (abductio). In relation to the wrist joint, it is customary to say radial adduction and ulnar abduction; Inward movement in the calcaneocuboid joint is adduction, outward movement is abduction. Movements around the longitudinal axis are called rotation (rotatio) internal and external. In relation to the forearm (Fig. 16.11), it is customary to call external rotation - supination (supinatio), and internal rotation - pronation (pronatio), just as the deviation of the foot in the subtalar joint from the axis of the lower limb inward is usually called supination, and outward - pronation (see . Fig. 16.15).

Movements in the joints can be performed by the patient actively or with the help of a researcher (passively). The range of motion is measured using goniometer, the branches of which are set along the axis of the limb segments, and the axis of the protractor - along the axis of movement of the joints (see Fig. 16.9).

Restriction of passive mobility in a joint is called contractures. Limitation of active mobility is not a contracture, but a condition associated with painful sensations, paralysis or muscle paresis.

Complete immobility in a joint is called ankylosis. A distinction is made between bone ankylosis, in which the articular ends of the articulating bones are fused together by bone substance, and fibrous ankylosis, in which the fusion consists of fibrous tissue. In the latter case, insignificant movements, barely noticeable to the eye, are possible.

To determine the volume of rotational movements of the limbs, rotatometers are used (Fig. 16.12). Measurement data is recorded in degrees. The limit of possible passive movement is the sensation of pain. The volume of active movements sometimes largely depends on the condition of the tendon-muscular system, and not just on changes in the joint. In these cases, there is a significant difference between the range of active and passive movements.

Movements in the elbow joint are possible within the following limits: flexion up to 40-45°, extension up to 180°. Pronation-supination movements of the forearm in the elbow joint are determined in the position shown in Fig. 16.13, and possibly within 180°.

In the wrist joint, movements occur within 70-80° of dorsiflexion and 60-70° of palmar flexion. Lateral movements of the hand are also determined - radial abduction within 20° and ulnar abduction within 30° (see Fig. 16.10).

In the fingers of the hand, extension is possible within 180°, flexion in the metacarpophalangeal joints is possible up to an angle of 70-60°, in the interphalangeal joints - up to 80-90°. Lateral movements of the fingers are also possible. It is especially important to determine the abduction of the first finger and the possibility of contact between the first and fifth fingers.

In the hip joint, the range of motion is normal: flexion up to 120°, extension 30-35° (angle between the horizontal plane and the axis of the thigh), abduction 40-50°, adduction 25-30° (angle between vertical axis torso and hip axis) (see Fig. 16.10, b).

Physiological movements in the ankle joint and foot occur within 20-30° of dorsiflexion (foot extension) and 30-50° of plantar flexion (see Fig. 16.9). Adduction of the foot is usually combined with supination (inward rotation of the foot), abduction is accompanied by pronation (outward rotation of the foot).

For convenience, physiological movements in the spine are determined both in degrees (which is more difficult) and in maximum movements of various sections.

In the cervical region, flexion is normally performed until the chin touches the sternum, extension - until horizontal

position of the back of the head, to the side - until contact auricle with shoulder girdle.

In the thoracic region, flexion and extension are carried out to a small extent. The thoracic vertebrae take a large part in the lateral movements of the spine, the range of rotational movements is 80-120°.

In the lumbar region, the greatest range of movements is determined in the anteroposterior direction, lateral and rotational movements are moderate.

The circumference of the limbs (sick and healthy) is measured in symmetrical places at a certain distance from the bone identification points: for the leg - from the anterior superior iliac spine, greater trochanter of the femur, articular space of the knee joint, head of the fibula; for the arms - from the acromion process, the internal epicondyle of the shoulder (Fig. 16.14).

Foot measurements are taken both with and without load (Fig. 16.15). Foot deformity resulting from static deficiency consists of a) pronation of the hindfoot

and compensatory relative supination of its anterior section; b) bending towards the rear of the forefoot in relation to the hindfoot, which is established in a position of plantar flexion (flattening of the foot); c) abduction of the forefoot (abduction) in relation to its rear part (Fig. 16.16).

F.R. Bogdanov recommends measuring the longitudinal arch of the foot by constructing a triangle, the identification points of which are easily accessible to palpation. These points are: the head of the first metatarsal bone, the calcaneal tubercle and the top of the inner malleolus (Fig. 16.17). By connecting these three points, a triangle is obtained, the base of which is the distance from the head of the first metatarsal bone to the calcaneal tubercle. The calculation is based on the height of the arch and the angles of the inner ankle and heel bone. Normally, the height of the arch is 55-60 mm, the angle at the ankle is 95°, and the angle at the heel bone is 60°. For flat feet: height

the arch is less than 55 mm, the angle at the ankle is 105-120°, the angle at the calcaneus is 55-50°.

To determine the degree of flatfoot, an x-ray examination method is used. The calculation is based on constructing a triangle, the vertices of which are the head of the metatarsal bone, the scaphoid bone and the tubercle of the calcaneus, and measuring the height of the arch and the angle at the scaphoid bone (Fig. 16.18).

Angulography- recording the angles of flexion and extension in the joints of the lower limb: hip, knee and others with the designation of interlink angles (B.C. Gurfinkel and A.Ya. Sysin, 1956). According to the angulogram data, it is possible to determine gait in normal and pathological conditions, as well as before and after treatment (Fig. 16.19). When treatment (rehabilitation) is applied, angulography begins to approach normal.

Ichnography- a method of recording tracks from both legs when walking, taking into account the step length of each leg, turn of the foot, step width, step angle (Fig. 16.20).

When analyzing footprints using foot prints, the spatial parameters of the step are measured.

Modification of the ichnography method - podography- use of recording electrical signals when the foot touches the floor (Fig. 16.21). A weak electric current is supplied to a special metallized track and a metal contact on the shoes; when such shoes touch the surface, it closes

The circuit passes through a current that is recorded on a device (for example, an oscilloscope). By placing contacts in certain places soles, you can record the phases of transfer of the limb, placing the heel on the support, rolling over the entire foot, lifting the heel, etc.

The participation of various muscles in the implementation of a motor act is studied through electromyography, i.e., by studying the electrical activity of muscles. For this purpose, abductor electrodes are applied to the human skin over the corresponding muscle. Multichannel electromyographs simultaneously record electrical activity several muscles.

EMG is recorded from the muscles of symmetrical segments of the limbs or symmetrical halves of the torso, or from antagonist muscles. The resulting EMG is assessed by the height of the oscillations, their frequency per unit time, and the entire recording as a whole. Training has been shown to increase the electrical activity of muscles (Fig. 16.22). This is especially noticeable during training (using walking, running, therapeutic exercises and other means) after an injury.

Measuring spinal flexibility. Flexibility is the ability to perform movements with a large amplitude. The measure of flexibility is the maximum range of motion. There are active and passive flexibility. The active test is performed by the subject himself, the passive test is performed under the influence of an external force. Flexibility depends on the condition of the joints, elasticity (extensibility) of ligaments, muscles, age, temperature environment, biorhythms, time of day, etc.

Typically, flexibility is determined by a person's ability to lean forward while standing on a simple device (Fig. 16.23). Moving

The bar on which divisions are marked in centimeters shows the level of flexibility.

Rachiocampsis can occur in three planes: a) frontal (lateral curvature - scoliosis); b) sagittal (round back, hump - kyphosis); c) horizontal (vertebral rotation - torsion).

Scoliosis is a disease of the skeletal and neuromuscular system in the spine, which causes a progressive lateral curvature of the latter with torsion, a change in the shape of the wedge-shaped vertebrae, with the development of rib deformities and the formation of costal humps, anterior and posterior, increased lumbar lordosis, thoracic kyphosis and development of compensatory arcs of curvature (Fig. 16.24).

General center of gravity of the body plays important role when solving various issues of movement mechanics. The balance and stability of the body is determined by the position of the central gravity.

total area supports - the area enclosed between the extreme points of the supporting surfaces, in other words, the area of ​​the supporting surfaces and the area of ​​the space between them (Fig. 16.25). The size of the support area for different body positions varies greatly.

In relation to the human body, two types of equilibrium are distinguished: stable and unstable. Stable balance is when the center of gravity of the body is located below the area of ​​support, and unstable balance is when the center of gravity of the body is located above the area of ​​support.

V. Braune and O. Fischer determined the position of the body's central gravity and the centers of gravity of its individual parts. It was revealed that the CG of the head lies posterior to the back of the sella turcica by approximately 7 mm; The center of gravity of the body is in front of the upper edge of the first lumbar vertebra (L,). Along the axis of the body, its CG is spaced from the cranial end by approximately 3/6 of the length, and from the caudal end by 2/5 of the length (see Fig. 2.9). The CG of the body divides the straight line between the transverse axes passing through the shoulder and hip joints in approximately a ratio of 4:5. According to Fisher, the isolated thigh, lower leg, shoulder and forearm have a CG in the place, the segments from which to the proximal and distal ends of these links are approximately

like 4:5. The center of gravity of the hand with slightly bent fingers is located 1 cm proximal to the head of the third metacarpal bone.

Knowing the position of the CG of each of the two parts of the body that articulate with each other (shoulder and forearm, thigh and lower leg, etc.), it is not difficult to determine the position of their common center of gravity (see Fig. 2.9). It is located on a straight line connecting the CG of each of the links, and divides this straight line in a ratio inversely proportional to their masses. By transforming two-link systems, it is possible to determine the position of the body's central gravity.

To determine the GCT, as well as to determine its trajectory, V.M. Abalakov proposed a device (Fig. 16.26).

The stability of a body is determined by the size of the support area, the height of the body's central center and the location of the vertical, lowered from the center of gravity, inside the support area (see Fig. 16.25). larger area support and the lower the body's central center of gravity is located, the greater the stability of the body.

To determine the center of mass of J.L. Parks (1959) proposed a dissection method that allowed the center of each segment, the mass, and the position of the center of mass to be determined (Fig. 16.27).

To study the area of ​​support, the plantar surface of the foot(s) is smeared with paint, for which the patient stands on

a flat surface covered with a thin layer of paint, and then carefully transfers to a sheet of clean paper. From the prints of the feet one can judge the arch of the foot and the nature of the distribution of the load on the foot (see Fig. 16.20). The fingerprint method is used to determine the features and nature of gait (see Fig. 16.20).

Gait analysis based on a footprint left on paper is carried out by measuring the step angle (angle, formed by a line movement and the axis of the foot), step width (the distance between the imprints of the edge of the heel of the same foot (Fig. 16.28).

good posture creates optimal conditions for activity internal organs, helps improve performance and, of course, has great aesthetic significance. Characteristics of the types of posture can be given

according to the results of goniometry of the spinal column (Fig. 16.29) and visually.

Goniometry- registration method relative movements parts of the body: electrical variable resistances (potentiometers) or inclinometers (on a hinge, or with retractable jaws, or disk) are used as sensors for angular movements in joints. The most widely used is the V.A. compass goniometer. Gamburtseva.

Using the goniometric method, a comprehensive measurement of the curvature and movements of the spine, pelvic tilt angles, range of motion of the joints of the limbs, deformation of the limbs, etc. is easily carried out.

The nature of the change in time of the joint angles of the leg in a plane close to the sagittal is shown in Fig. 16.30.

Cyclography- a method of recording human movements. In cyclography, successive poses of a moving person (or

one of his limbs) are recorded on the same photographic film. To do this, the person being examined puts on a suit made of black, non-shiny fabric. Small electric bulbs are attached to the corresponding joints and some other points of the body. The movement of the subject leaves a mark on the photographic film. In this case, each luminous light bulb on the film corresponds to its own light path in the form of a line.

To determine the speed of movement of individual parts of the body, a rotating disk with one or more holes is placed in front of the camera. Rotating at a uniform speed in front of the camera lens, the disk splits the light trajectories of the light bulbs into certain points spaced from each other at equal time intervals.

Processing the cyclogram using the method of N.A. Bernstein, one can analyze in detail the movements of the human body and its individual links in space and time. This allows not only to identify the actual and relative movements of the body and its individual points (segments), but also to determine the speeds and accelerations of these movements both along the longitudinal and vertical components.

Cyclograms allow you to see the holistic spatial movement of the body, which is formed as a result of the addition of the angular movements of many parts of the body relative to each other.

In Fig. 16.31 and fig. 16.32 shows cyclograms of a walking and running person.

Stabilography. Essentially, resilience is a person's ability to accommodate common center mass so that its projection onto the horizontal section of the support falls on the area limited by the feet. Maintaining a vertical posture is the muscular coordination of cyclic movements of the body. In this case, the body oscillates and the area described by the GCM may exceed the area of ​​the support. When conducting the “stability” test, the stabilogram is taken for 30 s, while the subject is asked to stand on the platform and try to independently maintain a vertical body position (first 30 s with eyes open, and then 30 s with eyes closed). In Fig. 16.33 shows statokinesigrams.

Analysis of statokinesigrams (SKG) is provided according to the following characteristics.

1. Mathematical expectation coordinates GCT (GCM) based on the mathematical expectation of the position of the center of pressure M x± c x,

And spectral analysis are carried out using methods studied in the basic course of medical and biological physics.

For research vestibular apparatus carry out special coordination tests and tests with rotation: rotation in the Barany chair, Romberg test, etc.

Orientation in space, as well as body stability, largely depend on the state of the vestibular analyzer. This is especially important in some complex sports (acrobatics, gymnastics, trampoline, diving, figure skating, etc.).

Romberg's test. Test to determine changes in proprioception. The Romberg test is carried out in four modes (Fig. 16.34) with a gradual decrease in the support area. In all cases, the subject's hands are raised forward, fingers spread and eyes closed. The stopwatch records the time it takes to maintain balance for 15 seconds. At the same time, all changes are recorded - swaying of the body, trembling of the hands or eyelids (tremor).

Tremorography. Tremor is hyperkinesis, manifested by involuntary, stereotypical, rhythmic oscillatory movements of the whole body or its components. Tremors are recorded using a seismic sensor on an ECG machine. An induction seismic sensor is placed on the subject's finger. Mechanical vibrations (tremors) of the hand and finger, converted into electrical signals, are amplified and recorded on an electrocardiograph tape (Fig. 16.35). The recording is made within 5-10 s. Then the shape of the resulting curve is analyzed in terms of amplitude and frequency. With fatigue and excitement, the amplitude and frequency of tremor increases. Improved fitness is usually accompanied by a decrease in the magnitude of tremor, as well as a decrease or disappearance of pain.

Yarotsky test. The test allows you to determine the sensitivity threshold of the vestibular analyzer. The test is performed in a standing position with eyes closed, while the athlete on command begins rotational movements head at a fast pace. The time of head rotation until the athlete loses balance is recorded. U healthy people the time for maintaining balance is on average 28 s, for trained athletes - 90 s or more, especially for those who engage in acrobatics, gymnastics, diving, etc.

Actography- this is a study motor activity person during sleep. Recording of actograms is carried out on an electrokymograph, where a 1.5 m long bicycle chamber is used as the receiving part, the pressure in which is 15-20 mm Hg. Art. The chamber is connected by a rubber tube to Marey's capsule. Ink scribes record the actogram on paper. When analyzing actograms, the duration of falling asleep, the duration of the state of complete rest, total time sleep and other components. The higher your rest score, the better your sleep.

Nomograms exist to determine the surface of the body based on measurements of body length and weight (Fig. 16.37). Body surface is a largely integrating feature physical development, which has a high correlation with many important functional systems org lowness.

Calculation of body surface area (S) according to Dubos: S = 167.2 l/L4 ■ D, Where M- body weight in kilograms; D- body length in centimeters.

The ratio of the mass and surface area of ​​the child’s body, depending on age, is given in Table. 16.1.

Determination of the thickness of skin-fat folds in children and adolescents. Measurement according to L.S. Trofimenko is produced using a Best caliper with a constant pressure of 10 g/mm 2 (Fig. 16.38). The thickness of the fold is measured at ten points of the body: cheek, chin, chest I (along the anterior axillary line at the level of the axillary fold), back of the shoulder, back, chest II (along the anterior axillary line at the level of the X rib), abdomen above the iliac crest, thigh, shin. The thickness of each fold is measured 3 times and the resulting data is added up.

In girls, the curve of the sum of folds between the ages of 7 and 17 years increases steadily; in boys, the peak of the curve increases at the age of 10-12 years, then there is a tendency to some

its reduction. Comparison of the obtained values ​​with the child’s body weight allows us to judge the preferential development of adipose tissue or the musculoskeletal system.

Muscle strength study. The functional capabilities of the musculoskeletal system (MSA) largely depend on the condition of the muscles.

To determine muscle strength, dynamometers, tonometers, electromyography, etc. are used (Fig. 16.39).

A Collen dynamometer is usually used to determine hand strength. The strength of the trunk extensors is measured using a backbone dynamometer. To measure the strength of the muscles of the shoulder and shoulder girdle, hip and leg extensors, as well as torso flexors, universal dynamometers are used

(Fig. 16.40).

Men reach maximum isometric strength around the age of 30, and then strength decreases. This process occurs faster in the large muscles of the lower limbs and torso. Arm strength

lasts longer. Table 16.2 shows the strength indicators of various muscle groups obtained from a survey of about 600 people (the average height of men is 171 cm, women - 167 cm).

Strength indices obtained by dividing strength indicators by weight and expressing them as a percentage (%). The average value of hand strength for men is considered to be 70-75% of weight, for women - 50-60%; for dead strength in men - 200-220%, in women - 135-150%. For athletes, respectively - 75-81% and 260-300%; for female athletes - 60-70% and 150-200%.

Pedagogical assessment

Automation of biomechanical control

Testing of motor qualities

Testing in biomechanics

Biomechanical measurements, measurement scales, measurement accuracy

Fundamentals of Biomechanical Control

The object of biomechanical control in sports is human motor skills, i.e. motor qualities and their manifestation.

As a result of biomechanical control, information is obtained about:

1. About the level of development physical qualities(strength, speed, endurance, flexibility, agility) and the proper level of their development for the selection and mastery of technical and tactical techniques

Identify general fitness (assessment of functional state, anthropometric measurements, level of development of physical qualities);

Identify special training;

Identify the dynamics of the development of physical qualities and sports results;

Study methods for selecting capable athletes;

Establish control standards for various stages of training in various types sports.

2. Techniques and tactics of motor activity

Knowledge about biomechanical characteristics is based on primary information obtained by various means (using control and pedagogical tests, measuring devices).

Measurement is the determination of the value of a physical quantity experimentally using special technical means..

Measurements according to the method of obtaining the desired value divided into: subjective (information from the senses), objective (use special technical means)

By method of obtaining a numerical value of the measured quantity, all measurements are divided into: direct, indirect and joint.

According to the amount of measurement information measurements can be single or multiple.

The basis for measuring a physical quantity is measurement scale - an ordered collection of quantity values.

The most common are four types: names (nominal), order, intervals and ratios.

Name scales (nominal)- the simplest one, in which numbers, letters and others symbols serve for the presence, detection and distinction of the objects being studied (for example, when analyzing game tactics, the numbers of field players in a tactical combination act as names).

Order scale occurs when the numbers that make up a scale are ordered by rank, but the intervals between the ranks cannot be accurately measured. The order scale makes it possible not only to establish the fact of equality or inequality, but also to determine the nature of inequality in the concepts of “more - less”, “better - worse”. Using order scales, “qualitative indicators” that do not have a strict quantitative measure (occupied place) are measured. The scale of order is infinite; there is neither a zero level nor a maximum best level.

Interval scale uses numeric values ​​separated a certain number units, its peculiarity is that the reference point is chosen arbitrarily (chronology, temperature, joint angle)

Relationship scale the most accurate. It makes it possible to determine not only better or worse, but also by how much, it has zero First level counting, the numbers are ordered by rank and separated by equal intervals. Quantitative indicators can be measured (body length and weight, speed)

These types of scales can be converted into each other, depending on what level of accuracy is needed.

In each measurement, the result obtained inevitably contains an error - this is the deviation of the measurement result from the actual (true) value of the measured value.

For reasons of error divided into instrumental (caused by imperfection of the measuring instrument), methodical (imperfect organization of the measurement procedure) and subjective (caused by individual characteristics subjects and researchers).

By shape the values ​​of the main and additional errors can be presented in both absolute and relative units.

Absolute error - a value equal to the difference between the measurement results and the true values ​​of the measured quantity (Ap = A - A 0). The result obtained by a more accurate method is taken as the true value. The absolute error is measured in the same units as the value itself.

IN practical work It is often more convenient to use not absolute, but relative size errors.

Relative error– the ratio of the absolute error to the true value of the measured value.

Measurement errors can be systematic or random.

Systematic is called an error, the value of which does not change from measurement to measurement. Due to this feature, systematic error can often be predicted in advance or, in extreme cases, detected and eliminated at the end of the measurement process.

To eliminate systematic errors, calibration of the device is used. Taring(from German tarieren) is called checking the readings measuring instruments by comparison with readings of exemplary values ​​of measures (standards) throughout the entire range possible values measured quantity.

Random errors arise due to various reasons that cannot be predicted in advance. They cannot be eliminated, but using methods mathematical statistics, you can estimate the magnitude of the random error and take it into account when explaining the measurement results.

Rice. 4. Determination of the range of motion in the joints: 1 measurement of the range of motion in the shoulder joint (a measurement of the abduction angle, b measurement of the flexion angle); 2 measurement of mobility in the elbow joint, 3 measurement of the angle of adduction of the hand, 4 measurement of mobility in the hip joint, 5 measurement of mobility in the hip joint with flexion contracture, 6 measurement of hip abduction, 7 measurement of flexion angle in knee joint 8 foot mobility measurement

Rice. 9. Location of the conditional axis of the ankle joint (a): 1 normal position of the foot; 2 outward deviation of the foot; 3 deviation of the foot inside. Normal and pathophysiological changes in the foot (zones of contact of the foot with the surface are marked in black) (b): 1 normal; 2 flat feet; 3 clubfoot

The ratio of mass to body surface of a child depending on age. Slide 16 Table 1. Age Body weight, kg Body surface area, m 2% to the average of adults body weight body surface area Newborns 3.50, months 5.00, » 7.50, year 10.00, years 15.00, years 23, 00, » -27.01, » , » * Adults 651.73100

Average values ​​of isometric strength of some muscle groups depending on age (according to E. Aztizzep, 1968). Slide 17. Table 2. Indicator (kg) Age, years 20"2535"4555 male.male.female.male.female.g^female.male. Hand strength (±16%)* 55,937,559,938,558,838,055,635,651,632.7 Torso extensor strength (±16%) 81,656,6 -87,458,390,759,289,857,785,749,1 Torso flexor strength (± 17%) 60,640,964,242,266,742,466,041,563,033.6 Sitting leg extension strength (±18.5% ) 295" *. " * Coefficient of variation

Let's consider one half-cycle of walking, since in the second half-cycle the phases and boundary poses are the same, only in their names the right leg must be replaced with the left, and the left with the right: 1. - lifting the foot of the right leg from the support; I - sitting down on the left (supporting) leg, bending it at the knee joint 2 - beginning to straighten the left leg; II – straightening of the left leg, its extension at the knee joint; 3. – the moment when the right leg began to lead in the process of transferring left leg; III – extension of the right leg with support on the entire foot of the left leg; 4 - separation of the heel of the left foot from the support; IV – extension of the right leg with support on the toe of the left leg; 5 – placing the right leg on a support; V - double support, transition of support from the left leg to the right; Slide 18.

When we are talking about the phase composition of a motor action, we mean movements of the whole body. When considering the phase composition of walking or running, we mean the movements of the legs, which is necessary to clarify the mechanisms of these locomotions, i.e. how and from what a person moves. There are four phases of running (Roman numerals) and four, separated friend from each other by boundary poses: 1. - lifting the left foot off the support; I. - foot spread; 2. – beginning to move the left leg forward; II – bringing the feet together with the left leg moving forward; 3. – placing the right foot on the support; III. – depreciation, or sitting down with bending of the right (supporting leg); 4. – beginning of extension of the right leg; IV. - push-off with straightening of the right leg until it lifts off the support. slide 18

MINISTRY OF SPORTS OF THE RUSSIAN FEDERATION

Department of Unified and IT

SRS No. 2 on the topic:
"Fundamentals of biomechanical control."

The work was completed by a student
II year DO, group 211
Shevtsov Sergey

Volgograd-2013

Measurement in biomechanics.

Bibliography.

Measurement in biomechanics.

A person becomes an object of measurement from early childhood. A newborn's height, weight, body temperature, sleep duration, etc. are measured. Later, at school age, knowledge and skills are included in the number of measured variables. How older person the wider the circle | his interests, the more numerous and varied the indicators characterizing him are. And the more difficult it is to make accurate measurements. How, for example, can we measure technical and tactical readiness, the beauty of movements, the geometry of the masses of the human body, strength, flexibility, etc.? This is discussed in this section.
In the English-language literature on physical education, a wider list of motor qualities is accepted, including the ability to perform balance exercises, dance exercises, etc.
Measurement scales and units of measurement
A measurement scale is a sequence of quantities that allows one to establish a correspondence between the characteristics of the objects being studied and the numbers. In biomechanical control, scales of names, ratios and order are most often used.
The naming scale is the simplest of all. In this scale, numbers, letters, words or other symbols act as labels and serve to detect and distinguish the objects being studied. For example, when controlling game tactics football team Field numbers help identify each player.
The numbers or words that make up the naming scale are allowed to be interchanged. And if they can be interchanged without compromising the accuracy of the value of the measured variable, then this variable should be measured on a scale of names. For example, the naming scale is used to determine the scope of equipment and tactics (this is discussed in the next section).
An order scale arises when the numbers that make up the scale are ordered by rank; the know-intervals between ranks cannot be accurately measured. For example, knowledge of biomechanics or skills and abilities in physical education lessons are assessed on a scale: “poor” - “satisfactory” - “good” - “excellent”. The order scale makes it possible not only to establish the fact of equality or inequality of measured objects, but also to determine the nature of inequality in qualitative concepts: “more - less”, “better - worse”. However, to the questions: “How much more?”, “How much better?” - response order scales do not provide answers.
Using order scales, they measure “qualitative” indicators that do not have a strict quantitative measure (knowledge, abilities, artistry, beauty and expressiveness of movements, etc.).
The scale of order is infinite, and there is no zero level in it. This is understandable. No matter how incorrect a person’s gait or posture may be, for example, an even worse option can always be found. And on the other hand, no matter how beautiful and expressive a gymnast’s motor actions are, there will always be ways to make them even more beautiful.
The relationship scale is the most accurate. In it, the numbers are not only ordered by rank, but also separated by equal intervals - units of measurement." The peculiarity of the ratio scale is that the position of the zero point is determined in it.
The ratio scale measures the size and mass of the body and its parts, the position of the body in space, speed and acceleration, strength, duration of time intervals and many other biomechanical characteristics. Illustrative examples of a ratio scale are: a scale of scales, a stopwatch scale, a speedometer scale.
The ratio scale is more precise than the order scale. It allows you not only to find out that one measurement object (technique, tactical option, etc.) is better or worse than another, but also gives answers to the questions of how much better and how many times better. Therefore, in biomechanics they try to use ratio scales and, for this purpose, record biomechanical characteristics.

Technical means and measurement techniques: video cyclography, electromyography, accelerometry, goniometry, strain dynamometry.

1. podometry - measurement of the time characteristics of a step;
2. goniometry - measurement of kinematic characteristics of movements in joints;
3. dynamometry - registration of support reactions;
4. electromyography - registration of surface EMG;
5. stabilometry - registration of the position and movements of the general center of pressure on the plane of support when standing.

Electromyographic measurement methods
Electromyography is a method for studying the neuromuscular system, based on recording and analysis of bioelectric potentials.
Electromyography stress reaction includes an assessment of the effect of stress response on striated muscles. EMG, in essence, can be considered as an indirect definition muscle tension. It is indirect in the sense that it measures the electrochemical activity of the nerves innervating a given striated muscle rather than the actual tension produced by muscle contraction. Striated muscle activity began to be considered as an indicator of stress response after one of the early works of E. Jacobson (Edmund Jacobson, 1938), in which he noted the existence of a high positive correlation between stress activation and tension of the striated muscle.
Although not unconditional, many researchers have concluded that recording EMG activity in the frontal region can be a useful indicator of generalized sympathetic nervous system activity. A practical advantage of using EMG recording of the stress response is its availability for measuring muscle groups. Most clinicians work with the frontal musculature, but the trapezius (upper), brachioradialis, and sternocleidomastoid muscle groups can also be used to measure stress.
The amplitudes of biopotentials range from 10 μV to several millivolts. The frequency range of the signals is from 1 to 20,000 Hz (there are references from some authors to the presence of EMG components with frequencies of the order of hundreds of kilohertz).
In electromyography, two types of electrodes are used according to their design - surface (cutaneous) and needle (subcutaneous).
Needle electrodes allow the action potential of one or a few nearby muscles to be recorded. These electrodes are either surgically implanted or inserted using a needle to subcutaneous injections. In a polygraph, surface electrodes are used to take EMG, which make it possible to measure the interference (total) EMG. Surface electrodes can be divided into metal, capacitive, resistive, and RC. It is most convenient to use flat metal electrodes in a polygraph. They are plates or disks made of silver, steel, tin, etc. with an area of ​​about 0.2–1 cm2. Two such electrodes are attached to the skin in the place where the muscle is contoured, along the course of its fibers. For better attachment, an elastic cuff is placed on the electrodes. The distance between the electrodes is 2 cm. To stabilize the distance and more uniformly press the electrodes to the skin, they are mounted in a plastic frame. To reduce the interelectrode resistance, the skin before applying the electrode is wiped with alcohol and moistened with an isotonic sodium chloride solution. To reduce the transition resistance of the skin - electrode, a special electrode paste is applied to the area of ​​skin-electrode contact.
Regardless of the type of electrodes, there are two methods of discharging electrical activity - mono and bipolar. In EMG, a lead is called monopolar when one electrode is located directly near the muscle area being studied, and the second in an area remote from it. The advantage of monopolar lead is the ability to determine the shape of the potential of the structure under study and the true phase of the potential deviation. The disadvantage is that with a large distance between the electrodes, potentials from other parts of the muscle or even from other muscles interfere with the recording.
A bipolar lead is a lead in which both electrodes are located at a fairly close and equal distance from the muscle area being studied. The bipolar lead records activity from distant potential sources to a small extent, especially when driven by needle electrodes. The influence on the potential difference of activity coming from the source to both electrodes leads to a distortion of the potential shape and the inability to determine the true phase of the potential. However, the high degree of locality makes this method preferable in clinical practice.
In addition to the electrodes, the potential difference of which is supplied to the input of the EMG amplifier, a surface grounding electrode is installed on the skin of the subject, which is connected to the corresponding terminal on the electrode panel of the electromyograph. The circuit of this electrode short-circuits the capacitive potential difference between the patient’s body and the ground and helps eliminate capacitive currents resulting from the action of alternating industrial current fields.
A modern electromyograph is a complex device consisting of electrodes for measuring muscle biopotentials, an amplifier unit, an oscilloscope, an EMG integrator, an analyzer, a reproducer, a computing device, and a device for outputting digital and graphic information.
The part of the electromyograph, consisting of an amplifier unit and an oscilloscope, is called a myoscope. The myoscope has from one to four amplification units independent from each other, which allows simultaneous examination of four electromyographic signals.
The EMG integrator is used to process the information contained in the electromyogram. An EMG analyzer is necessary to isolate the amplitude of individual components of the EMG frequency spectrum for subsequent processing. In modern electromyographs, the received information is processed using a computer.

Accelerometric measurement methods
Accelerometers are linear acceleration sensors and, as such, are widely used to measure body inclination angles, inertial forces, shock loads and vibration. They are widely used in transport, medicine, industrial measurement and control systems, and inertial navigation systems. Since 1965, they began to create accelerometers based on MEMS technology. The reduction in size led to mass mass production. Currently, the industry produces many types of accelerometers with different principles of operation, acceleration measurement ranges and other functional characteristics, weight, dimensions and prices. Based on the principle of operation, they distinguish following types accelerometers: capacitive, piezoresistive, piezoelectric, strain-resistive, thermal, tunnel. Capacitive-type accelerometers are the simplest, most reliable and easy to implement, which is why they are widely used. The principle of their operation is as follows. When the movement accelerates along the sensitivity axis, the elastic suspension, which is a movable electrode, deforms, while the stationary electrode is located on the surface of the substrate. Thus, the distance between the electrodes changes, and therefore the capacitance of the capacitor formed by them.
When developing and manufacturing capacitive-type micromechanical accelerometers, it is necessary to monitor their characteristics. Methods for measuring characteristics are an integral part of the production cycle of products and serve to promptly make adjustments to the designs and technologies of devices at the development stage. This work proposes a method for measuring the characteristics of capacitive-type micromechanical accelerometers, which provide measurement of accelerations in the range from 0 to 500 m/s2 with an accuracy of 0.05 m/s2, while the mass of the samples in the housing should not exceed 10 g, and the dimensions in the plane - 3 cm x 3 cm.
Before starting measurements, accelerometer samples must be mounted in a standard metal-ceramic housing. In this case, the contact pads on the samples must be welded to the contact pads on the body using ultrasonic welding.
The acceleration of the sample in the established measurement range is set using a vibration stand by adjusting the amplitude and frequency of vibration of the table with the experimental sample fixed.

Optical computer topography method

Stereophotogrammetry with an imaginary basis. Geometric model of stereo photography. Fixed point coordinates: X=90, Y=112, Z=-24 mm. Important information about the geometry of the human body, features and posture disorders can be obtained by studying special method computer topography. This modern and most accurate method allows quantitative high accuracy determine the coordinates of any anatomical point on the body surface. The duration of the examination is 1 - 2 minutes, so this method is successfully used for mass research.

Podography - registration of the time of support of individual parts of the foot while walking in order to study the rolling function is studied using special sensors mounted in the sole of the shoe.

Stabilogram of alternating standing on the right and left legs. Stabilography is an objective method of recording the position and projection of the general center of mass onto the plane of support - an important parameter of the mechanism for maintaining a vertical posture. Usually the area of ​​migration of the common center of mass (GCM) is recorded in the projection of the horizontal plane, combined with the outline of the foot

Electrogoniometry
To measure joint angles, instruments called goniometers are used.
A goniometer is two flat rectangular plates connected at one end on the same axis. To measure angles at the joints of body parts during movement, electrogoniometers are used, which ensure the conversion of the angular movements of the sensor into proportional electrical voltage. To assess the level of flexibility, it is necessary to measure the range of motion in the joints.

Dynamometry is the measurement of the forces developed by an athlete when performing various physical exercises.
Using a dynamometer platform, it is a rigid plate or frame supported by 4 load cells. The athlete stands on the platform and with the help of these sensors the force exerted on this platform is measured.
Using hand dynamometers, the strength of the muscles that flex the fingers is measured; with the help of a deadlift dynamometer, the strength of the muscles that straighten the torso (“dead” strength), etc.

Biomechanical control in volleyball.

Testing in volleyball
By definition, a test is a measurement or test conducted to determine the condition or ability of an athlete. The testing procedure requires the coach to understand what he is assessing and based on what indicators, as well as with what accuracy they are recorded. Testing is a tool for checking the correctness of the choice and justification of the training methodology.
Assessment of the jumping readiness of a volleyball player.
Dedicated to assessing the jumping ability of athletes a large number of works, although the term “jumping ability” itself is not strictly defined. Jump height is measured in different ways. The first is based on flight time recorded using a contact device. This time is divided in half, assuming that the body flies upward for the first half and downwards for the other half. Next, the height of the jump is determined by substituting the upward flight time of the body into the formula: But, when the feet are lifted from the contact device, the athlete has one pose (straightened legs and arms in front - at the top), and when landing - another pose (knees bent to 150 degrees, arms down down), therefore the downward movement lasted longer than the upward movement. And for some reason, when calculating, they divide the total flight time in half. This results in a large measurement error, which makes it possible to recognize this method as incorrect. In the second method, the jump height is measured using the Abalakov method. Pulling out a measuring tape tied to the athlete's belt while jumping. The disadvantages of this method are obvious: - the height of the extension of the tape attachment point is assessed, and not the body's center of gravity; - if an athlete does not jump perfectly upward (and this is exactly what happens in practice), then, with an equal jumping height, the mite will stretch more for the one of the two athletes who deviates from the vertical direction.
One of the most accurate methods for determining the height of a jump is its calculation through a force impulse recorded using a strain gauge platform: When conducting a correlation analysis between the height of a jump measured simultaneously by this method (standard) and the methods indicated above, a weak connection was found - g no more than 0.7. Therefore, according to the basics of test theory, the reliability of these measurements is unsatisfactory. Coaches began to give the greatest preference to simple way- jumping touch with chalked fingers, stand a. The height when standing on your toes with your arm extended upward is subtracted from this height.
You can also determine the height of a jump from filming by calculating, using Varignon’s theorem, the position of the athlete’s body’s central gravity at the moment the feet lift off the support and at the highest point of the trajectory. Testing using similar methods for recording jump heights allowed us to obtain a number of interesting data on the jumping training of volleyball players. For example, it is shown statistically a significant increase in the average jump height with age and with increasing skill of young volleyball players. The jumping value increases from 35.5 + 5.2 cm (at 12 years) to 48.3 ± 3.3 cm (at 17 years). Similar trends were found in the works based on these. trends, control standards for the physical fitness of young volleyball players in standing up and long jumps were calculated. In a similar way, the level of special physical fitness of highly qualified volleyball players was assessed. Using optical methods, it was established that when performing an upward jump with 2 - 3 run-up steps, the average height of top-class volleyball players reaches. , according to different authors, respectively 0.71 ± 004 m (average height 1.85 ± o.o5 m) and 0.88 m (0.66 - 1.08)

4. References:

Donskoy D.D., Zatsiorsky V.M. Biomechanics: Textbook for institutes of physical culture.-M. FiS, 1979-264
Biomechanical methods research in sports: Tutorial for students of IFK.-M., 1976.275
Kolodtsev I.Kh., Medvedev V.V. Quantitative Analysis movements of rotating balls in volleyball.
Kravtsev I.N., Orlov V.P. Control and measuring complex VNIIFKA, 1982
Popov G, I, et al. Experience of using high-speed cinematography in sports games, 1983

MINISTRY OF SPORTS OF THE RUSSIAN FEDERATION

Federal state budgetary educational institution of higher professional education.
"Volgograd State Academy of Physical Culture"

Department of Unified and IT

Abstract on the topic:
"Forces in the movements of athletes."

The work was completed by a student
II year DO, group 211
Shevtsov Sergey

Volgograd-2013

PLAN.
1. The role of forces in human movement.
2. Working and harmful resistance.
3. Driving and braking forces.
4. External and internal forces regarding the human body and their manifestations (swimming).
5. Forces of action of the environment.
6. Inertial forces in inertial and non-inertial reference systems.
7. Literature used.

1. The role of forces in human movement.
All forces applied to the human motor system constitute a system of external and internal forces. The system of external forces manifests itself more often in the form of resistance. To overcome resistance, the energy of human muscle tension is expended. There are working and harmful resistances. Overcoming working resistance is often left as the main goal of the athlete’s movements (for example, in overcoming weight, the goal of movements with a barbell is included). Harmful resistances absorb positive work.
External forces are used by a person as driving forces in his movements. To perform the necessary work to overcome resistance forces, weight, elastic forces, etc. can be used. External forces are in this case “free” sources of energy, since a person spends less internal muscle energy reserves.
A person overcomes the forces of muscular resistance with corresponding external forces and performs, as it were, two parts of work: a) work aimed at overcoming all resistances (working and harmful); b) work aimed at imparting acceleration to moving external objects.
In biomechanics, the force of human action is the force of influence on the external physical environment, transmitted through the operating points of the body. Working points, in contact with external bodies, transfer motion (quantity of motion, as well as kinetic momentum) and energy (translational and rotational motion) to external bodies.
The braking forces involved in resistance can be all external and internal forces, including muscular ones. Which of them will play the role of harmful resistance depends on the conditions of a particular exercise. Only reactive forces (support and friction reaction forces) cannot be driving forces; they always remain resistances (both harmful and working).
All forces, regardless of their source, act as mechanical forces, changing mechanical motion. In this sense, they are in unity as material forces: it is possible to perform (subject to appropriate conditions) their addition, decomposition, reduction and other operations.
Human movements are the result of the combined action of external and internal forces. External forces, expressing the influence of the external environment, determine many features of movements. Internal forces, directly controlled by a person, ensure the correct execution of specified movements.
As movements improve, it becomes possible to better utilize muscle forces. Technical mastery manifests itself in the increased role of external and passive internal forces as driving forces.
The main objectives of improving movements and increasing their effectiveness in the most general form are to increase the result of accelerating forces and reduce the effect of harmful resistance. This is especially important in sports, where all motor actions are aimed at increasing technical skill and athletic performance.
2. Working and harmful resistance.
The system of external forces manifests itself more often as resistance forces. To overcome resistance, the energy of movement and tension of human muscles is expended. There are working and harmful resistances.
Overcoming working resistance is often the main task of human movements (for example, overcoming the weight of a barbell is the goal of moving with a barbell).
Harmful resistances absorb positive work; they are, in principle, irremovable (for example, the friction force of skis on snow).
3. Driving and braking forces.
The forces applied to the parts of the human body, acting dynamically, lead to different results. Depending on how the forces are directed relative to the speed of a moving body, they are distinguished:
- driving forces that coincide with the direction of speed (passing) or form an acute angle with it and can perform positive work;
- braking forces that are directed opposite to the direction of speed (counter) or form an obtuse angle with it and can perform negative work;
- deflecting forces perpendicular to the direction of speed and increasing the curvature of the trajectory;
- restoring forces, also perpendicular to the direction of movement, but reducing the curvature of the trajectory.
Both latest groups forces do not directly change the magnitude of the tangential (tangential) velocity.
The result of their action also depends on the ratio of forces applied to each link of the body.
Driving force is a force that coincides with the direction of movement (concurrent) or forms with it sharp corner and at the same time can do positive work (increase the energy of the body).
However, in real conditions In human movements, there is always a medium (air or water), support and other external bodies (projectiles, equipment, partners, opponents, etc.) act. All of them can have an inhibitory effect. Moreover, there is simply no real movement without the participation of braking forces.
The braking force is directed opposite to the direction of movement (counter) or forms an obtuse angle with it. It can perform negative work (reduce the energy of the body).
Part driving force, equal in magnitude to the braking force balances the latter - this is the balancing force (Fyp).
The excess of the driving force over the braking force - the accelerating force (Fac) - causes the acceleration of a body with mass m according to Newton's 2nd law (Fy=ma).
4. External and internal forces regarding the human body and their manifestations (swimming).
External forces are forces acting on a body from outside. Under the influence of external forces, a body either begins to move if it was at rest, or the speed of its movement or the direction of movement changes. External forces in most cases are balanced by other forces and their influence is invisible.
External forces acting on a solid body cause changes in its shape, caused by the movement of particles.
Internal forces are forces acting between particles, these forces resist changing shape.
A change in the shape of a body under the influence of force is called deformation, and a body that has undergone deformation is called deformed.
The balance of internal forces from the moment an external force is applied is disrupted, the particles of the body move relative to each other to such a state and position when the internal forces arising between them balance external forces and the body retains the acquired deformation.
After the removal of the external force, if it has not exceeded a certain limit, the body returns to its original shape.
The property of a body maintaining acquired deformation after removing the load is called plasticity, and deformation is called plastic.
When two bodies come into contact, they act on each other and become deformed. There are no undeformed bodies. Any body is deformed when exposed to any amount of force. low strength. The magnitude of internal forces characterizes the strength of adhesion of particles of a given body.
When a body moves, it overcomes resistance forces, the magnitudes of which vary, from slight braking to resistance that stops the moving body. Resistance forces, in addition to internal forces, include the resistance of the medium (air, water), inertial forces, and friction forces.
The action of a force on a body, which consists in changing the state of this body, is completely determined by the following three factors: the point of application of the force, the direction of the force, and the magnitude of the force.
The point of application of force is the point of a given body on which the force directly acts, changing the state of the given body.
The direction of force is understood as the direction of movement that the body will receive under the influence of this force. The line of direction of a given force is called the line of action of this force.
Measuring the magnitude of a force means comparing it with a certain force taken as a unit. Strength is usually measured with dynamometers of various designs.
Force is a vector quantity, that is, it has not only a numerical value, but also a direction, therefore the effect of a force on a body is determined not only by its magnitude, but also by its direction.
Swimming is a locomotor, cyclic movement in water. It occurs in an environment unusual for humans and in a horizontal position unusual for them. In this case, the weight of the body decreases by the weight of the water it displaces.
Muscle function during swimming static forces insignificant. At the same time, the dynamic load is high. This is due to the difficulty of maintaining balance in water, as well as the fact that repulsion occurs from the liquid medium.
The force of gravity of the body, directed vertically downwards, and the pressure of water, directed vertically upwards, form a “couple of forces”, as a result of which the body should experience rotational movements. Equilibrium is achieved when the general center of gravity of the body and the center of its volume (located above) are on the same vertical. To do this, arms are extended in front of the head.
The high density of water and the difficulty of repelling from it determine the low speed of movement. But with a horizontal position of the body, the surface of resistance decreases. This position is unusual for a person and makes it difficult to coordinate movements.
5. Forces of action of the environment.
An athlete often has to overcome air or water resistance. The environment in which a person moves has its effect on his body. This action can be static (buoyant force) or dynamic (drag, normal ground reaction).
Buoyancy force is a measure of the action of a medium on a body immersed in it. It is measured by the weight of the displaced volume of liquid and is directed upward.
If the buoyant force (Q) is greater than the force of gravity of the body (G), then the body floats up. If the force of gravity of a body is greater than the buoyant force, then it sinks.
Drag is the force with which a medium prevents the movement of a body relative to it. The amount of drag (R x) depends on the cross-sectional area of ​​the body, its streamlining, the flatness and viscosity of the medium, as well as the relative speed of the body:
R x =S M C x pv 2 ; = MLT -2
where S M is the area of ​​the largest cross-section of the body (midsection), C x is the drag coefficient, depending on the shape of the body (streamlining) and its orientation relative to the direction of movement in the medium, p is the density of the medium (water - 1000 kg/m 3, air - 1.3 kg/m 3), v is the relative speed of the medium and the body.
By changing the cross-sectional area of ​​the body, you can change the effect of the environment. So, when a skier descends from a mountain in a high stance, this area is almost 3 times larger than in a low stance. This means that air resistance during descent can be changed by almost 3 times. By adopting a more streamlined position in the water, you need to reduce the resistance of the water. As you know, with increasing speed of movement, the resistance of water or air increases sharply (approximately proportional to the square of the speed).
The normal reaction of the medium is the force exerted by the medium on a body located at an angle to the direction of its movement. It depends on the same factors as drag:
Ry = S M C y pv 2 ; = MLT -2
where Su is the coefficient of normal reaction of the medium (in flight it is called lift).
The normal reaction of the environment during a stroke is directed perpendicular to the drag force. C.) the normal reaction of the environment as a lifting force has to be taken into account (for example, a swimmer while moving along a distance, a ski jumper while flying in
etc.................

Russian style- studio support Black Ice(c) 1999-2002

Chapter 3. Fundamentals of Biomechanical Control

Science begins as soon as they begin to measure.

Accurate knowledge is unthinkable without measure.

D. I. Mendeleev

From intuition to exact knowledge!

A person’s motor skill, his ability to move quickly, accurately and beautifully in any conditions, depends on the level of physical, technical, tactical, psychological and theoretical preparedness. These five factors of movement culture are leading in sports, in physical education of schoolchildren, and in mass forms of physical education. To improve motor skills and even to maintain it at the same level, it is necessary to control each of these factors.

The object of biomechanical control is human motor skills, i.e. motor (physical) qualities and their manifestations. This means that as a result of biomechanical control we obtain information:

1) about the technique of motor actions and tactics of motor activity;

2) about endurance, strength, speed, agility and flexibility, proper level which is a necessary condition high technical and tactical skill (In the English literature on physical education, a wider list of motor qualities is accepted, including the ability to perform balance exercises, dance exercises, etc.).

To put it even more simply: biomechanical control answers three questions:

1) What does a person do?

2) How well does it do this?

3) Why does he do this?

The biomechanical control procedure corresponds to the following scheme:

Measurements in biomechanics

A person becomes an object of measurement from early childhood. A newborn's height, weight, body temperature, sleep duration, etc. are measured. Later, at school age, knowledge and skills are included in the variables measured. The older a person is, the wider his range of interests, the more numerous and varied the indicators that characterize him. And the more difficult it is to make accurate measurements. How, for example, can we measure technical and tactical readiness, the beauty of movements, the geometry of the masses of the human body, strength, flexibility, etc.? This is discussed in this section.

Measurement scales and units of measurement

A measurement scale is a sequence of quantities that allows one to establish a correspondence between the characteristics of the objects being studied and the numbers. In biomechanical control, scales of names, ratios and order are most often used.

The naming scale is the simplest of all. In this scale, numbers, letters, words or other symbols act as labels and serve to detect and distinguish the objects being studied. For example, when monitoring the tactics of a football team, field numbers help identify each player.

The numbers or words that make up the naming scale are allowed to be interchanged. And if they can be interchanged without compromising the accuracy of the value of the measured variable, then this variable should be measured on a scale of names. For example, the naming scale is used to determine the scope of equipment and tactics (this is discussed in the next section).

An order scale occurs when the numbers that make up the scale are ordered by rank, but the intervals between the ranks cannot be accurately measured. For example, knowledge of biomechanics or skills and abilities in physical education lessons are assessed on a scale: “poor” - “satisfactory” - “good” - “excellent”. The order scale makes it possible not only to establish the fact of equality or inequality of measured objects, but also to determine the nature of inequality in qualitative concepts: “more - less”, “better - worse”. However, to the questions: “How much more?”, “How much better?” - order scales do not give an answer.

Using order scales, they measure “qualitative” indicators that do not have a strict quantitative measure (knowledge, abilities, artistry, beauty and expressiveness of movements, etc.).

The scale of order is infinite, and there is no zero level in it. This is understandable. No matter how incorrect a person’s gait or posture may be, for example, an even worse option can always be found. And on the other hand, no matter how beautiful and expressive a gymnast’s motor actions are, there will always be ways to make them even more beautiful.

The relationship scale is the most accurate. In it, the numbers are not only ordered by rank, but also separated by equal intervals - units of measurement 1. The peculiarity of the ratio scale is that it defines the position of the zero point.

The ratio scale measures the size and mass of the body and its parts, the position of the body in space, speed and acceleration, strength, duration of time intervals and many other biomechanical characteristics. Illustrative examples of a ratio scale are: a scale of scales, a stopwatch scale, a speedometer scale.

The ratio scale is more precise than the order scale. It allows you not only to find out that one measurement object (technique, tactical option, etc.) is better or worse than another, but also gives answers to the questions of how much better and how many times better. Therefore, in biomechanics they try to use ratio scales and, for this purpose, record biomechanical characteristics.