Diagnosis of human posture

At the current level of knowledge, the term "constitution" reflects the unity of the morphological and functional organization of a person, reflected in the individual characteristics of his structure and functions. Their changes are the body's response to constantly changing environmental factors. They are expressed in the developmental features of compensatory-adaptive mechanisms formed as a result of the individual implementation of the genetic program under the influence of specific environmental factors (including social ones).

In order to objectify the methodology for measuring the geometry of the human body, taking into account the relativity of its spatial coordinates, Laputin’s somatic coordinate system of the human body (1976) was introduced into the practice of studying movements.

The most convenient location for the center of the somatic coordinate trihedron is the anthropometric lumbar point 1i, located at the apex of the spinous process of the L vertebra (a-5). In this case, the numerical coordinate axis z corresponds to the direction of the true vertical, the axes x and y are located at right angles in the horizontal plane and determine movement in the sagittal (y) and frontal (x) directions.

Currently, a new direction is actively developing abroad, particularly in North America - kinanthropometry. This is a new scientific specialization that uses measurements to assess the size, shape, proportion, structure, development and general function of a person, studying problems related to growth, physical activity, performance and nutrition.

Kinanthropometry places humans at the center of study, allowing us to determine their structural status and various quantitative characteristics of body mass geometry.

For an objective assessment of many biological processes in the body associated with its mass geometry, it is necessary to know the specific gravity of the substance of which the human body consists.

Densitometry is a method of assessing the overall density of the human body. Density is often used as a means of assessing fat and fat-free mass and is an important parameter. Density (D) is determined by dividing the mass by the volume of the body:

D of body = body mass / body volume

Various methods are used to determine body volume, most commonly using hydrostatic weighing or a manometer to measure displaced water.

When calculating volume using hydrostatic weighing, it is necessary to make a correction for the density of water, so the equation will be as follows:

D _body = P1/ { (P1-P2)/ x1-(x2+G1g}}

Where p1 is the mass of the body under normal conditions, p2 _is the mass of the body in water, x1 is the density of water, x2 is the residual volume.

The amount of air in the gastrointestinal tract is difficult to measure, but due to its small volume (approximately 100 ml), it can be neglected. For compatibility with other measurement scales, this value can be adjusted for height by multiplying by (170.18 / Height)3.

Densitometry has been the best method for determining body composition for many years. New methods are usually compared to it to determine their accuracy. The weak point of this method is the dependence of the body density indicator on the relative amount of fat in the body.

When using a two-component body composition model, high accuracy is required to determine body fat density and lean body mass. The standard Siri equation is most often used to convert body density to determine body fat:

% body fat = (495/ Dbody) - 450.

This equation assumes a relatively constant density of fat and lean body mass in all individuals. Indeed, the density of fat in different areas of the body is virtually identical, with the generally accepted value being 0.9007 g cm ^-3. However, determining the density of lean body mass (D), which is 1.1 according to the Siri equation, is more problematic. To determine this density, it is assumed that:

• the density of each tissue, including the net body mass, is known and remains constant;
• in each type of tissue the proportion of net body mass is constant (for example, it is assumed that bone makes up 17% of net body mass).

There are also a number of field methods for determining body composition. The bioelectrical impedance method is a simple procedure that takes only 5 minutes. Four electrodes are placed on the subject's body - on the ankle, foot, wrist, and back of the hand. An imperceptible current passes through the tissues through the detail electrodes (on the hand and foot) to the proximal electrodes (wrist and ankle). The electrical conductivity of the tissue between the electrodes depends on the distribution of water and electrolytes in it. Lean body mass contains almost all of the water and electrolytes. As a result, the conductivity of lean body mass is significantly higher than that of fat mass. Fat mass is characterized by high impedance. Thus, the amount of current passing through the tissues reflects the relative amount of fat contained in a given tissue.

This method converts impedance readings into relative body fat readings.

The infrared interaction method is a procedure based on the principles of absorption and reflection of light using infrared spectroscopy. A sensor is placed on the skin above the measurement site, sending electromagnetic radiation through a central bundle of optical fibers. Optical fibers on the periphery of the same sensor absorb energy reflected by the tissue, which is then measured using a spectrophotometer. The amount of energy reflected indicates the composition of the tissue directly beneath the sensor. The method is characterized by a fairly high degree of accuracy when measuring in several areas.

Many measurements of the spatial arrangement of body biolinks were carried out by researchers on corpses. About 50 corpses have been dissected to study the parameters of human body segments over the past 100 years. In these studies, the corpses were frozen, dissected along the axes of rotation in the joints, after which the segments were weighed, the positions of the centers of mass (CM) of the links and their moments of inertia were determined mainly using the well-known physical pendulum method. In addition, the volumes and average densities of the tissues of the segments were determined. Research in this direction was also carried out on living people. Currently, a number of methods are used to determine the geometry of the human body mass during life: water immersion; photogrammetry; sudden release; weighing the human body in various changing poses; mechanical vibrations; radioisotope; physical modeling; the method of mathematical modeling.

The water immersion method allows us to determine the volume of segments and their volume center. By multiplying by the average tissue density of the segments, specialists then calculate the mass and location of the center of mass of the body. This calculation is made taking into account the assumption that the human body has the same tissue density in all parts of each segment. Similar conditions are usually applied when using the photogrammetry method.

In the methods of sudden release and mechanical vibrations, one or another segment of the human body moves under the action of external forces, and the passive forces of the ligaments and antagonist muscles are taken to be equal to zero.

The method of weighing the human body in various changing postures has been criticized because the errors introduced by the data taken from the results of studies on cadavers (the relative position of the center of mass on the longitudinal axis of the segment), due to interference from respiratory movements, as well as inaccuracy in the reproduction of postures in repeated measurements and determination of the centers of rotation in the joints, reach large values. In repeated measurements, the coefficient of variation in such measurements usually exceeds 18%.

The radioisotope method (gamma scanning method) is based on the well-known physics principle of the weakening of the intensity of a narrow monoenergetic beam of gamma radiation when it passes through a certain layer of some material.

The radioisotope method variant was based on two ideas:

• increasing the thickness of the detector crystal to improve the sensitivity of the device;
• refusal of a narrow beam of gamma radiation. During the experiment, the mass-inertial characteristics of 10 segments were determined in the subjects.

As the scanning progressed, the coordinates of anthropometric points were recorded, which serve as indicators of segment boundaries and the locations of planes separating one segment from another.

The physical modeling method was used by making casts of the subjects' limbs. Then, not only the moments of inertia were determined on their plaster models, but also the localization of the centers of mass.

Mathematical modeling is used to approximate the parameters of segments or the entire body. In this approach, the human body is represented as a set of geometric components, such as spheres, cylinders, cones, etc.

Harless (1860) was the first to propose the use of geometric figures as analogs of human body segments.

Hanavan (1964) proposed a model that divides the human body into 15 simple geometric figures of uniform density. The advantage of this model is that it requires a small number of simple anthropometric measurements to determine the position of the common center of mass (CCM) and the moments of inertia at any position of the links. However, three assumptions typically made when modeling body segments limit the accuracy of the estimates: segments are assumed to be rigid, the boundaries between segments are assumed to be clear, and the segments are assumed to have uniform density. Based on the same approach, Hatze (1976) developed a more detailed model of the human body. His 17-link model requires 242 anthropometric measurements to account for the individualization of each person's body structure. The model subdivides the segments into small mass elements with different geometric structures, allowing for detailed modeling of the shape and density variations of the segments. Moreover, the model does not make assumptions about bilateral symmetry and takes into account the peculiarities of the male and female body structure by adjusting the density of some parts of the segments (according to the content of the subcutaneous base). The model takes into account changes in body morphology, for example, caused by obesity or pregnancy, and also allows simulating the peculiarities of the body structure of children.

To determine the partial (partial, from the Latin word pars - part) dimensions of the human body, Guba (2000) recommends drawing reference lines (refer - landmark) on its biolinks, delimiting functionally different muscle groups. These lines are drawn between bone points determined by the author during measurements taken during dissection and dioptrography of cadaveric material, and also verified during observations of typical movements performed by athletes.

The author recommends drawing the following reference lines on the lower limb. On the thigh - three reference lines separating muscle groups that extend and flex the knee joint, and flex and adduct the thigh at the hip joint.

The external vertical (EV) corresponds to the projection of the anterior edge of the biceps femoris. It is drawn along the posterior edge of the greater trochanter along the outer surface of the thigh to the middle of the lateral epicondyle of the femur.

The anterior vertical (AV) corresponds to the anterior edge of the long adductor muscle in the upper and middle third of the thigh and the sartorius muscle in the lower third of the thigh. It is drawn from the pubic tubercle to the internal epicondyle of the femur along the anterointernal surface of the thigh.

The posterior vertical (3B) corresponds to the projection of the anterior edge of the semitendinosus muscle. It is drawn from the middle of the ischial tuberosity to the internal epicondyle of the femur along the posterior internal surface of the thigh.

Three reference lines are drawn on the shin.

The external vertical of the leg (EVL) corresponds to the anterior edge of the long peroneus muscle in its lower third. It is drawn from the top of the head of the fibula to the anterior edge of the lateral malleolus along the outer surface of the leg.

The anterior vertical of the tibia (AVT) corresponds to the crest of the tibia.

The posterior vertical of the leg (PVT) corresponds to the inner edge of the tibia.

Two reference lines are drawn on the shoulder and forearm. They separate the flexors of the shoulder (forearm) from the extensors.

The external vertical of the shoulder (EVS) corresponds to the external groove between the biceps and triceps muscles of the shoulder. It is carried out with the arm lowered from the middle of the acromial process to the external epicondyle of the humerus.

The internal vertical arm (IVA) corresponds to the medial humeral groove.

The external vertical forearm (EVF) is drawn from the external epicondyle of the humerus to the styloid process of the radius along its external surface.

The internal vertical forearm (IVF) is drawn from the internal epicondyle of the humerus to the styloid process of the ulna along its internal surface.

The distances measured between the reference lines allow us to judge the expression of individual muscle groups. Thus, the distances between the PV and HV measured in the upper third of the thigh allow us to judge the expression of the hip flexors. The distances between the same lines in the lower third allow us to judge the expression of the knee joint extensors. The distances between the lines on the shin characterize the expression of the flexors and extensors of the foot. Using these arc dimensions and the length of the biolink, we can determine the volumetric characteristics of muscle masses.

The position of the human body's GCM has been studied by many researchers. As is known, its localization depends on the placement of the masses of individual body parts. Any changes in the body associated with the movement of its masses and the disruption of their previous relationship also change the position of the center of mass.

The position of the common center of mass was first determined by Giovanni Alfonso Borelli (1680), who in his book "On Animal Locomotion" noted that the center of mass of the human body, in an upright position, is located between the buttocks and the pubis. Using the method of balancing (first-class lever), he determined the location of the CCM on corpses by placing them on a board and balancing it on a sharp wedge.

Harless (1860) determined the position of the common center of mass on individual parts of a corpse using Borelli's method. Then, knowing the position of the centers of mass of individual parts of the body, he geometrically summed up the gravitational forces of these parts and determined the position of the center of mass of the entire body in its given position from the drawing. Bernstein (1926) used the same method to determine the frontal plane of the body's GCM, and for the same purpose applied profile photography. He used a second-class lever to determine the position of the human body's GCM.

Much was done to study the position of the center of mass by Braune and Fischer (1889), who conducted their research on corpses. Based on these studies, they determined that the center of mass of the human body is located in the pelvic area, on average 2.5 cm below the sacral promontory and 4-5 cm above the transverse axis of the hip joint. If the torso is pushed forward when standing, then the vertical of the body's GCM passes in front of the transverse axes of rotation of the hip, knee and ankle joints.

To determine the position of the body's CM for different positions of the body, a special model was constructed based on the principle of using the method of principal points. The essence of this method is that the axes of the conjugate links are taken as the axes of the oblique coordinate system, and the joints connecting these links are taken with their center as the origin of coordinates. Bernstein (1973) proposed a method for calculating the body's CM using the relative weight of its individual parts and the position of the centers of mass of individual links of the body.

Ivanitsky (1956) generalized the methods for determining the human body mass index proposed by Abalakov (1956) and based on the use of a special model.

Stukalov (1956) proposed another method for determining the human body's GCM. According to this method, a human model was made without taking into account the relative mass of parts of the human body, but with an indication of the position of the center of gravity of individual links of the model.

Kozyrev (1963) developed a device for determining the human body's CM, the design of which was based on the principle of operation of a closed system of first-class levers.

To calculate the relative position of the CM, Zatsiorsky (1981) proposed a regression equation in which the arguments are the ratio of the trunk mass to the body mass (x1) and the ratio of the midsternal anteroposterior diameter to the pelvic-crestal diameter (x2 ₎. The equation has the form:

Y = 52.11+ 10.308x. + 0.949x ₂

Raitsyna (1976) proposed a multiple regression equation (R = 0.937; G = 1.5) to determine the height of the CM position in female athletes, including as independent variables data on leg length (x, cm), body length in the supine position (x, ₂ cm), and pelvic width (x, cm):

Y = -4.667 _Xl + 0.289x ₂ + 0.301x ₃. (3.6)

The calculation of relative values of the weight of body segments has been used in biomechanics since the 19th century.

As is known, the moment of inertia of a system of material points relative to the axis of rotation is equal to the sum of the products of the masses of these points by the squares of their distances to the axis of rotation:

The indicators characterizing the geometry of body masses also include the center of the body volume and the center of the body surface. The center of the body volume is the point of application of the resultant force of hydrostatic pressure.

The center of the body surface is the point of application of the resultant forces of the environment. The center of the body surface depends on the pose and direction of the environment.

The human body is a complex dynamic system, therefore the proportions, ratio of sizes and masses of its body throughout life constantly change in accordance with the laws of manifestation of genetic mechanisms of its development, as well as under the influence of the external environment, techno-biosocial conditions of life, etc.

The uneven growth and development of children is noted by many authors (Arshavsky, 1975; Balsevich, Zaporozhan, 1987-2002; Grimm, 1967; Kuts, 1993, Krutsevich, 1999-2002), who usually associate this with the biological rhythms of the body's development. According to their data, during the period

The greatest increase in anthropometric indicators of physical development in children is accompanied by an increase in fatigue, a relative decrease in working capacity, motor activity, and a weakening of the general immunological reactivity of the body. Obviously, in the process of development of a young organism, a genetically fixed sequence of structural-functional interaction in certain time (age) intervals is preserved. It is believed that this is precisely what should determine the need for increased attention from doctors, teachers, and parents to children during such age periods.

The process of biological maturation of a person covers a long period - from birth to 20-22 years, when the growth of the body is completed, the final formation of the skeleton and internal organs occurs. Biological maturation of a person is not a planned process, but occurs heterochronically, which is most clearly manifested already in the analysis of the formation of the body. For example, a comparison of the growth rates of the head and legs of a newborn and an adult shows that the length of the head doubles, and the length of the legs five times.

Summarizing the results of studies conducted by various authors, we can present some more or less specific data on age-related changes in body length. Thus, according to specialized literature, it is believed that the longitudinal dimensions of the human embryo are approximately 10 mm by the end of the first month of the intrauterine period, 90 mm by the end of the third, and 470 mm by the end of the ninth. At 8-9 months, the fetus fills the uterine cavity and its growth slows down. The average body length of newborn boys is 51.6 cm (varies in different groups from 50.0 to 53.3 cm), girls - 50.9 cm (49.7-52.2 cm). As a rule, individual differences in the body length of newborns during normal pregnancy are within 49-54 cm.

The greatest increase in body length in children is observed in the first year of life. In different groups, it fluctuates between 21 and 25 cm (on average 23.5 cm). By the age of one year, body length reaches an average of 74-75 cm.

In the period from 1 year to 7 years, both in boys and girls, annual increases in body length gradually decrease from 10.5 to 5.5 cm per year. From 7 to 10 years, body length increases by an average of 5 cm per year. From the age of 9, gender differences in growth rate begin to appear. In girls, a particularly noticeable acceleration of growth is observed between the ages of 10 and 15, then longitudinal growth slows down, and after 15 years it sharply slows down. In boys, the most intensive body growth occurs from 13 to 15 years, and then a slowdown in growth processes also occurs.

The maximum growth rate is observed during puberty in girls between the ages of 11 and 12, and 2 years later in boys. Due to the different times of the onset of pubertal growth acceleration in individual children, the average value of the maximum rate is somewhat underestimated (6-7 cm per year). Individual observations show that the maximum growth rate in most boys is 8-10 cm, and in girls - 7-9 cm per year. Since pubertal growth acceleration in girls begins earlier, the so-called "first crossing" of growth curves occurs - girls become taller than boys. Later, when boys enter the phase of pubertal growth acceleration, they again overtake girls in body length (the "second crossing"). On average, for children living in cities, the crossings of growth curves occur at 10 years 4 months and 13 years 10 months. Comparing growth curves characterizing the body length of boys and girls, Kuts (1993) indicated that they have a double crossing. The first crossing is observed from 10 to 13 years, the second - at 13-14. In general, the patterns of the growth process are the same in different groups and children reach a certain level of definitive body size at approximately the same time.

Unlike length, body weight is a very labile indicator, reacting relatively quickly and changing under the influence of exogenous and endogenous factors.

A significant increase in body weight is observed in boys and girls during puberty. During this period (from 10-11 to 14-15 years), girls have more body weight than boys, and body weight gains in boys become significant. The maximum increase in body weight for both sexes coincides with the greatest increase in body length. According to Chtetsov (1983), from 4 to 20 years, boys' body weight increases by 41.1 kg, while girls' body weight increases by 37.6 kg. Up to 11 years, boys have more body weight than girls, and from 11 to 15, girls are heavier than boys. The curves of body weight changes in boys and girls cross twice. The first crossing occurs at 10-11 years and the second at 14-15.

In boys, there is an intensive increase in body weight in the period of 12-15 years (10-15%), in girls - between 10 and 11 years. In girls, the intensity of body weight increase occurs more vigorously in all age groups.

Research conducted by Guba (2000) allowed the author to identify a number of features of the growth of biolinks of the human body in the period from 3 to 18 years:

• the dimensions of the body located in different planes increase synchronously. This is especially clearly seen when analyzing the intensity of growth processes or by the indicator of the increase in length per year, related to the total increase during the growth period from 3 to 18 years;
• within one limb, there is an alternation of the growth rate of the proximal and distal ends of the biolinks. As we approach adulthood, the difference in the growth rate of the proximal and distal ends of the biolinks steadily decreases. The same pattern was discovered by the author in the growth processes of the human hand;
• Two growth spurts were revealed, characteristic of the proximal and distal ends of the biolinks, they coincide in the magnitude of the increase, but do not coincide in time. Comparison of the growth of the proximal ends of the biolinks of the upper and lower limbs showed that from 3 to 7 years the upper limb grows more intensively, and from 11 to 15 years - the lower limb. Heterochrony of limb growth was revealed, that is, the presence of a craniocaudal growth effect, which was clearly revealed in the embryonic period, is confirmed in postnatal ontogenesis.

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