Human Anatomy (with the Fundamentals of Dynamic and Sports Morphology) - Ivanitsky, M. F. 2008

General Dynamic Morphology
Scheme of Anatomical Analysis of Body Positions and Movements

It is advisable to carry out an anatomical analysis of human body postures and movements in a specific, systematic sequence.

1. Description of the Morphology of a body posture or movement.

2. Characterization of the body posture or movement from the standpoint of the laws of mechanics.

3. Characterization of the functional activity of the motor apparatus.

4. Assessment of the mechanism of external Respiration, the state of support systems (respiratory, digestive, cardiovascular, etc.), and movement regulation systems (nervous, endocrine).

5. Determination of the degree and Nature of the exercise's impact on the body. This task, traditionally belonging to Dynamic Morphology, is currently addressed by sports morphology (see p. 485).

The morphology of a body posture or movement is studied based on the visual image generated through visual observation of the exercise being performed, as well as by utilizing photographic and cinematographic records. Attention is drawn to the Symmetry of the posture or movement, the presence and type of support, and the relative arrangement of body segments.

Movement morphology encompasses its general characterization, subdivision into distinct phases, and the examination of each phase.

Characterizing a body posture or movement from the perspective of mechanics is essential for understanding the function of the motor apparatus. For a morphologist, the biomechanical interpretation of the form and Structure of a human movement or posture is not an end in itself, but rather a crucial prerequisite for a detailed anatomical Analysis of the movement or posture. This involves examining the following factors:

— acting forces;

— THE POSITION OF the center of gravity (mass) of The Human Body and its individual segments;

— the position of the center of volume of the human body;

— the specific gravity value of the human body;

— the condition of the support base;

— the type of equilibrium;

— the conditions for maintaining body balance and its degree of stability.

Acting forces. Every movement performed by a person, and any posture they maintain, is determined by the Interaction of a number of forces. The forces acting on the human body are divided into external and internal.

External forces are applied to a person from the outside or arise from their interaction with external objects (an opponent, sports equipment, etc.). For the anatomical analysis of human postures or movements, The most significant are the force of gravity (gravitational force), the support reaction force, and the environmental resistance force. Each of these forces is characterized by its magnitude, direction, and point of application.

The force of gravity (gravitational force) is equal to the body mass, is applied at the center of gravity (COG) of the body, and is directed vertically downwards. When performing an exercise with added weight (a barbell, a shot put), it is necessary to account for the gravity of the “athlete-equipment” system.

The support reaction force represents the counteraction of the supporting surface to the pressure exerted upon it. In an upright posture, the support reaction force is equal in magnitude to the force of gravity (action is equal to reaction), but opposite in direction. During walking, running, or standing long jumps, the support reaction force is directed toward the body at an angle from the supporting surface and can be resolved, According to the parallelogram of forces rule, into two components: vertical and horizontal. The vertical component of the support reaction force (normal pressure force) is directed upward and interacts with the force of gravity, while the horizontal component (friction force) affects body displacement. Without friction, a person could neither walk nor run: the FOOT pushing off would slip backward, making body locomotion impossible (something similar can be observed when walking on slippery ice).

The environmental resistance force acts on the human body during movements in the air (during a strong wind or fast running) or Water (swimming). It depends on the frontal surface area of the body's resistance, the speed of movement, and the density of the medium. By reducing the frontal surface area (for instance, in a low cycling posture), environmental resistance is decreased.

Internal forces arise within the human body through the interaction of its parts. Internal forces are subdivided into passive and active. Passive internal forces include: the elastic tensile force of soft Tissues (ligaments, joint capsules, fasciae, Muscles, etc.), which occurs when they are stretched; the resistance force of bones and Cartilage, determined by their physicochemical properties; and the molecular adhesion force of the synovial fluid located within the joint cavities.

The primary active internal force is Muscle contraction force. The magnitude of muscle contraction force depends on Anatomical and physiological conditions (see p. 114). Its direction is determined by the resultant vector. The point of application of the muscle contraction force is the center of attachment of the muscle to the movable (displaced) segment.

If the forces acting on a body are balanced, the body remains at rest; if their resultant is non-zero, the body moves in the direction of that resultant. Each force can act either as a motive (driving) or braking (resisting) force. For example, gravity acts as a driving force during downward movement, and as a braking force during upward movement. During horizontal movement, gravity is conventionally considered neutral. A tailwind, for instance, acts as a driving force when walking, whereas a headwind acts as a braking force.

Center of gravity of the human body. A distinction should be made between the total center of gravity (center of mass) of the human body (body COG) and the centers of gravity of individual body parts.

The general center of gravity of the human body is the point of application of the resultant of all gravitational forces acting on its component parts (body segments). Each part of the human body, given a specific mass and spatial arrangement, has its own center of gravity. For instance, the center of gravity of the HEAD is located approximately 7 mm posterior to the sella turcica; that of the trunk is situated at 0.44 of the distance from the shoulder joint to the hip joint, anterior to the upper edge of the 1st lumbar vertebra. For the arm, forearm, and thigh, these values are 0.47, 0.42, and 0.44, respectively; for the leg, it is 0.42 of the distance from its proximal end. The center of gravity of the hand, with the fingers slightly flexed, lies approximately 1 cm proximal to the head of the 3rd metacarpal bone, while the center of gravity of the foot lies on its longitudinal axis, 0.44 of the foot's length away from its posterior edge.

Since human body segments are not arranged strictly vertically one above another—even in a standard upright posture, let alone during movement—angles are formed between them at the joints. Consequently, the vertical line of the body's center of gravity (CG) passes at a certain distance from the center of any given joint, generating a rotational moment (the product of the gravitational force and its moment arm). The greater the rotational moment, the higher the tension experienced by the muscle group working against gravity.

Knowing the position of a segment's center of gravity makes it possible to determine the moment arm of gravity relative to the joints and to calculate the rotational moment. The mass of individual body segments constitutes the following percentages of total body weight: head — 7%, trunk — 46.4%, arm — 2.6%, forearm — 1.8%, hand — 0.7%, thigh — 12.2%, leg — 4.6%, and foot — 1.4%. Hence, given a total body mass (weight) of 70 kg, the head weighs:

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Thus, the body's CG serves as an indicator of mass distribution within the human body, reflecting its physique to a greater or lesser extent. After all, neither girths nor linear dimensions, commonly used in anthropometric practice, provide an adequate measure of the actual mass corresponding to those dimensions. Even with identical linear dimensions, the mass they represent can vary due to differences in the specific gravity of tissues and Organs.

The higher the body's CG is located, the greater the mass concentrated in the upper half of the body. For example, in gymnasts, the CG is situated higher than in track-and-field runners, because gymnasts place heavy physical demands on their upper limb muscles, whereas runners rely primarily on their lower limbs. This results in distinct differences in muscle mass distribution.

When referring to the "center of gravity of the human body" in a living person, one does not mean a fixed geometric point, but rather a zone or sphere within which this point resides. Due to fluctuations in Blood Circulation, respiration, Digestion, and other physiological processes, body mass is continually redistributed, affecting the position of the CG, which constantly shifts slightly in one direction or another. As a general estimate, the diameter of the sphere within which the CG moves during a stationary posture is about 5–10 mm.

To establish the exact Location OF THE body's CG, it must be determined across three planes: frontal, horizontal, and sagittal. In any symmetrical posture, the CG lies within the median plane because the right and left halves of the body weigh approximately the same. That said, the mass of the Internal Organs on the right side is roughly 500 g greater than on the left, primarily because the larger portion of a massive organ like the Liver is housed on the right.

The position of the body's CG was first determined by Borelli in 1679, who noted that in an upright stance, it lies between the buttocks and the pubic bone. To find the CG, he used a balancing method based on THE PRINCIPLE OF the first-class lever: a person lying on a board was balanced on a wedge-shaped fulcrum, and the position of the wedge indicated the location of the CG (Fig. 159).

The position of the body's CG was also determined using Scheidt's method, based on the principle of the second-class lever (Fig. 160). In this method, the subject's height multiplied by the experimental weight reading equals the subject's natural body mass multiplied by the distance from the plantar surface of the foot to the body's CG.

Fig. 159. METHOD FOR DETERMINING the position of the body's CG using the first-class lever principle:

the dashed line indicates the plane of the body's CG; the lower horizontal line represents the subject's height in the supine position; the two upper lines show the distances from the plantar surface of the foot and from the top of the head to the body's CG, respectively.

Fig. 160. Method for determining the position of the body's CG using the second-class lever principle;

© — position of the body's CG;

X — distance from the plantar surface of the foot to the body's CG;

I — height of the test subject;

в — body weight indicator on the decimal scale

Fig. 161. Position of the body's CG in men and women (at the same height, the CG is located lower in women than in men)

M. F. Ivanitsky determined the location of the body's CG in the horizontal plane in 650 subjects. Relative to the longitudinal axis of the body, its position is expressed as an index: The ratio of the distance from the center of gravity to the plantar surface of the foot, divided by body height and multiplied by one thousand. Most frequently, this index ranges between 555 and 565, placing it slightly above the midpoint of the body. Another way to describe the CG's location is by its projection onto THE Vertebral Column and the abdominal wall. M. F. Ivanitsky's observations show that the body's CG can fall anywhere between the 1st and 5th sacral vertebrae. Its position relative to the longitudinal axis and the spine depends on multiple factors: sex, age, muscular development, skeletal mass, subcutaneous fat distribution, and others. Daily fluctuations in the CG's position can also occur due to body deformations caused by heavy physical exertion. Individual variations in its position relative to the spine are more pronounced than relative to body height. On the anterior surface of the body, the CG is projected above the Pubic Symphysis.

In newborns, the body's CG is located at the level of the 5th–6th thoracic vertebrae; by the age of two, it drops to the level of the 1st lumbar vertebra and continues to descend until ages 16–18, shifting gradually not only downward but also backward. In men, the CG is situated between the 3rd lumbar and 5th sacral vertebrae, whereas in women it ranges from the 5th lumbar to the 1st coccygeal vertebra (Fig. 161). The average relative height of the body's CG (relative to body length) is 572 in men and 559 in women. In older adults, the position of the CG is also influenced by posture characteristics.

Each somatotype exhibits distinct features in the positioning of the body's CG. In individuals with dolichomorphic body proportions, the CG is positioned relatively lower than in those with brachymorphics (Fig. 162). When subcutaneous fat is predominantly accumulated in the pelvic and thigh regions (as is typical in women), the CG lies lower than when fat is distributed more evenly.

Variations in body proportions and muscle mass distribution among athletes in different sports also account for differences in the position of the body's CG. Swimmers have a higher CG than tennis players, while cyclists have a lower one; ice hockey players have a lower CG than basketball players.

When conducting an anatomical analysis of movements, it is essential to know the trajectory of the center of gravity. Without this, it is impossible to determine the velocity, acceleration, or force experienced by the body or its individual segments during movement.

To determine the trajectory of the whole-body center of gravity (CG) during movement, one must use photographs or drawings derived from cinegrams of a human figure to sequentially plot the positions of the CG at each given moment of the movement. The line connecting these resulting points will represent the CG trajectory for that specific movement. Methods for Assessing the CG trajectory are studied in greater detail in the course of biomechanics.

The center of volume of the human body. Information regarding the center of volume of the human body is of particular importance for the anatomical analysis of swimming movements and for assessing a swimmer's hydrodynamic qualities. The center of volume of the body is defined as the point of application of all water pressure forces acting on its surface. The human center of volume is located slightly higher than the body's CG. This is confirmed by the fact that when a person lies on their back in the water with arms extended alongside the body, they typically transition from a horizontal to a vertical position as the lower part of the body sinks. Only a few individuals can maintain such a horizontal position in the water without moving. Equilibrium in the water can only be maintained when the vertical line of the body's CG coincides with the vertical line of its center of volume.

The position of the body's CG in men of equal height but with different body types (with a more developed upper body, the body's CG is located higher)

To determine the PROJECTION OF THE center of volume in the horizontal plane, the method of water displacement by the body in a graduated tank is used (Fig. 163).

The level of water poured into the tank is recorded, followed by the water level when the person is fully submerged, and the water level corresponding to half of that volume (the volume of the upper body must correspond to the volume of the lower body).

After this, the subject is asked to gradually submerge into the water until the water reaches the predetermined level that characterizes the position of the body's center of volume. As a rule, it is located 2–6 cm away from the level of the body's CG. During inhalation, the general center of volume will be positioned higher than during exhalation.

Specific gravity of the human body.

Specific gravity characterizes body density and represents its mass reduced to a unit of volume (1 cm3). This is one of the important indicators of physical development and health status, depending on many factors. In particular, it is associated with respiratory movements: it decreases during inhalation and increases during exhalation. In adult men with a height of 165 cm and a body mass of 64 kg, the specific gravity is 1.044. Taller men have a lower specific gravity than shorter men. Individuals with well-developed muscles have a higher specific gravity than those with weakly developed musculature. The specific gravity of women's bodies is lower than that of men due to a greater amount of body fat. In childhood, body specific gravity increases with age: in 11-year-old boys it is 1.019, at 13 years old — 1.026, at 15 years old — 1.033, and at 17 years old — 1.040. This is related to age-related changes in body mass components (for details, see p. 386). In girls, body specific gravity increases only up to the age of 13, after which it decreases. Differences in the age dynamics of body specific gravity between boys and girls are explained by the uneven rates of GROWTH AND DEVELOPMENT of the Organism (see p. 404).

Fig. 163. Method for determining the position of the center of volume:

A — water level before THE START OF the experiment; K — water level with the body fully submerged in water; B — water level corresponding to half of the body volume

The dynamics of specific gravity can be used to monitor changes in body mass components: an increase in specific gravity indicates an increase in muscle (active) body mass, and conversely, its decrease indicates an increase in the fat component.

Support area. The support area is determined by the area of the body's supporting surfaces and the size of the space enclosed between them. The support area is always taken into account when conducting an anatomical analysis of physical exercises. Body stability depends on it: stability is greater the larger the support area. Thus, body stability in a stride stance is greater than in a feet-together stance; in a two-leg stance — than in a one-leg stance; on skis — than on ice skates; in a fencer's or boxer's stance with spread legs than in a regular standing position (therefore, maneuverability of movements without loss of balance in a sports match is quite high).

Types of equilibrium. The type of equilibrium is determined by the ratio of the support area to the position of the body's CG. If the support area is located below the body's CG, the equilibrium is unstable or, as defined by D. D. Donskoy, limitedly stable. If the support area is located above the body's CG, the equilibrium is stable (a body displaced from this position can return to its original state without the involvement of internal forces).

Depending on the type of equilibrium, the acting forces behave differently. For instance, gravity in unstable or limitedly stable equilibrium exerts a compressive effect on individual body segments, while in stable equilibrium, it exerts a tensile (tensional) effect.

Conditions for maintaining body equilibrium and the degree of its stability. Body equilibrium in a given position is maintained provided that the vertical line of the body's CG passes within the support area. If it extends beyond the BOUNDARIES OF THE support area, equilibrium is disrupted — the body falls. The degree of body stability during exercise depends on the height of the body's CG and the magnitude of the support area. The lower the body's CG and the larger the support area, the greater the stability. The quantitative characteristic of the degree of body stability is the angle of stability. It is formed by the vertical line dropped from the body's CG and a line drawn from it to the edge of the support area. The larger the angle of stability, the greater the body's stability. The magnitude of the angle of stability determines the potential for body displacement without loss of balance.

For a correct anatomical interpretation of the work of the motor apparatus, it is first necessary to ascertain the conditions of movement, taking into account the equality of action and reaction, the manifestations of inertia, the conservation of angular momentum, and other regularities.

The work of the motor apparatus is characterized by:

— the position or movement of individual body segments in the joints;

— the muscle groups responsible for this position or movement;

— the state and functional nature of the muscles.

The Morphological Characteristics of The Musculoskeletal System, in relation to the specifics of motor activity, take into account the position of body segments in the joints, the range and direction of movement, the magnitude of joint angles, as well as the position of the vertical line of the body's CG relative to the axes of rotation in the joints.

Movements in joints can be determined through direct observation of a living person and measurement of mobility using a protractor, goniometer, or other specialized device. More precise data concerning joint Functions during a particular movement are provided by radiography and radioscopy, which make it possible to obtain a clear picture of bone positions at a specific moment of movement.

When characterizing the active component of the musculoskeletal system, it is necessary to determine: the functional muscle groups responsible for a given posture or movement, the direction of muscle pull or its resultant vector relative to a specific axis of rotation in the joint crossed by this muscle group.

Of significant importance are the state of the muscles (tensed, relaxed, shortened, lengthened), The Nature of muscle work (static, dynamic, overcoming, yielding, holding, etc.), the type of muscle support (proximal, distal, upper, lower), as well as the Specific characteristics of the torque generated by muscle pull.

Research Methods include: tonometry, which assesses muscle tone; photography, which records muscle shapes; kinography, which captures a sequence of successive changes in muscle shape during movement; X-ray imaging, which records the shape and movement of muscles on X-ray film (for example, Diaphragm movements during respiration); dynamometry and dynamography, which evaluate muscle strength; electromyography, which records Muscle Action currents, among others.

Assessment of the external respiration mechanism and the state of movement support and regulation systems includes determining the shape of the rib cage (whether it is expanded or compressed), the state of the intercostal muscles (the degree of their fixation at attachment sites), the position and excursion of the diaphragm (whether there is any Displacement of the diaphragm or obstruction to its movement), and the state of the Abdominal muscles (tensed or relaxed; when the abdominal muscles are tensed, the downward movement of the diaphragm during inhalation is hindered).

Based on the Movements of the chest (middle and lower regions), the type of breathing is determined (thoracic, abdominal, mixed). For this purpose, the following methods are used: anthropometry, which assesses the dimensions and mobility of the chest during breathing; photo-, kino-, and X-ray imaging; and in some cases, recording of rib movements using a goniometer, millimeter ruler, or kymograph.

To determine the state of the systems supporting The Mechanism of external respiration—such as the specific layout, structure, and function of internal organs, as well as the state of The Cardiovascular system—during the performance of physical exercises, primary research methods include X-ray imaging and X-ray kymography, along with functional tests⁷.

Determining The Effect of body positions or movements on the human body takes into account The impact of exercises on the Skeletal System, joint mobility, Muscle Development, posture, foot condition, as well as other organs and systems (see p. 485).

Thus, the anatomical analysis of human postures and movements, as well as physical exercises performed, should contribute to the optimization of methods for physical impact on the human body (including for therapeutic and rehabilitation purposes), assist in The Development of methodological recommendations for a more effective and economical use of the body's reserve capacities, and promote the improvement of athletic technique and the harmonious Development of the human body.

⁷ Functional tests are covered in the course of sports medicine.