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

Morphological Support of Mass Physical Culture and Sports (Sports Morphology)
General Theoretical Foundations of the Theory of Adaptation

METABOLISM/2.html">THE CONCEPT OF Adaptation

Adaptation (from Latin adaptatio) is the adjustment of an Organism, population, or other biological system to altered living or functional conditions. The principles of materialist dialectics regarding the dialectical unity of Structure and function provide for their simultaneous and coordinated modification during the adaptation process.

Adaptation occurs at both the genotypic and phenotypic levels. Genotypic adaptation is characteristic of a specific segment of humanity and develops over many generations, historically emerging as an adjustment to particular ecological conditions. An example is The formation of racial traits: Skin color, facial and cranial structure, among others. Phenotypic adaptation takes place during the individual development of an organism and is not fixed in the human genotype¹⁰.

In the course of training and competition, an athlete's body is subjected to numerous external influences, the most crucial of which is physical exertion. Adaptation to these loads entails bringing the STRUCTURE AND Functions of the body into alignment with the demands of athletic activity.

Adaptation to increasing physical loads, changing Temperature regimes, shifts in air composition, or the action of other factors manifests in both general ways (associated with the nonspecific defense of the body against these influences) and specific ways. The presence of general reactions makes it possible to use certain environmental factors to prepare (preadapt) the organism for the effects of others. For example, exposure to low oxygen conditions—a hypoxic factor—creates a state of preadaptation to high motor loads. Engaging in certain sports can foster preadaptation to success in others (wrestling and weightlifting, or cycling and speed skating, represent such combinations).

¹⁰ Hereinafter, the term "adaptation" refers to Changes in the structure and Functions of the organism that arise during individual development at the phenotypic level—in The process of adaptomorphosis.

Adaptation to any given influence affects the state of the organism as a whole, involving all its Organs and systems: the executive system, which includes the musculoskeletal apparatus; the support systems (digestive, respiratory, excretory, and cardiovascular); and the regulatory and control systems (Endocrine glands and The Nervous system with its Sense Organs).

Any motor act is performed with the participation of the musculoskeletal organs (bones, their joints, and Muscles) that execute movements, the cardiovascular and Blood systems that supply nutrients to the executive organs, and the central and peripheral nervous systems that regulate movement. In a certain sense, the entire organism—not merely the named organs and systems—takes part in the regulation and support of movements. The endocrine apparatus provides humoral regulation (complementing the nervous system), the Digestive System helps saturate the blood with substances necessary for nourishing working organs, the Respiratory system enriches the blood with oxygen, the sense organs correct movements, and the excretory organs help cleanse the body of harmful Metabolic waste products:

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Adaptation depends on numerous conditions, the most critical of which are the Specificity and intensity of the external stimulus and the organism's reaction norm, which determines its susceptibility or resistance to a given environmental factor.

The Dependence of Adaptation on Stimulus Intensity

Physical loads of varying intensity exert different effects on the body. Mild loads cause no noticeable changes, whereas moderate loads stimulate morphofunctional remodeling of the organism in accordance with a new level of activity and accelerate growth (Fig. 186). High loads inhibit these processes, creating a gap between the organism's biological capabilities and the volume of activity. Ultra-high loads cause Functional and Structural disorders. The discrepancy between what the organism is capable of and what it is required to perform becomes excessively large. This serves as a source of latent and overt damage and injuries that frequently compel athletes to abstain from their usual activities for prolonged periods. From the foregoing, it follows that the optimal load level is the moderate one. However, an organism's susceptibility to any environmental influence is individual. What constitutes a moderate load for one person will act as a light load for another and a heavy load for a third. This is generally considered to be related to differences in the organism's reaction norm to external influences (its reactivity).

Fig. 186. Differences in the growth intensity of the Femur in inbred rats depending on the animals' reaction norm (top — August strain, bottom — Wistar strain) and their level of physical loading from left to right: control (C), the result of prolonged hypokinesia (H), and the results of three sequentially increasing load regimes following prior hypokinesia—ranging from moderate (I) to significant (II) and excessive (III) mechanical loading. Restoration of normal bone dimensions in August rats occurs at level III, whereas in Wistar animals it occurs at level II, with a suppression of growth activity observed at level III

The Reaction Norm and the Factors Regulating It

The reaction norm refers to the individual characteristics of an organism's susceptibility to the action of a specific environmental factor. An organism's reaction norm, or reactivity, depends on hereditary traits, age, sex, prior experience, constitution, physiological state, health status, and other factors.

The organism's reaction norm determines the threshold of its susceptibility to environmental factors, the levels of optimal and excessive dosage of a factor, and the degree of functional and structural Variability during adaptation to new operating conditions. As a rule, an inverse relationship exists between the level of an organism's susceptibility to external influences and the degree of genetic determination of its life processes at a given stage of ontogenesis. Twin studies have demonstrated that the degree of genetic determination of vital processes changes with age: it is low in the first years of life and drops again during Puberty. Consequently, early childhood and puberty render the developing organism more vulnerable to external influences, including physical loads.

The degree of an organism's susceptibility to external influences also depends on sex (see p. 402). There is a view that the female body is biologically more resistant to external influences. Women have a higher average Life expectancy and are less susceptible to many diseases (for example, cardiovascular disorders). Although facts of a different nature also exist; for instance, women are more emotionally unstable under stressful environmental conditions. During athletic competitions, the psychological readjustment of the female body is more pronounced than that of the male.

An important factor determining organismal reactivity as well as the dynamics of GROWTH AND DEVELOPMENT is constitution. This represents the integrity of morphological and functional traits, both innate and acquired. As is evident from the definition itself, the organism's reaction norm is an integral component of human constitution (see p. 472).

The reaction norm of an organism to external influences also depends on its physiological state, which changes with a certain regularity throughout the day, month, or year, revealing a specific cyclicity—daily, monthly, and so forth. The reaction norm likewise undergoes cyclical fluctuations.

The reaction norm depends on the level of training and prior experience interacting with the perceived environmental factor. All people possess tactile sensitivity, but through training, it can be perfected in some individuals. It is particularly well-developed in the blind and deaf-blind. Undoubtedly, in the course of athletic training, the body's susceptibility to physical loads changes. Heredity determines the limits of potential fluctuations in the reaction norm.

The reaction norm also changes under certain pathological states of the organism.

It remains to be added that the reaction norm is not uniform across different structures and functions of the body. This is due to the fact that each of them possesses its own developmental characteristics, genetic determination, and so on.

Stress as a Mechanism of Adaptation

External influences on an organism induce functional and structural alterations within it, disrupting Homeostasis—the constancy of the internal environment.

When facing severe external influences, the body needs protection and Maintenance of Homeostasis. This self-protective mechanism is the so-called stress reaction, thoroughly described back in the 1930s by Canadian pathophysiologist H. Selye. The stress reaction, or General adaptation syndrome, is a restructuring of the body's neuroendocrine regulation that sequentially passes through three phases: the alarm phase, the resistance phase, and the exhaustion phase. Morphologically, stress manifests as thickening and increased activity of the adrenal cortex, atrophy of organs of immunological protection (the Thymus gland and Lymph Nodes), and the formation of ulcerations on the mucosal surface of the gastrointestinal tract.

The alarm phase is accompanied by enhanced production of the hormone adrenaline by The adrenal medulla. Its effect is similar to that of the Autonomic nervous system mediator, noradrenaline, and it exerts a vasoconstrictive action, which ultimately leads to the formation of ulcerations on the mucosal surface.

The Hormones of the adrenal cortex—corticoids—possess protective and anti-inflammatory properties and stimulate growth. Therefore, during the resistance phase, the body's vital activity and growth processes are intensified. However, the body's adaptive capacity is not limitless. The duration of the resistance phase depends on the innate adaptability of the organism and the intensity of the external impact. In response to extremely strong or prolonged stress, adrenal activity becomes exhausted, and the protective effect disappears.

The adaptation of the organism to an environmental factor leads to the latter ceasing to trigger a stress reaction. The production of hormones by the adrenal cortex decreases, and the formation of new bodily structures is inhibited.

Thus, there is the following sequence of processes associated with the stress reaction: external factor → stress reaction → release of a large amount of corticoids into the blood → activation of Cell Division and adaptation to the external impact → cessation of the stress reaction → decrease in corticoid production → inhibition of cell division.

The training process aims to adapt the athlete's body to increasing loads. Its physiological mechanism is the stress reaction, the manifestation of which relies on the gradual increase in the load level.

Pathways of the body's adaptation to physical loads

The shaping influence of physical activity, including sports, on the organism is undeniable.

During the evolutionary phase of ontogenesis (see p. 361), this occurs mainly due to the effects of physical loads that differentiate growth processes in the so-called growth zones (for example, the epiphyseal and articular Cartilage zones, which determine the longitudinal growth of tubular bones). These exert not only a local effect but also a generalized one, mediated by the restructuring of neuroendocrine regulatory systems.

In the stable phase of ontogenesis, when growth processes are largely completed, physical loads affect the body through compensatory-adaptive processes occurring within it.

In the involutionary phase of ontogenesis, physical loads act on the organism by regulating Aging processes across organs and systems.

The adaptation of the body involves the creation of certain structural formations and the destruction of others. This illustrates F. Engels' well-known proposition that to live is to die.

Compensatory-adaptive processes are realized According to the same morphological laws reflected in The Theory of regeneration, i.e., the renewal of bodily structures (see p. 21). The following forms of regeneration are distinguished:

— molecular — renewal of molecules;

— intraorganoid — normalization of The structure of individual cell Organelles and their hypertrophy;

— organoid — increase in the number of organelles and hyperplasia of the nuclear apparatus;

— cellular — cell division.

The first three forms are united under the single concept of intracellular regeneration.

Regeneration that ensures the body's vital activity under normal conditions is called physiological, while regeneration during tissue damage is termed reparative (restorative). In complete regeneration, the defect is filled with tissue identical to the destroyed one. In incomplete regeneration, the defect is filled with Connective Tissue.

In the mid-19th century, two mechanisms of organ size increase were specified in Morphology: hypertrophy (due to an increase in cell volume) and hyperplasia (due to an increase in their number). However, the enlargement of any body structure is always based on an increase in the number of its smaller components: cellular hypertrophy is associated with an increase in the number of its organelles, and the hypertrophy of each organelle is linked to an increase in the number of its ultrastructures. A decrease in the number of cell organelles and of the Cells themselves leads to atrophy.