Biochemical Foundations of Human Body Vital Activity - Volkov N.I., Nesen E.N. 2000

Biochemistry of Sports
Regularities of Biochemical Adaptation in the Process of Sports Training
Regularities of the Development of Biochemical Adaptation and Training Principles

The Development of adaptation in response to training with progressively increasing physical loads is described by the well-known biological "dose-response" relationship. Low physical loads that do not yet reach the threshold value required to trigger adaptive Changes in the body will not stimulate the Development of the trained function and are therefore generally classified as ineffective loads. To ensure a pronounced increase in a trained function under METABOLISM/18.html">The Influence of a specific type of physical load, its magnitude must exceed this threshold value. Compliance with this requirement in order to foster necessary adaptive changes through physical loads has led to The Emergence of the overload principle in sports training theory. According to this principle, prominent adaptive changes resulting from training will occur only if the volume and intensity of the load sufficiently challenge the trained function and stimulate its development.

The heightened functional intensity of leading systems and individual Organs during training provides the necessary stimulus to accelerate Energy Metabolism and enhance the synthesis of Nucleic Acids and Proteins that constitute these organs and systems, ultimately leading over time to the required Structural and functional reorganizations in the body.

The existence of a load threshold and The phenomenon of overload during training are due to the fact that the development of adaptive changes in the body in response to any novel and sufficiently strong stimulus is mediated by two distinct functional systems: first, The system of intracellular energy metabolism and associated vegetative support Functions, which respond specifically to the given type of stimulus in direct proportion to its intensity; and second, the hormonal sympathoadrenal and pituitary-adrenocortical systems, which respond nonspecifically to A wide variety of stimuli and are activated only when the intensity of these stimuli exceeds a certain threshold level. This nonspecific reaction to a sufficiently strong stimulus is termed the "stress syndrome," and the stimuli that provoke this reaction are generally referred to as stress factors or stressors. Stressors operating during training may include not only physical loads but also other external factors: bioclimatic, pharmacological, psychogenic, social, and so forth.

The onset of the General adaptation syndrome in response to physical loads applied in training leads to the excitation of vital autonomic centers and, consequently, to the activation of the sympathoadrenal and pituitary-adrenocortical systems. As a result of this intensified hormonal activity, the concentrations of catecholamines and glucocorticoids increase in the Blood and Tissues. Both of these hormonal factors possess a wide range of actions, specifically facilitating the mobilization of the body's energy and plastic resources. Thus, a physical load that reaches stress-level proportions induces a generalized mobilization reaction in the body, facilitating the emergence of necessary adaptive changes in the trained functions.

Research findings indicate that the threshold load sufficient to activate the sympathoadrenal and pituitary-adrenocortical systems is approximately 50—60% of an individual's VO₂max. This means that in order to elicit progressive adaptive changes in the body, the magnitude of the training load applied must not fall below the anaerobic threshold (AnT).

Once the applied load exceeds the threshold value, any change in its magnitude across a fairly wide range will be accompanied by a proportional increase in the trained function. Within this range of effective loads, precise management of the athletes' condition becomes possible. However, the potential for continuously increasing the total volume of performed loads and achieving boundless growth in trained functions is not unlimited. In each specific case, there is an individual limit of adaptation for a given function or for the Organism as a whole. As this limit is approached, The rate of increase in the leading function gradually slows down and eventually ceases altogether at a certain load magnitude. If the load is set beyond this critical level, a paradoxical reaction occurs: as the intensity of the load increases, the organism's response decreases. Such a reaction is characteristic of adaptation breakdown, i.e., the development of overtraining. Limit loads typically occur during competitions and control testing, but they cannot be used frequently because they rapidly lead to the depletion of the dominant systems responsible for adaptation.

Individual tolerance to limit loads is largely determined by the adaptation reserve of the sympathoadrenal and pituitary-adrenocortical systems. Highly trained athletes with a high adaptation limit are distinguished by a more economical response from the sympathoadrenal system, yet they are capable of achieving significantly higher peak blood catecholamine concentrations.

The dose-response relationship, which determines the correlation between the volume of completed training work and the increment in the trained function, can be used for the quantitative assessment of adaptation to physical loads. Theoretically, five main TYPES OF RELATIONSHIPS exist between changes in the trained function and the volume of performed work (Fig. 192). In the initial stage of adaptation development (fragment 1), the dose-response relationship is represented by an exponentially rising curve; under normal training conditions, it appears as a straight line (fragment 2), which, like the rising exponent, indicates that the limits of adaptation have not yet been reached and the volume of performed work can continue to be increased.

When loads close to the limit are used in training, the dose-response relationship transforms from a linear dependence into a constant curve reaching a plateau (fragment 3). I.G. Fales (1988) investigated The Effect of high-intensity interval training, used in the preparation of top-division soccer players, on changes in the body's aerobic power indicators. In this case, the maximum oxygen uptake increased linearly until the volume of interval loads in the soccer players' training reached 420 hours per year (Fig. 193). At higher load volumes, VO₂max changed no further, approaching its peak values. Based on this finding, the author concluded that it is impractical to increase the total volume of interval work beyond 420 hours per year to develop aerobic power in soccer players, since the emergence of this type of relationship with increasing work volume points to the danger of overstrain and adaptation breakdown.

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Fig. 192 Main Variants of the dose-response relationship observed during the development of adaptation in the training process

Even greater caution must be exercised when training within the range of limit loads, where the dose-response relationship takes the form of a parabolic curve (Fig. 192, fragment 4). In this load range, the increment in the developed function ceases. If the volume of applied loads continues to increase beyond this point, a noticeable decline in the training effect is observed (fragment 5). This principle is clearly illustrated by data on changes in total oxygen debt as a function of the volume of anaerobically oriented training work identified in soccer players (Fig. 194). The peak of the parabolic relationship, indicating the volume of interval loads that exerts the greatest impact on the anaerobic functions of soccer players, is located at a level of 240 hours per year. At higher volumes, these loads no longer contributed to the development of the body's anaerobic capacity and instead led to a decrease in the training effect.

A decline in the rate of adaptation development as the volume of training work increases can be prevented by modifying training conditions, as well as The Nature and magnitude of the training load.

In addition to the overload principle, which is directly linked to the Analysis of the dose-response relationship, sports training theory postulates other principles based on the regularities of biological adaptation. These primarily include the following principles (Volkov N.I., 1986): Specificity, reversibility, positive interaction, sequential adaptation, and cyclicality.

Fig. 193 Increase in maximum oxygen uptake as a function of the total annual volume of training loads in the preparation of elite soccer players

Fig. 194 Increase in maximum oxygen debt as a function of the annual volume of anaerobic training loads in the preparation of elite soccer players

THE PRINCIPLE OF specificity postulates that the most pronounced adaptive changes induced by training occur in the organs and functional systems most heavily taxed during the execution of physical loads. In accordance with the nature and magnitude of the selected load, a dominant system is formed within the body, the hyperfunction of which ensures the development of adaptation. This heavily loaded system provides the body with advantages in plastic and energy metabolism compared to organs and systems not directly involved in performing the given load.

During training, excessive strain and ADAPTATION TO A specific type of load can at some point deplete the functional reserves of the dominant system and impair the function of other systems not directly involved in the response to the load (a condition referred to as overtraining). Therefore, alongside the selective impact on "leading" (dominant) functions during training, it is necessary to ensure a regular shift in the focus of the training stimulus in order to achieve an effective and comprehensive adaptation of the organism to all factors manifesting themselves under the conditions of the given sport.

The principle of reversibility is based on the instability of adaptive changes in the body induced by training in a specific type of load, since the cessation of physical loads or a break in training leads to the gradual decline and disappearance of positive structural and functional shifts in the dominant system.

This principle is most clearly manifested through the delayed training effect observed after physical load. In this case, changes induced in energy metabolism quickly return to baseline and, at a certain point, exceed it (this enhancement constitutes the supercompensation phase). Upon completion of the supercompensation phase, the indicators of energy metabolism undergo periodic fluctuations before gradually returning to normal. Based on this regularity of recovery processes, it follows that for adaptation to develop, the training process must not be interrupted, and repeated loads should be administered during the supercompensation phase (Fig. 195). The principle of reversibility applies equally to cumulative training effects. High physical performance achieved over a long period of training declines after training is discontinued or when its intensity is reduced.

The principle of positive interaction states that the cumulative effect resulting from the repeated application of a load is not a simple addition of a certain number of acute and delayed training effects. Each subsequent load acts upon the adaptive effect of the preceding load and can modify it. If the result of this summation of training effects leads to an enhancement of adaptive changes in the body, a positive interaction occurs. If each subsequent load diminishes the effect of the previous one, a negative Interaction of Training effects takes place. Finally, if a subsequent load has no noticeable effect on the training outcome of the preceding load, a neutral interaction is observed. Effective adaptation over a prolonged period of training can be achieved only through positive interaction between individual loads. The training effects of physical loads can also be influenced by other nonspecific training factors, particularly Nutrition, physiotherapy and pharmacological agents, bioclimatic conditions, and so forth. These additional factors designed to enhance adaptation to physical loads can be successful if their specific effects interact positively with the training effects of the loads.

Fig. 195 Summation of training effects upon repeated execution of loads at various rest intervals during the Phases of the consolidated state (a), supercompensation (b), and underrecovery (c)

The principle of sequential adaptation is based on well-established facts regarding the heterochronism (temporal asynchrony) of biochemical changes that occur in the body during training. Specifically, when an acute training effect develops in response to a single bout of Physical Exercise, the fastest adaptive changes in individual energy systems occur within the alactate anaerobic system, followed by the anaerobic Glycolysis system, while the slowest response is observed in mitochondrial Respiration and Oxidative Phosphorylation. During the recovery period following exercise, supercompensation is achieved most rapidly for creatine phosphate content in Muscles, followed by Glycogen, and finally by Lipids and proteins that form subcellular structures. In The process of long-term adaptation, indicators of bioenergetic process power change the fastest, followed by energy capacity, and only at The final stage of adaptation do indicators of metabolic efficiency improve markedly.

The principle of cyclicity stems from the phased nature of adaptive processes in the body during training, wherein Observed changes in the rate of adaptation across leading functions exhibit varying amplitudes and wavelengths. For adaptation to develop, the training effects of different loads must be accumulated according to specific rules, creating a cohesive cycle of impact on key functions. In this case, the cycle should be repeated multiple times over a certain training period dedicated to a specific pedagogical objective. Such extended training cycles, which successively replace one another from stage to stage in accordance with the regular development of adaptation in leading functions and qualities, form higher-order cycles that Structure the "key" milestones of athletes' participation in major competitions.