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

Biochemistry of Sports
Regularities of Biochemical Adaptation in the Process of Sports Training
Specificity of Adaptive Changes in the Body During Training

The Specificity of adaptive changes occurring in the body during training is clearly manifested in the indicators of both acute and cumulative training effects. This specificity can be readily traced across all levels—from the subcellular level to the Organism as a whole. For instance, endurance runners exhibit (all other anthropometric characteristics being equal) a relatively lower body mass and a lower percentage of fat mass, whereas shot putters, discus throwers, and hammer throwers possess a greater body mass and a higher percentage of body fat.

Athletes engaged in sports that require significant endurance, such as ultra-distance runners, cross-country skiers, and road cyclists, are characterized by high levels of maximal aerobic power. In contrast, athletes in aesthetically-coordinated and speed-strength sports, such as divers, weightlifters, and gymnasts, show little difference in these indicators compared to the norm established for untrained individuals.

In accordance with The Nature of the applied training means and Methods during systematic sports participation, the body develops only those functional properties and qualities that are crucial for achieving success in the chosen exercise discipline. For example, when training sprinters compared to long-distance runners, the functional qualities reflecting the power and capacity of the alactic anaerobic system undergo preferential development. At the same time, in the preparation of master stayers, Indicators of Aerobic power (maximal O₂ uptake) and aerobic efficiency increase more significantly, which is reflected in a relatively smaller increase in lactic acid production in response to a standard workload.

The specific nature of adaptive changes developing under METABOLISM/18.html">The Influence of training in a chosen sport is manifested not only in the absolute values of the level of development of leading Functions, but also in a more complete utilization of acquired abilities in the selected type of exercise. This is well illustrated by the data presented in Fig. 196. Athletes who underwent specialized training in one of three sports—rowing, cycling, or cross-country skiing—were subjected to tests to determine their $\text{VO}_2$ max during treadmill running and while performing exercises specific to each sport. As can be seen from the data presented, athletes achieve the highest $\text{VO}_2$ max values in exercises specific to their particular sport.

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Fig. 196 Features of adaptation manifestation in specific types of sports activities

The features of Specific Adaptation developing under the influence of training are determined by the Selection not only of a specific type of exercise, but also of Specific characteristics of the physical load. Depending on the chosen combination of basic load characteristics, an acute training effect is formed, determined by the magnitude and direction of the physiological changes occurring in the body. With a sufficient number of load repetitions yielding a specific acute training effect, specific adaptive changes arise in the body, which manifest as the cumulative effect of a given type. Fig. 197 illustrates the dependence of Changes in the level of O₂ consumption on running speed. Typically, this relationship is depicted as a straight line across a wide range of running speeds, and only when the limits of O₂ supply to working Tissues come into play—which is detected near The values of the critical running speed—does it transition into an exponential curve, the limit of which corresponds to the $\text{VO}_2$ max. The slope of the rectilinear portion of this curve reflects the efficiency of aerobic Energy Expenditure, the infinite value of which corresponds to O₂ expenditure per 1 unit of body mass and per 1 m of distance. As seen from the graph, changes in O₂ consumption levels in highly qualified long-distance runners in the section corresponding to running speeds most frequently used in training deviate significantly from the linear dependence, demonstrating a pronounced reduction in energy expenditure when performing exercises of a given intensity.

Fig. 197 Changes in oxygen consumption levels at various running speeds in highly qualified athletes specializing in middle and long-distance running

A specific training regimen, much like exercise intensity, directly influences The Nature and magnitude of adaptive changes in skeletal Muscles. The study by E.A. Andris and N.I. Volkov investigated The Effect of a 16-week experimental training program involving prolonged continuous and interval running on The Development of aerobic and anaerobic metabolic systems in the skeletal muscles of rats. Following such training under these regimens, The activity of succinate dehydrogenase (SDH)—one of the Key Enzymes of the respiratory cycle in muscles bearing the primary load during running—increased markedly (Fig. 198).

The degree of SDH activity depended on The amount of work performed during the experimental training period. The highest magnitude of SDH activity and the most rapid rates of its increase were observed when utilizing the interval training regimen. To achieve a comparable increase in SDH activity in the Cell/35.html">Mitochondria of working muscles using the continuous long-duration work method, significantly greater training volumes were required.

The general orientation of the load's impact, which depends on the chosen dosages of its primary characteristics, is most fully manifested in the magnitude and Nature of the bioenergetic shifts occurring during work. The dependence of The rate of energy transformation in various metabolic processes on the relative power of the performed exercise was shown above. These quantitative criteria can also be successfully used to assess the cumulative impact of loads applied over a prolonged period. Based on this dependence, the training loads used in athletic preparation have been proposed to be divided into four ranges, differing in their impact on individual bioenergetic Properties of the organism. Specifically, the following types of physical loads were identified:

✵ loads of predominantly aerobic impact, the intensity of which does not exceed the anaerobic threshold;

✵ loads of mixed aerobic-anaerobic impact, which are usually subdivided into subcritical intensity loads, not exceeding maximal O₂ uptake values, and supercritical intensity loads, exceeding critical power values;

✵ loads of anaerobic glycolytic impact, the intensity of which roughly corresponds to exhaustion power, where the greatest shifts in anaerobic glycolytic energy production are achieved;

✵ loads of alactic anaerobic impact with an intensity close to maximal anaerobic power.

Fig. 198 Effect of continuous (1) and interval (2) running training on SDH activity in the skeletal muscles of rats

Metabolic shifts in the body during the performance of loads whose intensity does not exceed the anaerobic threshold are characterized by a steady state in aerobic metabolic processes. The energy supply for such loads is provided predominantly through aerobic metabolism processes under a sufficient supply of oxygen to the tissues.

Loads whose intensity exceeds the anaerobic threshold level but does not yet surpass the critical power value exert a simultaneous impact on the development of both aerobic and anaerobic functions.

When performing loads whose intensity is close to or even slightly exceeds critical power, changes in the sphere of aerobic metabolism reach maximal values, but simultaneously, anaerobic shifts increase rapidly as well. Such loads contribute to an increase in maximal aerobic power while simultaneously improving indicators of anaerobic work capacity.

The impact of loads whose relative intensity is close to exhaustion power is aimed primarily at improving indicators of Anaerobic Metabolism. The accumulation of lactic acid and shifts in the acid-base balance of the Blood reach their highest values in this process. Such loads help increase the intensity of glycolytic anaerobic transformations in tissues and stimulate the development of specific adaptation to work under conditions of significant oxygen debt.

Performing loads close to the values of maximal anaerobic power contributes most to increasing the capacity of phosphagen reserves, enhancing myofibrillar ATPase activity, and activating the synthesis of contractile Proteins in working muscles.

The most difficult challenge in developing systems for the quantitative accounting of performed loads is the accurate assessment of their volume and intensity. The volume of training loads is defined as the product of the duration of each session and the frequency of their application over a given time period. In establishing training load volume, quantities of different dimensions are used. For example, the volume of loads in cyclic exercises is measured in kilometers of distance covered, the volume of resistance exercises in kilograms of weight lifted, and the volume of exercises with complex coordination structures in units of time spent on their execution or the number of repetitions of individual elements. When assessing load intensity, as a rule, only the intensity indicators of the exercise being performed are taken into account—such as running speed—which in itself, as shown earlier, does not fully determine the training effect of the load. Based on the fact that the specificity of a load's impact is determined by changes in Energy Metabolism, a quantitative assessment of load intensity should utilize indicators of the relative metabolic level (RML units), representing The ratio of the exercise's energy demand level to the individual's maximal O₂ consumption level. Data regarding the relative metabolic level and criteria for loads of different orientations are presented in Table 36.

When determining load volume, it should be taken into account that the magnitude of adaptive changes occurring in the body depends on the duration of the stimulus action. The duration of physical load exposure comprises three components: exercise execution time ($T_{\text{ex}}$), rest interval between exercise repetitions ($T_{\text{rest}}$), and recovery time following the completion of the load ($T_{\text{rec}}$):

For example, if a middle-distance runner performs a repeated training session of 10 x 400 m with 1 min of rest between repetitions, taking 1 min to cover each 400 m segment, the standard method of quantifying the workload by distance gives a total volume of 10 x 400 m = 4000 m. At the given running speed, this corresponds to the total time spent actively performing the exercise:

TABLE 36. Criteria for Training Load Intensity

However, recording only the active exercise time does not fully account for the total dose of the load, which also includes rest intervals and recovery time following the work. In the given example, the total time indicator characterizing the duration of the load effect is

When accounting for rest and recovery pauses, the total time volume is approximately 2.5 times greater than the volume determined solely by active exercise time or total running distance covered during the workout. Performing the exercise merely provides the necessary stimulus to trigger adaptive restructuring within the body, but these adaptations are finalized and consolidated into a stable adaptive response during the post-work recovery period. Therefore, to determine the nature and magnitude of the training effect, tracking rest time is just as important as accurately recording the duration of actual physical work.

Temporal indicators of training volume are less dependent on the specific conditions of a given sport than the parameters of the exercise itself. Consequently, they enable the comparison and analysis of workloads applied across various sports utilizing a wide range of different exercises. As an example, Table 37 presents data on the volumes of training loads of different orientations utilized by athletes in specific sports during year-round preparation.

TABLE 37. Volume of Training Loads of Various Orientations