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
Reversibility of Adaptation Changes during Training

The reversible nature of adaptive changes arising in response to applied loads is most vividly manifested in The phenomenon of supercompensation. It is commonly asserted that a positive training effect is achieved only when subsequent loads are introduced during the supercompensation phase following the preceding load.

With short intervals between repeated loads, which are insufficient for supercompensation to occur, as well as with excessively long intervals during which load-induced shifts manage to return to baseline, a progressive increase in the body's adaptive changes cannot be achieved. It should be noted that the rule of applying subsequent loads during the supercompensation phase applies fully only to large training cycles—weekly or even monthly. Within individual training sessions and microcycles, this rule does not necessarily have to be strictly observed. Within these timeframes, the primary task of training is to more fully engage the leading function, thereby stimulating the further deployment of adaptive processes in the body with a delayed achievement of a more pronounced supercompensation phase. Therefore, in individual training sessions or microcycles where repeated loads are applied during the phase of incomplete recovery, a progressive decrease in the indicators of training Structure occurs (Fig. 199).

In each training microcycle, repeated loads are applied under conditions of incomplete recovery, leading to a marked decrease in the indicators of the leading function. At the same time, rest between individual training cycles ensures the achievement of supercompensation of the leading function. Therefore, with each successive repetition of the microcycle, a noticeable enhancement of the training effect is observed.

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Fig. 199 One of the options for the correct alternation of work and rest that elicits a positive training effect

The reversibility of adaptive changes occurring in the body during the systematic application of intensive loads is most clearly evident in the indicators of the cumulative training effect. A noticeable improvement in the indicators of the leading function is lost after training cessation at approximately the same rate at which it was built up during the period of load application. Achieving a pronounced improvement in most bioenergetic indicators typically requires 4–8 weeks of training. The decline of these indicators to baseline levels after training cessation occurs within approximately the same timeframe (Fig. 200).

The Development of deadaptation in the post-training period reflects the Specific features of the training regimens applied. With frequent repetition of workouts with a high load buildup from session to session, the growth of leading function indicators occurs rapidly, but declines just as quickly after loads are reduced or stopped. With a gradual and prolonged buildup of training loads, the growth of leading function indicators and their regression during the period of load reduction or cessation occur more slowly.

To maintain a trained function at the achieved level after changing the general focus of work, it is sufficient to maintain the orientation of the loads applied during the intensive period in just one or two sessions per week.

Resuming training after a sufficiently long break leads to the restoration of the trained function level at approximately the same rate as in previous training periods (Fig. 201). However, if its decline during training interruptions is too great and forces an acceleration of the load to restore sports fitness, the body's adaptive reserves will quickly become depleted, leading to a decrease in work capacity and a deterioration in athletic performance. For example, in two middle-distance runners over a three-year training period, VO2max values were regularly measured at different stages of seasonal preparation (Fig. 202). In the first year of training, one of the observed athletes was forced to stop training for three months at the end of the season due to injuries and colds, which caused a drop in his VO2max by 14.3 ml ⋅ kg^-1⋅ min^-1 (from 66.2 to 51.9 ml ⋅ kg^-1⋅ min^-1). Seeking to make up for the forced break in preparation, he forced the loads at the beginning of the next season and soon regained the lost level of maximum aerobic power. However, forced training continued throughout the season, and as a consequence, the athlete's aerobic work capacity steadily declined. Accelerated preparation followed by a drop in work capacity repeated in the third season. Dissatisfied with his competitive results, the athlete quit running. In the other athlete, whose preparation showed no unjustified load buildup and no sharp fluctuations in maximum aerobic power, sports work capacity remained steadily high and improved from season to season.

Fig. 200 Changes in Indicators of Aerobic (a, c, d) and anaerobic (b) METABOLISM during interval training and after its cessation

Fig. 201 Changes in maximum oxygen uptake during two consecutive training stages separated by a deadaptation interval

Fig. 202 Changes in maximum oxygen uptake in two middle-distance runners over three consecutive training seasons

The given example demonstrates that the repeated cycling of "adaptation—readaptation" carries a high functional "cost" and depletes the body's reserve capacities. The most effective pathway of adaptation is training with consistently applied loads of adequate magnitude targeting the leading function, which helps maintain it at a stably high level.

The main causes underlying the reversibility of adaptation during training are associated with intracellular Mechanisms of Genetic apparatus activation. A decrease in Gene activity upon training cessation causes a reduction in The rate of nucleic acid and Protein Synthesis, as well as an increase in The breakdown of inactive intracellular structures. The intensification of these processes, which "erase" the traces of previous training and activate the development of deadaptation, serves as an important biological adaptation developed in the course of evolution. The elimination of unused biological structures frees up the body's plastic resources and creates the opportunity to utilize them for The formation of new adaptations involving different functional systems.