From a biological point of view, physical training is a process of directed adaptation of the organism to training influences. Loads used in the process of physical training, serve as an irritant, which causes adaptive changes in the body.

The training effect is determined by the direction and magnitude of the physiological and biochemical changes occurring under the influence of the applied loads. The depth of the shifts occurring in the body depends on the main characteristics of physical activity:.

• the intensity and duration of the exercises;.

• the number of repetitions of exercises;.

• the duration and nature of the rest intervals between repetitions of exercises.

A certain combination of these physical stress parameters leads to the necessary changes in the body, to the reorganization of the metabolism and, ultimately, to an increase in fitness.

The process of adaptation of the organism to the effects of physical exertion is of a phase nature. Therefore, there are two stages of adaptation: urgent and long-term (chronic).

The stage of urgent adaptation is reduced mainly to changes in energy metabolism and related functions of vegetative provision on the basis of the already established mechanisms for their implementation, and represents a direct response of the body to single effects of physical exertion.

With repeated repetition of physical influences and summation of many traces of loads, a long-term adaptation gradually develops.

This stage is associated with the formation in the body of functional and structural changes that occur as a result of stimulation of the genetic apparatus of cells loaded during operation. In the process of long-term adaptation to physical loads, the synthesis of nucleic acids and specific proteins is activated, resulting in an increase in the capabilities of the musculoskeletal system, improving its energy supply.

The phase nature of the processes of adaptation to physical loads makes it possible to distinguish three varieties of effects in response to the work performed.

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