Associate professor, Dr. Biol. Sciences V.А. Kolupaev,
Ph.D. I.L. Kolupaeva
Ural State University of Physical Culture, Chelyabinsk

Keywords: aerobic exercise, homeostasis, neutrophils, seasons, skilled athletes and rated athletes.

Introduction. In addition to the amount and power of muscular work performed during a workout, the condition of an athlete’s body is known to depend on the effects of environmental and anthropogenic factors that have a significant impact on the absorptive capacity of peripheral blood neutrophils, the activity level of which is generally considered as one of the main criteria for the state of compensatory and adaptive capabilities of the body [1, 2, 3, 5 et al.]. In conditions of middle latitudes, the impact of permanent loads on an athlete's body in the course of training is realized against the background of seasonal variations in metabolism and state of the neuroendocrine regulatory mechanisms, which have an immediate effect on phagocytosis of neutrophils. In turn, peripheral blood neutrophils are involved not only in elimination of microorganisms [5, 7], but also in realization of non-specific resistance mechanisms on exposure of the body to moderate and intensive stimuli [1], in realization of the mechanisms of sanitation of internal environment and degradation of depleted and genetically engineered molecules, necrotic and apoptotic cells during the body balance control [6], as well as in realization of regulatory functions of the body [2, 3 et al.].

Thus, affected by muscle activity, neutrophils start to intensively migrate to tissues and muscle neutrophil infiltration, ensuring motor activity, enhances [4]. An increase in enzymatic activity of neutrophils, having migrated to muscle tissue, provides for disruption of depleted structures, thus activating the process of physiological recovery and angiogenesis [3]. The role of neutrophil phagocytosis in protection against infections, as well as in realization of the regulatory functions and compensatory and adaptive responses in the body under the influence of environmental factors, including various loads, determines the relevance of studying physiological and ecological patterns of change of their phagocytic activity.

The purpose of the study was to determine changes in the indices of phagocytic activity of peripheral blood neutrophils in skilled athletes and rated athletes with different dynamics of aerobic loads in the annual cycle.

Materials and methods. To study the dynamics of compensatory and adaptive capabilities of the body under the influence of environmental conditions and exercise, we conducted a retrospective analysis of the findings of the investigations of 2004-2007 by the status of indicators of phagocytic activity of peripheral blood neutrophils in skilled athletes and rated athletes of the Chelyabinsk Region with predominantly aerobic energy supply of motor activity (racing skiers and race walkers). Over 3.5 years, racing skiers and race walkers have been examined in winter (January-February), spring (March-April), summer (late May-June) and autumn (October-November) within comparable timeframes (±5 days). In skilled racing skiers and skiers of mass categories the amount and intensity of aerobic exercise in autumn and winter increased significantly compared with spring and summer, and in skilled race walkers and rated race walkers, on the contrary, the level of aerobic exercise in spring and summer far exceeded that of autumn and winter. Apparently healthy athletes with no complaints about overall health who were purposefully training for competitions were involved in the experiment.

Phagocytosis of neutrophils in athletes was studied based on the model of uptake of polystyrene latex using the traditional methods with determination of the content and amount of phagocytizing peripheral blood neutrophils, phagocytic index, phagocytic number and cumulative phagocytic activity of these cells [5], which was carried out at the premises of SRI of Immunology of South Ural State Medical University (rector of SUSMU: Merited scientist of the RF, Corresponding member of RAMS, M.D., professor I.I. Dolgushin).

Results and discussion. According to our sources, the mean neutrophil phagocytic index ranged significantly in the annual cycle in athletes from all the examined groups, while the mean value of the total phagocytic activity of these cells, according to the Kruskal–Wallis test, did not change statistically significantly with seasons. The latter is associated with compensatory effects of the dynamics of the content and amount of peripheral blood neutrophils on the level of phagocytic activity of these cells. Moreover, the mean phagocytic activity and neutrophil phagocytic index in skilled race walkers and ranked race walkers were significantly lower in winter than in spring or summer, in the period of the most rigorous aerobic loads. In the group of racing skiers of mass categories, as with race walkers, the dynamics of the mean phagocytic activity of neutrophils and phagocytic index of these cells, was marked by an increase in spring and summer rather than in winter, however, unlike the latter, an increase of these indices fell within the period of physical loads of lowest intensity in the annual cycle. On the other hand, despite the fact that these indicators increased significantly in other season (in autumn, rather than in spring or summer), in skilled racing skiers, as well as in race walkers, the peak of their mean values coincided with the period of the significant increase of the level of aerobic load just before the phase of the actual training for competitions.

Moreover, it should be noted that in the group of skilled racing skiers and race walkers the identified trends of the indicators of phagocytic activity of neutrophils and their phagocytic index are associated with the corresponding changes in the percentage of neutrophils capable of phagocytosis and their absorptive capacities, while in the group of ranked race walkers we observed an alternative tendency between the dynamics of the average amount of neutrophils capable of phagocytosis and the level of their absorptive capacities. It can be assumed that in ranked race walkers, unlike skilled athletes, an increase in neutrophil phagocytic index and the level of phagocytic activity of these cells under the influence of physical loads is due to the increase in the number of phagocytes against the background of downward trend in their absorptive capacity. In the group of racing skiers of mass categories a significant decrease in the mean phagocytic index and phagocytic activity of neutrophils in winter, as with ranked race walkers, was stipulated by the significant decrease of these cells' absorptive capacity and, unlike the latter, in the regular season was not compensated by the corresponding increase in the number of phagocytes.

A considerable increase in the number of white blood cells in ranked skiers in winter enabled only to maintain stability in the amount of phagocytizing peripheral blood neutrophils in different seasons, and at the same time did not fully compensate for a decrease in phagocytic index and phagocytic activity of these cells. Obviously, a decrease in neutrophil phagocytic number and, consequently, in their absorptive capacity in ranked athletes due to the significant increase of the level of exercise in the course of adaptation to seasonal environmental conditions can be accompanied by a considerable decrease of the level of phagocytic index and phagocytic activity of these cells, which, in turn, stipulates a significant decrease in compensatory and adaptive capabilities of the body. In this view, lowering of the level of phagocytic index and phagocytic activity of neutrophils in racing skiers of mass categories in winter suggests that a lower level of sports results is to a great extent limited by a higher degree of tension of the mechanisms of non-specific resistance of the body while adapting to seasonal environmental conditions in the regular season.

The findings of the analysis of the dynamics of phagocytic activity of peripheral blood neutrophils in skilled athletes in response to acute and chronic exposure of aerobic exercise and seasonal environmental conditions can be generalized as follows. With a considerable increase of the level of motor activity in autumn and winter, the effects of exposure to physical loads intensify seasonal tendencies to an increase in the total number of neutrophils in circulation, including an increase in the content and number of phagocytizing cells by expanding migration of cells of the medullary pool to peripheral blood circulation. With that, against the background of a winter decrease in the level of absorptive capacities of phagocytizing cells, this compensatory mechanism provides for the stable phagocytic activity and phagocytic index of neutrophils. In case there is an increase in the frequency and degree of impact of loads exceeding the time interval necessary for proliferation and proper cell differentiation in bone marrow, there occurs a reduction of the mature peripheral blood neutrophil pool and a decrease in the level of their absorptive capacity. This process is accompanied by a consistent decrease of phagocytic activity and corresponding slowdown of non-specific resistance mechanisms, which predetermines less efficient adaptation to loads [1, 3, et al.] and results in excess risk of infectious diseases [2, 5-7, et al.].

The importance of the influence of seasonal environmental conditions and loads on the state of phagocytosis of neutrophils is proved by significantly positive correlations registered in the representatives of each sport between blood neutrophils, percentage of phagocytizing cells, phagocytic index and phagocytic activity on the one hand, and the level of intensity of sports training of racing skiers and race walkers on the other. Herewith, the modulating effect of dynamic loads on racing skiers was manifested in the negative correlation relationships between the studied indices of neutrophil phagocytosis and daylight hours, and on race walkers - in positive ones.

The figure below represents the most extensively studied of probable ways of influence of physical loads and environmental conditions on the content of peripheral blood neutrophils and state of their functional and secretory activity.

Figure 1. Factors affecting the state of peripheral blood neutrophils

As seen from figure 1, when the internal milieu is destabilized, which is normally accompanied by changes in the products of phospholipid and protein metabolism, as well as in cytokine content and activity of plasma enzyme systems (1), the neutrophil content in circulation and their functional state change, too. At the same time, direct exposure of biotic factors of environment by means of recognition of lipopolysaccharide components of cell walls of the G-ve bacteria through the CD₁₄⁺-receptors and pathogen-associated molecular patterns (PAMP) through the TOLL-, NOD- and RIG- pattern recognition receptors (PRR) of neutrophils also promotes functional activity of these cells. And finally, exposure of abiotic factors by means of activation of nervous and neuroendocrine regulatory mechanisms (3) has a modulating effect on the state of neutrophils. In the latter case, the use of the mechanisms of voluntary control over dosing of anaerobic and aerobic muscle work during sports activity makes it possible to purposefully control the state of neutrophils and interrelated system functions of the body.

Conclusions. Such different tendencies in the dynamics of phagocytic index and phagocytic activity of neutrophils in the annual cycle in skilled athletes and athletes of mass categories prevent from giving a decisive answer to the question: what particularly determines the changes in these indicators - a circumannual rhythm of the mechanisms of neurohumoral regulation in the process of adaptation to seasonal environmental conditions or a physiological rhythm of adaptation of the body to aerobic loads. Management of athletes' training without due regard to the tendencies in the state of peripheral blood neutrophils in response to muscle work and seasonal dynamics in environmental conditions does not allow making efficient observation of the changes in the state of compensatory and adaptive capabilities of the body of athletes and thus, exerting purposeful control over their functional state when during pre-season.

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Corresponding author: vitalico@mail.ru