Associate professor, Ph.D. O.A. Novoselova
Dr.Med., Professor E.I. L'vovskaya
Associate professor, Ph.D. M.V. Treneva
Ural State University of Physical Culture, Chelyabinsk

Keywords: school-leavers, stress, adaptation, allostasis, lipid peroxidation (LPO), antioxidant activity (AOA), sympathoadrenal system, adrenaline (A), noradrenaline (NA), autonomic regulation.

Introduction. Acute and chronic diseases, hypodynamia may lead to the change in pupils' homeostasis, formation of a dissimilar state of dynamic equilibrium of the body's internal environment, known as allostasis, i.e. achieving stability through change. Accumulation of allostatic load may be the cost of such adaptation [6, 7]. However, one and the same level of stress evokes different responses in different children, depending, on the one hand, on genetic factors, and on the other - on the level of their motor activity [7, 8]. Therefore, a contradiction between the complication and intensification of school curricula, on the one part, and deterioration of pupils' health, stipulated by school-related stress, current disease progression, lack of motor activity and accumulation of "allostatic load", on the other part, remains preserved.

We assume that lipid peroxides, the AOA level, catecholamine excretion, cardiointervalography data would be the highly sensitive homeostatic state markers.

The purpose of the study was to determine the typology of homeostatic states of pupils depending on the level of their motor activity.

Materials and methods. 221 11th grade pupils of Chelyabinsk with different levels of motor activity were tested in October (I stage), December (II stage), May (III stage) and June (IV stage). The pupils of the secondary school № 23 (G1₁₁, n = 95) learnt the material of the integrated physical education curriculum in full. In the general school at the music institute (G2₁₁, n = 46) some sections of the curriculum (ski training, volleyball) were partially or fully substituted depending on the chosen music specialization. The volume of motor activity of these children was slightly lower than in other schools. In the secondary school № 63 (G3₁₁, n = 80) physical education classes were conducted basing on the experimental methodology with due regard to children's age and individual characteristics.

The level of lipid peroxidation in saliva was measured using the spectrophotometric method [10]. Separately, in the isopropanol extract phase, we estimated the intensity of induced LPO (AOA1 and AOA2) [2]. The sympathoadrenal system activity was evaluated by the level of urinary catecholamine excretion using the fluorimetric method of E.Sh. Matlina [4]. Urine and saliva for the analysis were collected in the morning. Pupils' heart rate was measured using the method of variational pulsometry according to R.M. Baevsky [1]. Additionally, the Kerdo’s vegetative index (KVI) was measured [2].

Results and discussion. At the I stage of the experiment, in the general school leavers with different levels of motor activity we observed some differences in the primary (PISP) and secondary (SISP) isopropanol-soluble products of LPO in saliva and the corresponding levels of antioxidant activity (AOA), in urinary excretion of adrenaline (A) and noradrenaline (NA), in the KVI values, by the value of tension index (TI) - an integrated index reflecting the degree of tension of the central mechanisms of heart rate regulation. By a number of indices: АОА1, Мо, АМо, TI the differences between G8₁₁ and G9₁₁ were on the level of statistical significance (р < 0.05). There were no statistically significant differences in the examination data between the groups G7₁₁ and G8₁₁, as well as between G7₁₁ and G9₁₁.

Throughout the academic year (II stage), under the influence of strenuous training loads against the background of decreased motor activity, the studied parameters underwent a number of changes [6]. There is a general tendency to accumulation of the LPO products of all categories and a decrease of the AOA level. Other changes are irregular: in pupils with lower motor activity (G2₁₁) the mean group values of catecholamine excretion, TI, KVI decreased, which is interpreted as the manifestation of fatigue [9]. In the group of pupils who trained according to the traditional integrated physical education curriculum, we generally observed an increase of TI, KVI, NA and A against the background of decreasing AOA. In the group G3₁₁ the signs of tension and fatigue were less evident on the whole, all the studied parameters were close to the baseline values [8].

At the end of the academic year (III stage), upon examination of all the school-leavers, we detected three variants of changes in the indices under study. Variant 1: the content of ISP LPO, catecholamines, the TI value exceeded the initial level significantly (with a simultaneous decrease of AOA1, AOA2 and Mo). Variant 2: the studied parameters reduce considerably. The concentration of the LPO products increases, while the AOA level is decreased.

At the III stage of the experiment, when analyzing the activity of the LPO-AOP, SAS, and CVS systems, we found that according to the first variant PISP in G1₁₁ increased in 42.6%, SISP - in 35% of the cases, consequently, there was detected a decrease in the AOA1 level in 42%, AOA2 level - in 45.6% of students. The A excretion increased in 41.8%, of NA - in 36.3%. TI increased in 59%, KVI - in 54%.

In G2₁₁ PISP increased in 20.5% of the cases, SISP – in 20%, the АОА1 level decreased accordingly in 16% of pupils, АОА2 – in 21.6%. The A excretion increased in 16.6%, of NA – in 13.3%. TI increased in 37.5%, KVI – in 33.8%.

In G3₁₁ PISP LPO increased in 21.7% of the cases, SISP – in 20%, the АОА1 level decreased in 20.2% of students, АОА2 – in 40%. The A excretion increased in 27%, of NA – in 17.3%. TI increased in 35.5%, KVI – in 33.8%.

In G1₁₁, according to the schedule of the second variant, no significant changes were found in the baseline values in 31.5% – by PISP LPO, in 42% – by SISP, in 33.6% – by the АОА1 level, by АОА2 – in 31.5%, by the TI value – in 15.25%, KVI – in 20.3%. The A excretion remained unchanged in 32.7% of pupils, and NА – in 29.6%.

In G2₁₁ the baseline values did not change significantly by PISP LPO in 26.1% and by SISP in 34.8%, by the АОА1 level – in 30.4%, by АОА2 – in 27.8%, by the TI value – in 9.4%, KVI – in 15.6%. The A excretion slightly changed in 16.6% of pupils, NА – in 13.3.%.

In G3₁₁ the baseline values did not change statistically significant by PISP LPO by 66.7% and by SISP in 64.55%, by the АОА1 level – in 71%, by АОА2 – in 60.5%, by the TI value – in 48.4 %, KVI – in 38.7%. The A excretion remained close to the baseline values – in 57.7%, NА – in 71.1% of school-leavers.

In G1₁₁ at the III stage, in accordance with the second variant, the PISP content increased in 25.5%, SISP in 22.8% of the cases, consequently, the АОА1 level decreased in 24.4%, АОА2 – in 22.9% of students, the A excretion decreased in 26.15%, NА – in 34.5%. TI reduced in 24.42%, KVI – in 25.5%.

In G2₁₁, in correspondence with the third variant, the PISP concentration increased in 54.5 % of the cases, SISP – in 45.2 %, the АОА1 level decreased accordingly in 53.7%, АОА2 – in 52.3% of schoolchildren. The A excretion decreased in 53.3%, NА – in 63.3%. TI decreased in 53%, and KVI – in 43.7%.

According to the third type of response, in G3₁₁ at the III stage the PISP content increased in 11.6% of the cases, SISP – in 15.55%, the АОА1 level decreased in 9, АОА2 – in 14.6%. The A excretion decreased in 15.3% of students, NА – in 11.6%. TI decreased in 16.1%, and KVI – in 27.4%.

Therefore, at the II stage of examination we observed a consistent performance of the body adaptive systems in G1₁₁ – in 15–35% of the cases (by various parameters), in G2₁₁ – in 9.4–32%, and in G3₁₁ – in 39–68%.

The IV stage of examination was carried out in June, after the final exams. We found that in the majority of schoolchildren the concentration of LPO products, catecholamines, the AOA level, TI and KVI returned to their baseline values. According to the obtained data, in G1₁₁ the body functioning returned to the baseline values in 52.5–74.9% of the cases (by different studied parameters), in G2₁₁ – in 40.6–65.2 %, in school-leavers from G3₁₁ – in 77.4–88.7% of the cases. Therefore, most school-leavers are able to deal with stress, but a considerable part of them still have indices typical for stress situations. The research has shown that it is primarily characteristic of schoolchildren from G2₁₁, who were subject to smaller physical loads.

Upon the final exams, the formation of LPO products in G1₁₁ was still increased in 25.2% by PISP, by SISP - in 30% of the cases, AOA1 remained at the low level in 26.6%, AOA2 - in 28.4% of pupils. An increased A excretion in G1₁₁ was preserved in 20%; NA - in 16.43%. TI in the tension zone remained unchanged in 32.2%, and KVI, testifying to the predominance of sympathetic effects, - in 22%. In G7₁₁ in 25.42 % – decreased TI; decreased A excretion – in 26.15%, and low level of NA – in 34.5%.

In G2₁₁ high concentration of PISP LPO in saliva remained unchanged in 41.3%, SISP – in 35 % of school-leavers, the АОА1 level was still decreased in 39.2%, АОА2 – in 38% of pupils. An increased A excretion – in 16.6%, NА – in 13.3 %. An increased TI was preserved in 31.25 %, KVI – in 28 %. In G2₁₁ the levels of catecholamine in urine remained lower than the initial level in 36.6%, the TI value – in 28%.

In G3₁₁ the following parameters were higher than the baseline ones: the concentration of PISP in saliva in 11.3%, SISP - in 13.75%; adrenaline in urine - in 11.5%; noradrenaline - only in 5.8% of school-leavers. The AOA1 level remained low in 8.75%, AOA2 - in 11.25% of pupils. The TI values remained at the high level in 16.1%; KVI, testifying to the predominance of sympathetic effects, - in 17.7% of school-leavers. Moreover, in 9.6% of the examined pupils in G3₁₁ the A excretion turned out to be lower than the baseline values, in 5.8% - the excretion of NA. TI was decreased in 6.5%, KVI - in 21% of school-leavers.

The obtained data enable us to single out 3 types of homeostatic changes in the body of schoolchildren depending on the level of their motor activity (Fig. 1).

Type I - the body's homeostatic system responds adequately to distress, all physiological parameters are normalized after some time, i.e. the system is stable enough. In this situation, by the IV stage of the examination, the studied parameters after the increase did not differ significantly from the baseline values by the generalized mean value in G1₁₁ – in 28.2±3.1%, in G2₁₁ –22.6 ±1.3%, and in G3₁₁ – 49.6±2.8% of the cases.

Fig. 1. Distribution of pupils with different levels of motor activity by types of adaptive responses, %

Type II - markers of the homeostatic state oscillate around a certain well-established value, the work of the homeostatic system is damped, physiological parameters return to the baseline values after some time. If there is no return, the system switches to the III type of adaptive changes. In our case, the studied parameters, having ranged significantly, returned, by the generalized mean value in G1₁₁ – in 41.3±4.2% of the cases, in G2₁₁ – in 40.9±3.7%, and in G3₁₁ – in 32.6±2.4% to the baseline values at the IV stage of examination.

Type III - response of the homeostatic system is inadequate, the transition process is delayed, the physiological parameters do not reach the baseline values ​​(heterostasis, according to Selye) or the response of the system is excessive. In both cases a different state of dynamic equilibrium of the internal environment - allostasis - is formed in the body.

At the IV stage of the experiment, the transition process did not terminate in some school-leavers, the studied parameters were not restored, by the generalized mean value in G1₁₁ – 30.4±2.3% of the cases, in G2₁₁ – 36.3±4.4%, in G3₁₁ – 14.7±1.2%.

Conclusion. The assumption on the information value of the analysis of the nature and dynamics of the relationship between the links of heart rate regulation, catecholamine excretion rates and activity of the LPO-AOS system of school-leavers with different levels of motor activity has been confirmed. Homeostatic changes according to the I type, indicating adequate adaptation to the requirements, were detected in 49.6% of the pupils, who train more, which was significantly higher than that of school-leavers who have restrictions in motor activity (p<0.05 ).

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Corresponding author: serikov06@mail.ru