A.V. Shakhanova, professor, Dr.Biol.
Adygei state university, Maikop
A.A. Kuz’min, Ph.D
Research institute of complex problems Adyghe state university, Maikop

Key words: cardiovascular system, heart rate variability, regulatory adaptive status, somatotype, young football players.

 Introduction. Nowadays investigation of the influence of physical exercises on the specifics of children’s and adolescents’ ontogenetic development for the purpose of obtaining of adequate level of operation of life systems and limitation of the physiology “cost” of adaptation is one of crucial aspects in children’s sports physiology. Despite of the issue of adaptation of children’s and adolescents’ body to physical loadings well covered in research works, the final adaptive result is usually considered regardless of the status of regulatory mechanisms, i.e. physiological “cost” of its achievement.

Currently, one of the pressing issues in pediatric sports physiology is the study of the influence of sports physical activity on the features of ontogenetic development of children and adolescents in order to achieve an adequate level of functioning of life support systems and minimize the physiological “cost" of adaptation. Despite the fact that the issues of adaptation of bodies of children and adolescents to physical loads are well covered in research works [4, 7, 8, 14, 23], they generally consider the adaptive end result without considering regulatory mechanisms, i.e. physiological "cost" of achieving it.

The transition from the urgent phase to stable long-term adaptation is based on the formation of functional changes primarily in the cardiovascular system and its regulatory mechanisms [11, 12, 16, 22]. The morphofuncitonal development and regulatory adaptive abilities of the body depend on effectiveness and efficiency, reserve capacity and quality of control of cardiovascular system [1-2, 13, 19, 15]. It is known that disorders in the state of regulatory mechanisms of cardiovascular system precede the appearance of hemodynamic, metabolic, energy and structural abnormalities in the executive organs, i.e. are the earliest predictive prenosological states [1]. The analysis of heart rate variability is currently widely used in physiology to detect disorders in the state of regulatory mechanisms, as well as to study their age-related changes in the body [2, 5, 6, 26, 27]. In the pediatric sports physiology such studies are fragmentary, longitudinal and integrated studies are lacking, the peculiarities of heart rate variability in young athletes are studied without reference to somatotype, physical working capacity and endurance of the body, which prevent from full characterizing the regulatory adaptabilities of the body of young athletes and revealing the mechanisms of individual adaptation.

In this regard, the examined set of indicators of somatic development, general endurance, physical working capacity and heart rate variability is an integral model of morphofunctional and adaptive development of the body of young athletes. The search for the dependence of functional and regulatory adaptive features on somatotype will bring us significantly closer to solving the problem of differentiated standardization of physical loads and increase the motivation of children and teenagers to do playing sports. The need for a thorough study of this issue is stipulated by the fact that in the fundamentally changed demographic situation and socio-psychological sphere of society more children of different ages, with different levels of health and working capacity are being involved.

The purpose of the research was to study functional and regulatory adaptive abilities of young football players aged 10-15 years with different somatotypes in the dynamics of the training process.

Materials and methods. The 3 year long experiment was conducted in the longitudinal mode with the same children and adolescents regularly doing sports in sports sections of the specialized children’s sports school of Olympic reserve (SCSSOR) in the town of Maikop.

60 male football players aged 10-15 years were examined. Control group (CG) consisted of 60 students aged 10-15 years from the secondary school № 7 with the traditional motor mode (2 physical education lessons a week). Sports personal history and health history were studied carefully. Healthy children took part in the experiment on the voluntary basis. To standardize the conditions all researches were conducted before noon (9-12 h) at comfort temperature (18-20^оС) on the basis of the laboratory of physiology of child development of the Research institute of Complex Problems of Adyghe State University. The examination was conducted twice a year: autumn (October-November) and spring (March-April), as during these periods the optimal level of adaptation to physical loads is observed or, alternatively, fatigue in the case of irrationally organized training classes.

When estimating age we proceeded on the methodological guidelines of A.V. Stavitskaya and D.I. Aron [17]. In accordance with the age periodization, recommended by the Institute of Age Physiology of Russian Academy of Education (1965), when analyzing somatotypes the examined subjects were divided into two age periods of development: second childhood (10-12 years) and adolescence (13-15 years).

The assessment of physical working capacity and general endurance of young football players included:

• determination of physical working capacity in the test PWC170;

• determination of the maximum oxygen consumption (MOC) .

PWC170 was determined using the hardware-software complex "Poly-Spectrum-Ergo" produced by Neurosoft (Ivanovo town). Power load PWC170 was modeled on a cycle ergometer with the control of ECG (electrocardiograph "Poly-Spectrum-12"). PWC170 and MOC were calculated automatically in relative units per kilogram of body weight using the program "Poly-Spectrum" with the formula of V.L. Karpman [9].

The wave structure of heart rate variability was studied in vitro in compliance with the requirements provided by the "International standard" for short records. Electrocardiograms were recorded using the hardware-software complex "Poly-Spectrum-12”. Rhythmograms obtained were controlled manually to avoid possible artifacts.

The power of VLF-waves showing the cerebral ergotropic component, LF-waves - the sympathetic influence, HF-waves - parasympathetic effects in the spectrum of heart rate variability was measured in percentage of the total spectral power (TP).

Based on the integrated analysis of somatic indicators, young football players were distributed into three somatotypes within each age period of development (second childhood and adolescence) using the software "Anthropometry", compiled by the methodology of N. Shevkunenko, modified by S.Yu. Morgalev: brachymorphic (B), mesomorphic (M), dolichomorphic (D). The indicators of physical working capacity (PWC170, kgm/min/kg), general endurance (MOC, ml/min/kg) and heart rate variability were analyzed depending on somatic type of the subjects.

The statistical handling was performed using the software package STATISTICA 6.0. Since the experiment took place in the longitudinal mode with the same subjects, even relatively small differences of the averages of indicators are usually statistically significant, which was confirmed by treating using the Student’s paired comparisons [18, 21].

Results and discussion. Proceeding from the studies of heart rate variability of young football players, there is a phenomenon of tension of regulatory systems at rest at the age of 10 and 11 years. The ratio of fast (HF-waves) and slow (LF-, VLF-waves) in the heart rate spectrum indicates the predominance of sympathetic and cerebral-ergotropic regulation mechanisms (Table 1). In the context of the active orthostatic test the sympathetic component of regulation (LF-waves) is slightly activated, indicating a reduction of the functional reserves of regulatory mechanisms of cardiac activity.

Table 1. HRV at rest and under AOT in young football players aged 10-15 years

Table 2. Indices of physical working capacity (PWC170 kgm/min/kg) and general endurance (MOC ml/min/kg) in young football players aged 10-15 years, M ± m

In the age range of 13-15 years the favorable autonomic balance is established in young football players at rest, characterized by dominating parasympathetic influences (HF-waves) over sympathetic ones (LF-waves) at the stable level of influence of central regulation (VLF-waves) of heart work. This condition is described as the most optimal combination of centralization and autonomy of control of heart rate [19, 20, 24]. However, during the AOT the tension of regulatory adaptive mechanisms of the body was detected in young football players aged 14 years amid the pubertal growth spurt. It is known that on this background disintegration phenomenon is intensified [10, 25].

The analysis of the distribution of somatotypes according to the overall level of variation of total body sizes showed the progress of the mesomorphic somatotype (M-type) (66.7 % of cases at the age of second childhood and 73.3 % in adolescence) among the surveyed young football players. This somatotype is characterized by the well developed bone and muscle components, a minimal amount of subcutaneous fat and harmonious body proportions.

Representatives of the dolichomorphic somatotype (D-type) comprised 20,0% both in the second childhood and adolescence. Persons with the dolichomorphic somatotype differ by slenderness, lightness, dominating transverse dimensions, relatively longer limbs, low development of muscles and adipose tissue, relatively thin narrow bones.

The contingent with the brachymorphic somatotype (B-type) is presented to a lesser extent, their share decreased with age and improved fitness: from 13.3% at the age of the second childhood (2-4 years of experience) to 6.7 % in adolescence (5-7 years of experience). The brachymorphic somatotype is characterized by the predominance of transverse dimensions, fatness, the representatives are not very tall, and have weakly developed muscles.

In the context of football training the highest indices of physical working capacity and general endurance belong to young football players of the M-type at the early phases of the training process. They are characterized by the predominance of parasympathetic part (HF-waves) in the regulation of heart rate along with the moderate activity of the sympathetic one (LF-waves) and relatively little activity of suprasegmental centers (VLF-waves) (Tab. 3). This autonomic balance indicates good functional-adaptive status of young M-type athletes. With age and growth of sports experience they had an increase in the indices of physical working capacity and general endurance. The increase in the heart rate spectrum of the share of HF-waves and the decrease of the share of LF- and VLF-waves indicate the progress in the regulatory adaptive mechanisms, high functional-adaptive abilities of the body.

It should be noted that at all phases of the training process, representatives of the mesomorphic somatotype had the highest functional and regulatory adaptive abilities of the body compared with football players of the dolichomorphic and the brachymorphic types.

Table 3. Indices of physical working capacity and general endurance in the period of second childhood and adolescence in young football players with different somatotypes

Representatives of the B-type had the lowest indices of physical working capacity and general endurance, they had predominating sympathetic influences (LF-waves) over parasympathetic ones (HF- waves) in the heart rate spectrum, along with the highly active suprasegmental centers (VLF-waves) of the cardiovascular regulation. It is believed that the dominance of VLF-wave in the spectrum of heart rate variability reflects the introduction of the cerebral regulatory circuit when the process of adaptation at the segmental level becomes inefficient. The involvement of suprasegmental mechanisms indicates the increase of the physiological "cost" of adaptation of the body [1]. Despite the fact that a rise of physical working capacity and general endurance was observed in this group of surveyed with age and rise of sports experience, which occurred along with significant tension of regulatory adaptive mechanisms of the body.

During the long-term training process the difference in the indices of physical working capacity and general endurance of young football players between the M- and D-types becomes less significant. However, the representatives of the D-type, especially at advanced phases of the training process, in the heart rate spectrum are characterized by the high enough influence on heart rate of the slow-wave component (LF-waves) and central regulatory mechanisms (VLF-waves), indicating the development of the phenomenon of stress of adaptation.

The obtained data on constitutional types of young athletes can be useful at professional qualification, designing and individualizing the training process in football. Owing to morphofunctional correspondence to regulations athlete can achieve big results in sport at minimal cost.

Conclusion                                             

The age of 12 years is a nodical period of ontogenesis in the development of autonomic regulation mechanisms of young football players, when the age reorganization of vegetative regulation of heart rate is finished, the parasympathetic nervous system increases significantly. The age of 12 is also a critical period for young football players, as the regulatory mechanisms were observed in the active orthostatic test and against this background – decline of PWC170 and MOC indices. Starting from the age of 13-15 years, the optimal combination of centralization and autonomy of heart rate control is established in young football players, the high level of physical working capacity is being developed.

Young football players of the mesomorphic somatotype have the highest rates of PWC170 and MOC, they are distinguished by a more cost-effective activity of cardiovascular system using the domination of the total power spectrum of heart rate variability of the waves reflecting activity of parasympathetic regulation (HF-waves).

Young football players of the dolichomorphic somatotype in the spectrum of heart rate variability the power of high-frequency HF-waves is reduced along with the increase of power of very slow VLF-waves, indicating the inclusion of the central mechanisms of cardiovascular regulation and the energy-deficient condition.

The risk group consists of representatives of the brachymorphic somatotype, in which low levels of PWC₁₇₀ and MOC are combined with the tension of the mechanisms of regulation of cardiac activity, indicating the high levels of physiological "cost" of adaptation

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Author’s contacts: Kuz@maykop.ru