O.G. Litovchenko^₁, professor, Dr.Biol.
V.V. Apokin¹, associate professor, Ph.D.
A.A. Semenova¹, postgraduate
O.L. Nifontova², Dr.Biol.
¹ Surgut State University, Surgut
² Surgut State Pedagogical University, Surgut

Key words: cardiovascular system, students, natives of the Middle Ob region.

The body of residents of the northern territories functions under the influence of a number of rather severe climatic factors influencing the functional status, as some organs and body system reserves are involved in adaptation processes and aimed at providing adaptive responses of homeostasis [7]. Cardiovascular system is an indicator of body's adaptabilities and the level of its operation can be regarded as a key indicator of the balance in the body and the environment [2]. It is impossible to study human adaptation to specific climatic geographic conditions without studying the functional status of the circulatory system: it serves as a marker of the manner of adaptation processes [3, 4, 6].

Student age in the ontogenetic aspect is the period when human biological maturation ends and all indicators reach certain amounts. Hemodynamic parameters, ECG and cardiointervalographic indicators in the juvenile period of ontogenesis are close to those of adults, but still have their own specific characteristics. Stable adaptation of the circulatory system to high loads is characterized by the increased functional reserve system. Northern athletes adapt affected both by physical load and specific environmental factors.

We studied the functional status of the cardiovascular system of students aged 17-20 from Surgut universities specializing in physical education, born and living in specific natural and social conditions of the Middle Ob region. The subjects of the examination were young males aged 17-18 years - 30, 19-20 years - 32, females aged 17-18 years - 35, 19-20 years - 30. Owing to the sport specialization of the examined students, major physical load was focused on development of their endurance. The indicators evaluated were as follows: heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressure, functional index (FI). Electrocardiographic (ECG) and сardiointervalographic (CIG) indicators were recorded and processed using the hardware and software complex "Ankar" (produced in Taganrog). All the studies were conducted during the so-called steady period of the academic year, particularly in February, i.e. when it is not the examination period, and there is no emotional stress.

Hemodynamic indicators were indicative of the consistent adaptive change in the cardiovascular system under the influence of regular physical loads, a deceleration of heart rate was registered influenced by parasympathetic effects on the automatism of the heart. Blood pressure is one of the indicators of the cardiovascular system functioning, which reflects the inotropic effects of the heart. The systolic and diastolic blood pressure indicators were stable enough, there were no significant differences in various groups (Table 1).

Table 1. Some hemodynamic indicators in young males and females aged 17-20, Surgut, M±m

The integrated indicator of the complex structure of functional relationships - FI of the examined male and female students equaled 2.05 c.u., which complies with the "satisfactory adaptation" level of functioning of the circulatory system.

In order to study the cardiac chronotropic function we evaluated the temporal ECG indices, which help obtain vital information on the functional status of the cardiovascular system. The duration of particular intervals is a free-standing diagnostic criterion used to study the integrative effects of realization of the temporal organization of ECG [5].

All the temporal ECG indices of student-athletes of the Middle Ob region corresponded to the age standards, and correlated with other indicators of the cardiac chronotropic functions (Table 2). However, what comes under notice is: the Macruz index we have measured which was higher than the standard value: in the examined group, the signs of the left atrial enlargement were observed in 15% of young males and 13% of females. The reason for this must be related with the peculiarities of the heart functioning in hypocomfortable climatic geographic conditions of the Middle Ob region. Hypertrophy of the functional units of the pulmonary circuit in the northerners is associated with the specific redistribution of the functions of the left and right atriums [1]. We observed the signs of the left ventricular hypertrophy in 4% of the examined students. However, there were no signs of the right atrial enlargement. In general, the signs of the ventricular hypertrophy were less pronounced in comparison with those of the atrial enlargement, which suggests the advanced and heavier tension of the receivers of blood in the heart.

Sinus rhythm was registered in all the young male and female subjects, which proves the stability of automatism.

Table 2. Some temporal indices of electrocardiography in young males and females aged 17-20, Surgut, M±m

Changes in heart rate are a universal prompt response of the body to any external impact. It is based on the provision of the balance between the sympathetic and parasympathetic nervous systems. The status of autonomic regulation of heart rate in the students was tested with the method of variational pulsometry according to R.M. Baevsky [2]. The cardiointervalographic indicators in the student-athletes of the Middle Ob region revealed a favorable reaction of the body to a set of factors taking their effect in living conditions (Table 3).

Mostly, we observed the balance between the sympathetic and parasympathetic tone, or aethonium, which is typical for a healthy well adapted organism.

One of the major indicators of variational pulsometry is mode (Mo), the most frequent value RR, which is indicative of the dominating level of functioning of the sinus node. In the case of sympathicotonia, Mo is minimal, but in the case of parasympathicotonia - maximal.

Table 3. Cardiointervalographic indicators in young males and females aged 17-20, Surgut, M±m

Standard deviation (SD), variation range and autonomic balance were within the normal range or within the range of moderate parasympathicotonia in the examined group. The tension index value, indicating the degree of centralization of the heart rate regulation, was within the range of the so-called adaptive changes of regulation (not less than 80 and not more than 160 c.u.), which conformed with the normotonic type of regulation of the cardiovascular system.

In general, physical loads under the conditions of the Middle Ob region have a positive effect on the functional status of the body. Hemodynamic parameters, ECG and CIG indicators, FI, which help determine the status of adaptation compensatory-adaptive mechanisms involved in the maintenance of the functional status of the circulatory system, were indicative of adaptation of juvenile natives of the Middle Ob region of the first and second generations, who were under regular physical loads focused mostly on development of their endurance.

The obtained values of the physiological characteristics of the cardiovascular system will help estimate the functional status of student-athletes and take it into account while developing and implementing training loads and rehabilitation and recreational measures.

References

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Corresponding author: apokin_vv@mail.ru