Dr.Biol., Professor Y.S. Vanyushin¹
PhD, Associate Professor R.R. Khayrullin¹
PhD D.E. Yelistratov^1
1Kazan State Agrarian University, Kazan

Keywords: adaptation, cardiorespiratory system, step load, gas exchange, rheogram, cycle ergometer.

Introduction. In modern physiology, increasingly greater attention is being paid to the parameters formed under the influence of interaction both between individual elements of the functional system and between different functional systems as such [1, 2, 9]. This interaction creates a complicated pattern of elements that display the processes forming the basis of physiological functions and ensuring the integrity of the body characteristics, formation of a planned and effective adaptive response to external stimuli [6, 10]. Among such stimuli is step load, which is a prototype of loads occurring during athletic training and in everyday life.

Adaptation to motor activity leads to activation of various functional systems being key for mutual contributions of vegetative functions to the end result [1, 5]. One such a system is the cardiorespiratory one providing oxygen supply to the body. It is a unique indicator of adaptive activity characterized by the functional shifts in response to ever changing external and internal conditions, being the main component of maintenance of homeostasis and ensuring the necessary level of redox processes in cells [3]. Its functionality is to be evaluated not only by performance results, but also with due regard to the peculiarities of the process leading to a specific end result - vegetative support under different conditions of human vital activity [4, 5].

The research objective was to determine the coefficient of comprehensive assessment of the cardiorespiratory system in endurance athletes of different age groups, when exposed to step load.

Methods and structure of the study. The study involved 72 male athletes of 15 to 60 years of age engaged in endurance sports. They were divided into 4 groups according to age: 1st group – 11 adolescent athletes aged 15-16 years; 2nd group – 22 young athletes aged 17-21 years; 3rd group – 20 adult athletes aged 22-35 years; 4th group – 19 adult athletes aged 36-60 years.

To study immediate adaptive responses and make comprehensive assessment of the cardiorespiratory system of endurance athletes of different age groups and sport qualifications, we examined their cardiovascular system, external respiration and gas exchange using cycle ergometer. For this purpose, differential and spatial rheogram, ECG, indicators of external respiration and gas exchange were recorded [5]. Step load on a cycle ergometer from 50 to 200 Watts without rest was applied in the study. Each level of load lasted 4 minutes. Pedaling speed was 60 rpm.

Results and discussion. It is the system of body’s oxygen supply that is of high priority in most endurance sports, as it is essential for the high physical working capacity and leads to the mobilization of the circulation and respiratory organs, which can be considered as two transport systems providing a single body function - its gas exchange. Herewith, the most perfect mechanisms are those associated with increasing values of minute volume and oxygen utilization coefficient that, according to the research results, are typical for the groups of young and adult athletes, while for the groups of adolescent athletes and athletes aged 36-60 years they are associated with increasing values ​​of respiratory minute volume (Table 1).

In terms of the theory of functional systems [2, 6], muscular activity leads to the active mutual contributions of vegetative functions to the end result. In our study, oxygen supply to the body serves as a useful effect of adaptation. To evaluate the efficiency of oxygen supply, based on the integrated approach since neither physiological system nor function taken by itself is determining, it is necessary to introduce an indicator of the cardiovascular and respiratory system response, during which positive shifts are formed during sports training. It is assumed that this is due to the system of motor-visceral reflexes. As a rule, the cardiovascular system acts as a limiting link in the chain of oxygen transport to working muscles, and breathing balances it out in some cases. This is a result of a decreased "transport capacity" of the heart, as under submaximal and high-intensity loads, cardiac output increases 4-5-fold, and the volume of air pumped through the lungs - 15-20-fold. Therefore, as the evaluation criterion we would recommend oxygen transport efficiency, which would increase gradually due to increasing load intensity and could be considered as a result of interaction of heart pump function, external respiration and gas exchange [7-8]. In this view, we proposed the coefficient of comprehensive assessment of the cardiorespiratory system to physical load, which is presented as a ratio of products: expressed as a percentage [5]

The values ​​of the coefficient of comprehensive assessment of the body’s oxygen supply in the group of athletes decreased under step load, and most significantly - in the groups of adolescent athletes and athletes aged 36-60 years, which testifies to the leading role of breathing in oxygen supply in these groups (Table 2). Some researchers consider that, at the initial stage of the educational and training process, working capacity is conditioned by the external respiration apparatus. However, this type of oxygen supply to the body of athletes is viewed as ineffective since most of the oxygen delivered to the body is aimed to meet the energy demands of the respiratory muscles. The organs of external respiration take on the meaning of the leading factor of body’s oxygen supply in adolescent athletes and athletes aged 36-60 years. Herewith, heart pump function is balanced out by stable stroke volume. Consequently, the compensation of cardiac efficiency in these groups is of "respiratory" type. Based on the value of the coefficient of comprehensive assessment of the cardiorespiratory system, statistically significant differences can be revealed between the age groups, which is important for identification of the mechanisms of evaluation of oxygen supply during motor activity.

Conclusion. The conducted quantitative analysis of the indicators of the cardiovascular and respiratory systems has revealed that the changes in the cardiorespiratory parameters vary significantly depending on the athletes’ age-specific characteristics. The set load is maintained due to the mix of combinations of oxygen transport and utilization systems interacting between each other. The proposed coefficient of the comprehensive assessment of the cardiorespiratory system can be used for evaluation of the compensatory and adaptive reactions of the body of athletes under step loads, both in vitro and in vivo.

References

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Table 1. Cardiorespiratory system indicators (HR, bpm; SV, ml; RMV, l/min; О₂UC, ml/l) in groups of adolescent (1^st group), young (2^nd group) and senior (3^rd, 4^th groups) athletes under step load

Note.  HR – heart rate, SV – stroke volume, RMV – respiratory minute volume, О₂UC – oxygen utilization coefficient. Statistical significance of differences: ⁺ - between the 1^st and 2^nd group athletes; * - between the 1^st and 3^rd group athletes; ^v -  between the 1^st and 4^th group athletes; ^о – between the 2^nd and 3^rd group athletes; ^х – between the 2^nd and 4^th group athletes; • - between the 3^rd and 4^th group athletes.

Table 2. Cardiorespiratory system comprehensive assessment ratio in groups of adolescent (1^st group), young (2^nd group) and senior athletes (3^rd, 4^th groups) under step load

Corresponding author: kaf.fv.kgau@mail.ru

Abstract

The research objective was to determine the coefficient of comprehensive assessment of the cardiorespiratory system in endurance athletes of different age groups, when exposed to step load. The study involved 72 male athletes of 15 to 60 years of age engaged in endurance sports. They were divided into 4 groups according to age. The quantitative analysis of the indicators of the cardiovascular and respiratory systems has revealed that the changes in the cardiorespiratory parameters vary significantly depending on the athletes’ age-specific characteristics. The set load is maintained due to the mix of combinations of oxygen transport and utilization systems interacting between each other.

The proposed coefficient of the comprehensive assessment of the cardiorespiratory system can be used for evaluation of the compensatory and adaptive reactions of the body of athletes under step loads, both in vitro and in vivo.