Professor, Dr. Biol. Y.S. Vanyushin
Associate Professor, PhD R.R. Khayrullin
Associate Professor, PhD M.I. Rakhimov
¹Kazan State Agrarian University, Kazan
²Kazan (Volga region) Federal University, Kazan

Keywords: cardiorespiratory system, chronotropic and inotropic types of adaptation, athletes, step load, threshold.

Introduction. Sufficient delivery of oxygen in an athlete’s body is the most important condition for achieving high performance, especially in sports associated with endurance. Cardiac output increase as a result of growth in the chronotropic and inotropic components in the form of increased HR and SV is considered to be one of the mechanisms of such delivery. According to some researchers, the inotropic mechanism is more perfect, as in this case HR is reduced while an increase in cardiac output is achieved by increasing SV [1, 3]. At the same time quite a high level of physical work capacity is maintained [2, 4]. Relevant literature suggests there is a connection close to linear between HR and the load capacity, while another ratio is observed between the load capacity and SV. 

Objective of the study was to define the threshold of adequate hemodynamic response in athletes with various types of adaptation of the cardiorespiratory system under step load.    

Methods and structure of the research. The study involved male athletes aged 18-35 (59 persons) training in various sports and having various qualifications from Masters of Sport to mass sport categories. A comprehensive assessment of the cardiorespiratory system consisting of simultaneous recording of cardiovascular and respiratory systems indicators was performed to obtain the necessary data [3]. Step load on a cycle ergometer without breaks for rest, 50-200 watts, was used. All the subjects were divided into groups depending on the type of adaptation of their cardiorespiratory systems. Cardiorespiratory system reaction to a load of 200 watts on a cycle ergometer was taken as the basis of allocation of athletes by adaptation type. A set of elements with its coefficient of variation (CV) not exceeding 10% was considered homogeneous in terms of a certain feature [5]. As a result, the subjects were divided into 5 groups depending on the type of adaptation of their cardiorespiratory system: chronotropic, inotropic, respiratory, chronotropic-respiratory and inotropic-respiratory [2] (Table 1).

Table 1. Allocation of athletes by their cardiorespiratory systems adaptation type under the load of 200 watts on a cycle ergometer

Note. HR – heart rate, SV – stroke volume, RMV – respiratory minute volume. Statistical significance of differences: * – between the indicators with the chronotropic type of adaptation and the other types; ⁺ – between the indicators with the inotropic type of adaptation and the other types; ^– – between the indicators with the respiratory type of adaptation and the other types; ^{^} – between the indicators with the chronotropic-respiratory type of adaptation and the inotropic-respiratory type.

Results and discussion. The resting SV values were the same in the groups of athletes with the chronotropic and inotropic types of adaptation of the cardiorespiratory system. However, starting with the 50 watts load and up to the 200 watts load, the SV values were significantly higher in the group of athletes with the inotropic type of adaptation compared with the group of athletes with the chronotropic type. The mechanism of a considerable SV increase under step load in the group of athletes with the inotropic type of adaptation may probably be explained by the fact that diastolic and systolic volumes of their left ventricle are larger than those of athletes of the other groups [3]. A gradual increase of SV values in all the groups of athletes took place up to the load of 100 watts. At the load of 150 watts a reduction of the SV values was observed in the group of athletes with the chronotropic type of adaptation, and at the load of 200 watts SV decreased in the groups of athletes with the respiratory and chronotropic-respiratory types of adaptation. Starting with the initial state and up to the load of 200 watts the highest SV values were observed in the groups of athletes with the inotropic and inotropic-respiratory types of adaptation (Table 2).

Table 2. Stroke volume indicators (ml) in groups of athletes with various types of adaptation of the cardiorespiratory system under step load                                      

Note. Statistical significance of differences: * – between the indicators with the chronotropic type of adaptation and the other types; ⁺ – between the indicators with the inotropic type of adaptation and the other types; ^– – between the indicators with the respiratory type of adaptation and the other types; ^{^} – between the indicators with the chronotropic-respiratory type of adaptation and the inotropic-respiratory type; ^о – between the indicators of the initial state and the load of 50 watts; ^∆ – between the indicators under the load of 50 watts and that of 100 watts; ^□ – between the indicators under the load of 100 watts and that of 150 watts; ^х – between the indicators under the load of 150 watts and that of 200 watts.

A phenomenon when the growth of the stroke volume stops is called a threshold of adequate hemodynamic response [6]. The research results show that in the group of athletes with the chronotropic type of adaptation the threshold of adequate hemodynamic response was observed under the load of 50 watts (Figure 1).

Figure 1. Threshold of adequate hemodynamic response under the load of 50 watts

Under the load of 150 watts the SV values tended to decrease in the group of athletes with the chronotropic type of adaptation compared with the previous load, which had a negative impact on the cardiac output indicator which proved to be lower by a significant value than that in the group of athletes with the inotropic type of adaptation. This is probably due to the fact that in case of a high chronotropic cardiac response to the load of 150 watts a considerable shortening of the diastole takes place and as a result blood filling of the ventricles is affected.    

In the groups of athletes with the inotropic, respiratory, chronotropic-respiratory and inotropic-respiratory types of adaptation the threshold of adequate hemodynamic response was observed under the load of 100 watts (Figure 2).

Figure 2. Threshold of appropriate hemodynamic response under the load of 100 watts

Conclusion. The threshold of adequate hemodynamic response depends on the types of adaptation of the cardiorespiratory system and the intensity of the performed load. The higher the threshold of appropriate hemodynamic response, the more functional and reserve capacities of athletes manifest themselves, which is better assessed by SV changes under step load. Therefore, the threshold of adequate hemodynamic response can be regarded as an indicator of functional and reserve capacities of athletes’ bodies.  

References

1. Vanyushin Yu.S. Vozrastnyie osobennosti obespecheniya organizma sportsmenov kislorodom. Sovremennyie tendentsii razvitiya nauki i tehnologii (Age-specific features of delivery of oxygen in athlete's body. Modern trends in development of science and technology) / Yu.S. Vanyushin. – Belgorod, 2016. – № 1-4. – P. 8-10. 
2. Vanyushin Yu.S. Fizicheskaya rabotosposobnost sportsmenov s razlichnyimi tipami adaptatsii kardiorespiratornoy sistemy (Physical work capacity of athletes with various types of adaptation of cardiorespiratory system) / Yu.S. Vanyushin, R.R. Khayrullin // Fiziologiya cheloveka. – 2008. – V. 34. – № 6. – P. 131-133.
3. Vanyushin Yu.S. Kardiorespiratornaya sistema kak indikator funktsionalnogo sostoyaniya organizma sportsmenov (Cardiorespiratory system as athletes' functional state indicator) / Yu.S. Vanyushin, R.R. Hayrullin // Teoriya i praktika fizicheskoy kultury.  – 2015. – № 7. – P. 11-14.
4. Yelistratov D.E. Osobennosti adaptatsii serdtsa yunoshey k fizicheskoy nagruzke v zavisimosti ot tipa krovoobrascheniya i urovnya dvigatelnoy aktivnosti: avtoref. dis. ... kand. biol. nauk (Features of young man's heart adaptation to physical load, depending on circulation type and physical activity level: abstract of PhD thesis) / D.E. Yelistratov. – Kazan, 2013. – P. 21.    
5. Oganov R.G. Differentsirovannyiy podhod k razrabotke fiziologicheskih normativov i ego znachenie dlya profilakticheskoy kardiologii (Differentiated approach for development of physiological standards and its implications for preventive cardiology) / R.G. Oganov, A.N. Britov, I.A. Gundarov et al. // Kardiologiya (Cardiology). – 1984. – V. 24. – № 4. – P. 52.
6. Uglov F.G. Otsenka gemodinamicheskoy reaktsii pri vozrastayuschey fizicheskoy nagruzke (Assessment of hemodynamic response under increasing physical load) / F.G. Uglov, V.I. Gavrilenkov, V.V. Gritsenko // Meditsinskiy ref. zhurnal. – 1982. – № 11. – P. 244.

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

Abstract
Objective of the study was to identify the threshold of adequate hemodynamic response in athletes grouped by different cardio-respiratory system adaptation types and exposed to step loads. Step (50 W to 200 W) cycle ergometer tests were used to apply the varying physical loads, with no rest breaks in the process. The subject athletes were grouped by different cardio-respiratory adaptation types, with the loads up to 200 W in the cycle ergometer step tests being applied for the above athletes’ grouping. Based on the tests, the subjects were grouped into 5 groups based on the following cardio-respiratory system adaptation types: chronotopic, inotropic, respiratory, chronotropic-respiratory and inotropic-respiratory. Subject to the study were 18-35 years old men athletes (n=59) engaged in different sports and having sport qualifications from Masters of Sport down to mass Class Athletes. The adequate hemodynamic response threshold was found to depend on the cardio-respiratory system adaptation types and load intensities. The higher was the adequate hemodynamic response threshold, the higher were the functional and reserve capacities of the athletes as verified by the SBV (specific blood volume) rate variations under the graduated loads. Therefore, the adequate hemodynamic response threshold may be applied as a body functional and reserve capacity indicator.