PhD, Associate Professor A.S. Bakhareva¹
PhD, Associate Professor A.A. Pletnev¹
PhD, Associate Professor E.Yu. Savinykh¹
A.S. Aminova^1
1South Ural State University (National Research University), Chelyabinsk

Keywords: central venous pressure, stroke volume, diastolic heart-filling wave, circulating blood deficiency, intrathoracic pressure.

Introduction. It is the individual aerobic energy generation ability that is a key for the working capacity in modern cross country skiing since the bodily energy costs including those covered by the anaerobic energy sources are eventually connected with the oxidizing phosphorylation [13]. Scarcity of oxygen and oxidation energy affects the concentration of calcium ions (Ca²⁺) in the cytosol due to the fact that two Ca²⁺ ions are transported for each ATP hydrolyzed [11]. At the same time, ATP, besides its macroergic function, acts as a synaptic modulator [8]. While modeling the oxygen regimen in the skeletal muscle, it was found that an increase in the volume of interstitium from 9 to 25%, with a higher O₂ level, leads to a decrease by about 20% in the O₂ diffusion resistance on its way from the capillary tube to the mitochondria in the fiber [2]. Since blood oxygenation in the alveoli is constant, despite its volume and blood flow velocity [5], it is the index of stroke volume that determines the oxygen transport function in the racing skiers’ body.

Objective of the study was to obtain the significant blood flow rates indicative of the racing skiers’ adaptation process efficiency under physical loads.

Methods and structure of the study. Subject to the study were 18-23 year-old male racing skiers (n=17) grouped as follows: Group 1 was composed of the individuals with RUS points under 67.89 in the racing events; and Group 2 of the skiers having RUS points in excess of 73.22. The groups were formed based on the Russian Cross Country Skiing Federation rating database. The study was held during the qualifying starts (February-March). For the purposes of the study, the sample was tested using bio-impedance tetrapolar reopolygraphy based on the "Kentavr PC" and "MARG 10-01" computer systems by "Microlux" [1] and a noninvasive blood analyzer system (AMP, Ukraine). The data obtained were subject to statistical analysis.

Results and discussion. The negative chronotropic and positive inotropic effects in Group 2 (see Table 1) were indicative of the dominant functional role of the stroke volume in the blood flow control and better heart adaptability to physical loads. According to A.A. Melnikov et al. [7], moderate bradycardia and decreasing MOC when adapting to physical loads result from an increase of the oxygen transport function, which contributes to "economization" of the cardiac activity at rest.

Table 1. Mean (M) values of cardiorespiratory function in racing skiers and their measure of significance during races

However, along with the filling pressure rates, the hemodynamic reaction to fluctuating loads can be more accurately predicted by the level of intrathoracic (central) blood volume [6]. According to several authors, negative ITP, being more pronounced in leaders, results in a decrease of the cardiac muscle pressure gradient and limits the diastolic filling of the ventricles [4]. In his studies B.I. Tkachenko [9] showed that decreasing intrathoracic pressure leads to a decrease of CVP, which is also accompanied by a decrease in the stroke volume. According to S. Gelman [10], decreasing CVP rates are a prerequisite for creating a gradient between the central and peripheral venous pressure. Such a mechanism promotes sanguimotion to the right heart and into the thoracic vessels [3]. Previously published works demonstrated that the lungs act as a blood depot due to the dilatation of their vascular systems, and the main blood vessels in the lungs are pulmonary veins containing more than half of the blood volume circulating along a small circle [12]. This is due to the fact that the internal organs venous compliance is greater than that of the limbs.

Conclusion. The racing skiers’ resting central venous pressure rates below 63 mmHg determine the effects of interaction of intrathoracic hemodynamics and respiration biomechanics, which leads to an increase in venous return, cardiac output and oxygen homeostasis under physical loads.

References

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Corresponding author: bakharevaas@susu.ru

Abstract

It is the individual aerobic energy generation ability that is a key for the working capacity in modern cross country skiing since the bodily energy costs including those covered by the anaerobic energy sources are eventually connected with the oxidizing phosphorylation. The study was designed to obtain and analyze the blood flow (haemodynamic) rates indicative of the racing skiers’ adaptation process efficiency under physical load. Subject to the study were 18-23 year-old male racing skiers (n=17) grouped as follows: Group 1 was composed of the individuals with RUS points under 67.89 in the racing events; and Group two of the skiers having RUS points in excess of 73.22. For the purposes of the study, the sample was tested using a bio-impedance tetrapolar reopolygraph and a blood analyzer system. The negative chronotropic and positive inotropic effects in Group 2 were indicative of the dominant role of the stroke volume in the blood flow control and better heart adaptability to the physical loads. It was also found that the low resting central venous pressure rates varying at 63.86 mm Hg enabled trained racing skiers to keep their performance under 67.89 RUS-points in the racing events as reported by the Russian Cross Country Skiing Federation rating database.