Ph.D. S.K. Saryg
Postgraduate A.D. Lopsan
Professor, Dr.Biol. L.K. Buduk-ool
Tuvinian state university, Kyzyl

Keywords: heart rate, volleyball players, wrestlers, hemodynamics, sympathetic regulation.

Introduction. Sports activity is a specific type of activity, a specially organized process aimed at detecting human reserve capabilities. Objective criteria for assessing the level of functional fitness of an athlete are physiological indicators reflecting the functioning of the sympathetic and parasympathetic sections of the human nervous system, especially the mechanisms of vegetative regulation of the functioning of the cardiovascular system.

In recent decades much attention has been paid to the research of heart rate during adaptation to training and competitive loads. Heart rate and force are very sensitive to any stress stimulation and indicate the state of their regulatory systems and regulatory and adaptive capabilities of the body. They improve depending on the degree of increase of parasympathetic regulation, developing in the course of training [5]. The growing sympathetic regulation under physical or emotional stress leads to decreased adaptive capabilities of heart rate and affects the baseline heart rate characteristics [2].

Heart rate variability (HRV) research is being widely used for athletes to estimate the effect of training loads. The issue of neurohumoral mechanisms of heart rate regulation is among the most researched in sports physiology and medicine at the moment, due to the fact that heart rate shows the fundamental relations in functioning of not only the cardiovascular system, but the whole body, as it reflects the functioning of the autonomic nervous system.

The method of studying HRV is simple to measure, informative, highly resistant to inaccuracies and measurement errors and therefore is very reliable. At the same time, the number of works related to the study of heart rate variability of athletes is extremely small.  This accounts for the relevance of the present research.

The purpose of the research was to examine heart rate indicators of volleyball players and freestyle wrestlers of the College of Olympic reserve in Kyzyl (Republic of Tyva).

Materials and methods. A research was conducted involving an assessment of the resting functional state of the cardiovascular system (CVS) of volleyball players and freestyle wrestlers of the College of Olympic reserve of the Republic of Tyva (COR RT). There were 55 Tuvinian young men of various skill levels in total, including 21 volleyball players and 34 wrestlers aged 15 to 22 (mean age – 17.52±0.29). The training load was 2 hours 6 days a week.  

The functional state of CVS was assessed by the indicators of heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressure, mean arterial pressure (MAP) by the formula of J.B. Hickam, cardiac index (CI), indicator of vegetative balance (Kerdo index) by the technique of Gene V.G., adaptive capacity (AC) by the method of R.M. Baevsky, physical fitness index (PFI) and double product (DP) [3].

Time baseline indicators of heart rate variability were assessed: standard deviation of the RR interval (SDNN, ms), root mean square of successive differences of cardiointervals (RMSSD, ms), share of successive intervals that differ by more than 50 ms (pNN50, %), coefficient of variation of number of intervals R-R (CV, %) using VNS-Rhythm device produced by the Neurosoft Company (Ivanovo, Russia). Spectral indices of heart rate variability were also studied: total spectral power (TP, ms²), high frequency spectrum power (HF, ms²), power of waves in normalized units (HF norm, n.u. and LF norm, n.u.) and their ratio LF/HF.

Mathematical processing of the research results was carried out using the STATISTICA 6 software. Differences were considered statistically significant at р<0.05.

Results and discussion. Significant differences between the volleyball players and the wrestlers in terms of the studied parameters have not been detected in the study of HR, SBP and DBP. The values corresponded to the physiological norm (Table 1). Great “economic efficiency” [4] of the functioning of the hemodynamics system is characteristic of the volleyball players compared with the wrestlers, which is manifested by a smaller value of CI.   

MAP, CI, Kerdo indices and AC values of all the athletes indicated overstraining of CVS. Fatigue had been detected according to the MAP index of the examined volleyball players and wrestlers. Physical or mental loads of the afferent systems during operation are the major cause of fatigue [7].

AC, as an indicator of the degree of adaptation of the whole body, has detected strain of the mechanisms of adaptation to physical loads, i.e. sufficient functional capacities are provided at the expense of the functional reserves. It has been found that if adaptive characteristics worsen, the AC values increase, specific changes emerge leading to illness [1]. CI revealed eukinetic type of blood circulation, indicating the moderately high peripheral resistance of the systemic circulation. DP characterizing the systolic heart function indicates the average functional capacity of heart muscles and the average maximum aerobic capacity. Quantitative estimation of PFI provides important information about health status and capabilities of the body. So the necessary measures can be taken to prevent disease and improve PFI. The examined trainee athletes’ PFI is “above average”, which means unsafe health status, since the average physical fitness level can be regarded as critical.

Table 1. Indicators of central hemodynamics of volleyball players and wrestlers of the College of Olympic reserve in a state of relative rest (M±m)

The methods of time-line and spectral analysis were chosen for HRV analysis. Table 2 shows indicators of HRV time-line analysis in the compared groups. As seen from Table 2, the average duration of the normal cardio intervals RRNN of the wrestlers is 6.44 % longer and amounts to 942.9±26.5 compared with the volleyball players whose value is 882.1±60.6 (р>0.05).

SDNN is the most common indicator for the overall assessment of HRV. According to published data, a change of SDNN value indicates a shift of the autonomic balance towards predominance of one of the ANS divisions: increase of SDNN indicates that the parasympathetic part is growing, and decrease of the values shows that the sympathetic regulation of the heart rate is strengthening [5]. In our research, the trainee wrestlers’ SDNN level is high (76.5±8.87) unlike that of volleyball players (47.9±5.97) (р>0.05), indicating strengthening of the parasympathetic regulation of heart rate which is consistent with the published data of other authors (Table 2).

Table 2. Time-line indicators of heart rate variability of volleyball players and wrestlers of the College of Olympic reserve in a state of relative rest (M±m)

Note: * р<0.05 – compared with volleyball players.

In our study, the RMSSD indicator of the wrestlers tended to be high (78.8±12.5) compared with that of the volleyball players (943.4±8.58) (р>0.05), which also reflects some predominance of the parasympathetic division over the sympathetic one (Table 2). According to the published works of M.A. Popova et al. (2013) it has been established that involvement in extreme sports does not have a unidirectional influence on the SDNN and RMSSD indicators of the time-line analysis, and their increase reflects activation of the parasympathetic ANS [6].

The indicator of the number of pairs of successive cardio intervals NN that differ by more than 50 ms during the entire recording (pNN50, %) was also higher in case of wrestlers, by 48.2 % (р<0.05). Higher pNN50 value promotes more active parasympathetic nervous system. The wrestlers’ variability coefficient (CV) was slightly high (7.98±0.78) compared with that of the volleyball players (5.30±0.40) (р>0.05), indicating a certain increase of the total regulation indicator.

The following results were obtained while analyzing the spectral baseline indicators (Table 3). Total spectral power indicator (TP) of the wrestlers was higher (6757.7±604.4) than that of the volleyball players (2673.4±481.0) (р>0.05), which indicates an increase in the activity of the parasympathetic part (Table 2). This indicates a greater impact on the heart of regulatory actions aimed at recovering after loads. These findings are consistent with the published data that indicates that physical exercise contributes to the growth of the overall power of HRV which is associated with the activation of the vagal tone in the autonomic nervous system [9].

Table 3. Spectral indicators of heart rate variability of volleyball players and wrestlers of the College of Olympic reserve in a state of relative rest (M±m)

Note: * р<0.05 – compared with volleyball players.

Results of the analysis of the other spectral values of heart rate (HF, LF norm, HF norm and LF/HF), reflecting the activity of the autonomic nervous system in all the athletes, have not shown significant changes (Table 3).

Conclusions. The research found no significant differences in the cardiovascular system of the Tuvinian trainee volleyball players and wrestlers, but the functional state indicates the presence of strain of the adaptation mechanisms. The level of physical fitness is rated as “above average”. While analyzing the autonomic regulation of heart rate of the trainee athletes engaged in freestyle wrestling the parasympathetic type of the autonomic nervous system has been identified, which ensures an optimal supply of oxygen to the body of an athlete while at rest and a recovery after loads, an economization of the cardiovascular system activity [8].

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