Features of the wave structure of heart rate variability (HRV) usually reflect the dynamics of regulatory processes in humans and animals. However, most of the studies on physiological characteristics are conducted on men. The problem of the heart rate fluctuations frequency structure during long-term mental pressure with a significant psycho-emotional component in women hasn’t been studied properly. Therefore, the purpose of the study was to investigate the wave structure of the cardiac rhythm in women in different phases of the ovarian-menstrual cycle (OMC) under the conditions of psycho-emotional pressure. Materials and methods. 32 female students in the prone condition were examined while performing a 10-minute mental pressure using the method of M.V. Makarenko. Each of the trials was performed three times: in follicular phase (I), ovulation (II) and luteal phase (III) of ovarian-menstrual cycle. The power of the R-R spectrum was calculated in the standard frequency bands 0-0.04 Hz (VLF), 0.04-0.15 Hz (LF), 0.15-0.4 Hz (HF), 0-0.4 Hz (TP), normalize the power in the range of 0.15-0.4 Hz (HFnorm). In addition, the spectral density (aLF) and the frequency (tLF) of the highest amplitude peak in the range 0.04-0.15 Hz were estimated. In order to find out the features of the wave structure in this range, a median spectrograph was constructed with a step of 0.01 Hz. Due to the abnormality of the data distribution, their processing was carried out using nonparametric statistical methods. Results. It was found out that there were no significant differences between the levels of the analyzed parameters of HRV, depending on the phase of OMC. Under the conditions of psycho-emotional pressure in all phases of OMC, a high (p<0.001) decrease in R-R, HF, HFnorm, TP was observed. The reactivity to the loading of LF in phase I (18.1 [-31.6; 75.1]%) significantly differed from the changes in the II phase (-17.6 [-51.7, 50.2]%) and III (-23.9 [-64.6, 69.7]%) of the phases of the OMC. The decrease in HFnorm in the III phase was the lowest compared to the II and higher than on the first phase. In terms of psycho-emotional stress, there is a significant difference between the levels of LF and TP in III compared to the II and I phases. The activation of the sympathetic part of the VNS by the HFnorm index was highest in the follicular and luteal phases. It is noteworthy that the greatest deviation of the values of the reactivity to the emotional pressure and the intragroup variation is typical for the indicators that characterize the frequency range of the oscillations R-R from 0.04 to 0.15 Hz. In this connection, a detailed analysis of the distribution of the waves of the heart rate in it was carried out in a normalized median spectrogram. Conclusions. It was found out that under the conditions of psycho-emotional pressure changes in the wave structure were expressed the most during the first phase, the less – during the III phase. The nature of spectral power distribution in phase I of the OC under conditions of psycho-emotional pressure was significantly different from the distribution under the other conditions. The presence of two peaks, which can characterize the influence of various regulatory mechanisms, was also observed.
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