Symbolic Analysis of the Heart Rate Variability During the Plateau Phase Following Maximal Sprint Exercise.

Jorge L Storniolo,Paolo Cavallari,Beatrice Cairo,Alberto Porta

doi:10.3389/fphys.2021.632883

Jorge L Storniolo, Paolo Cavallari + Show 2 more

Open Access

https://doi.org/10.3389/fphys.2021.632883

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Abstract

Cardiac autonomic control is commonly assessed via the analysis of fluctuations of the temporal distance between two consecutive R-waves (RR). Cardiac regulation assessment following high intensity physical exercise is difficult due to RR non-stationarities. The very short epoch following maximal sprint exercise when RR remains close to its lowest value, i.e., the PLATEAU, provides the opportunity to evaluate cardiac regulation from stationary RR sequences. The aim of the study is to evaluate cardiac autonomic control during PLATEAU phase following 60-m maximal sprint and compare the results to those derived from sequences featuring the same length as the PLATEAU and derived from pre-exercise and post-exercise periods. These sequences were referred to as PRE and POST sequences. RR series were recorded in 21 subjects (age: 24.9 ± 5.1 years, 15 men and six women). We applied a symbolic approach due to its ability to deal with very short RR sequences. The symbolic approach classified patterns formed by three RRs according to the sign and number of RR variations. Symbolic markers were compared to more classical time and frequency domain indexes. Comparison was extended to simulated signals to explicitly evaluate the suitability of methods to deal with short variability series. A surrogate test was applied to check the null hypothesis of random fluctuations. Over simulated data symbolic analysis was able to separate dynamics with different spectral profiles provided that the frame length was longer than 10 cardiac beats. Over real data the surrogate test indicated the presence of determinism in PRE, PLATEAU, and POST sequences. We found that the rate of patterns with two variations with unlike sign increased during PLATEAU and in POST sequences and the frequency of patterns with no variations remained unchanged during PLATEAU and decreased in POST compared to PRE sequences. Results indicated a sustained sympathetic control along with an early vagal reactivation during PLATEAU and a shift of the sympathovagal balance toward vagal predominance in POST compared to PRE sequences. Time and frequency domains markers were less powerful because they were dominated by the dramatic decrease of RR variance during PLATEAU.

Highlights

Heart rate variability (HRV), defined as the beat-to-beat variations of the time interval between two consecutive R-wave peaks (RR) detected over the electrocardiogram, has been historically processed to infer cardiac autonomic control in physiological and pathological conditions (Pomeranz et al, 1985; Task Force of the European Society of Cardiology the North American Society of Pacng Electrophysiology, 1996; Qiu et al, 2017)
The aim of this study is to examine the beat-to-beat RR variability during PLATEAU observed just after a maximal sprint exercise via symbolic analysis
At the end of the sprint the RR remain stable for 20 cardiac beats and this period is labeled as PLATEAU

Summary

Introduction

Heart rate variability (HRV), defined as the beat-to-beat variations of the time interval between two consecutive R-wave peaks (RR) detected over the electrocardiogram, has been historically processed to infer cardiac autonomic control in physiological and pathological conditions (Pomeranz et al, 1985; Task Force of the European Society of Cardiology the North American Society of Pacng Electrophysiology, 1996; Qiu et al, 2017). In order to assure a reliable estimation of the amplitude of the LF and HF oscillations a typical rule of thumb suggests to take a series length longer than 5 times the slowest meaningful oscillation that the spectral analysis would like to resolve (i.e., 0.04 Hz). This requirement imposes that short-term frequency domain analysis of HRV is carried out over RR series longer than 125 s (i.e., longer than 125 RR values with a RR mean of 1 s). Shorter series are usually analyzed only in time domain because in this domain no specific HRV features were extracted and descriptive statistical quantities are the typical target (i.e., mean and variance)

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