Heart rate variability analysis

The expansion of heart rate variability analysis has been facilitated by the remarkable development of computer sciences and digital signal processing during the last thirty years. The beat-to-beat fluctuation of the heart rate originates from the momentary summing of sympathetic and parasympathetic influences on the sinus node. According to the extensive associations of the autonomic nervous system, several factors affect heart rate and its variability such as posture, respiration frequency, age, gender, physical or mental load, pain, numerous disease conditions, and different drugs. Heart rate variability can be quantitatively measured by time domain and frequency domain methods that are detailed in the paper. Non-linear methods have not spread in the clinical practice yet. Various cardiovascular and other pathologies as well as different forms of mental and physical load are associated with altered heart rate variability offering the possibility of predicting disease outcome and assessing stress.     

Heart rate variability in healthy humans during night sleep

Polysomnography has been performed and heart rate variability has been studied during night sleep in healthy young subjects of both sexes. It has been shown that, on average, a shift in autonomic support towards parasympathicotonia occurs during sleep, with a maximum at stages III and IV of NREM sleep. At stage II of NREM sleep and during REM sleep, a short-term activation of the sympathetic nervous system comparable to wakefulness is observed.     

Heart rate variability in weightlifters

On the basis of the literature and original data, heart rate variability (HRV) in weightlifters has been studied. The results showed that the distribution mode (a parameter of mathematical analysis that is equal to the most frequent length of RR intervals) indicates the intensity of physical exercise. Specific changes in the autonomic balance in athletes as dependent on their degree of training and sports qualification are important characteristics of adaptations to physical loads. For example, the degree of training of weightlifters is reflected by the level of the respiratory component as an index of the activity of the parasympathetic nervous system. Adaptation to physical exercise leads to an increase in the power of the spectrum of neurohumoral modulation and to changes in the ratio between the levels of the total spectral power of HRV.     

Heart rate variability and sports

This article presents a review of the literature and some author’s data on the problem of using heart rate variability in sports and sports medicine practice.     

Heart rate variability changes during high frequency yoga breathingand breath awareness

Background  

Pre and post comparison after one minute of high frequency yoga breathing (HFYB) suggested that the HFYB modifies the autonomic status by increasing sympathetic modulation, but its effect during the practice was not assessed.     

Heart rate variability and body temperature during the sleep onset period

Heart rate variability (HRV) and body temperature during the sleep onset period was examined. The core body temperature and electrocardiogram were recorded continuously beginning 1 h before lights out (LO) until the end of the first rapid eye movement sleep (REM) in 14 young healthy subjects. HRV was calculated by the MemCalc method. The time course changes in body temperature and HRV was analyzed before and after sleep onset, and during the following eight consecutive phases: the 60 min before LO, the 30 min before LO, LO, first stage 2 (sleep onset), first slow wave sleep (SWS), stage 2 just before REM, start of REM, and end of REM. A clear decline was observed in the ratio of the low frequency (LF) to high frequency (HF) component of HRV (LF/HF), normalized LF (LF/(LF + HF)), and body temperature prior to sleep onset both in the time course of the sleep onset period and in the consecutive phases. The HF increased prior to sleep onset in the consecutive phases, while no clear increase was observed in the time course of sleep onset period. Changes in LF/(LF + HF) and LF/HF preceded SWS and REM. These results suggest the existence of a strong coupling between the cardiac autonomic nervous system and body temperature at the sleep onset period that may not be circadian effects. Furthermore, LF/(LF + HF) and LF/HF may possibly anticipate sleep and the onset of each sleep stage.

     

Heart rate variability analysis in general medicine

Autonomic nervous system plays an integral role in homeostasis. Autonomic modulation can frequently be altered in patients with cardiac disorders as well as in patients with other critical illnesses or injuries. Assessment of heart rate variability is based on analysis of consecutive normal R-R intervals and may provide quantitative information on the modulation of cardiac vagal and sympathetic nerve input. The hypothesis that depressed heart rate variability may occur over a broad range of illness and injury, and may inversely correlated with disease severity and outcome has been tested in various clinical settings over the last decade. This article reviews recent literature concerning the potential clinical implications and limitations of heart rate variability assessment in general medicine.     

Heart rate and arterial pressure variability in humans during different orthostatic load.

The influence of posture on the rhythms in blood pressure, heart rate and respiration was tested by means of spectral analysis in 14 healthy subjects. During squatting, standing and sitting, the finger blood pressure was recorded by the non-invasive Penáz technique together with cardiac intervals and respiratory movements. The power spectra obtained from five-minute samples showed that the respiratory components of cardiac interval and pulse pressure were reduced significantly in standing. Compared to squatting, a significant increase of total power in the medium frequency band (0.05-0.15 Hz) for cardiac interval, diastolic and mean pressure could be detected.     

Heart rate variability in elite American track-and-field athletes

Prolonged training leads to changes in autonomic cardiac balance. This sympathetic and parasympathetic balance can now be studied using heart rate variability (HRV). Studies have shown that endurance athletes have an elevated level of parasympathetic tone in comparison to sedentary people. The effect of resistance training on autonomic tone is less clear. We hypothesized a significant difference in HRV indices in endurance-trained vs. power-trained track-and-field athletes. One hundred forty-five athletes (58 women) were tested prior to the 2004 U.S.A. Olympic Trials. Heart rate variability data were collected using the Omegawave Sport Technology System. Subjects were grouped according to training emphasis and gender. The mean age of the athletes was 24.8 years in each group. There were significant (p < 0.01) differences by sex in selected frequency domain variables (HFnu, LFnu, LH, LHnu) and for PNN50 (p < 0.04) for the time domain variables. Two-factor analyses of variance showed differences for only the main effect of sex and not for any other grouping method or interaction. Elite athletes have been shown to have higher parasympathetic tone than recreational athletes and nonathletes. Our data show differences by sex, but not between aerobically and power-based athletes. Whether this is due to an aerobic component of resistance training, an overall prolonged training effect, or some genetic difference remains unclear. Further study is needed to assess the impact of resistance training programs on autonomic tone and cardiovascular fitness. This information will be valuable for the practitioner to use in assessing an athlete's response to a prescribed training regimen.     

Heart rate variability in normal and complicated pregnancies

The sympathetic division (SD) of the autonomic nervous system (ANS) was assessed by 23 tachometric parameters in 176 pregnant women using a Valenta medical diagnostic system. The activity of the ANS SD was shown to increase in the first trimester of pregnancy, progressively rise during the second and third trimesters, and decrease immediately before delivery. This is considered as a mechanism of adaptation to pregnancy. The activity of the ANS SD in pregnant women remained unchanged in mild gestosis; increased in moderate gestosis; and decreased in chronic hypertension, hypertensive circulatory disorders, and threatened preterm delivery. The role of the activity of the ANS SD in normal pregnancy and in obstetric complications is discussed.     

Heart rate variability in young hockey players at rest and during active orthostatic test

Heart rate variability of 27 young (10- to 11-year-old) athletes (ice hockey players) was studied. Special autonomic regulatory mechanisms that function both at a supine position and during active orthostatic test were found, which probably reflect the adaptation of the cardiovascular system to sports activity.     

Heart rate variability in subjects with different respiratory rates

The variability of the cardiac rhythm was studied in males with different initial respiratory rates. At rest and during voluntarily controlled breathing, subjects with medium respiratory rates were found to have a less variable heart rate than their counterparts with low or high respiratory rates.