Heart Rate Variability and Blood Pressure during Dynamic and Static Exercise at Similar Heart Rate Levels

Aim was to elucidate autonomic responses to dynamic and static (isometric) exercise of the lower limbs eliciting the same moderate heart rate (HR) response. Method: 23 males performed two kinds of voluntary exercise in a supine position at similar heart rates: static exercise (SE) of the lower limbs (static leg press) and dynamic exercise (DE) of the lower limbs (cycling). Subjective effort, systolic (SBP) and diastolic blood pressure (DBP), mean arterial pressure (MAP), rate pressure product (RPP) and the time between consecutive heart beats (RR-intervals) were measured. Time-domain (SDNN, RMSSD), frequency-domain (power in the low and high frequency band (LFP, HFP)) and geometric measures (SD1, SD2) as well as non-linear measures of regularity (approximate entropy (ApEn), sample entropy (SampEn) and correlation dimension D2) were calculated. Results: Although HR was similar during both exercise conditions (88±10 bpm), subjective effort, SBP, DBP, MAP and RPP were significantly enhanced during SE. HRV indicators representing overall variability (SDNN, SD 2) and vagal modulated variability (RMSSD, HFP, SD 1) were increased. LFP, thought to be modulated by both autonomic branches, tended to be higher during SE. ApEn and SampEn were decreased whereas D₂ was enhanced during SE. It can be concluded that autonomic control processes during SE and DE were qualitatively different despite similar heart rate levels. The differences were reflected by blood pressure and HRV indices. HRV-measures indicated a stronger vagal cardiac activity during SE, while blood pressure response indicated a stronger sympathetic efferent activity to the vessels. The elevated vagal cardiac activity during SE might be a response mechanism, compensating a possible co-activation of sympathetic cardiac efferents, as HR and LF/HF was similar and LFP tended to be higher. However, this conclusion must be drawn cautiously as there is no HRV-marker reflecting “pure” sympathetic cardiac activity.     

Aerobic Exercise during Pregnancy and Presence of Fetal-Maternal Heart Rate Synchronization

It has been shown that short-term direct interaction between maternal and fetal heart rates may take place and that this interaction is affected by the rate of maternal respiration. The aim of this study was to determine the effect of maternal aerobic exercise during pregnancy on the occurrence of fetal-maternal heart rate synchronization.

Methods

In 40 pregnant women at the 36^th week of gestation, 21 of whom exercised regularly, we acquired 18 min. RR interval time series obtained simultaneously in the mothers and their fetuses from magnetocardiographic recordings. The time series of the two groups were examined with respect to their heart rate variability, the maternal respiratory rate and the presence of synchronization epochs as determined on the basis of synchrograms. Surrogate data were used to assess whether the occurrence of synchronization was due to chance.

Results

In the original data, we found synchronization occurred less often in pregnancies in which the mothers had exercised regularly. These subjects also displayed higher combined fetal-maternal heart rate variability and lower maternal respiratory rates. Analysis of the surrogate data showed shorter epochs of synchronization and a lack of the phase coordination found between maternal and fetal beat timing in the original data.

Conclusion

The results suggest that fetal-maternal heart rate coupling is present but generally weak. Maternal exercise has a damping effect on its occurrence, most likely due to an increase in beat-to-beat differences, higher vagal tone and slower breathing rates.     

Evaluation of an Exercise Field Test Using Heart Rate Monitors to Assess Cardiorespiratory Fitness and Heart Rate Recovery in an Asymptomatic Population

Purpose

Measures of cardiorespiratory fitness (CRF) and heart rate recovery (HRR) can improve risk stratification for cardiovascular disease, but these measurements are rarely made in asymptomatic individuals due to cost. An exercise field test (EFT) to assess CRF and HRR would be an inexpensive method for cardiovascular disease risk assessment in large populations. This study assessed 1) the predictive accuracy of a 12-minute run/walk EFT for estimating CRF () and 2) the accuracy of HRR measured after an EFT using a heart rate monitor (HRM) in an asymptomatic population.

Methods

Fifty subjects (48% women) ages 18–45 years completed a symptom-limited exercise tolerance test (ETT) (Bruce protocol) and an EFT on separate days. During the ETT, was measured by a metabolic cart, and heart rate was measured continuously by a HRM and a metabolic cart.

Results

EFT distance and sex independently predicted. The average absolute difference between observed and predicted was 0.26±3.27 ml·kg⁻¹·min⁻¹ for our model compared to 7.55±3.64 ml·kg⁻¹·min⁻¹ for the Cooper model. HRM HRR data were equivalent to respective metabolic cart values during the ETT. HRR at 1 minute post-exercise during ETT compared to the EFT had a moderate correlation (r = 0.75, p<0.001).

Conclusion

A more accurate model to estimate CRF from a 12-minute run/walk EFT was developed, and HRR can be measured using a HRM in an asymptomatic population outside of clinical settings.     

基于互信息和自相关函数的睡眠期间心率变异性研究

目的：研究互信息和自相关函数在睡眠各阶段心率变异性（heart rate variability,HRV）分析中的应用。方法：采用网络公开数据库SleepHeart Rateand Stroke VolumeDataBarhk,将RR序列分为30S一段,并以每30S数据为中心截取5minRR序列作为待分析对象。提取5minRR序列的互信息特征BDM、PDM和自相关函数特征BDC、PDC,然后用统计方法分析各特征在觉醒瓜EM／浅睡／深睡四种睡眠状态下的差异。结果：浅睡和深睡期间,BDM、PDM显著高于觉醒和REM睡眠（P〈0．001）。而BDC显著低于觉醒和REM睡眠（P〈0．001）,PDC无显著差异（P〉0．05）。结论：①BDM、PDM和BDC从不同角度反映了不同睡眠阶段下RR序列的特征,它们或许与HRV不同的调节机制有关。@BDM、PDM和BDC可作为辅助HRV睡眠分期的新指标。     

Effects of Biofeedback Training on Voluntary Heart Rate Control During Dynamic Exercise

The aims of this study were to (1) compare the effect of biofeedback with that of verbal instructions on the control of heart rate during exercise on a treadmill, (2) test the possible effect of workload on this control, and (3) examine the effect of workload on baseline heart rate at rest and during exercise. The study involved 35 participants who were randomly assigned to each of 4 experimental conditions generated by combining the 2 independent variables: training strategy for heart rate control (heart rate biofeedback or verbal control instructions) and work level (30 or 50% of maximal heart rate). By the end of 5 experimental sessions, participants trained with heart rate biofeedback showed a greater attenuation of the increase in heart rate produced by exercise than participants trained with verbal control instructions. The workload did not influence the voluntary control of heart rate, nor did it affect resting baseline heart rate, but it did affect exercise baseline heart rate.     

Analysis of Heart Rate Variability Based on the Graph Method

A method of analysis of heart rate variability based on the graph theory principle was suggested. The main parameters of the heart rate graph structure were determined and analyzed using models of harmonic oscillations, white noise, and various functional tests (including controllable respiration and mental load). The efficiency of the use of parameters of the heart rate graph for diagnosing some functional states was considered. A correlation of the parameters of the heart rate graph structure with the frequency characteristics of heart rate variability was studied. A general model of changes in the heart rate graph structure parameters at different levels of mental activity was constructed in terms of entropy changes.     

Changes in Non-Enzymatic Antioxidants in the Blood Following Anaerobic Exercise in Men and Women

Purpose

The aim of this study was to compare changes in total oxidative status (TOS), total antioxidative capacity (TAC) and the concentration of VitA, VitE, VitC, uric acid (UA), reduced (GSH) and oxidized glutathione (GSSG) in blood within 24 hours following anaerobic exercise (AnEx) among men and women.

Methods

10 women and 10 men performed a 20-second bicycle sprint (AnEx). Concentrations of oxidative stress indicators were measured before AnEx and 3, 15 and 30 minutes and 1 hour afterwards. UA, GSH and GSSH were also measured 24 hours after AnEx. Lactate and H⁺ concentrations were measured before and 3 minutes after AnEx.

Results

The increase in lactate and H⁺ concentrations following AnEx was similar in both sexes. Changes in the concentrations of all oxidative stress indicators were significant and did not differ between men and women. In both sexes, TOS, TAC, TOS/TAC and VitA and VitE concentrations were the highest 3 minutes, VitC concentration was the highest 30 minutes, and UA concentration was the highest 1 hour after AnEx. GSH concentration was significantly lower than the initial concentration from 15 minutes to 24 hour after AnEx. GSSG concentration was significantly higher, while the GSH/GSSG ratio was significantly lower than the initial values 1 hour and 24 hour after AnEx.

Conclusions

With similar changes in lactate and H⁺ concentrations, AnEx induces the same changes in TAC, TOS, TOS/TAC and non-enzymatic antioxidants of low molecular weight in men and women. Oxidative stress lasted at least 24 hours after AnEx.     

Nonstationary Heart Rate Variability during the Head-Down Tilt Test

Biophysics - Abstract—A new method has been proposed for processing the nonstationary rhythmogram signal recorded in the head-down tilt test (HDT). The method is based on the continuous...     

基于复杂度的心率变异性分析研究进展

心率变异性（HRV）是当前心电图分析的一个前沿热点,它反映了交感神经和副交感神经对心血管系统的综合调节作用,是评价心血管系统功能的重要指标。随着非线性动力学和复杂性科学的发展,HRV信号被普遍认为是混沌或含有混沌成分的信号。复杂度是用来表征一个心率非线性动力学系统复杂程度的量度,以其简单快速的优点引起了众多研究者的兴趣,并广泛应用于心率变异性分析。本文综述了国内外复杂度算法的研究进展及基于复杂度的心率变异性分析的临床应用及前景。     

Mechanisms of Periodic Heart Rate Oscillations: A Study Using Controlled Breathing Tests

An orthostatic test with frequency-controlled breathing (with periods of 4, 6, 8, 10, and 12 s) was used to analyze frequency estimates of the heart rate variability (HRV) spectrum in the low frequency (LF) and high frequency (HF) ranges in 36 volunteers (26 men and 10 women) aged 19–21 years without signs of heart or respiratory pathology. The subjects took a breath at the moment of an auditory signal. There were no other requirements for the respiration rhythm. Variables were compared using Wilcoxon’s test for pairwise comparisons; correlations were estimated by Spearman’s rank correlation R test. The sensitivities of the LF and HF ranges of the HRV spectrum to periodic respiratory perturbations at different frequencies were demonstrated to differ from each other. Autonomous 0.10- and 0.25-Hz circuits of oscillatory processes were found in HRV. The transition zone of influence of these circuits was located in the region around 0.125 Hz. The characteristics of the 0.10- and 0.25-Hz oscillations in HRV were studied. It was demonstrated that the 0.10-Hz oscillatory process is a potent mechanism of heart rate control, is affected by external factors, and determines the dynamics of the autonomic nervous state of the body, while the 0.25-Hz process is a regulatory mechanism of medium strength, is resistant to external factors, and characterizes the adaptation reserve of the autonomic nervous control of the heart rate, as well as the autonomic nervous state of the body. Resonance responses in the HRV spec-trum can be used for studying the characteristics of the 0.10- and 0.25-Hz oscillations.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 3, 2005, pp. 76–83.Original Russian Text Copyright © 2005 by Kiselev, Kirichuk, Posnenkova, Gridnev.     

Peculiarities of the Heart Rate Control during Competitive Entrance Examinations

A study was made of the dynamics of psychophysiological parameters and the activities of the systems regulating the heart rate in prospective post-secondary students taking competitive entrance examinations. The responses of the regulatory systems to examination stress were of two types, sympathetic and parasympathetic, depending on the initial state of the autonomic nervous system and the psychophysiological personality traits.     

孕早期胎心率意义的探讨

目的:探讨监测孕早期胎心率(fetal heartrate,FHR)对胎儿生存预后的预测价值,尤其对已有流产征兆或有重复、习惯性流产史患者的胎儿不良生存结局的预测价值.方法:收集自2003到2007年至我院门诊要求生育的正常早孕孕妇以及有先兆流产征象或重复、习惯性流产病史、孕周在5-9+6周要求生育的孕妇415例.采用超声测定孕囊(gestational sac,GS)平均直径、胚胎头臀径(crown-rump length,CRL)、FHR.如果胎儿存活,则在孕中期11-14周时测量胎儿颈项皮肤层厚度(nuchal translucency,NT).采用X检验分析孕早期胎心率与胎儿存活率及NT值的关系.结果:胎心率低时,胎儿存活率降低(P<0.05),NT值异常升高发生率增多(P<0.05).结论:孕早期胎心率测定对预测胎儿生存预后有一定的临床意义,并且胎心率减慢还与孕中期NT值异常升高相关,因此,孕早期胎心率可作为筛查和预测中晚期妊娠胎儿畸形的重点监测对象.     

Heart Rate Variability during Performance of Various Resultive Tasks

Heart rate variability was studied in 30 subjects before and after the assembling of a single-type color mosaic. The heart rate analysis was performed by evaluating its statistical structure (variation curves, scatter plots, and standard deviation). The wave structure of a series of cardiointervals was assessed by calculating and plotting the autocorrelation function. Certain heart rate parameters in different subjects reflected to various extents their success in achieving the useful end result of the visuomotor design task.     

A Real-Time Atrial Fibrillation Detection Algorithm Based on the Instantaneous State of Heart Rate

Atrial fibrillation (AF), the most frequent cause of cardioembolic stroke, is increasing in prevalence as the population ages, and presents with a broad spectrum of symptoms and severity. The early identification of AF is an essential part for preventing the possibility of blood clotting and stroke. In this work, a real-time algorithm is proposed for accurately screening AF episodes in electrocardiograms. This method adopts heart rate sequence, and it involves the application of symbolic dynamics and Shannon entropy. Using novel recursive algorithms, a low-computational complexity can be obtained. Four publicly-accessible sets of clinical data (Long-Term AF, MIT-BIH AF, MIT-BIH Arrhythmia, and MIT-BIH Normal Sinus Rhythm Databases) were used for assessment. The first database was selected as a training set; the receiver operating characteristic (ROC) curve was performed, and the best performance was achieved at the threshold of 0.639: the sensitivity (Se), specificity (Sp), positive predictive value (PPV) and overall accuracy (ACC) were 96.14%, 95.73%, 97.03% and 95.97%, respectively. The other three databases were used for independent testing. Using the obtained decision-making threshold (i.e., 0.639), for the second set, the obtained parameters were 97.37%, 98.44%, 97.89% and 97.99%, respectively; for the third database, these parameters were 97.83%, 87.41%, 47.67% and 88.51%, respectively; the Sp was 99.68% for the fourth set. The latest methods were also employed for comparison. Collectively, results presented in this study indicate that the combination of symbolic dynamics and Shannon entropy yields a potent AF detector, and suggest this method could be of practical use in both clinical and out-of-clinical settings.     

Evaluation of Changes in Correlation Dimension of a Time Series of RR Intervals during a Functional Exercise Test

Changes in the cardiac rhythm (CR) structure were analyzed from the viewpoint of nonlinear dynamics. The purpose was to evaluate the changes in the chaotic element (the correlation dimension D) of CR during a functional exercise test (the Harvard step test) in ten healthy males aged 17–18. Distinct changes in D of CR were observed during the test. Some general trends and individual differences were revealed. D always decreased in comparison with the background value at the first minutes of exercise and recovery and increased sharply at the third and/or fourth minutes of exercise. The chaotic element of CR changed together with the functional state of the body depending on the stage of exercise.     

The Influence of the Rate of Stimulus Temperature Rise on Local Skin Thermal Thresholds

The influence of the rate of stimulus temperature rise on the interthreshold interval of the appearance of thermal sensitivity of the skin was studied in 14 male volunteers using the MarStock method. The maximal skin thermal sensitivity was shown to occur at the optimum rate of stimulus increase equal to 0.2°C/s, while an increase in the interthreshold interval at other rates of stimuli predominantly occurs due to the increase in the temperature thresholds of the appearance of warmth sensations. A rapid reaction of the acquisition of a new temperature sensitivity level with a sharp change in the rate of stimulus increase was revealed. A critical view was taken of the increased (up to 1 to 3°C) rate of thermal stimulus presentation used in clinical practice. The physiological mechanisms underlying the regularities obtained are discussed on the basis of known data.     

耗竭性游泳对大鼠心肌线粒体膜功能的影响

耗竭性游泳对大鼠心肌线粒体膜功能的影响王文信,丁树哲,许豪文（华东师范大学体育系运动生化实验室,上海２０００６２）关键词心肌线粒体,内膜表面电位,游离钙,总钙,合成活力长时间耗竭性游泳或跑步引起心肌、骨骼肌、肝脏等线粒体结构和功能变化,这些变化可能与...     

Comparison of the Effects of Septoplasty and Sinus Lifting Simulation in Rats on Changes in Heart Rate Variability

Doklady Biochemistry and Biophysics - The effects of septoplasty and sinus lifting simulation in rats on changes in the frequency domain of heart rate variability were compared. In the early...     

24h睡眠剥夺后作业效率与心率变异性的变化

目的:探索24h睡眠剥夺(Sleep Deprivation,SD)后作业效率和心率变异性的变化.方法:通过观察8名健康男性在24h睡眠剥夺前后的作业效率、主观脑力负荷和心率变异性的变化,寻找与脑力疲劳相关的敏感指标.结果:在24h睡眠剥夺后,NASA-TLX评分呈显著性增加(p＜0.05),75°立位时HF呈显著性减少(p＜0.05),TINN、LF/HF呈显著性增加(p＜0.05).结论:NAsA-TLX量表从主观感受上很好的反映了脑力疲劳后工作绩效下降的变化,HRV的变化主要原因在于24h SD后迷走神经活性降低,交感神经相对加强.