Acute and training effects of resistance exercise on heart rate variability

Heart rate variability (HRV) has been used as a non‐invasive method to evaluate heart rate (HR) regulation by the parasympathetic and sympathetic divisions of the autonomic nervous system. In this review, we discuss the effect of resistance exercise both acutely and after training on HRV in healthy individuals and in those with diseases characterized by autonomic dysfunction, such as hypertension and fibromyalgia. HR recovery after exercise is influenced by parasympathetic reactivation and sympathetic recovery to resting levels. Therefore, examination of HRV in response to acute exercise yields valuable insight into autonomic cardiovascular modulation and possible underlying risk for disease. Acute resistance exercise has shown to decrease cardiac parasympathetic modulation more than aerobic exercise in young healthy adults suggesting an increased risk for cardiovascular dysfunction after resistance exercise. Resistance exercise training appears to have no effect on resting HRV in healthy young adults, while it may improve parasympathetic modulation in middle‐aged adults with autonomic dysfunction. Acute resistance exercise appears to decrease parasympathetic activity regardless of age. This review examines the acute and chronic effects of resistance exercise on HRV in young and older adults.     

Influence of age and gender on autonomic regulation of heart

Heart rate variability (HRV) is a non-invasive method to measure cardiac autonomic function. Impairments in HRV have been proposed as independent risk factor for increased cardiac mortality and morbidity. Cardio protective phenomenon in females has been hypothesized to be due to differential autonomic tone. Age related loss of vagal control has been reported as predisposing factor for the development of cardiovascular disease. In this study we assessed effect of age and gender on autonomic regulation of heart in healthy volunteers. HRV data of 189 subjects (114 males and 75 females) were analyzed in time and frequency domains using customized program. Artifact free 5 min electrocardiogram segment was used for analysis. It was ensured that none of the subject had medical illness such as diabetes, hypertension, thyroid disorders, cardiac disorders, diseases potentially related with autonomic neuropathy and major psychiatric illness by careful history and clinical examination. HRV recordings were done under standard laboratory condition. On correlation analysis SDNN, RMSSD, total power negatively correlated with age suggesting reduced autonomic regulation of heart with increase in age (SDNN: r = ?0.444, p < 0.01; RMSSD: r = ?0.552, p < 0.01; total power: r = ?0.474, p < 0.01); similarly High frequency power (HF.nu) negatively correlated with age (r = ?0.167, p = 0.02), denoting loss of vagal tone with aging. LF/HF ratio correlated positively with age (r = 0.19, p < 0.01) suggesting a relative increase of sympathetic activity with increase in age. On multiple regression analysis to control for effect of age and heart rate while comparing males and females, LF.nu showed significant reduction suggesting lower sympathetic tone in females (β = ?6.64; p < 0.01) and HF.nu showed increase at trend level (β = 4.47; p = 0.053). In conclusion, there is overall reduction in autonomic control of heart with increase in the age. Sympathetic tone predominates and vagal tone diminishes with aging process. Females showed greater vagal tone than male. This differential autonomic tone indicate age, gender related predisposition to cardiovascular disease.     

Ventral medial prefrontal cortex and cardiovagal control in conscious humans

The autonomic nervous system plays a critical role in regulating the cardiovascular responses to mental and physical stress. Recent neuroimaging studies have demonstrated that sympathetic outflow to the heart is modulated by the activity of the anterior cingulate cortex (ACC). However, the cortical modulation of cardiovagal activity is still unclear in humans. The present study used functional MRI to investigate the cortical network involved in cardiovagal control. Seventeen healthy individuals performed graded handgrip exercise while heart rate (HR) and cortical activity were recorded. Muscle sympathetic nerve activity (MSNA), mean arterial pressure (MAP) and HR were measured while participants repeated the same protocol in a parallel experiment session. The handgrip exercise elevated HR and MAP without concurrent elevations in MSNA supporting earlier conclusions that the cardiovascular responses are mainly modulated by vagal withdrawal. The imaging data showed activation in the insular cortex, thalamus, parietal cortices and cerebellum during the exercise period. Consistently across all the participants, the HR response correlated with the deactivation in the ventral medial prefrontal cortex (vMPFC), which has substantial anatomical connection with the subcortical autonomic structures. The deactivation of the vMPFC was independent of the motor control and was observed commonly in both left and right hand exercise. Stronger vMPFC deactivation was observed when participants completed a higher intensity exercise that elicited a larger HR response. Our findings support the hypothesis that the vMPFC is involved in modulating the vagal efferent outflow to the heart and the suppression of its activity elevates cardiovascular arousal in conscious humans.     

Autonomic nervous system profile in fibromyalgia patients and its modulation by exercise: a mini review

This review imparts an impressionistic tone to our current understanding of autonomic nervous system abnormalities in fibromyalgia. In the wake of symptoms present in patients with fibromyalgia (FM), autonomic dysfunction seems plausible in fibromyalgia. A popular notion is that of a relentless sympathetic hyperactivity and hyporeactivity based on heart rate variability (HRV) analyses and responses to various physiological stimuli. However, some exactly opposite findings suggesting normal/hypersympathetic reactivity in patients with fibromyalgia do exist. This heterogeneous picture along with multiple comorbidities accounts for the quantitative and qualitative differences in the degree of dysautonomia present in patients with FM. We contend that HRV changes in fibromyalgia may not actually represent increased cardiac sympathetic tone. Normal muscle sympathetic nerve activity (MSNA) and normal autonomic reactivity tests in patients with fibromyalgia suggest defective vascular end organ in fibromyalgia. Previously, we proposed a model linking deconditioning with physical inactivity resulting from widespread pain in patients with fibromyalgia. Deconditioning also modulates the autonomic nervous system (high sympathetic tone and a low parasympathetic tone). A high peripheral sympathetic tone causes regional ischaemia, which in turn results in widespread pain. Thus, vascular dysregulation and hypoperfusion in patients with FM give rise to ischaemic pain leading to physical inactivity. Microvascular abnormalities are also found in patients with FM. Therapeutic interventions (e.g. exercise) that result in vasodilatation and favourable autonomic alterations have proven to be effective. In this review, we focus on the vascular end organ in patients with fibromyalgia in particular and its modulation by exercise in general.     

Heart rate recovery: a practical clinical indicator of abnormal cardiac autonomic function

The autonomic nervous system (ANS) and cardiovascular function are intricately and closely related. One of the most frequently used diagnostic and prognostic tools for evaluating cardiovascular function is the exercise stress test. Exercise is associated with increased sympathetic and decreased parasympathetic activity and the period of recovery after maximum exercise is characterized by a combination of sympathetic withdrawal and parasympathetic reactivation, which are the two main arms of the ANS. Heart rate recovery after graded exercise is one of the commonly used techniques that reflects autonomic activity and predicts cardiovascular events and mortality, not only in cardiovascular system disorders, but also in various systemic disorders. In this article, the definition, applications and protocols of heart rate recovery and its value in various diseases, in addition to exercise physiology, the ANS and their relationship, will be discussed.     

Heart rate recovery: a practical clinical indicator of abnormal cardiac autonomic function

The autonomic nervous system (ANS) and cardiovascular function are intricately and closely related. One of the most frequently used diagnostic and prognostic tools for evaluating cardiovascular function is the exercise stress test. Exercise is associated with increased sympathetic and decreased parasympathetic activity and the period of recovery after maximum exercise is characterized by a combination of sympathetic withdrawal and parasympathetic reactivation, which are the two main arms of the ANS. Heart rate recovery after graded exercise is one of the commonly used techniques that reflects autonomic activity and predicts cardiovascular events and mortality, not only in cardiovascular system disorders, but also in various systemic disorders. In this article, the definition, applications and protocols of heart rate recovery and its value in various diseases, in addition to exercise physiology, the ANS and their relationship, will be discussed.     

Autonomic Nervous System Controlled Closed Loop Cardiac Pacing

A multicenter clinical study is presented, which focuses on the reestablishment of closed loop cardiac control in patients with chronotropic insufficiency. Using the information about sympathetic tone contained in the myocardial contractility, it is possible to reconnect the heart rate to the physiological control mechanisms. Intracardiac impedance is measured with the ventricular electrode and the ventricular inotropic parameter (VIP) is derived from that. The VIP serves directly as input to the control of heart rate by the pacemaker. Over 200 patients have received autonomic nervous system (ANS) controlled pacemakers. The patientpacemaker system was investigated in different ways. This included standard exercise tests, long-term studies of every day activities over 24 hours, psychological, and pharmacological challenges. To prove the validity of the approach we specifically looked at (1) the appropriateness of changes in paced heart rate with sympathetic tone during exercise, (2) the correlation between heart rate and sinus rate, if detectable, and (3) the correlation between the echocardiographically determined preejection period (PEP) and the VIP controlled heart rate.     

Autonomic activity in trauma patients based on variability of heart rate and respiratory rate

OBJECTIVE: To evaluate the effects of sympathetic and parasympathetic nervous system activity on the heart rate and other hemodynamic variables in acute emergency patients with mild to moderately severe trauma. DESIGN: Clinical study. SETTING: Level 1 university-run trauma service. PATIENTS: Fourteen trauma patients studied immediately after admission to the emergency department. INTERVENTIONS: We measured heart rate and respiratory rate variability by spectral analysis in the early period of mildly to moderately injured patients and compared the patterns of the low- (Lfa) and high-frequency (Hfa) areas of variability. MEASUREMENTS AND MAIN RESULTS: The Lfa is the area under the spectral analysis curve within the frequency range of 0.04-0.10 Hz. This area reflects primarily the tone of the sympathetic nervous system as mediated by the cardiac nerve. The respiratory area or Hfa is a 0.12 Hz-wide frequency range centered around the fundamental respiratory frequency defined by the peak mode of the respiratory power spectrum. It is indicative of vagal outflow reflecting parasympathetic nervous system activity. The Lfa/Hfa, or "L/R ratio," reflects the balance between the sympathetic and parasympathetic nervous systems. The hemodynamic effects of bursts of autonomic activity in response to injury were explored by heart rate and respiratory rate variability measured with non-invasive hemodynamic monitoring consisting of bioimpedance cardiac output, heart rate, and mean arterial pressure to measure cardiac function and transcutaneous oxygen (PtcO2) to reflect tissue perfusion. During sudden surges of autonomic activity, we described increased heart rate variability reflecting increased Lfa and to a lesser degree to Hfa. Slightly later there was increased heart rate, mean arterial pressure, and cardiac index but decreased tissue perfusion indicated by the decreased PtcO2/FIO2 ratio. CONCLUSIONS: Surges in autonomic activity in the period immediately after emergency department admission of trauma patients were associated with pronounced increases in cardiac index, mean arterial pressure, and heart rate and reduced tissue oxygenation.     

Autonomic nervous control of the heart rate during dynamic exercise in normal man

The relative contribution of the efferent components of the sympathetic and parasympathetic nervous systems to the heart rate (HR) response to dynamic physical exercise was evaluated in 23 normal males. The dynamic exercise was performed on a bicycle ergometer at work loads of 25, 50 and 100 W, before and after pharmacological blockade with atropine (13 individuals) or propranolol (10 individuals). Parasympathetic blockade significantly depressed the rapid HR response at the beginning of the exercise period at all levels of intensity, whereas sympathetic blockade only affected the slow-response phase (1-4 min), especially at the highest level of effort. The present results suggest that the tachycardia evoked by dynamic exercise is mediated by a biphasic mechanism initially depending on rapid vagal release, which increases progressively with increasing effort. An increased sympathetic activity manifests itself in a more delayed manner, especially at the higher levels of activity. Continuous monitoring of HR during the entire period of activity at different levels of intensity permits the utilization of dynamic exercise as a simple and non-invasive method for the functional evaluation of the two components of the autonomic nervous system of the heart.     

Effects of whole‐body vibration on heart rate variability: acute responses and training adaptations

Heart rate variability (HRV) is a noninvasive and practical measure of cardiac autonomic nervous system function, mainly the sympathetic and parasympathetic modulations of heart rate. A low HRV has been shown to be indicative of compromised cardiovascular health. Interventions that enhance HRV are therefore beneficial to cardiovascular health. Whole‐body vibration (WBV) training has been proposed as an alternative time‐efficient exercise intervention for the improvement of cardiovascular health. In this review, we discuss the effect of WBV both acute and after training on HRV. WBV training appears to be a useful therapeutic intervention to improve cardiac autonomic function in different populations, mainly through decreases in sympathovagal balance. Although the mechanisms by which WBV training improves symphathovagal balance are not yet well understood; enhancement of baroreflex sensitivity, nitric oxide bioavailability and angiotensin II levels seem to play an important role.     

Baroreflex Sensitivity as a Cardiac and Arrhythmia Mortality Risk Stratifier

The last two decades have provided clear evidence for the tight and casual relation existing between arrhythmic mortality and the autonomic nervous system, particularly with imbalances characterized by decreases in vagal and/or increases in sympathetic activity. A series of compelling experimental results has represented the driving force for the clinical evaluation of the potential prognostic value of baroreflex sensitivity (BBS), a measure that can provide information on the capability to augment vagal activity. This article reviews the methodology more commonly used to quantify the clinical evaluation of this parameter, and then focuses on the key clinical studies highlighting those performed in postmyocardial infarction patients. Among them the most informative is ATRAMI, a multicenter prospective study involving almost 1300 patients. The main conclusion is that both heart rate variability and BRS are strong and independent risk factors for post-infarction mortality, thus demonstrating the clinical usefulness of autonomic markers.     

Cardiac vagal tone predicts outcome in neurosurgical patients.

OBJECTIVE: To evaluate the relationship between presurgical levels of cardiac vagal tone and outcome in neurosurgical patients. DESIGN: Prospective series. SETTING: Respiratory ICU in a university hospital. PATIENTS: Fifty-one adults admitted to the respiratory ICU between 1982 and 1985. Forty-two patients were scheduled for elective neurosurgery, and nine patients suffered from head trauma. INTERVENTIONS: Ten minutes of electrocardiographic (EKG) data were recorded before medical intervention. Neurosurgical patients scheduled for surgery had EKG data recorded 24 hrs before their operation. Trauma patients had EKG data recorded immediately after arrival in the respiratory ICU. MEASUREMENTS AND MAIN RESULTS: Cardiac vagal tone was evaluated using a vagal tone index, quantified from the EKG. Cardiac vagal tone monitored before surgical intervention significantly distinguished between the outcome groups only for the elective neurosurgical patients. Age, gender, heart rate, Glasgow Coma Scale scores, and tumor location, size, and malignancy were not related to outcome in the elective neurosurgery group. However, within the trauma group, low Glasgow Coma Scale scores were significantly related to poor outcome. CONCLUSIONS: Cardiac vagal tone may offer important predictive value by alerting the physician to the functional consequence of head injury. Information relating to autonomic nervous system functioning, such as the vagal tone index used in this study, may provide additional information that will complement the computed tomography scan results. This study demonstrates that the vagal tone index is a predictive factor that may be efficiently extracted from the heart rate pattern routinely monitored in ICUs.     

Treatment of hypertension in patients with diabetes mellitus

Antihypertensive treatment in diabetes mellitus, especially in diabetics known to have cardiac autonomic neuropathy, may have to consider the status of the autonomic nervous system. In diabetic subjects with cardiac autonomic neuropathy, vagal activity during the night is often reduced. The reduction results in relative or absolute sympathetic activation, which could increase cardiovascular risk. Pathophysiological and clinical data suggests that antihypertensive treatment should reduce rather than induce sympathetic activity in this setting. Beta blocking agents, ACE inhibitors, calcium antagonists of verapamil or diltiazem type and selective imidazoline receptor agonists reduce sympathetic activity and, therefore, may have a beneficial effect in diabetic patients with disturbed sympathovagal balance.     

Insights Into the Pathogenesis of Sudden Cardiac Death From Analysis of Circadian Fluctuations of Potential Triggering Factors

Sudden cardiac death continues to be a poorly understood event in terms of its underlying pathophysiological mechanisms. The observation of a circadian variability in the incidence of this catastrophic event with a prominent peak in the early morning hours provides an opporfunity to study triggering factors that may play a causative role in the genesis of sudden cardiac death. As reviewed in this article, there is convincing evidence that transient disturbances in autonomic tone and the resulting consequences may predispose the heart to increased electrical vulnerability. This evidence is based for instance on circadian fluctuations of spontaneous ventricular ectopic activity and transient ischemia, which may serve as trigger factors for the genesis of sustained ventricular tachyarrhythmias. Analysis of heart rate variability provides further evidence of reduced vagal and elevated sympathetic tone during the morning hours particularly in patients with compromised left ventricuiar function. Diurnal variations in ventricular repolarization as indicated by QT interval changes in the surface ECG also support the concept of triggering factors in the genesis of sudden cardiac death. Therapeutic measures aiming at a reduction in sympathetic input to the heart have been successful in preventing ventricular fibrillation and thus indicate the importance of unbalanced sympathetic tone in patients prone to sudden cardiac death.     

Autonomic nervous system changes during Reiki treatment: a preliminary study

OBJECTIVES: to investigate if a complementary therapy, Reiki, has any effect on indices of autonomic nervous system function. DESIGN: Blind trial. SETTING/LOCATION: Quiet room in an out-patient clinic. SUBJECTS: Forty-five (45) subjects assigned at random into three groups. Interventions: Three treatment conditions: no treatment (rest only); Reiki treatment by experienced Reiki practitioner; and placebo treatment by a person with no knowledge of Reiki and who mimicked the Reiki treatment. OUTCOME MEASURES: Quantitative measures of autonomic nervous system function such as heart rate, cardiac vagal tone, blood pressure, cardiac sensitivity to baroreflex, and breathing activity were recorded continuously for each heartbeat. Values during and after the treatment period were compared with baseline data. RESULTS: Heart rate and diastolic blood pressure decreased significantly in the Reiki group compared to both placebo and control groups. CONCLUSIONS: The study indicates that Reiki has some effect on the autonomic nervous system. However, this was a pilot study with relatively few subjects and the changes were relatively small. The results justify further, larger studies to look at the biological effects of Reiki treatment.     

The prognostic value of heart rate variability in the elderly, changing the perspective: from sympathovagal balance to chaos theory

Heart rate variability (HRV) is the temporal beat-to-beat variation in successive RR intervals on an electrocardiographic (ECG) recording and it reflects the regulation of the heart rate (HR) by the autonomic nervous system (ANS). HRV analysis is a noninvasive tool for the assessment of autonomic function that gained momentum in the late 1980s when its clinical relevance as a predictor of mortality was established by a milestone study by Kleiger et al. in patients with postacute myocardial infarction. In the last few decades, the increasing availability of commercial ECG devices offering HRV analysis has made HRV a favorite marker for risk stratification in the setting of cardiovascular disease. The rapid aging of the world population and the growing popularity of HRV have also fueled interest for the prognostic value of HRV in the elderly, outside a specific cardiological context. However, the discussion of HRV measures in the elderly is still very much centered on the rather reductionistic model of sympathovagal balance, with the orthosympathetic and parasympathetic limbs of the ANS exercising opposing effects on the heart via autonomic tone. The expanding application of nonlinear dynamics to medicine has brought to the forefront the notion of system complexity, embedded in the mathematical concepts of chaos theory and fractals, and provides an opportunity to suggest a broader interpretation for the prognostic significance of HRV, especially in the elderly. Although the use of novel indices of HRV may be hampered by practical issues, a more holistic approach to HRV may still be safeguarded if traditional time- and frequency-domain measures are viewed in terms of autonomic modulation. This review focuses on HRV in geriatric populations. It considers studies on the prognostic value of HRV in elderly subjects, discussing the potential confounding effect of erratic rhythm, and concentrates on the conceptual distinction between autonomic tone and autonomic modulation. It also briefly addresses the question of the practicality of ECG recordings and identifies a promising area for future research in the effects of common noncardioactive drugs on HRV.     

Recovery from sauna bathing favorably modulates cardiac autonomic nervous system

ObjectiveSauna bathing is becoming a common activity in many countries and it has been linked to favorable health outcomes. However, there is limited data on the heart rate (HR) and heart rate variability (HRV) responses to an acute sauna exposure.DesignWe conducted a single-group, longitudinal study utilizing a pre-post design to examine acute effects of sauna bathing on the autonomic nervous system as reflected by HRV. A total of 93 participants (mean [SD] age: 52.0 [8.8] years, 53.8% males) with cardiovascular risk factors were exposed to a single sauna session (duration: 30 min; temperature: 73 °C; humidity: 10–20%) and data on HRV variables were collected before, during and after sauna.ResultsTime and frequency-domain HRV variables were significantly modified (p < 0.001) by the single sauna session, with most of HRV variables tending to return near to baseline values after 30 min recovery. Resting HR was lower at the end of recovery (68/min) compared to pre-sauna (77/min). A sauna session transiently diminished the vagal component, whereas the cooling down period after sauna decreased low frequency power (p < 0.001) and increased high frequency power in HRV (p < 0.001), favorably modulating the autonomic nervous system balance.ConclusionsThis study demonstrates that a session of sauna bathing induces an increase in HR. During the cooling down period from sauna bathing, HRV increased which indicates the dominant role of parasympathetic activity and decreased sympathetic activity of cardiac autonomic nervous system. Future randomized controlled studies are needed to show if HR and HRV changes underpins the long-term cardiovascular effects induced by regular sauna bathing.     

Sympatho-vagal interaction in the recovery phase of exercise

Reciprocal autonomic regulation occurs during incremental exercise. We hypothesized that sympatho-vagal interplay may become altered after exercise because of the differences in recovery patterns of autonomic arms. The cardiac vagal activity was assessed by measurement of beat-to-beat R-R interval oscillations using a Poincaré plot method (SD1), and muscle sympathetic nervous activity (MSNA) was measured from peroneus nerve by a microneurography technique during and after exercise in 16 healthy subjects. Autonomic regulation was compared between the rest and after exercise (3·5 ± 1·0 min after exercise) at equal heart rates (HR). SD1 was at the equal level at the recovery phase (40 ± 21 ms) compared to the resting condition (38 ± 16 ms, P = ns) at comparable HR (57 ± 10 for both). MSNA was higher at the recovery phase (40 ± 19 burst per 100 heartbeats) than at rest (25 ± 13 burst per 100 heartbeats, P<0·0001). The difference of MSNA activity between rest and late recovery phase had a strong positive correlation with the difference in SD1 (r = 0·78, P<0·001) at equal HRs. Subjects who have a higher sympathetic activity in the recovery phase of exercise have a more augmented cardiac vagal activity resulting in an accentuated sympatho-vagal outflow. The altered autonomic interaction observed here may partly explain the clustering of various cardiovascular events to the recovery phase of exercise.     

Heart rate recovery in migraine and tension-type headache

OBJECTIVE: There are reports proposing that migraine and tension-type headache (TTH) may affect the autonomic nervous system (ANS). Abnormalities in both sympathetic and parasympathetic nervous system have been suggested in migraineurs. However, in TTH, reports on the ANS function are limited and only associated with sympathetic system. Techniques for evaluating parasympathetic activity are more limited when compared with sympathetic function. Hence, the aim of the study was to measure heart rate recovery (HRR), an index of vagal activity, in migraine, TTH, and control subjects. METHODS: Forty-seven episodic migraine, 10 episodic TTH, 11 chronic TTH, and 25 control subjects underwent exercise tolerance test according to modified Bruce protocol, and HRR at 1 minute and 3 minutes (HRR1 and HRR3) were calculated. RESULTS: The HRR 1 and 3 were found to be similar in 3 groups of subjects. However, resting heart rate of migraine and chronic TTH were found to be higher than episodic TTH, but not different from the control group. CONCLUSION: These results suggest that parasympathetic function has not been affected in migraine and TTH patients. However, sympathetic tonus, which is evaluated by resting heart rate, is higher in migraine and chronic TTH than in episodic TTH.     

劳力型心绞痛患者的基础心率变异性及冠状动脉支架植入术的影响

[目的]探讨劳力型心绞痛（EAP）患者心率变异性（HRV）的特点并了解冠状动脉支架植入术（PCI）对HRV的影响.[方法]对25例EAP患者（EAP组）和20例健康人（对照组）行24 h动态心电图检查,进行HRV对比分析,并对EAP患者在接受PCI治疗后重复进行动态心电图检查以观察HRV的变化.[结果]EAP组各项HRV指标均显著低于对照组（P均＜0.01）.经PCI治疗后各指标明显改善,且差异均有显著性（P＜0.05）.[结论]EAP患者存在明显的自主神经功能紊乱,表现为交感神经活性增高、迷走神经张力下降.PCI治疗能有效改善单支血管病变EAP患者的心脏自主神经功能.