Improvements in heart rate variability with exercise therapy

Autonomic modulation of heart rate in paraplegic wheelchair basketball players: Linear and nonlinear analysis

This study aimed to evaluate the autonomic modulation of heart rate in sedentary paraplegics and paraplegic wheelchair basketball players with thoracic spinal cord injury below T6. Seven paraplegic wheelchair basketball players (active paraplegic group), five paraplegics who were not involved in regular exercise (sedentary paraplegic group) and 10 able-bodied participants (control group) took part in the study. The heart rate variability was evaluated by linear (low frequency and high frequency band in normalised units and low frequency/high frequency ratio) and nonlinear methods (Shannon entropy, corrected conditional entropy, and symbolic analysis). The sedentary group presented significantly higher values for low frequency, low frequency/high frequency ratio and symbolic index with no significant variations (0V%), and also lower values for the high frequency and symbolic index with two significant unlike variation (2ULV%) compared to active paraplegic group. Shannon entropy and corrected conditional entropy analyses revealed significantly lower values in the sedentary group than in the control or active paraplegic groups. Paraplegic individuals who regularly undertake physical exercise have higher complexity of R-R interval time series, lower sympathetic modulation, and higher parasympathetic modulation than sedentary paraplegic participants.

Long-chain, n-3 fatty acids and physical activity--independent and interactive associations with cardiac autonomic control

BACKGROUND/OBJECTIVES

Intake of the marine-based, n-3 fatty acids and engagement in physical activity are inversely related to cardiac morbidity and mortality. Among putative mechanisms, both n-3 fatty acids and physical activity may act through modulation of autonomic control of the cardiovascular system. This investigation examined the independent and interactive associations of n-3 fatty acids (eicosapentaenoic and docosahexanenoic acid; EPA, DHA) and physical activity with heart rate variability (HRV).

METHODS

Subjects were 259 healthy 30-54 year-old adults. Serum phospholipid fatty acid composition was employed as a biomarker of dietary n-3 fatty acid exposure. Physical activity based on the Paffenbarger questionnaire was coded as < or ≥ 2000 kcal/week. Standard time-domain (standard deviation of normal-to-normal intervals and root-mean squared of successive differences; SDNN, RMSSD) and frequency domain (high frequency and low frequency power) measures of HRV were derived from resting electrocardiographic recordings.

RESULTS

In linear regression models with covariate adjustment for age, gender and race, greater n-3 fatty acid exposure was associated with greater SDNN and RMSSD, and high physical activity was associated with greater RMSSD. n-3 fatty acid exposure also predicted variation in SDNN, RMSSD, and high-frequency power in interaction with physical activity. Specifically, n-3 fatty acid exposure covaried positively with these three HRV indices only among participants expending 2000 kcal per week or more in physical activity. These latter findings were noted for DHA but not EPA.

CONCLUSIONS

These results suggest that the cardiovascular benefits of n-3 fatty acid consumption may be mediated, in part, by effects on cardiac autonomic control and may be dependent upon concomitant habitual exercise.

Caffeine Enhances Heart Rate Variability in Middle-Aged Healthy, But Not Heart Failure Subjects

BACKGROUND

In chronic heart failure (CHF) due to left ventricular dysfunction, diminished heart rate variability (HRV) is an independent predictor of poor prognosis. Caffeine has been shown to increase HRV in young healthy subjects. Such an increase may be of potential benefit to patients with CHF.

OBJECTIVE

We hypothesized that intravenous infusion of caffeine would increase HRV in CHF, and in age-matched healthy control subjects.

METHODS

On two separate days, 11 patients (1F) with CHF (age=51.3±4.6 years; left ventricular ejection fraction=18.6±2.7%; mean±standard error) and 10 healthy control subjects (age=48.0±4.0) according to a double-blind randomization design, received either saline or caffeine (4 mg/kg) infusion. We assessed HRV over 7 minutes of supine rest (fast Fourier Transform analysis) to determine total spectral power as well as its high-frequency (HF) (0.15-0.50 Hz) and low-frequency (LF) (0.05-0.15 Hz) components, and recorded muscle sympathetic nerve activity (MSNA) directly from the peroneal nerve (microneurography).

RESULTS

In healthy control subjects, compared with saline, caffeine reduced both heart rate and sympathetic nerve traffic (p≤0.003) and increased the ratio of HF/total power (p≤0.05). Baseline LF power and the ratio LF/HF were significantly lower in CHF compared with controls (p=0.02), but caffeine had no effect on any element of HRV.

CONCLUSIONS

Caffeine increases cardiac vagal heart rate modulation and reduces MSNA in middle-aged healthy subjects, but not in those with CHF.

Exercise training improves heart rate variability in older patients with heart failure: a randomized, controlled, single-blinded trial

Reduced heart rate variability (HRV) in older patients with heart failure (HF) is common and indicates poor prognosis. Exercise training (ET) has been shown to improve HRV in younger patients with HF. However, the effect of ET on HRV in older patients with HF is not known. Sixty-six participants (36% men), aged 69±5 years, with HF and both preserved ejection fraction (HFPEF) and reduced ejection fraction (HFREF), were randomly assigned to 16 weeks of supervised ET (ET group) vs attention-control (AC group). Two HRV parameters (the standard deviation of all normal RR intervals [SDNN] and the root mean square of successive differences in normal RR intervals [RMSSD]) were measured at baseline and after completion of the study. When compared with the AC group, the ET group had a significantly greater increase in both SDNN (15.46±5.02 ms in ET vs 2.37±2.13 ms in AC, P=.016) and RMSSD (17.53±7.83 ms in ET vs 1.69±2.63 ms in AC, P=.003). This increase was seen in both sexes and HF categories. ET improved HRV in older patients with both HFREF and HFPEF.

Stressed brain, diseased heart: a review on the pathophysiologic mechanisms of neurocardiology

Cardiovascular diseases are traditionally related to well known risk factors like dyslipidemia, smoking, diabetes and hypertension. More recently, stress, anxiety and depression have been proposed as risk factors for cardiovascular diseases including heart failure, ischemic disease, hypertension and arrhythmias. Interestingly, this association has been established largely on the basis of epidemiological data, due to insufficient knowledge on the underlying pathophysiologic mechanisms. This review will revisit evidence on the interaction between the cardiovascular and nervous systems, highlighting the perspective on how the central nervous system is involved in the pathogenesis of cardiovascular diseases. Such knowledge is likely to be of relevance for the development of better strategies to treat patients in a holistic perspective.

Exercise effects on sleep physiology

This mini-review focuses on the effects of exercise on sleep. In its early days, sleep research largely focused on central nervous system (CNS) physiology using standardized tabulations of several sleep-specific landmark electroencephalogram (EEG) waveforms. Though coarse, this method has enabled the observation and inspection of numerous uninterrupted sleep phenomena. The research on the effects of exercise on sleep began, in the 1960s, with a focus primarily on sleep related EEG changes (CNS sleep). Those early studies found only small effects of exercise on sleep. However, more recent sleep research has explored not only CNS functioning, but somatic physiology as well. Sleep should be affected by daytime exercise, as physical activity alters endocrine, autonomic nervous system (ANS), and somatic functions. Since endocrinological, metabolic, and autonomic changes can be measured during sleep, it should be possible to assess exercise effects on somatic physiology in addition to CNS sleep quality, evaluated by standard polysomnographic (PSG) techniques. Additional measures of somatic physiology have provided enough evidences to conclude that the auto-regulatory, global regulation of sleep is not the exclusive domain of the CNS, but it is heavily influenced by inputs from the rest of the body.

Impact of aerobic exercise training on heart rate variability and functional capacity in obese women after gastric bypass surgery

BACKGROUND

Obesity is a major public health concern on a global scale. Bariatric surgery is among the treatment options, resulting in significant and sustainable weight loss as well as amelioration of comorbidities. The purpose of this study was to evaluate whether a 12-week aerobic exercise program positively impacts heart rate variability (HRV) and functional capacity after gastric bypass surgery (GBS) in a female cohort.

METHODS

Of the 52 patients initially recruited, 21 were randomized to a training group (TG) or control group and successfully completed the study. Patients were tested on two occasions: 1 week before GBS and 4 months after GBS. Anthropometric variables, body composition, record of heart rate and R-R intervals, and 6-min walk test (6MWT) were assessed at both time points. The TG underwent an aerobic exercise training program on a treadmill (1-h session, totaling 36 sessions over 12 weeks).

RESULTS

The main findings from this study were: (1) only the TG demonstrated a significant increase (p < 0.05) in all indexes of heart rate variability (HRV) after 12 weeks of aerobic exercise training and (2) only the TG demonstrated a significant increase (p < 0.05) in 6MWT distance and decrease in diastolic blood pressure after aerobic exercise training.

CONCLUSIONS

We conclude that 12 weeks of aerobic exercise training improves cardiac autonomic modulation and functional capacity 4 months after GBS.

Exercise, inflammation and aging

Aging results in chronic low grade inflammation that is associated with increased risk for disease, poor physical functioning and mortality. Strategies that reduce age-related inflammation may improve the quality of life in older adults. Regular exercise is recommended for older people for a variety of reasons including increasing muscle mass and reducing risk for chronic diseases of the heart and metabolic systems. Only recently has exercise been examined in the context of inflammation. This review will highlight key randomized clinical trial evidence regarding the influence of exercise training on inflammatory biomarkers in the elderly. Potential mechanisms will be presented that might explain why exercise may exert an anti-inflammatory effect.

Dose-response effects of exercise training on the subjective sleep quality of postmenopausal women: exploratory analyses of a randomised controlled trial

OBJECTIVE

To investigate whether a dose-response relationship existed between exercise and subjective sleep quality in postmenopausal women. This objective represents a post hoc assessment that was not previously considered.

DESIGN

Parallel-group randomised controlled trial.

SETTING

Clinical exercise physiology laboratory in Dallas, Texas.

PARTICIPANTS

437 sedentary overweight/obese postmenopausal women.

INTERVENTION

Participants were randomised to one of four treatments, each of 6 months of duration: a non-exercise control treatment (n=92) or one of three dosages of moderate-intensity exercise (50% of VO(2peak)), designed to meet 50% (n=151), 100% (n=99) or 150% (n=95) of the National Institutes of Health Consensus Development Panel physical activity recommendations. Exercise dosages were structured to elicit energy expenditures of 4, 8 or 12 kilocalories per kilogram of body weight per week (KKW), respectively. Analyses were intent to treat.

PRIMARY OUTCOME MEASURES

Continuous scores and odds of having significant sleep disturbance, as assessed by the Sleep Problems Index from the 6-item Medical Outcomes Study Sleep Scale. Outcome assessors were blinded to participant randomisation assignment.

RESULTS

Change in the Medical Outcomes Study Sleep Problems Index score at 6 months significantly differed by treatment group (control: -2.09 (95% CI -4.58 to 0.40), 4 KKW: -3.93 (-5.87 to -1.99), 8 KKW: -4.06 (-6.45 to -1.67), 12 KKW: -6.22 (-8.68 to -3.77); p=0.04), with a significant dose-response trend observed (p=0.02). Exercise training participants had lower odds of having significant sleep disturbance at postintervention compared with control (4 KKW: OR 0.37 (95% CI 0.19 to 0.73), 8 KKW: 0.36 (0.17 to 0.77), 12 KKW: 0.34 (0.16 to 0.72)). The magnitude of weight loss did not differ between treatment conditions. Improvements in sleep quality were not related to changes in body weight, resting parasympathetic control or cardiorespiratory fitness.

CONCLUSION

Exercise training induced significant improvement in subjective sleep quality in postmenopausal women, with even a low dose of exercise resulting in greatly reduced odds of having significant sleep disturbance.

TRIAL REGISTRATION NUMBER

clinicaltrials.gov identifier: NCT00011193.

Exercise is an effective treatment modality for reducing cancer-related fatigue and improving physical capacity in cancer patients and survivors: a meta-analysis

The use of exercise interventions to manage cancer-related fatigue (CRF) is a rapidly developing field of study. However, results are inconsistent and difficult to interpret across the literature, making it difficult to draw accurate conclusions regarding the true effectiveness of exercise interventions for CRF management. The aims of this study were to apply a meta-analysis to quantitatively assess the effects of exercise intervention strategies on CRF, and to elucidate appropriate exercise prescription guidelines. A systematic search of electronic databases and relevant journals and articles was conducted. Studies were eligible if subjects were over the age of 18 years, if they had been given a diagnosis of or had been treated for cancer, if exercise was used to treat CRF as a primary or secondary endpoint, and if the effects of the intervention were evaluated quantitatively and presented adequate statistical data for analysis. A total of 16 studies, representing 1426 participants (exercise, 759; control, 667) were included in a meta-analysis using a fixed-effects model. The standardized mean difference effect size (SMD) was used to test the effect of exercise on CRF between experimental and control groups. The results indicate a small but significant effect size in favour of the use of exercise interventions for reducing CRF (SMD 0.26, p < 0.001). Furthermore, aerobic exercise programs caused a significant reduction in CRF (SMD 0.21, p < 0.001) and overall, exercise was able to significantly improve aerobic and musculoskeletal fitness compared with control groups (p < 0.01). Further investigation is still required to determine the effects of exercise on potential underlying mechanisms related to the pathophysiology of CRF.

Dissociation of heart rate variability and heart rate recovery in well-trained athletes

The purpose of this investigation was to examine the relationships between aerobic fitness, volume of physical activity (PA), heart rate variability (HRV), and heart rate recovery (HRR) in a group of well-trained endurance athletes. Nineteen endurance athletes participated in this study and had aerobic capacities that placed them above the 99th percentile based on normative values (VO(2max): 67.1 ± 2 ml kg(-1) min(-1)). HRV was obtained via an EKG collected during supine rest and reported as high-frequency (HF), low-frequency (LF), and total power (TP). Natural log (ln) transformation was applied when variables violated assumptions of normality. HRR recovery was reported as the reduction in heart rate from peak exercise to the heart rate 1 min after cessation of exercise and PA was estimated from a questionnaire. HRR was significantly correlated with PA and VO(2max) (r = 0.67, P = 0.003 and 0.51, P = 0.039, respectively), but not with any index of HRV. Age was significantly correlated with lnHF (r = -0.49, P = 0.033), lnLF/lnHF (r = 0.48, P = 0.037), and normalized units (NU) of LF (r = 0.47, P = 0.042) and HF (r = -0.47, P = 0.042). Stepwise regression revealed that the strongest predictor of HRR was PA (R (2) = 0.45) and that VO(2max) did not add significant predictive value to the model. The relationship between HRV and age is evident in well-trained endurance athletes, whereas the relationship between HRV and PA/aerobic fitness is not. The maintained relationship between HRR and PA/aerobic fitness suggests that HRR may be a better marker of fitness-related differences in autonomic control in this population.

Effects on blood pressure and autonomic nervous system function of a 12-week exercise or exercise plus DASH-diet intervention in individuals with elevated blood pressure

AIM

Hypertension is related to abnormalities in autonomic nervous system (ANS) function, with increased sympathetic output and decreased parasympathetic tone. Lifestyle interventions are the first line of treatment in hypertension, and decreased blood pressure (BP) effects may be related to changes in ANS function. Using heart rate recovery (HRR) from exercise as an index of parasympathetic tone and plasma noradrenaline as an index of sympathetic tone, we investigated the effects of lifestyle interventions on ANS function in patients with elevated BP.

METHODS

Sedentary participants with elevated BP were randomly assigned to either an exercise only (N = 25), exercise plus dietary approaches to stop hypertension (DASH) diet (N = 12), or waitlist control (N = 15) 12-week intervention. Plasma noradrenaline was measured at rest and participants performed a peak exercise test before and after the intervention. HRR was calculated as peak heart rate (HR) minus HR at 1 min post-exercise.

RESULTS

Heart rate recovery showed a significant group by time interaction; both intervention groups showed increases in HRR from pre- to post-intervention, while waitlist showed no change. Similarly, both exercise plus diet and exercise groups, but not waitlist, showed significant reductions in BP from pre- to post-intervention. Linear regression revealed that BP post-intervention was significantly predicted by change in HRR when controlling for pre-BP, age, gender and BMI.

CONCLUSIONS

Lifestyle interventions induced training-reduced BP and altered autonomic tone, indexed by HRR. This study indicates the importance of behavioural modification in hypertension and that increased parasympathetic function is associated with success in reduction of BP.

Determinants for heart rate variability in a normal Korean population

This study examined the normal ranges and the determinants for various parameters of the short-term heart rate variability (HRV) measurements in a large Korean sample of healthy people. HRV measurements were obtained in 2,748 healthy men and 735 healthy women 18-65 yr of age. The mean total power (TP), low frequency (LF), high frequency (HF), and LF/HF ratio were 1,358.9 ± 1,840.8 ms(2), 417.3 ± 807.6 ms(2), 254.1 ± 414.1 ms(2), and 2.4 ± 20.9 ms(2) in the frequency-domain spectral analysis. The mean standard deviation of the normal-to-normal (NN) interval (SDNN) and the square root of the mean squared differences of successive NN intervals (RMSSD) were 39.6 ± 22.1 ms and 29.7 ± 18.1 ms in the time-domain analysis. The female subjects had significantly higher SDNN, RMSSD, and HF values than the male subjects. After controlling for age, there was no statistically significant difference in the SDNN. Quantile regression analysis showed that age and mean heart rate had a significant impact on short-term HRV measurement. Given that both clinicians and researchers are increasingly relying on short-term HRV assessment in measuring stress, our work suggests that age and gender should be considered as independent determinants for HRV.

Improvement of heart rate variability by eurythmy therapy after a 6-week eurythmy therapy training

BACKGROUND

Eurythmy therapy (EYT) is a mind-body therapy used in anthroposophic medicine. Recently, the authors were able to show that at comparable workloads, EYT stimulated heart rate variability (HRV) whereas conventional ergometer training attenuated HRV. Furthermore, a long-term improvement of quality of life (QoL) and stress coping strategies by EYT could be shown.

OBJECTIVE

This study aimed to evaluate the long-term effects of EYT training on HRV.

DESIGN

A total of 23 healthy women (mean age = 44.57 ± 8.04 years) performed 10 hours of EYT over a period of 6 weeks. Electrocardiograms were recorded before and after the EYT trial. HRV was quantified by the extent of high (HF), low (LF), very low (VLF), and ultra low frequency (ULF) oscillations of heart rate.

RESULTS

Autonomic regulation was significantly changed following the EYT training compared with baseline. Especially the proportion referring to the total power (P) of HF/P and LF/P increased, whereas ULF/P and (ULF+VLF)/P decreased after the training period.

CONCLUSION

EYT shifted the autonomic regulation proportionally referring to the total power mainly caused by changes of ULF and VLF components of HRV. The LF and HF spectral components were also decreased following EYT while their proportion in relation to the total variance of the power spectrum was increased. The proportional enhancement of the higher frequency and the decrease of the ULF and VLF components are probably an indicator of an improvement of autonomic regulation processes by more relaxed physical activity after the EYT training, thus supporting the plausibility of the improved QoL and better stress coping strategies.

Exercise mitigates homocysteine - β2-adrenergic receptor interactions to ameliorate contractile dysfunction in diabetes

We tested the hypothesis that exercise ameliorates contractile dysfunction by interfering with homocysteine - β2-adrenergic receptor (AR) interactions, inducing β2-adrenergic response and Gs (stimulatory G adenylyl cyclase dependent protein kinase), and lowering homocysteine level in diabetes. The effect of homocysteine on β2-AR was determined by (a) scoring the β2-AR in the cardiomyocytes treated with high dose of homocysteine using flow cytometry, and (b) co-localizing homocysteine with Gs (an inducer of β2-AR) in the cardiomyocytes obtained from C57BL/ 6J (WT) and db/ db mice using confocal microscopy. The effect of exercise on the protein-protein interactions of homocysteine and β2-AR in diabetes was evaluated by co-immunoprecipitation in the four groups of db/db mice: (1) sedentary, (2) treated with salbutamol (a β2-AR agonist), (3) swimming exercise, and (4) swimming + salbutamol treatment. The effect of exercise on β2-AR was determined by RT-PCR and Western blotting while cardiac dysfunction was assessed by echocardiography, and contractility and calcium transient of cardiomyocytes from the above four groups. The results revealed that elevated level of homocysteine decreases the number of β2-AR and inhibits Gs in diabetes. However, exercise mitigates the interactions of homocysteine with β2-AR and induces β2-AR. Exercise also ameliorates cardiac dysfunction by enhancing the calcium transient of cardiomyocytes. To our knowledge, this is the first report showing mechanism of homocysteine mediated attenuation of β2-AR response in diabetes and effect of exercise on homocysteine - β2-AR interactions.

Exercise improves the dilatation function of mesenteric arteries in postmyocardial infarction rats via a PI3K/Akt/eNOS pathway-mediated mechanism

Myocardial infarction (MI) has been shown to induce endothelial dysfunction in peripheral resistance arteries and thus increase peripheral resistance. This study was designed to investigate the underlying mechanisms of post-MI-related dysfunctional dilatation of peripheral resistance arteries and, furthermore, to examine whether exercise may restore dysfunctional dilatation of peripheral resistance arteries. Adult male Sprague-Dawley rats were divided into three groups: sham-operated, MI, and MI + exercise. Ultrastructure and relaxation function of the mesenteric arteries, as well as phosphatidylinositol-3 kinase (PI3K), Akt kinases (Akt), endothelial nitric oxide synthase (eNOS) activity, and phosphorylation of PI3K, Akt, and eNOS by ACh were determined. Post-MI rats exhibited pronounced ultrastructural changes in mesenteric artery endothelial cells and endothelial dysfunction. In addition, the activities of PI3K, Akt, and eNOS, and their phosphorylation by ACh were significantly attenuated in mesenteric arteries (P < 0.05-0.01). After 8 wk of exercise, not only did endothelial cells appeared more normal in structure, but also ameliorated post-MI-associated mesenteric arterial dysfunction, which were accompanied by elevated activities of PI3K, Akt, and eNOS, and their phosphorylation by ACh (P < 0.05-0.01). Importantly, inhibition of either PI3K or eNOS attenuated exercise-induced restoration of the dilatation function and blocked PI3K, Akt, and eNOS phosphorylation by ACh in the mesenteric arteries. These data demonstrate that MI induces dysfunctional dilation of peripheral resistance arteries by degradation of endothelial structural integrity and attenuating PI3K-Akt-eNOS signaling. Exercise may restore dilatation function of peripheral resistance arteries by protecting endothelial structural integrity and increasing PI3K-Akt-eNOS signaling cascades.