The effect of aerobic training and cardiac autonomic regulation in young adults

Aerobic Exercise Attenuates Doxorubicin-Induced Cardiomyopathy by Suppressing NLRP3 Inflammasome Activation in a Rat Model

Doxorubicin (DOX) is a potent chemotherapeutic agent with well-documented dose-dependent cardiotoxicity. Regular exercise is recognized for its cardioprotective effects against DOX-induced cardiac inflammation, although the precise mechanisms remain incompletely understood. The activation of inflammasomes has been implicated in the pathogenesis and treatment of DOX-induced cardiotoxicity, with the nucleotide-binding domain-like receptor protein 3 (NLRP3) inflammasome emerging as a key mediator in cardiovascular inflammation. This study aimed to investigate the role of exercise in modulating the NLRP3 inflammasome to protect against DOX-induced cardiac inflammation. Male Sprague-Dawley rats were randomly assigned to receive a 10-day course of DOX or saline injections, with or without a preceding 10-week treadmill running regimen. Cardiovascular function and histological changes were subsequently evaluated. DOX-induced cardiotoxicity was characterized by cardiac atrophy, systolic dysfunction, and hypotension, alongside activation of the NLRP3 inflammasome. Our findings revealed that regular exercise preserved cardiac mass and hypertrophic indices and prevented DOX-induced cardiac dysfunction, although it did not fully preserve blood pressure. These results underscore the significant cardioprotective effects of exercise against DOX-induced cardiotoxicity. While regular exercise did not entirely prevent DOX-induced hypotension, our findings demonstrate that it confers protection against DOX-induced cardiotoxicity by suppressing NLRP3 inflammasome activation in the heart, underscoring its anti-inflammatory role. Further research should explore the temporal dynamics and interactions among exercise, pyroptosis, and other pathways in DOX-induced cardiotoxicity to enhance translational applications in cardiovascular medicine.

Effects of Exercise Training on Heart Rate Variability in Healthy Adults: A Systematic Review and Meta-analysis of Randomized Controlled Trials

This meta-analysis was conducted to investigate the effects of exercise training on heart rate variability (HRV) parameters associated with the autonomic nervous system (ANS) activity. Randomized controlled trials (RCTs) involving healthy adults (aged ≥ 18 years) were included. We searched PubMed, Scopus, Web of Science, and EBSCO databases to identify relevant studies. A random-effects meta-analysis was performed using the standardized mean difference (SMD) and 95% confidence interval (CI). Sixteen RCTs with a total of 623 participants were selected for the final analysis. The analysis showed that exercise training improved the standard deviation of normal-to-normal intervals (SDNN) (SMD: 0.58 (0.16, 1.00); p = 0.007), the root mean square of successive differences in heart period series (RMSSD) (SMD: 0.84 (0.36, 1.31); p = 0.0005), and the absolute power of high-frequency band (HF) (SMD: 0.89 (0.27, 1.51); p = 0.005) parameters compared to the control group. Analysis of the moderator variables showed that the effect of exercise on HRV indices may be influenced by sex, age, and type of exercise used, specifically in HF band, absolute power of low-frequency band (LF), and LF/HF ratio parameters. Despite the limited number of existing RCTs related to the subject, the results suggest that exercise training enhances HRV parameters associated with vagal-related activity (RMSSD and HF) and both sympathetic and parasympathetic activities (SDNN). This study overcomes the lack of meta-analyses on the effects of exercise training on autonomic modulation among healthy adults and may bridge the gap in understanding the potential physiological underpinnings of the acknowledged positive health benefits of exercise.

Tai Chi Effects on Heart Rate Variability: A Systematic Review and Meta-Analysis

Background: Tai Chi, originating in China, is a mind-body exercise that integrates mind training, Qi training, and body training. While Tai Chi practice has demonstrated beneficial physical and psychological health benefits, how it achieves effects has been less studied. In recent years, some researchers have begun to explore the potential of heart rate variability (HRV) changes as balancing the autonomic nervous system (ANS) to achieve results, but only a few studies have directly tested how Tai Chi impacts HRV, and results have been mixed. Objective: This study systematically evaluates the effects of Tai Chi on HRV. Methods: Electronic databases including Web of Science, PubMed, Scopus, Cochrane Library, and EBSCOhost direct from inception until December 2020 were searched to obtain eligible studies. The primary outcomes examined were HRV parameters (time domain and frequency domain), and secondary analysis was whether breathing was emphasized during Tai Chi interventions. Results: Based on the 11 randomized controlled trials included comparing Tai Chi with non-active control condition, meta-analyses showed significantly beneficial effects on HRV parameters (low-frequency power [LF], mean difference [MD] = -200.40, 95% confidence interval [CI]: 365.31 to -35.49, p = 0.02; normalized low-frequency power [nLF], MD = -7.39, 95% CI: -12.48 to -2.29, p = 0.004; total power [TP], MD = -649.82, 95% CI: -1180.54 to -119.11, p = 0.02; very low-frequency power [VLF], MD = -200.55, 95% CI: -349.63 to -51.46, p = 0.008; root mean square of the square sum of the difference between adjacent normal heartbeat intervals [RMSSD], MD = 2.59, 95% CI: -7.23 to 12.41, p < 0.0001; standard deviation of the heartbeat interval [SDNN], MD = 8.33, 95% CI: 0.69 to 15.98, p = 0.03). The effect of Tai Chi on certain HRV parameters compared with active control conditions was less favorable (nLF, MD = 6.42, 95% CI: 3.74 to 9.09, p < 0.00001; normalized high-frequency power [nHF], MD: -6.13, 95% CI: -8.76 to -3.50, p < 0.00001; low-frequency/high-frequency power ratio [LF/HF], MD = 1.00, 95% CI: 0.68 to 1.33, p < 0.00001). In addition, studies describing an emphasis on breathing in the Tai Chi intervention showed positive impact on HRV (nLF, MD = -3.22, 95% CI: -5.32 to -1.12, p = 0.003; nHF, MD = 3.80, 95% CI: 0.80 to 6.81, p = 0.01; SDNN, MD = 5.55, 95% CI: 4.85 to 6.25, p < 0.00001). Conclusions: Meta-analysis results showed that Tai Chi compared with non-active control conditions has a positive impact on key HRV parameters associated with the ANS balance. However, active control condition comparisons showed greater HRV improvements than for Tai Chi. Considering the limited number of studies and their heterogeneity, further robust studies are necessary to verify findings and investigate differential effects of Tai Chi on HRV.

Move for Your Heart, Break a Sweat for Your Mind: Providing Precision in Adolescent Health and Physical Activity Behaviour Pattern

PURPOSE

Adolescent health benefits of different physical activity (PA) intensities, especially of lower intensities, are debated due to challenges in accelerometer data processing and analyses. Using a new accelerometer data processing method and multivariate pattern analysis, this study investigated the association of PA intensities with indicators of cardiovascular and mental health.

METHODS

Adolescents (n = 1,235, mean age 13.6 years, 41% males) were examined for cardiovascular health: body mass index (BMI) z-score, waist circumference (WC), resting heart rate and blood pressure, white blood cell count (WBC), pulse wave velocity (PWV), and answered questionnaires assessing stress and psychosomatic symptoms. Sex, age, and socioeconomic status were confounders. Hip-worn accelerometer data were processed with 10 Hz frequency extended method and a spectrum of 22 PA intensity categories was analyzed for association with health using partial least squares regression.

RESULTS

Total explained variances for BMI z-score, WC, resting heart rate, stress, and psychosomatic symptoms were higher (3.3%-8.7%) compared to diastolic blood pressure, WBC, and PWV (0.9%-1.4%). We found positive associations of high-end moderate PA and vigorous PA with cardiovascular and mental health indicators. More sedentary time and lower level of light PA were associated with higher BMI z-score, WC, resting heart rate, diastolic blood pressure, WBC, and PWV, but not with mental health indicators. Very vigorous PA was negatively associated with resting heart rate, stress, and psychosomatic symptoms.

DISCUSSION

In adolescents, PA of varying intensities were generally found to be positively associated with better cardiovascular health, but only higher intensity PA was associated with better mental health.

Home-Based Exercise Training and Cardiac Autonomic Neuropathy in Kidney Transplant Recipients with Type-II Diabetes Mellitus

This randomized clinical trial aimed to examine the effects of a 6-month home-based, combined exercise training program on Cardiac Autonomic Neuropathy (CAN) in kidney transplant recipients (KTRs) with diabetes. Twenty-five KTRs (19 men (76.0%), with a mean age of 54.4 ± 11.3 years old, CAN and type II Diabetes Mellitus (DM-II)), were randomly assigned into two groups: A (n1 = 13 KTRs), who underwent a home-based exercise training program for 6 months, and B (n2 = 12 KTRs), who were assessed at the end of the study. A cardiopulmonary exercise testing (CPET), sit-to-stand test in 30 s (30-s STS), isokinetic muscle strength dynamometry, and 24-h electrocardiographic monitoring were applied to all participants, both at the baseline and at the end of the clinical trial. At first, there were no statistically significant differences between groups. After 6 months, group A showed higher values in exercise time by 8.7% (p = 0.02), VO2peak by 7.3% (p < 0.05), 30-s STS by 12.0% (p < 0.05), upper limb strength by 46.1% (p < 0.05), and lower limb strength by 24.6% (p = 0.02), respectively, compared to the B group. Furthermore, inter-group changes at the end of the 6-month study indicated that group A statistically increased the standard deviation of R-R intervals (SDNN) by 30.3% (p = 0.01), root mean square of successive differences between normal heartbeats (rMSSD) by 32.0% (p = 0.03), number of pairs of successive NN (R-R) intervals that differ by more than 50 ms (pNN50) by 29.0% (p = 0.04), high frequency (HF (ms2)) by 21.6% (p < 0.05), HF (n.u.) by 48.5% (p = 0.01), and turbulence slope (TS) by 22.5% (p = 0.02), and decreased the low frequency (LF (ms2)) by 13.2% (p = 0.01), LF (n.u.) by 24.9% (p = 0.04), and LF/HF ratio by 24% (p = 0.01), compared to group B. Linear regression analysis after the 6-month study showed that there was a strong positive correlation between VO2peak and SDNN (r = 0.701, p < 0.05) in group A. Moreover, multiple regression analysis showed that KTRs' participation in the exercise program showed favorable modifications to sympathovagal balance and aerobic capacity, as measured with SDNN and VO2peak, respectively. To summarize, diabetic KTRs' cardiac autonomic function and functional capacity can be improved after a home-based long-term exercise training program.

High-frequency variability in heart rate is related to COVID-19-associated worries six years later

Elevated resting heart rate variability (HRV) in the high frequency range has been proposed to be protective against worrying when facing environmental stressors. Yet, prospective studies using real-life stressors are still scarce.

The present study set out to replicate the previous finding of reduced resting HRV predicting COVID-19-associated worries in a larger, more homogenous sample over a longer period of time (N = 123; age: 42.32 [SD:10.72]; 65.9 % female; average time lag: six years). In addition, we were interested in investigating the specificity of this effect with respect to worry content, other physiological markers of autonomic functions, and additional potentially relevant covariates with a special focus on a potential moderating effect of sex on this association.

In regression analyses adjusting for age, sex, BMI and smoking status, the interaction between HRV and sex was significant, with women depicting a stronger association between HRV and COVID-19 associated worries. Further sensitivity analyses revealed the specificity of the effect for HRV as distinct from mean heart rate, as well as its dependence on previous COVID-19 infection, but not COVID-19 vaccination status and chronic stress level.

These data are in line with theories that propose that higher HRV levels can be protective against the deleterious effects of real-life environmental stressors. However, our results also point to the specificity of this effect, especially with respect to worry content and sex.

Determining the direction of prediction of the association between parasympathetic dysregulation and exhaustion symptoms

Stress-related exhaustion symptoms have a high prevalence which is only likely to increase further in the near future. Understanding the physiological underpinnings of exhaustion has important implications for accurate diagnosis and the development of effective prevention and intervention programs. Given its integrative role in stress-regulation, the parasympathetic branch of the autonomic nervous systems has been a valid starting point in the exploration of the physiological mechanisms behind exhaustion. The aim of the present study was to examine the directionality and specificity of the association between exhaustion symptoms and vagally-mediated heart rate variability (vmHRV), a relatively pure measure of parasympathetic tone. Exhaustion symptoms and vmHRV were measured at four annually assessment waves (2015-2018) of the Dresden Burnout Study. A total sample of N = 378 participants who attended at least two of the four annual biomarker measurements were included in the present analyses. Cross-lagged multi-level panel modelling adjusting for various covariates (e.g., age, sex, BMI) revealed that vmHRV was meaningfully predictive of exhaustion symptoms and not vice versa. In addition, these effects were specific for exhaustion symptoms as no effect was shown for the other burnout sub-dimensions, or for depressive symptoms. Our findings indicate a clear link between exhaustion symptoms and vmHRV which may hold great potential for both enhancing the diagnosis and treatment of exhaustion symptoms.

The importance of physical activity and cardiorespiratory fitness for patients with heart failure

The present review highlights current research on the importance of PA and fitness for patients with heart failure and recommendations with respect to heart failure phenotypes and special populations. Furthermore, the evidence for various exercise types and intensities/doses as an "exercise prescription", are discussed. The strong association between heart failure and traditional risk factors, physical inactivity and low fitness, underlines the importance of regular PA and exercise for prevention and treatment of heart failure. This is illustrated by cardiac stiffness which typically accelerates in middle-life and could be reversed by aerobic exercise. In patients with HFpEF, regular PA counteracts many of the changes observed, both metabolic and functional. Indeed, exercise-based cardiac rehabilitation has received a class 1A recommendation in current guidelines [1], in order to improve functional capacity, quality of life and lower the risk of rehospitalization. An individually tailored plan based on risk stratification, clinical assessment and cardiopulmonary exercise testing is encouraged before initiation of exercise training in patients with heart failure. In general, a combination of aerobic exercise and resistance training protocols is recommended (Table 1) [2], preferably throughout life. More studies are needed, regarding the role of PA and exercise in specific populations, such as frail patients with heart failure.

Stress and aging: A neurovisceral integration perspective

Darwin emphasized the intimate relationship between the brain and the heart over 150 years ago. Healthy aging is associated with significant changes in both the brain and the heart. The changes between these, the two most important organs of the body, are linked via the vagus nerve. In this review, we examine the normative changes with aging and the effect that stress may have on how the brain-heart connection changes with age. We provide a framework based on the concept of neurovisceral integration and propose that stress regulation is emotion regulation. As such, studies that have investigated emotion regulation may yield insights into successful stress regulation that helps protect people from age-related decline. In addition, interventions that improve brain health also improve heart health and vice versa. We conclude by noting that significant sex and ethnic differences exist but that future studies are needed to more fully explicate how they may moderate the associations between stress and aging.

Active women demonstrate acute autonomic and hemodynamic shifts following exercise in heat and humidity: A pilot study

The purpose of this study was to assess autonomic and hemodynamic recovery in women who performed moderate-intensity exercise in heat. Seven women (31.7 ± 7.6 years, 67.5 ± 4.4 kg, 25.7 ± 5.6% Fat, 43.9 ± 5.1 mL/kg/min) completed two identical bouts of graded treadmill walking (~60% VO₂peak). One bout was hot (37.5 ± 1.4°C, 46.5 ± 4.6% relative humidity (RH)), and the other was moderate (20.7 ± 1.1°C, 29.9 ± 4.1% RH). For 24 h before and one h after each bout, participants had heart rate variability monitored. After each exercise bout HR and BP were measured during 30 min of supine recovery and 10 min of orthostatic challenge. HF power and RMSSD were lower and LF power and LF:HF ratio greater following exercise in the heat and remained different from the moderate condition for 30 min (p < 0.05). During supine recovery, heat exposure led to higher HR (p = 0.002) and lower DBP (p = 0.016). SBP (p = 0.037) and DBP (p = 0.008) were both lower after 10 min of supine recovery following hot exercise than after moderate temperature. Average response did not reveal orthostatic hypotension despite heat causing a higher HR (p = 0.011) and lower SBP (p = 0.026) after 10 min of orthostatic exposure. Trained women exhibit an autonomic shift toward sympathetic dominance for at least 30 min after exercise in heat. Women who exercise in heat should be wary of an exacerbated HR response after exercise and low recovery blood pressures.

The Impact of Aerobic Training on Cardiovascular Reactivity to and Recovery From Psychological and Orthostatic Challenge

OBJECTIVE

Elevated cardiovascular reactivity to, and reduced recovery from, challenging events may increase the risk of cardiovascular disease, and exercise training may reduce this reactivity. However, in a randomized controlled trial of aerobic versus strength training in sedentary, healthy young adults, we found no training group differences in reactivity or recovery. Because strength training also may have a reactivity-reducing effect, we conducted a secondary analysis of data from another trial, this time with a wait-list control condition.

METHODS

One hundred nineteen healthy, young, sedentary adults were randomized to a 12-week aerobic training program or wait-list control. Before (T1) and after (T2) training and after 4 weeks of sedentary deconditioning (T3), we measured heart rate (HR), heart rate variability, and blood pressure at rest and in response to and recovery from psychological and orthostatic challenge. Data were analyzed using a group (aerobic versus wait-list) by session (T1, T2, and deconditioning) and by period (baseline, psychological challenge, recovery, standing) three-way analysis of variance with prespecified contrasts.

RESULTS

Aerobic capacity significantly increased at T2 and decreased at T3 only in the aerobic training group. The groups did not differ on HR, heart rate variability, or blood pressure reactivity to or recovery from challenge. Without baseline adjustment, there were no significant treatment differences in response to challenges. With baseline adjustment, there were significant treatment by session effects for HR (Cohen d = 0.54, p = .002), systolic blood pressure (d = 0.44, p = .014), diastolic blood pressure (d = 0.74, p = .002), and root mean squared successive difference (d = 0.48, p = .006) reactivity from T1 to T2 only for orthostatic challenge: at T2, reactivity in the aerobic group was nonsignificantly reduced, compared with T1. In the wait-list group, reactivity significantly increased after T1.

CONCLUSIONS

This study raises further doubt about attenuation of cardiovascular reactivity or enhancement of recovery as a cardioprotective mechanism of aerobic exercise training.Clinical Trial Registration:ClinicalTrials.gov Unique identifier: NCT01335737.

Elevated resting heart rate in adolescent men and risk of heart failure and cardiomyopathy

Aims

This study aims to investigate the association of resting heart rate (RHR) measured in late adolescence with long‐term risk of cause‐specific heart failure (HF) and subtypes of cardiomyopathy (CM), with special attention to cardiorespiratory fitness.

Methods and results

We performed a nation‐wide, register‐based cohort study of all Swedish men enrolled for conscription in 1968–2005 (n = 1 008 363; mean age = 18.3 years). RHR and arterial blood pressure were measured together with anthropometrics as part of the enlistment protocol. HF and its concomitant diagnoses, as well as all CM diagnoses, were collected from the national inpatient, outpatient, and cause of death registries. Risk estimates were calculated by Cox‐proportional hazards models while adjusting for potential confounders. During follow‐up, there were 8400 cases of first hospitalization for HF and 3377 for CM. Comparing the first and fifth quintiles of the RHR distribution, the hazard ratio (HR) for HF associated with coronary heart disease, diabetes, or hypertension was 1.25 [95% confidence interval (CI) = 1.13–1.38] after adjustment for body mass index, blood pressure, and cardiorespiratory fitness. The corresponding HR was 1.43 (CI = 1.08–1.90) for HF associated with CM and 1.34 (CI = 1.16–1.54) for HF without concomitant diagnosis. There was an association between RHR and dilated CM [HR = 1.47 (CI = 1.27–1.71)] but not hypertrophic, alcohol/drug‐induced, or other cardiomyopathies.

Conclusions

Adolescent RHR is associated with future risk of HF, regardless of associated aetiological condition. The association was strongest for HF associated with CM, driven by the association with dilated CM. These findings indicate a causal pathway between elevated RHR and myocardial dysfunction that warrants further investigation.

Greater Influence of Aerobic Fitness on Autonomic Support of Blood Pressure in Young Women Than in Older Women

Aging increases autonomic support of blood pressure; however, the impact of aerobic fitness on autonomic support of blood pressure has not been addressed in women. As such, we hypothesized that aerobic fitness would be related to the change in blood pressure during ganglionic blockade such that women with greater aerobic fitness would have a blunted fall in blood pressure during ganglionic blockade due to increased vagal tone. Thirteen young premenopausal and 13 older postmenopausal women completed a screening visit where aerobic fitness (maximal oxygen consumption, VO_2max) was measured. On a separate study day, participants were instrumented for assessment of muscle sympathetic nerve activity, heart rate (electrocardiography), and beat by beat blood pressure (arterial catheter and pressure transducer) and underwent pharmacological blockade of the autonomic ganglia using trimethaphan camyslate. Heart rate, blood pressure, and muscle sympathetic nerve activity were analyzed before and during ganglionic blockade. In young women, there was a significant relationship between aerobic fitness and the change in blood pressure during ganglionic blockade (r=0.761, P=0.003). In older women, there was no relationship between aerobic fitness and the change in blood pressure during ganglionic blockade (r=-0.106, P=0.73). Measures of heart rate variability were related to fitness in young women, but not older women (root mean square of successive differences between normal heartbeats, r=0.713, P=0.006 versus r=-0.172, P=0.575). Our data suggest that in young women, autonomic support of blood pressure is attenuated in those that are highly fit; however, this relationship is not significant in older women.

Improving Cognition via Exercise (ICE): Study Protocol for a Multi-Site, Parallel-Group, Single-Blind, Randomized Clinical Trial Examining the Efficacy of Aerobic Exercise to Improve Neurocognition, Daily Functioning, and Biomarkers of Cognitive Change in Individuals with Schizophrenia

Individuals with schizophrenia (SZ) display cognitive deficits that have been identified as major determinants of poor functioning and disability, representing a serious public health concern and an important target for interventions. At present, available treatments offer only minimal to moderate benefits to ameliorate cognitive deficits. Thus, there remains an urgent need to identify novel interventions to improve cognition in people with SZ. Emerging evidence from animal and basic human research suggests aerobic exercise training (AE) has beneficial effects on cognition. Preliminary findings suggest that AE is efficacious in improving cognitive functioning in SZ, however the extant studies have been limited by small samples, a dearth of information on biologically-relevant covariates, and limited information on impact on daily functioning. Additionally, while AE-related cognitive benefits have been linked to Brain-Derived Neurotrophic Factor (BDNF) upregulation, this putative mechanism needs confirmation. The present report describes a study protocol designed to address these limitations-we review and summarize the current literature on treatment of cognitive deficits in SZ, state the rationale for employing AE to target these deficits, and describe the current protocol-a multi-site, single-blind, randomized clinical trial aiming to recruit 200 community-dwelling individuals with SZ. Participants are randomized to one of two 12-week interventions: AE using active-play video games (i.e., Xbox Kinect) and traditional cardiovascular exercise equipment or a stretching-and-toning (ST) control intervention. Participants undergo assessments of aerobic fitness, cognition, and daily functioning, as well as BDNF and other biomarkers of cognitive change, at baseline and after 6-and 12-weeks.

The association between individual differences in executive functioning and resting high-frequency heart rate variability

Both resting high-frequency heart rate variability (HF-HRV) and executive functioning (EF) are individual differences implicated in vulnerability to a wide range of adverse outcomes. The overlapping set of associations, along with theoretical models positing connections between the brain regions subserving the executive functions and the parasympathetic nervous system, suggest that the two factors should be correlated. Seeking to address limitations in prior research, the current study examined the association between EF, measured comprehensively with individually-administered neuropsychological tests and controlling for lower-order cognitive processes, and resting physiology, measured with impedence cardiography, in healthy, community participants (68% female; mean age = 27, SD = 6.5). Results confirmed a significant association between EF and resting HF-HRV, but no association with resting state sympathetic nervous system activation (pre-ejection period). These findings may inform future investigation of transdiagnostic mechanisms related to these two individual difference factors.

Individual Adaptation in Cross-Country Skiing Based on Tracking during Training Conditions

Research on heart rate (HR), mean arterial pressure (MAP) and blood pressure (BP) during specific training stages is less common in endurance athletes, whereas resting BP and HR are less studied in relationship to HR_max. In the current study, the objective was to conduct a medium-term HR, BP and MAP analysis while tracking individual training outcomes. The study was conducted during the 2017–2018 season, over 43 days and 1033 km of training volume, on 12 competitive male cross-country ski athletes. One VO_2max test was performed 10 days before the start of the training program. After the test, training volume and intensity was preset for each subject, according to the general training methodology. Early morning HR, MAP and BP measurements were taken as part of the basic functional analysis. Training volume was correlated to both distance (p = 0.01, r = 0.85, CI95% = 0.80 to 0.88) and training HR%, namely the percentage of HR_max (p = 0.01, r = −0.47, CI95% = −0.58 to −0.34). Both the supine (sHR) and orthostatic HR (oHR) values were significantly correlated with the training intensity. We obtained a significant correlation between sHR and oHR values and the training objective (p = 0.01). An increased oHR was correlated to high intensity training activity (HIT) during the second training session (p = 0.01). Heart rate and blood pressure measurements represent predictive functional adaptation parameters over different training phases. We highlight a link between sHR, oHR, MAP data, and the athletes’ ability to perform in lower effort zones during physical exertion. However, we failed to validate MAP as a cardiovascular stress indicator following high intensity training.

Transcranial direct current stimulation to enhance athletic performance outcome in experienced bodybuilders

Transcranial direct current stimulation (tDCS) is currently under investigation as a promising technique for enhancement of athletic performance through modulating cortical excitability. Through consecutive randomization, 12 experienced bodybuilders were randomly assigned to two arms receiving either sham or real tDCS over the primary motor cortex (leg area) and left temporal cortex (T3) for 13 minutes in the first session. After 72 hours, both groups received the inverse stimulation. After the brain stimulation, cerebral hemodynamic response (using frontopolar hemoencephalography) was examined upon taking three computer-based cognitive tasks i.e. reasoning, memory and verbal ability using the Cambridge Brain Science-Cognitive Platform. Subsequently, the bodybuilders performed knee extension exercise while performance indicators including one-repetition maximum (1RM), muscular endurance (SEI), heart rate (ECG), motivation (VAS), surface electromyography over quadriceps femoris muscle (sEMG) and perceived exertion (RPE) were evaluated. The real tDCS vs. sham group showed decreased RPE and HR mean scores by 14.2% and 4.9%, respectively. Regarding muscular strength, endurance, and electrical activity, the 1RM, SEI, and sEMG factors improved by 4.4%, 16.9%, and % 5.8, respectively. Meanwhile, compared to sham, real tDCS did not affect the athletes’ motivation. Incidentally, it turned out that subjects who underwent T3 anodal stimulation outperformed in memory (p = 0.02) and verbal functions (0.02) as well as their corresponding frontopolar hemodynamic response [(memory HEG (p = 0.001) and verbal HEG (p = 0.003)]. Our findings suggest that simultaneous tDCS-induced excitation over the M1 leg area and left temporal area may potentially improve the overall athletic performance in experienced bodybuilders (Trial registration: IRCT20181104041543N1, Registered on 4 Nov. 2018, retrospectively registered).

The effects of low-volume high-intensity interval versus moderate intensity continuous training on heart rate variability, and hemodynamic and echocardiography indices in men after coronary artery bypass grafting: A randomized clinical trial study

BACKGROUND

Heart rate variability (HRV) declines after coronary artery bypass grafting (CABG). The purpose of this study was to evaluate the effect of low-volume high-intensity interval training (LV-HIIT) and moderate-intensity continuous training (MICT) on HRV as well as, hemodynamic and echocardiography indices.

METHODS

Forty-two men after CABG (55.12 ± 3.97 years) were randomly assigned into LV-HIIT, MICT, and control (CTL) groups. The exercise training in LV-HIIT consisted of 2-minute interval at 85-95 percent of maximal heart rate (HRmax), 2-minute interval at 50% of HRmax and 40-minute interval at 70% of HRmax in MICT for three sessions in a week, for 6-weeks. HRV parameters were evaluated by 24-hour Holter electrocardiography (ECG) recording, and echocardiography parameters at baseline and end of intervention were measured in all 3 groups.

RESULTS

At the end of the intervention, left ventricular ejection fraction (LVEF) significantly increased in LV-HIIT group (58.53 ± 7.26 percent) compared with MICT (52.26 ± 7.91 percent) and CTL (49.68 ± 7.27 percent) groups (P < 0.001). Furthermore, mean R-R interval, root mean square successive difference (RMSSD) of R-R interval, and standard deviation of R-R interval (SDRR) in LV-HIIT group considerably increased compared with MICT group (P < 0.001). High-frequency power (HF) significantly increased in LV-HIIT and MICT groups compared with CTL group (P < 0.001). On the other hand, low frequency (LF) and LF/HF ratio significantly decreased in LV-HIIT group in comparison with MICT group (P < 0.010).

CONCLUSION

These results suggest that LV-HIIT has a greater effect on improvement of cardiac autonomic activities by increasing R-R interval, SDRR, RMSSD, and HF, and decreasing LF and LF/HF ratio in patients after CABG.

Resting heart rate in late adolescence and long term risk of cardiovascular disease in Swedish men

AIM

To investigate the association of resting heart rate (RHR) measured in late adolescence with the long term risk of myocardial infarction (MI), ischemic stroke (IS), heart failure (HF), atrial fibrillation (AF), cardiovascular- and all-cause death.

METHODS AND RESULTS

We followed a cohort of Swedish men enrolled for conscription in 1968-2005 (n = 1,008,485; mean age = 18.3 years) until December 2014. Outcomes were collected from the national inpatient - (IPR), outpatient - (OPR) and cause of death registries. Cox proportional hazard models were used to analyze the longitudinal association between RHR and outcomes while adjusting for potential confounders. While we found no independent association between RHR and risk of IS or MI when comparing the highest with the lowest quintile of the RHR distribution, but a positive association persisted between RHR and incident HF (Hazard ratio (HR) = 1.39 [95% confidence interval (CI) = 1.29-1.49]) after adjustment for body mass index (BMI) and blood pressure (BP). In similarly adjusted models, an inverse association was found for AF while there were weaker associations with death from cardiovascular disease (CVD) and all causes (adjusted HR = 1.12 [CI = 1.04-1.21] and 1.20 [CI = 1.17-1.24]). After further adjustment for cardiorespiratory fitness (CRF), the associations persisted for HF (HR = 1.26 [1.17-1.35] for any diagnostic position and HR = 1.43 [1.28-1.60] for HF as a main diagnosis) and for all-cause death (HR 1.09 [1.05-1.12]) but not for CVD death.

CONCLUSION

Adolescent RHR is associated with future risk of HF and death, independently of BP, BMI and CRF, but not with CVD death, MI or IS, suggesting a causal pathway between elevated heart rate and myocardial dysfunction.

Exercise and non-pharmacological treatment of POTS

Recent research has demonstrated that cardiovascular deconditioning (i.e., cardiac atrophy and hypovolemia) contributes significantly to the Postural Orthostatic Tachycardia Syndrome (POTS) and its functional disability. Therefore, physical reconditioning with exercise training and volume expansion via increased salt and fluid intake should be initiated early in the course of treatment for patients with POTS if possible. The use of horizontal exercise (e.g., rowing, swimming, recumbent bike, etc.) at the beginning is a critical strategy, allowing patients to exercise while avoiding the upright posture that elicits their POTS symptoms. As patients become increasingly fit, the duration and intensity of exercise should be progressively increased, and upright exercise can be gradually added as tolerated. Supervised training is preferable to maximize functional capacity. Other non-pharmacological interventions, which include: 1) chronic volume expansion via sleeping in the head-up position; 2) reduction in venous pooling during orthostasis by lower body compression garments extending at least to the xiphoid or with an abdominal binder; and 3) physical countermeasure maneuvers, such as squeezing a rubber ball, leg crossing, muscle pumping, squatting, negative-pressure breathing, etc., may also be effective in preventing orthostatic intolerance and managing acute clinical symptoms in POTS patients. However, randomized clinical trials are needed to evaluate the efficacies of these non-pharmacological treatments of POTS.

Autonomic Nervous System and Stress to Predict Secondary Ischemic Events after Transient Ischemic Attack or Minor Stroke: Possible Implications of Heart Rate Variability

Transient ischemic attack (TIA) and minor stroke have high risks of recurrence and deterioration into severe ischemic strokes. Risk stratification of TIA and minor stroke is essential for early effective treatment. Traditional tools have only moderate predictive value, likely due to their inclusion of the limited number of stroke risk factors. Our review follows Hans Selye’s fundamental work on stress theory and the progressive shift of the autonomic nervous system (ANS) from adaptation to disease when stress becomes chronic. We will first show that traditional risk factors and acute triggers of ischemic stroke are chronic and acute stress factors or “stressors,” respectively. Our first review shows solid evidence of the relationship between chronic stress and stroke occurrence. The stress response is tightly regulated by the ANS whose function can be assessed with heart rate variability (HRV). Our second review demonstrates that stress-related risk factors of ischemic stroke are correlated with ANS dysfunction and impaired HRV. Our conclusions support the idea that HRV parameters may represent the combined effects of all body stressors that are risk factors for ischemic stroke and, thus, may be of important predictive value for the risk of subsequent ischemic events after TIA or minor stroke.

Exercise training and cardiac autonomic function in type 2 diabetes mellitus: A systematic review

Cardiac autonomic neuropathy (CAN) is a common complication of type 2 diabetes mellitus (T2DM). It has been found to independently predict all cause and cardiovascular disease (CVD) mortality. It remains unclear whether exercise training could improve autonomic control in T2DM patients. The purpose of this study was to systematically review the effects of exercise training on cardiac autonomic function in T2DM patients. Electronic databases (MEDLINE, CENTRAL, PEDro, Scopus and Web of science) were systematically searched to retrieve relevant evidence. Clinical trials administering exercise training for at least 4 weeks and examining either heart rate variability (HRV), baroreflex sensitivity (BRS), heart rate recovery (HRR) as outcome measures were eligible. Eighteen articles were found to be relevant and were then assessed for characteristics and quality. Fifteen studies out of 18 found that exercise training leads to positive improvements in autonomic function of T2DM patients. Exercise participation enhances cardiac autonomic function of type 2 diabetics and therefore should be implemented in their management programs.

From psychological moments to mortality: A multidisciplinary synthesis on heart rate variability spanning the continuum of time

Heart rate variability (HRV) indexes functioning of the vagus nerve, arguably the most important nerve in the human body. The Neurovisceral Integration Model has provided a structural framework for understanding brain-body integration, highlighting the role of the vagus in adaptation to the environment. In the present paper, we emphasise a temporal framework in which HRV may be considered a missing, structural link between psychological moments and mortality, a proposal we label as Neurovisceral Integration Across a Continuum of Time (or NIACT). This new framework places neurovisceral integration on a dimension of time, highlighting implications for lifespan development and healthy aging, and helping to bridge the gap between clearly demarcated disciplines such as psychology and epidemiology. The NIACT provides a novel framework, which conceptualizes how everyday psychological moments both affect and are affected by the vagus in ways that have long-term effects on mortality risk. We further emphasize that a longitudinal approach to understanding change in vagal function over time may yield novel scientific insights and important public health outcomes.

Resting Bradycardia, Enhanced Postexercise Heart Rate Recovery and Cardiorespiratory Fitness in Recreational Ballroom Dancers

PURPOSE

In a cross-sectional study design, we evaluated the resting heart rate (HR_baseline) and exercise and postexercise stress test-related chronotropic responses in male practitioners of recreational ballroom dancing (BD; n = 25, M_age = 26.6 ± 6.1 years) compared to a control group of insufficiently active nondancers (CG; n = 25, M_age = 25.9 ± 4.5 years).

METHOD

All participants underwent a submaximal exercise test. At 85% of the maximal predicted HR, the recovery protocol was started, and heart rate recovery (HRR) was recorded during 1-min intervals for 5 min.

RESULTS

Compared with CG, BD showed lower HR_baseline (70 beats per minute [bpm] vs. 62 bpm, respectively, U = 143, p < .05, ES = .46), lower preexercise HR (94 bpm vs. 86 bpm, U = 157, p < .05, ES = .42), longer exercise test duration (346 s vs. 420 s, U = 95.5, p < .05, ES = .59), and higher HRR for 5 min postexercise (U = 1.29-1.89, p < .05, ES = .33-.50) as follows: 1st min (32 bpm vs. 40 bpm), 2nd min (45 bpm vs. 53 bpm), 3rd min (51 bpm vs. 58 bpm), 4th min (55 bpm vs. 59 bpm), and 5th min (59 bpm vs. 63 bpm). The coefficient of HRR from the 1st min to the 5th min postexercise was similar in both groups (U = 229-311, p > .05, ES = < .10-.22).

CONCLUSION

Heightened cardiovascular functional status characterized by favorable enhanced chronotropic dynamics appears to occur in practitioners of recreational ballroom dancing, which suggests that this modality of exercise may result in health benefits.

A Physiological Approach to Prolonged Recovery From Sport-Related Concussion

Management of the athlete with postconcussion syndrome (PCS) is challenging because of the nonspecificity of PCS symptoms. Ongoing symptoms reflect prolonged concussion pathophysiology or conditions such as migraine headaches, depression or anxiety, chronic pain, cervical injury, visual dysfunction, vestibular dysfunction, or some combination of these. In this paper, we focus on the physiological signs of concussion to help narrow the differential diagnosis of PCS in athletes. The physiological effects of exercise on concussion are especially important for athletes. Some athletes with PCS have exercise intolerance that may result from altered control of cerebral blood flow. Systematic evaluation of exercise tolerance combined with a physical examination of the neurologic, visual, cervical, and vestibular systems can in many cases identify one or more treatable postconcussion disorders.

Measures of Heart Rate Variability in Individuals With Somatic Symptom Disorder

OBJECTIVE

Little is known about autonomic nervous system activity in individuals with somatic symptom disorder (SSD) as defined by DSM-V criteria. The aims of this study were to investigate whether individuals with SSD differ from healthy controls in heart rate variability (HRV) measures of autonomic nervous system activity and whether sex has a moderating effect on this association.

METHODS

We recruited 168 individuals with SSD (35.1% men) and 106 healthy controls (27.4% men). Demographics, HRV, and psychological factors were measured using the Patient Health Questionnaire-15, Health Anxiety Questionnaire, Beck Depression Inventory-II (BDI-II), and Beck Anxiety Inventory. Multiple regression analysis was used to examine the association of SSD with HRV, adjusting for demographic and psychological measures.

RESULTS

Individuals with SSD had lower levels of total-power HRV and low-frequency HRV, but no differences in high-frequency (HF)-HRV were found. HRV differences between SSD and controls varied by sex and age (triple interaction TP-HRV β = -0.222, p < .001; low-frequency HRV β = -0.332, p < .001; and HF-HRV β = -0.167, p = .006). Whole-sample multiple regression analyses revealed significant sex differences in the magnitudes of the association between BDI-II with HF-HRV (β of sex*BDI-II: 0.761, p = .005) and analyses stratified by sex indicated that HF-HRV was significantly correlated with depression in men with SSD (r = -0.491, p < .001) but not in women with SSD (r = 0.057, p = .558).

CONCLUSIONS

These results suggest that patients with SSD demonstrate different patterns of HRV and the patterns of association between HRV indices and psychological factors vary between men and women.

Sympathetic enhancement in futsal players but not in football players after repeated sprint ability test

BACKGROUND

Heart rate variability (HRV) can disclose the specific adaptation of sympathovagal modulation to exercise. This study investigated the change in HRV measures after anaerobic and aerobic intermittent exercises in university football and futsal players.

METHOD

36 male university students with physically active lifestyle (n=14), football (n=12), and futsal (n=10) participated in this study. The participants completed the repeated sprint ability (RSA) test and Yo-Yo (YY) intermittent recovery test level 1 in randomised order. ECG signals of the participants were recorded in supine position 15 min before and 30 min after exercises. Before exercise, and 5 and 30 min after exercise, the blood pressures were also taken.

RESULTS

In the RSA protocol, the percentage changes in normalised high-frequency power (nHFP) were significantly decreased, while the percentage changes in the very low/high frequency power ratio (VLHR) and low/high frequency power ratio (LHR) were significantly increased in futsal players after exercise, as compared with the controls. No significant changes in all HRV indices were found in the YY protocol, except the respiratory frequency.

CONCLUSIONS

After exercise, the percent decrease in vagal modulation in futsal players was significantly reduced, while the percentage increase in sympathetic modulation in futsal players was significantly enhanced in the RSA test, but not in the YY test, as compared with the control group. The increase in sympathetic activity and the decrease in vagal activity in the futsal players were greater than the corresponding increase and decrease in the football players in the RSA test.

Autonomic function and brain volume

OBJECTIVE

The aim of this study is to review the evidence on the role of the autonomic nervous system as a determinant of brain volume. Brain volume measures have gained increasing attention given its biological importance, particularly as a measurement of neurodegeneration.

METHODS

Using an integrative approach, we reviewed publications addressing the anatomical and physiological characteristics of brain autonomic innervation focusing on evidence from diverse clinical populations with respect to brain volume.

RESULTS

Multiple mechanisms contribute to changes in brain volume. Autonomic influence on cerebral blood volume is of significant interest.

CONCLUSION

We suggest a role for the autonomic innervation of brain vessels in fluctuations of cerebral blood volume. Further investigation in several clinical populations including multiple sclerosis is warranted to understand the specific role of parenchyma versus blood vessels changes on final brain volume.

Factors related to heart rate variability among firefighters

OBJECTIVES

The aim of this study was to investigate factors associated with heart rate variability in firefighters working in a metropolitan city in South Korea.

METHODS

Self-administered questionnaires including Korean Occupational Stress Scale (KOSS) as well as surveys collecting socio-demographic characteristics and work-related factors were given to 962 firefighters. After exclusion for missing data, 645 firefighters were included, and analysis of covaiance adjusted for the general risk factors and job characteristics were used to assess the relationship between heart rate variability and associated factors.

RESULTS

SDNN and RMSSD and were decreased in the area of occupational climate of the group with high job stress (p = 0.027, p = 0.036). HF(ln) was decreased in the area of organizational system and occupational climate of the group with high stress that statistically significant level (p = 0.034, p = 0.043).

CONCLUSIONS

Occupational climate and organizational system are associated with reduction of heart rate variability. Preventive medical care plans for cardiovascular disease of firefighters through the analysis and evaluation of job stress factors are needed.

The beneficial effects of horse trekking on autonomic nervous activity in experienced rider with no disability

The aim of this study was to determine whether autonomic nervous activity of a rider with no disability was altered by one practical and applicable horse trekking (HT) exercise. Changes in autonomic nervous activity were analyzed by heart rate variability (HRV). Twenty-three participants with no disability rode horses along a predetermined HT course at trotting and walking for 60 min. HRV was sampled at 60 min before and immediately, following 60 min, and 120 min after HT. As a control, the same measurements were performed for 22 age-matched participants during their rest. Only in the HT group, the value of normalized unit in high frequency component (HF nu), an index of parasympathetic nervous activity, was higher at 120 min after treatment than before HT (P < 0.05). The low / high frequency ratio (LF / HF), believed to reflect sympathetic nervous activity, was lower in the HT group than those in the control group at 60 min (P < 0.05) and 120 min after treatment (P < 0.01). These findings suggest that a single HT shifted the autonomic nervous balance of a rider toward parasympathetic dominance. The results obtained by the present study could accelerate the use of horses for human health.

Improving aerobic capacity through active videogames: A randomized controlled trial

AbstractThe rate of peak workload improvement between different types of Active Video Games (AVG) in young sedentary adults was investigated. Aerobic capacity improvement after a 6-week intervention between AVG types was also compared. Twenty participants, after baseline assessments, were randomized into one of three parallel groups: structured AVG (n= 6), unstructured AVG (n= 7) and a control group (n= 7). Participants played their respective AVG 3 times a week for 6-weeks (30 minutes-session). The control group maintained normal activities. Both structured and unstructured AVG improved peak workload after four weeks but only the structured group maintained this improvement through week five and six. Aerobic capacity improved in the unstructured (Pre: 36.0 ± 5.2ml.kg.min-¹,Post: 39.7 ± 4.9ml.kg.min-¹, p = .038) and structured AVG (Pre: 39.0 ± 5.9ml.kg.min-¹,Post: 47.8 ± 4.3ml.kg.min-¹, p = .006) groups. Structured AVG provide greater health benefits to aerobic capacity and peak workload in young sedentary but otherwise healthy males relative to unstructured AVG.

Transição metabólica no teste progressivo de pessoas treinadas com musculação e corrida

INTRODUÇÃO: A especificidade das adaptações cardiorrespiratórias e metabólicas do treinamento aeróbio e de força evocam respostas distintas durante o teste cardiopulmonar de exercício (TCPE). Objetivo: Descrever o comportamento cardiorrespiratório durante a transição metabólica (TM) do TCPE, de praticantes de corrida e musculação, comparados a um grupo controle.MÉTODOS: Homens de 21 a 55 anos foram agrupados em: grupo de corredores (GC, n = 30), grupo de musculação (GM, n = 23) e grupo controle (GCON, n = 38). Foram submetidos à avaliação antropométrica e TCPE com análise do limiar anaeróbio ventilatório (LAV) e do ponto de compensação respiratória (PCR). Calculou-se a economia de corrida pela relação entre VO2 e velocidade do teste (ECINCLINA).RESULTADOS: Na fase de transição metabólica, a carga (km/h) foi superior no GC (4,2 ± 1,6) vs. GCON (2,7 ± 1,6) e GM (2,8 ± 1,0); P < 0,05. O GC apresentou maior VO2LAV; VO2PCR e VO2MÁX.(36 ± 8; 46 ± 8; 51 ± 8 vs. 24 ± 6; 35 ± 5; 40 ± 6 e 26 ± 6; 35 ± 6; 40 ± 7 ml.kg-1.min-1; P < 0,05), comparado com GCON e GM, respectivamente, mesmo após a correção alométrica. A FCREP foi menor entre GC e GCON (CE = 52 ± 6; CON = 60 ± 8 bpm;P < 0,05). Na fase de TM, o GC apresentou maior aumento da carga de trabalho e menor alteração do pulso de oxigênio comparado ao GCON e ao GM. O VO2 durante a TM não difere entre os grupos. O GC apresentou menor ECINCLINA nos instantes finais do teste, comparado a GCON e GM.CONCLUSÃO: O GC apresentou maior eficiência metabólica nas transições progressivas de intensidade de esforço em relação a GCON e GM e o GM não exibe capacidade de transição aprimorada no TCPE, até mesmo quando comparados a indivíduos sedentários.

Changes in biochemical and functional parameters for men during exercise

Benefits of physical activity are undeniable. The aim of the present research was to determine the effects of physical activity and age on cholesterol and glucose levels in the blood, as well as changes in the functional parameters of the cardiovascular system, during stepwise increases in physical load for men employed in the same place, but with different levels of physical activity. The subjects were 95 military officers who were divided into groups according to the level of physical activity of their occupation, with veloergometry used as physical load. Cholesterol and glucose levels in the blood were taken as biochemical indices. The results showed that occupational physical activity had a positive effect on biochemical and cardiovascular functional parameters before, during, and after the physical load. Only the cardiovascular rate (systolic blood pressure) in older subjects was significantly higher than that of the younger persons; for all other parameters, age had no effect at all.

Relação entre a variabilidade da frequência cardíaca e VO 2pico em mulheres ativas

OBJETIVO: Ava+liar a associação entre os índices da variabilidade da frequência cardíaca (VFC) e a aptidão cardiorrespiratória.MÉTODOS: Sessenta e duas mulheres (idade 22,1 ± 3,3 anos) foram divididas em quatro grupos: treinamento aeróbio (AER, n = 15), treinamento de força (FOR, n = 13), treinamento combinado (aeróbio e força) (AER+FOR, n = 15) e controle (C, n = 19). O teste cardiopulmonar foi realizado para avaliar a aptidão cardiorrespiratória a partir do consumo de oxigênio pico (VO2pico). A FC foi coletada em repouso na postura supina. A VFC foi analisada a partir de métodos lineares e não lineares.RESULTADOS: Os grupos AER e AER+FOR apresentaram maiores índices da VFC (lineares e não lineares) indicadores da modulação vagal e menores índices da VFC indicadores da modulação simpática, em relação ao grupo C. Os grupos AER e AER+FOR apresentaram maior complexidade e menor regularidade dos intervalos RR e maior VO2pico em relação aos grupos FOR e C. O VO2picoapresentou correlação com os índices da VFC.CONCLUSÃO: Este estudo mostrou que o treinamento físico aeróbio e combinado contribuíram significativamente para maior modulação autônoma da FC e aptidão cardiorrespiratória. A modulação autônoma da FC, avaliada a partir de métodos lineares e não lineares, está associada ao maior consumo de oxigênio.

Maternal physical activity mode and fetal heart outcome

BACKGROUND

Maternal leisure-time physical activity (LTPA) improves cardiac autonomic function in the fetus. The specific physical activity attributes (e.g., mode) that produce this benefit are not well understood.

AIM

To determine if more time spent performing non-continuous LTPA during pregnancy is significantly associated with lower fetal heart rate (HR) and increased heart rate variability (HRV).

STUDY DESIGN

This paper presents a retrospective analysis of previously reported data. Fetal magnetocardiograms (MCG) were recorded from 40 pregnant women at 36-wk gestational age.

OUTCOME MEASURES

Metrics of fetal HR and HRV, self-reported min of continuous and non-continuous LTPA performed during the 3-months preceding the 36-wk assessment point and covariates (maternal weight change pre to 36-wk, age, and resting HR and fetal activity state during MCG recordings.

RESULTS

Positive correlations were significant (p<0.05) between min of continuous LTPA, the time domain metrics that describe fetal overall HRV, short-term HRV and a frequency domain metric that reflects vagal activity. Time spent in non-continuous LTPA was positively correlated (p<0.05) with two HRV metrics that reflect fetal overall HRV. In the multiple regression analyses, minutes of non-continuous LTPA remained associated with fetal vagal activity (p<0.05) and the relationships between minutes of non-continuous LTPA and fetal overall HRV (p<0.005) persisted.

CONCLUSION

These data suggest non-continuous physical activity provides unique benefits to the fetal autonomic nervous system that may give the fetus an adaptive advantage. Further studies are needed to understand the physiological mechanisms and long-term health effects of physical activity (both non-continuous and continuous) performed during pregnancy to both women and their offspring.

Greater BOLD response to working memory in endurance-trained adults revealed by breath-hold calibration

BACKGROUND

Cardiorespiratory fitness is associated with increased frontal and parietal activation during executive function tasks. While these findings suggest fitness-related enhancement of neuronal response, the utility of functional magnetic resonance imaging (fMRI) may be limited by potential fitness-related differences in global vascular reactivity. The aim of this study was to determine if highly fit adults display differential activation during working memory after calibration for vascular reactivity relative to their sedentary counterparts.

METHODS

Thirty-two endurance-trained and 24 sedentary adults, aged 40-65 years, completed a 2-Back verbal working memory task and a breath-hold challenge during fMRI. Group differences in blood oxygen level-dependent (BOLD) response during working memory were examined across the whole brain and in a priori regions of interest (ROI) before and after breath-hold calibration using non-parametric permutation testing. Multiple regression was used to explore the association between cardiorespiratory fitness (VO2 max), age, and calibrated 2-Back-related activation within the one a priori ROI with significant group effects.

RESULTS

In comparison to the endurance-trained group, the sedentary group exhibited greater BOLD signal changes in response to the breath-hold task. After, but not before calibration, the endurance-trained group displayed significantly higher 2-Back-related activation in the right middle frontal gyrus (P = 0.049). Older age predicted lower 2-Back-related activation (ß = -0.308, P = 0.031), whereas fitness predicted higher activation (ß = 0.372, P = 0.021) in this region.

CONCLUSIONS

Breath-hold calibration increased detection of working memory-related BOLD response differences between sedentary and endurance-trained adults. Moreover, cardiorespiratory fitness appeared to mitigate age-related changes in BOLD during working memory in this region.

Reduced respiratory sinus arrhythmia in adults born at extremely low birth weight: evidence of premature parasympathetic decline?

Individuals born at extremely low birth weight (ELBW; <1000 g) are exposed to early adversity in multiple forms. Given that substantial development of the autonomic nervous system (ANS) occurs during the third trimester of gestation, ANS functioning may be altered in adults who were born before reaching 28 weeks of gestational age. The aims of the study were to: (1) determine whether two indices of ANS functioning [resting heart period (HP) and respiratory sinus arrhythmia (RSA)], differed between adult ELBW survivors and normal birth weight (NBW) controls, and (2) ascertain whether ANS functioning was differentially vulnerable to age-related decline in the ELBW participants. Resting HP and RSA (reflecting cardiac efficiency and responsive cardiac control, respectively) were assessed in 30 non-impaired ELBW survivors and 47 NBW controls at ages 22-26 and again at 30-35 years. At each assessment, resting RSA was significantly lower in the ELBW group than in the NBW comparison group. In addition, individual differences in RSA within the ELBW group were poorly preserved over time. These findings are suggestive of a premature decline in parasympathetic functioning in some adult ELBW survivors.

Exercise is the real polypill

The concept of a "polypill" is receiving growing attention to prevent cardiovascular disease. Yet similar if not overall higher benefits are achievable with regular exercise, a drug-free intervention for which our genome has been haped over evolution. Compared with drugs, exercise is available at low cost and relatively free of adverse effects. We summarize epidemiological evidence on the preventive/therapeutic benefits of exercise and on the main biological mediators involved.

Cardiac autonomic modulation is determined by gender and is independent of aerobic physical capacity in healthy subjects

BACKGROUND

Aerobic physical capacity plays an important role in reducing morbidity and mortality rates in subjects with cardiovascular diseases. This action is often related to an improvement in the autonomic modulation of heart rate variability (HRV). However, controversies remain regarding the effects of physical training on cardiac autonomic control in healthy subjects. Therefore, our objective was to investigate whether aerobic capacity interferes with the autonomic modulation of HRV and whether gender differences exist.

METHODS

Healthy men and women (N=96) were divided into groups according to aerobic capacity: low (VO2: 22-38 ml/kg(-1) min(-1)), moderate (VO2: 38-48 ml/kg(-1) min(-1)) and high (VO2 >48 ml/kg(-1) min(-1).) We evaluated the hemodynamic parameters and body composition. The autonomic modulation of HRV was investigated using spectral analysis. This procedure decomposes the heart rate oscillatory signal into frequency bands: low frequency (LF=0.04-0.15Hz) is mainly related to sympathetic modulation, and high frequency (HF=0.15-0.5Hz) corresponds to vagal modulation.

RESULTS

Aerobic capacity, regardless of gender, determined lower values of body fat percentage, blood pressure and heart rate. In turn, the spectral analysis of HRV showed that this parameter did not differ when aerobic capacity was considered. However, when the genders were compared, women had lower LF values and higher HF values than the respective groups of men.

CONCLUSION

The results suggest that aerobic physical capacity does not interfere with HRV modulation; however, the cardiac modulatory balance differs between genders and is characterized by a greater influence of the autonomic vagal component in women and by the sympathetic component in men.

Potential side effects of unhealthy lifestyle choices and health risks on basal and reactive heart rate variability in college drinkers

OBJECTIVE

Emerging adults often begin making independent lifestyle choices during college, yet the association of these choices with fundamental indicators of health and adaptability is unclear. The present study examined the relationship between health risks and neurocardiac function in college drinkers.

METHOD

Heart rate variability (HRV) was assessed at baseline and in reaction to a paced breathing challenge in 212 college drinkers (53.8% women). Basal HRV served as a general indicator of health. Reactive HRV (during paced breathing) was used as a marker of an individual's adaptability to challenge. The relationship of HRV to alcohol use, cigarette use, exercise, sleep, and body mass index (BMI) was assessed.

RESULTS

Greater alcohol use and less exercise were associated with lower basal HRV. BMI was unrelated to basal HRV but was negatively associated with reactive HRV during the breathing challenge.

CONCLUSIONS

High levels of alcohol use and lack of exercise are negative correlates of cardiovascular and general health, even in apparently healthy college drinkers. The negative relationship between BMI and reactive HRV suggests that overweight individuals have reduced ability to psychophysiologically adapt to challenges; understanding the temporal course of this relationship is needed. This study highlights the importance of examining HRV at baseline and in response to a challenge to capture the active neurocardiac processes that contribute to health and adaptive responding. The suppressive effects of health risks on HRV are modifiable; thus, HRV may be useful in evaluating the health benefits of lifestyle change and in promoting change behaviors in college drinkers.

Resistance exercise improves autonomic regulation at rest and haemodynamic response to exercise in non-alcoholic fatty liver disease

Autonomic dysfunction has been reported in patients with NAFLD (non-alcoholic fatty liver disease) and is associated with clinical presentations. To date, there are no therapies to improve autonomic regulation in people with NAFLD. The present study defines the impact of a short-term exercise programme on cardiac autonomic and haemodynamic regulation in patients with NAFLD. A total of 17 patients with clinically defined NAFLD [age, 55±12 years; BMI (body mass index), 33±5 kg/m²; liver fat, 17±9%] were randomized to 8 weeks of resistance exercise or a control group to continue standard care. Resting and submaximal exercise (50% of peak oxygen consumption) autonomic and cardiac haemodynamic measures were assessed before and after the intervention. Resistance exercise resulted in a 14% reduction in HR (heart rate) and 7% lower SBP (systolic blood pressure) during submaximal exercise (16 beats/min, P=0.03 and 16 mmHg, P=0.22). Sympathovagal balance, expressed as LF/HF (low-frequency/high-frequency) ratio of the mean HR beat-to-beat (R-R) interval, was reduced by 37% (P=0.26). Similarly sympathovagal balance of DBP (diastolic blood pressure) and SBP variability decreased by 29% (P=0.33) and 19% (P=0.55), respectively in the exercise group only. BRS (baroreflex sensitivity) increased by 31% (P=0.08) following exercise. The mean R-R interval increased by 23% (159 ms, P=0.09). Parasympathetic regulation was decreased by 17% (P=0.05) and overall sympathovagal balance in BP regulation (LF/HF ratio) increased by 26% (P=0.02) following resistance exercise. Resting haemodynamic measures remained similar between groups. Resistance exercise therapy seems to improve autonomic and submaximal exercise haemodynamic regulation in NAFLD. Further studies are required to define its role in clinical management of the condition.

Aerobic exercise and strength training effects on cardiovascular sympathetic function in healthy adults: a randomized controlled trial

OBJECTIVE

Exercise has widely documented cardioprotective effects, but the mechanisms underlying these effects are not entirely known. Previously, we demonstrated that aerobic but not strength training lowered resting heart rate and increased cardiac vagal regulation, changes that were reversed by sedentary deconditioning. Here, we focus on the sympathetic nervous system and test whether aerobic training lowers levels of cardiovascular sympathetic activity in rest and that deconditioning would reverse this effect.

METHODS

We conducted a randomized controlled trial contrasting the effects of aerobic (A) versus strength (S) training on indices of cardiac (preejection period, or PEP) and vascular (low-frequency blood pressure variability, or LF BPV) sympathetic regulation in 149 young, healthy, and sedentary adults. Participants were studied before and after conditioning, as well as after 4 weeks of sedentary deconditioning.

RESULTS

As previously reported, aerobic capacity increased in response to conditioning and decreased after deconditioning in the aerobic, but not the strength, training group. Contrary to prediction, there was no differential effect of training on either PEP (A: mean [SD] -0.83 [7.8] milliseconds versus S: 1.47 [6.69] milliseconds) or LF BPV (A: mean [SD] -0.09 [0.93] ln mm Hg(2) versus S: 0.06 [0.79] ln mm Hg(2)) (both p values > .05).

CONCLUSIONS

These findings, from a large randomized controlled trial using an intent-to-treat design, show that moderate aerobic exercise training has no effect on resting state cardiovascular indices of PEP and LF BPV. These results indicate that in healthy, young adults, the cardioprotective effects of exercise training are unlikely to be mediated by changes in resting sympathetic activity.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT00358137.

The association of cardiac vagal control and executive functioning--findings from the MIDUS study

Cardiac vagal control (CVC), an index of parasympathetic contribution to cardiac regulation, has been linked to enhanced executive functioning (EF). However, findings to date have been based on small or unique samples. Additionally, previous studies assessed the CVC-EF link only during rest or recovery period from a cognitive challenge, but not during both states. In the present study, data on 817 socioeconomically diverse participants were obtained from the Midlife Development in the United States (MIDUS) study. As part of this study, participants completed cognitive tests, including EF, along with laboratory-based measures of CVC during rest and following recovery from a cognitive challenge. Regression analyses adjusting for respiratory rate revealed no effect of CVC at rest or during recovery on a global index of EF. However, exploratory post-hoc analyses of the components of the global EF index revealed a significant association between faster vagal recovery and better attention-switching and response inhibition abilities, as indexed by faster reaction time to the mixed SGST. This association remained significant after controlling for demographic, clinical (BMI, diseases and medications altering cardiac autonomic functioning, etc.), and health behavior covariates (Beta = .148, p = .010). Our findings suggest that future studies may need to investigate the links of CVC to specific EF abilities, rather than global measures of EF. Additionally, our results highlight the importance of assessing CVC during both rest and recovery from a cognitive challenge. The authors discuss the putative neurobiological underpinning of this link, as well as suggestions for future basic and clinical research.

Adiposity, muscle, and physical activity: predictors of perturbations in heart rate variability

OBJECTIVES

This study examines cross-sectional associations of indices of adiposity, lean body mass, and physical activity, with heart rate variability (HRV), a marker for parasympathetic cardiac vagal control.

METHODS

The study population consists of 360 officers from the Buffalo New York Police Department. Indices of adiposity include body mass index, waist circumference, and a fat-mass index taken from dual-energy X-ray absorptiometry (DEXA) measurements. Lean body mass indices were derived from DEXA measurements of trunk mass and extremity lean mass. Physical activity was measured using a 7-day self-report questionnaire. HRV was obtained from 5-min electrocardiogram measurements by means of parametric spectral analysis resulting in estimates for high-frequency (HF) and low-frequency (LF) HRV.

RESULTS

Both HF and LF HRV were significantly associated with markers for adiposity, two components of lean mass and physical activity with all associations being in the expected direction except that for trunk lean mass. This unexpected result is explained by the possibility that trunk mass is a marker for visceral adiposity rather than lean mass. Body mass index did not explain any additional variance in HRV above and beyond waist circumference and the DEXA indices.

CONCLUSIONS

Higher levels of physical activity, lower levels of markers for central adiposity and higher lean mass in the extremities predict higher levels of HRV in this population of police officers. This association between modifiable risk factors and markers for autonomic function suggest possible interventions that may improve health and performance.