Heart Rate Variability Variables Research Articles

The Influence of an Acute Bout of High-Intensity Interval Exercise on Heart Rate Variability Indices and Stress Index in the Absence of Cardiometabolic Diseases

Introduction: The maximal rate of oxygen consumption is the gold standard when determining cardiorespiratory fitness (CF) in healthy and diseased populations. CF has been shown to influence the improvement of cardiac autonomic modulation (CAM) and lower the risk of morbidity and mortality rates. High-intensity interval exercise (HIIE) has been shown to influence CAM post-exercise in various populations. Heart rate variability (HRV) is a non-invasive way to assess CAM during, before, and after exercise. The purpose was to determine if a single acute bout of HIIE is influenced by age and CF when correlated to HRV variables to determine CAM in healthy and fit individuals. Methods: Thirty-four healthy individuals (n= 21 male; n = 13 female) completed a single acute bout of HIIE session to quantify CAM via HRV. HRV was assessed pre, 1-hour, and 24-hours post-exercise using time and frequency domains, and stress index (SI). Results: HRV time and frequency domains were not significantly changed. The SI was significantly different between pre, 1-hour, and 24-hours post-exercise (p = 0.001). The SI was also significantly different between age groups (p = 0.025). Conclusion: The lack of significant difference in CAM can be attributed to the participants high CF, which helps maintain their HRV as they age. Additionally, the SI appears to be a good metric to assess CF as individuals age.

Temporal Variation Measure Analysis: An Improved Second‐Order Difference Plot

In this study, an improved second‐order difference plot is proposed to analyze the variability of heart rate variability. Although the variation of the physiological status of the cardiovascular system can be shown graphically by the second‐order difference plot, the descriptive ability of existing indicators for this plot is insufficient. As a result, the physiological information contained in the second‐order difference plot cannot be extracted adequately. Addressing the problem, the temporal variation measure analysis is presented to describe distribution patterns of scatter points in the second‐order difference plot quantitatively and extract the acceleration information for a variation of heart rate variability. Experiment results demonstrate the effectiveness of the temporal variation measure analysis. As a quantitative indicator, the temporal variation entropy is properly designed and successfully applied in the recognition and classification of the physiological statuses of the heart.

Effect of Stress on Heart Rate Variability in Medical Students: A Cross-sectional Study

Introduction: Medical education can impose significant psychological stress on undergraduate students. A considerable degree of psychological morbidity has been reported among medical students ranging from stress, interpersonal problems, and suicidal ideation to psychiatric disorders and they tend to have greater psychological distress than the general population. Stress is one of the factors known to cause variation in heart rate variability. Heart Rate Variability (HRV) is a proven reliable non invasive marker of cardiovascular health and has been used in cardiovascular risk stratification. Aim: To study the effect of stress on heart rate variability in medical students. Materials and Methods: The cross-sectional study was conducted in the Department of Physiology at JSS Medical College, Mysuru, Karnataka, India, from December 2017 to February 2018. Total 58 healthy first-year MBBS medical students aged between 18-25 years with normal Body Mass Index (BMI) were included in the study. The Medical Student Stressor Questionnaire (MSSQ), a validated instrument to identify sources of stress in medical students was used to assess the level of stress. AD Instruments PowerLab (Data Acquisition System) was used to record the frequency and time domain analysis of HRV from the limb leads. Kruskal-Wallis test was applied to assess the association between stress domains and HRV domains, using Statistical Package for Social Sciences (SPSS) version 23.0. Results: Most of the medical students had mild to moderate degrees of stress in all the domains of the MSSQ. There was no statistically significant (p-value>0.05) association found between domains of stress with the time and frequency domains of the HRV. Conclusion: Though it was found that medical students were exposed to significant stressors during their medical training, the stress was of mild to a moderate degree which had no significant effect on HRV.

Assessment of meditation effects using heart rate variability analysis

Meditation is claimed to regularise the autonomic nervous system (ANS) and causes reduced metabolic movement, inciting physical and mental relaxation. It is being looked upon as the future integrative means of improving quality of life. The most accessible organ for the assessment of ANS activities is the heart and its oscillations. The heart rate variability (HRV) analysis has emerged as a successful non-invasive method that elucidates changes of sympathetic and vagal activity. The alternations of a heart are complex and constantly changing, which allows the cardiovascular system to rapidly adjust to sudden physical and psychological changes. In this paper, the exhaustive overview of HRV analysis attempts for evaluating meditation effects is presented. Moreover, HRV metrics, their clinical significance, applications and reported usefulness in meditation assessment are presented. The variations in HRV have been analysed using both linear and nonlinear parameters for both meditators and non-meditators. The effects of two meditation techniques namely, Chi and Kundalini yoga meditation on HRV have been investigated extensively, and significance of these techniques have been evaluated using statistical analysis.

Utonomic and hemodynamic effects of pre-anesthetic use of clonidine in healthy dogs

The aim of this study was to evaluate the effects of pre-anesthetic use of clonidine on time-domain heart rate variability (HRV) and arterial blood pressure in healthy anesthetized dogs. Six healthy adult mixed-breed dogs were administered a clonidine (clonidine group, CLG) and 30 days later, a placebo (control group, CG) preanesthetic protocol, in addition to propofol, isoflurane, and an bolus of tramadol and the continuous infusion thereafter. The total time mean values of HRV meanNN, SDNN, SDANN, SDNNI, and rMSSD were higher in the CL group, as observed in some HRV variables on tramadol bolus time (T4), tramadol continuous infusion (T8), and tracheal extubation time (T10). No significant differences in arterial blood pressure were observed, however, two dogs had a second-degree atrioventricular block (Mobitz II) at the tramadol bolus time (T4). These results led us to conclude that the clonidine anesthetic protocol resulted in sympathetic outflow block and an increase in parasympathetic tone, without significant effects on blood pressure. Notably, cardiac electrical disturbance in two dogs in the CL group. Although the pre-anesthetic use of clonidine in dogs with fear-based behavioral problems should be considered, its association with tramadol should be avoided or carried out with caution owing to the existing cardiovascular risk.

Different acquisition systems for heart rate variability analysis may lead to diverse outcomes

Heart rate variability (HRV) is a relevant physiological variable for the estimation of cardiac autonomic function. Although the gold standard for HRV registration is the electrocardiogram (ECG), several applications (APPs) have been increasingly developed. The evaluation carried out by these devices must be compatible with ECG standards. The aim of this study was to compare the data obtained simultaneously with ECG and APP with chest heart rate transmitters. Fifty-six healthy individuals (28 men and 28 women) were evaluated at rest through a short simultaneous HRV measurement with both devices. Data from both acquisition systems were analyzed separately using their own analysis software and exported and analyzed using a validated software. Signal recordings were compatible between the two acquisition systems (Pearson r=0.99; P<0.0001). Although a high correlation was found for the HRV variables obtained in the time domain (Spearman r=0.99; P<0.0001), the correlation decreased in the frequency domain (Pearson r=0.85; P<0.0001) when two software programs were used. Comparison of the averages of spectral analysis parameters also showed differences when HRV data were analyzed separately in each device for low-frequency (LF) and high-frequency (HF) bands. Although the portability of these mobile devices allows for optimal HRV evaluation, the direct analysis obtained from these devices must be carefully evaluated with respect to frequency domain parameters.

Correlation between short-term heart rate variability and QT-Interval with left ventricular systolic function in patients with stable Coronary Artery Disease (CAD): a cross-sectional study

Background: The ischemic process in stable Coronary Artery Disease (CAD) causes cardiac remodeling and dysfunction, signaling the progress towards irreversible heart failure. Early identification for the presence of Left ventricular (LV) remodeling and dysfunction is important. Several methods can be used to assess LV dysfunction using echocardiography, including peak Global Longitudinal Strain (GLS) and ejection fraction measurements. Short-term Heart Rate Variability (HRV) and QT interval are considered practical parameters in electrocardiography identifying LV dysfunction. This study aimed to determine the relationship between short-term HRV and QT interval with LV systolic function in stable angina pectoris patients.Methods: This cross-sectional study was conducted in Prof. Dr. R. D. Kandou Hospital, Manado, from March to September 2021. All study subjects who met the inclusion criteria underwent a clinical history and further examinations, including electrocardiography, laboratory, and echocardiography examinations. The relationship of HRV variables and QT interval with LV systolic function were analyzed using Pearson correlation and linear regression models by SPSS version 21 for Windows.Results: A total of 33 subjects were included with a mean age of 62.3±8.9 years. Non-parametric correlation analysis between HRV variables and left ventricular systolic function showed no significant correlation. There was a significant correlation between QTc interval by Fridericia and LV peak GLS, but not with ejection fraction (r=0.426; p=0.013). The univariate regression analysis showed a relationship between QTc interval by Bazett and Fridericia with peak GLS (Bazett B=0.036; ?=0.35; R2=0.122; p=0.046; Fridericia B=0.052; ?=0.426; R2=0.181; p=0.013).Conclusion: There was a weak and moderate positive correlation between the QTc interval by Bazett and Fridericia formula with left ventricular systolic function. There was no statistically significant correlation between the short-term HRV variable and left ventricular systolic function.

Endocannabinoids and Heart Rate Variability Alterations after Exposure to Prolonged Intensive Physical Exercise of the Hellenic Navy SEALs.

Background: Recent research indicates that both endocannabinoids (eCB) and heart rate variability (HRV) are associated with stress-induced experiences. However, these underlying mechanisms are not elucidated. The present study aims to investigate whether exposure to acute and chronic stress conditions can give rise to measurable changes, both to the peripheral eCB ligands and HRV. Methods: Thirteen candidates under intense preparation for their enlistment in the Hellenic Navy SEALs (HNS) participated in the study. All subjects underwent mental state examination, while HRV variables in time and frequency domain recordings were acquired. Furthermore, at baseline and 30 days after prolonged and intensive physical exercise, hair was collected to measure eCB ligands, such as anandamide (AEA), 2-arachidonoylglycerol (2-AG), and the N-acyl ethanolamine (NAE) molecules: palmitoylethanolamide (PEA) and oleoylethanolamide (OEA). Results: Comparing basal hair concentrations of eCB ligands before and after intense physical exercise, we found that AEA, PEA, and OEA were notably increased, whereas no differences were observed regarding the ligand 2-AG. Furthermore, there were observed associations between the concentrations of peripheral eCB ligands, both at baseline and after the prolonged physical exercise and the time and frequency domains of HRV. Conclusions: These findings suggest that endocannabinoid–HRV interrelations might share a short-term, and long-term adaptability of the changes in self-regulation associated with stress. Further studies will be required to determine the validity of peripheral eCB signaling and HRV as a biomarker for different aspects of the stress response.

Effect of Intensity on Changes in Cardiac Autonomic Control of Heart Rate and Arterial Stiffness After Equated Continuous Running Training Programs.

Background: It is well known that exercise training has positive effects on both cardiac autonomic function and arterial stiffness (AS). However, it is not clear that which exercise training variables, intensity or volume, or both, play a crucial role in this regard. This study investigates the chronic effects of high-volume moderate-intensity training (HVMIT) and low-volume high-intensity training (LVHIT) on heart rate variability (HRV) and AS in sedentary adult men.Materials and Methods: Notably, 45 males (age: 42 ± 5.7 years) were randomly assigned to a control (n = 15), HVMIT (n = 15), or LVHIT (n = 15). The HVMIT group ran three times per week on a treadmill at 50–60% of VO2max for 45–60 min, while the LVHIT trained at 70–85% of VO2max for 25–40 min. Both training protocols were equated by caloric expenditure. HRV, pulse wave velocity (PWV), hemodynamic variables, and body composition were measured before and after 12 weeks.Results: Both protocols (i.e., HVMIT and LVHIT) significantly increased the SD of normal sinus beat intervals (SDNN) and high-frequency (HF) bands (p < 0.05) after 12 weeks. Whereas the low-frequency (LF)-HF ratio decreased significantly in both training protocols (p < 0.05); however, these changes were significantly greater in the LVHIT protocol (p < 0.05). Furthermore, the root mean square of successive RR interval differences (RMSSD) significantly increased only in the LVHIT (p < 0.05). Moreover, a significant decrease in LF and PWV was only observed following the LVHIT protocol (p < 0.05). Some measures of HRV and PWV were significantly correlated (r = 0.275–0.559; p < 0.05).Conclusion: These results show that the LVHIT protocol was more efficient for improving HRV variables and PWV than the HVMIT protocol after 12 weeks of continuous running training. Interestingly, changes in some HRV parameters were related to changes in PWV. Further studies should elaborate on the link between central and peripheral cardiovascular adaptations after continuous and intermittent training regimens differing in intensity.

Effects of a single session of cathodal transcranial direct current stimulation primed intermittent theta-burst stimulation on heart rate variability and cortical excitability measures

Objectives: Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) have been used as neuromodulators in neuropsychiatric conditions. This study is aimed to find the effects of a single session of priming cathodal tDCS with intermittent theta-burst stimulation (iTBS) over left dorsolateral prefrontal cortex on heart rate variability (HRV) and cortical excitability parameters before and after perturbation. Materials and Methods: The neuromodulatory techniques used in the study were Cathodal tDCS for 20 min followed by iTBS for 3 min on the left dorsolateral prefrontal cortex (DLPFC). HRV variables and TMS parameters were recorded before and after this intervention of combined neuromodulation in 31 healthy volunteers (20 males and 11 females; age range of 19–35 years with Mean ± SD = 24.2 ± 4.7 years). Results: The results showed an overall increase in cortical excitability and parasympathetic dominance in healthy volunteers. Other measures of cortical excitability and HRV did not change significantly following single session of combined neuromodulation. Conclusion: This study showed that there is an overall increase in cortical excitability and parasympathetic dominance in the cohort of healthy volunteers following a combination of neuromodulation involving cathodal tDCS followed by iTBS over left DLPFC. Future studies exploring the effects of other possible combinations with sham stimulation could be carried out to explore the utility of dual stimulation as add-on therapy in disorders.

Validation study of the use of the HRVCAM software for the evaluation of heart rate and heart rate variability at rest.

The existing instruments for assessing heart rate (HR) and heart rate variability (HRV) require contact area. This is difficult to obtain from specific groups of patients and from those moving. The aim of this study was to validate the use of the HRVCam software for measuring HR and HRV in healthy adults. The HR and HRV variables were evaluated in terms of time and frequency using a webcam and Polar® S810i. The Shapiro-Wilk test was used to test the normality of the data, and the Pearson's correlation coefficient (r) was used to identify the possible correlation between the two instruments. The size of the effect was calculated based on a generalized linear model, and the Bland-Altman plots were used to analyse the agreement between the methods. The level of significance for all analyses was set at P < 0.05. We evaluated 102 participants, of whom 52% were men; 83.3% were aged between 18 and 29.9 years; and 84.3% were single. There was a good agreement and moderate to strong correlations among all analysed variables. The biases were low, except for the low frequency/high frequency measures. Moreover, the difference between the samples was small to moderate. The results of this study corroborate the use of HRVCam for measuring HR and HRV.

Gender Differences in Cardiac Chronotropic Control: Implications for Heart Rate Variability Research

There is a continuing debate concerning “adjustments” to heart period variability [i.e., heart rate variability (HRV)] for the heart period [i.e., increases inter-beat-intervals (IBI)]. To date, such arguments have not seriously considered the impact a demographic variable, such as gender, can have on the association between HRV and the heart period. A prior meta-analysis showed women to have greater HRV compared to men despite having shorter IBI and higher heart rate (HR). Thus, it is plausible that men and women differ in the association between HRV and HR/IBI. Thus, the present study investigates the potential moderating effect of gender on the association between HRV and indices of cardiac chronotropy, including both HR and IBI. Data from 633 participants (339 women) were available for analysis. Cardiac measures were assessed during a 5-min baseline-resting period. HRV measures included the standard deviation of inter-beat-intervals, root mean square of successive differences, and autoregressive high frequency power. Moderation analyses showed gender significantly moderated the association between all HRV variables and both HR and IBI (each p < 0.05). However, results were not consistent when using recently recommended HRV variables “adjusted” for IBI. Overall, the current investigation provides data illustrating a differential association between HRV and the heart period based on gender. Substantial neurophysiological evidence support the current findings; women show greater sensitivity to acetylcholine compared to men. If women show greater sensitivity to acetylcholine, and acetylcholine increases HRV and the heart period, then the association between HRV and the heart period indeed should be stronger in women compared to men. Taken together, these data suggest that routine “adjustments” to HRV for the heart period are unjustified and problematic at best. As it relates to the application of future HRV research, it is imperative that researchers continue to consider the potential impact of gender.

Autonomic Tone Variations Prior to Onset of Paroxysmal Atrial Fibrillation.

BackgroundVariations of heart rate variability (HRV) before paroxysmal atrial fibrillation (PAF) onset are still controversial. We aimed to observe the autonomic tone variations before PAF onset based on HRV analysis.Material/MethodsWe prospectively investigated 24-h Holter recordings of 60 patients with PAF (M/F: 34/26) and 40 healthy people in sinus rhythm (M/F: 18/12). According to clinical information and Poincaré scatter plot, 60 PAF patients were divided into sympathetic group (n=20) and vagus group (n=40). Time domain and frequency domain parameters of HRV were respectively measured before PAF episodes in 3 subgroups. Five time periods were studied using the ANOVA.ResultsNo significant variations were observed for the HRV parameters during 60 minutes preceding PAF in sympathetic group. A significant and linear change in SDNN, RMSSD, PNN50, HF and LF/HF during 60 minutes preceding PAF onset in vagus group. Compared with controls, RMSSD, LF and HF were significantly longer in patients with PAF during 60 minutes before PAF. Comparing sympathetic group and vagus group, we observed the same pattern of autonomic variations with a progressive decrease in LF and HF. A progressive decrease in PNN50 and LF/HF of sympathetic group and a significant increase in PNN50 and LF/HF of vagus group were also observed.ConclusionsPatients with PAF mediated by different autonomic nerves have HRV variations, especially vagus PAF, there was a progressive increase with vagal tone during 60 minutes before PAF onset. The findings may help clinicians better intervene in PAF.

A Pilot Study of Temporal Associations Between Psychological Stress and Cardiovascular Response.

Psychological stress (PS) in daily life can trigger acute changes in cardiovascular function and may lead to increased risk of cardiovascular problems. Prior laboratory-based studies provide little evidence on temporal changes in the associations between PS and cardiovascular responses in natural settings. We hypothesized that daily PS would be associated with higher heart rate (HR) and lower heart rate variability (HRV). Using smartphones, ten participants (four females, 21.1±1.1 years) completed ecological momentary assessment (EMA) 6 times a day for two weeks regarding their current affective state. Participants rated levels of PS, as well as 3 high-arousal negative affect (HNA: Anxious, Annoyed, and Upset), and 3 low-arousal negative affect (LNA: Sluggish, Bored, and Sad) states. They also wore a chest-mounted heart-rate monitor and a wrist accelerometer to monitor cardiovascular response and physical activity, respectively. HR and HRV variables in the time intervals (5, 30, 60 min) before and after EMA were used as indicators of cardiovascular response. Multilevel modeling was used to examine the association between affect and HR/HRV, controlling for physical activity. Higher HR and lower HRV were related to subsequent greater feelings of stress at the 5 and 30-min time intervals. No significant associations were observed between cardiovascular parameters and subsequent affective states, suggesting that the acute exaggerated cardiovascular responses occurred due to PS. Higher LNA was related to antecedent/subsequent lower HR or higher HRV within 2 hours, while HNA was unrelated to HR or HRV for all time intervals, suggesting that both high/low arousal NA were not related to exaggerated cardiovascular response. Understanding psychological feelings of stress and LNA may be helpful in the management of daily cardiovascular health.

Cardiovascular autonomic nervous system function and hip fracture risk: the Cardiovascular Health Study.

Autonomic nervous system function modulates bone remodeling in rodent osteoporosis models. We tested whether cardiovascular autonomic function is associated with hip fracture risk in humans. Participants were 1299 subjects from the Cardiovascular Health Study (mean age 72.8years). Eight heart rate variability (HRV) measures (time and frequency domains, detrended fluctuation analysis variables, and heart rate turbulence) were derived from 24-h Holter monitor scans in sinus rhythm. Median follow-up for incident hip fracture was 14.7years [IQR 9.1, 20.2]. Cox proportional hazards models were used to calculate hazard ratios (95% confidence intervals, CI). There were 144 hip fractures among 714 women (1.31 [1.06, 1.61] per 100-person years) and 46 among 585 men (0.62 [0.43, 0.90] per 100 person-years). From among HRV variables examined, a one standard deviation (SD) higher variation between normal heart beats over 24h (the SD of NN intervals [SDNN]) was associated with a multivariable-adjusted lower hip fracture risk (HR [Formula: see text] 0.80; 95% CI 0.65-0.99; p = 0.04) in women. The adjusted association between very low frequency power, and hip fracture was borderline statistically significant in women (HR [Formula: see text] 0.82; 95% CI, 0.66-1.00; p = 0.06). When the 8 HRV variables were considered conjointly and adjusted for each other's association with hip fracture risk, a 1 SD higher SDNN value was significantly associated with reduced hip fracture risk in women (HR 0.74; 95% CI, 0.50-0.99; p = 0.05). No HRV variables were associated with hip fracture in men. In older women, increased heart rate variation is associated with hip fracture risk.

Social affiliation moderates the link between depressive symptoms and heart rate variability in healthy middle‐aged and older individuals: An intensive ecologic momentary assessment study

Depressive symptoms have been associated with lower cardiac autonomic control, thus contributing to cardiovascular diseases, especially among older adults. Interpersonal factors have been found to attenuate physiologic stress responses, but little is known about whether these factors (e.g., perceived affiliation) would moderate the relation of depressive symptoms and cardiovascular activation. The present research aimed to investigate the interplay of depressive symptoms and momentary-assessed interpersonal perceptions on cardiac vagal tone as indexed by heart rate variability (HRV). The sample consisted of 78 late middle-aged and older community-dwelling participants (48.7% male, mean age = 59.15years). Participants reported on depressive symptoms and other personal characteristics by questionnaire. Perceptions of interpersonal affiliation, ambulatory HRV, and contextual variables were recorded using ecologic momentary assessment and portable electrocardiogram (ECG) monitoring device throughout 1week (with a maximum of seven times daily). Multilevel analyses found that depressive symptoms were correlated with lower HRV, whereas momentary interpersonal perceptions of higher affiliation were associated with elevated HRV. A significant association was revealed between depressive symptoms and momentary affiliation perceptions on HRV. When individuals were involved in social interactions with higher affiliation, the effect of depressive symptoms on reducing HRV was attenuated. These findings suggested that the effects of subthreshold depressive symptoms on vagal control of the heart could be altered by the quality of interpersonal experiences.

Cardiac Autonomic Modulation Response Before, During, and After Submaximal Exercise in Older Adults With Intellectual Disability.

The analysis of the heart rate variability (HRV) consists of changes in the time intervals between consecutive R waves. It provides information on the autonomic nervous system regulation and it is a predictor of adverse cardiovascular events. Several studies analyzed this parameter in youth and adults with Intellectual Disability (ID). Nevertheless, there is a lack of information regarding the HRV before, during, and after exercise in older adults with ID. Therefore, we aimed to describe and compare the cardiac autonomic modulation before, during, and after the six-minute walk test (6MWT) in older adults with and without ID. Twenty-four volunteers with ID and 24 without ID (non-ID) participated in this study. HRV was assessed by R-R intervals at rest, during and after the 6MWT. At rest and recovery periods, the participants remained sited. The symbolic analysis was used to evaluate non-linear HRV components. The recovery HR kinetics was assessed by the mean response time, which is equivalent to time constant (τ)+time delay (TD). Between groups differences in HRV variables were not significant. During the recovery period, HR kinetics time variables showed significant better results in non-ID participants (TD: 6±5s vs. 15±11s; τ: 19±10s vs. 35±17s; and MRT: 25±9s vs. 50±11s, all p<0.050). In conclusion, our results suggest that the HRV in older adults with and without ID is similar during rest, exercise, and recovery. Recovery HR kinetics after the 6MWT was slower in older adults with ID. The reason for these results may be a reduced post-exercise vagal rebound in older adults with ID.

Heart Rate Variability Reflects Similar Cardiac Autonomic Function in Explosive and Aerobically Trained Athletes.

Autonomic cardiac function can be indirectly detected non-invasively by measuring the variation in microtiming of heart beats by a method known as heart rate variability (HRV). Aerobic training for sport is associated with reduced risk for some factors associated with cardiovascular diseases (CVD), but effects on autonomic function in different athlete types are less known. To compare cardiac autonomic modulation using a standard protocol and established CVD risk factors in highly trained intercollegiate athletes competing in aerobic, explosive, and cross-trained sports. A total of 176 college athletes were categorized in distinct sports as explosive (EA), aerobic (AA), or cross-trained (mixed) athletes. Eight different HRV measures obtained at rest were compared across training type and five health factors: systolic (SBP), diastolic blood pressure (DBP), body weight (BW), sex, and race. All athletic types shared favorable HRV measures that correlated with low CVD risk factors and indicated normal sympathovagal balance. A significant correlation was reported between DBP and pNN50 (% RR intervals > 50 ms) (β = −0.214, p = 0.011) and between BW and low-frequency (LF) power (β = 0.205, p = 0.006). Caucasian and African American athletes differed significantly (p < 0.05) with respect to four HRV variables: pNN50, HF power, LF power, and LF/HF ratios. Explosive, aerobic and mixed athletes had similar cardiovascular and autonomic HRV results in all eight HRV parameters measured. All athletes reported LF and pNN50 values that were significantly correlated with two CVD risk factors: DBP and BW. Compared with Caucasian teammates, African American athletes demonstrated lower LF/HF and higher pNN50, indicating an even more favorable resting sympathovagal activity and healthy CV function.

Endocannabinoids and heart rate variability alterations after exposure to prolonged intensive physical exercise of the Hellenic Navy SEALs

Abstract Background Recent research indicates that endocanabinoids (eCB) and heart rate variability (HRV) are associated with stress-induced experiences. However, these underlying mechanisms have not been elucidated. Purpose The aim of the present study is to investigate if exposure to acute and chronic stress promotes measurable changes concurrently to the peripheral eCB ligands and the HRV. Methods 13 candidates under intense preparation for their enlistment in the Hellenic Navy SEALs (H.N.S.) participated in the study. All subjects underwent mental state examination, while HRV variables in time and frequency domains recordings were acquired. Furthermore, at baseline and 30 days after prolonged and intensive physical exercise hair were collected in order to measure eCB ligands, such as anandamide (AEA), 2-arachidonoylglycerol (2-AG), and the N-acyl ethanolamine (NAE) molecules: palmitoylethanolamide (PEA) and oleoylethanolamide (OEA). Results Comparing basal hair concentrations of eCB ligands before and after intensive physical exercise, we found that AEA, PEA and OEA were notably increased (p&amp;lt;0.01, p&amp;lt;0.05 and p&amp;lt;0.01 respectively) whereas no differences were observed regarding the ligand 2-AG. Regarding time domain features of HRV, a strong positive correlation was found between mean HR, AEA and PEA [r(13)=0.934, p&amp;lt;0.05, (r(13)=0.902, p&amp;lt;0.05]. Regarding frequency domain, a strong negative correlation was found between low frequency (LF) HRV and PEA (r(13)=−0.853, p&amp;lt;0.01). No statistically significant associations were noted between high frequency HRV and EC ligands. Conclusions These findings suggest that endocannabinoid-HRV interrelations might share a short-term, and long-term adaptability of the changes in self-regulation associated with stress. Further studies are required to determine the validity of peripheral eCB signaling and HRV as a biomarker for different aspects of stress response. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Region of Attica

Resilience of the hellenic navy SEALs assessed by heart rate variability during cognitve tasks

Abstract Background The interaction between high physical performance under extreme conditions and simultaneous control of the cognitive executive functioning has been a subject of research in literature for the past few decades. Stroop test and Heart-rate variability (HRV), have been verified clinical tools for the assessment of cerebral and autonomic/ cardiovascular stress responses respectively. Purpose The investigation of HRV adaptive response to stress and cognitive stress resilience under extremely strenuous conditions. Methods 34 consecutive subjects were enrolled. Of them, 18 were candidates under intense preparation for their enlistment in the Hellenic Navy SEALs (HNS) and 16 were healthy controls (HC). All subjects underwent stroop tasks, along with mental state and personality examination. HRV variables in time and frequency domains recordings were acquired, during each aforementioned cognitive testing procedure. Results HNS's performance on both cognitive and emotion stroop tasks were equivalent to controls. During the size comparison of the number stroop and emotion stroop, HC had statistically significantly higher power content at different HRV frequency bands compared to HNS participants (p=0.036 and p=0.06 respectively). Finally, in a between group comparison of the psychometric tools, HNS had significantly higher somatization (p&amp;lt;0.01), anxiety (p=0.037) and neuroticism (p=0.047) than HC. Correlation was conducted for each group separately, between the psychometric tools and the measurements of HRV for both number and emotion stroop. Moderate negative correlations were found between SDNN (Standard deviation of normal-to-normal RR-intervals) during the size comparison of number stroop and three out of nine categories of psychometric questionnaire; somatization (r(23)=−0.452, p&amp;lt;0.05), anxiety (r(23)=−0.457, p&amp;lt;0.05) and hostility (r(23)=−0.445, p&amp;lt;0.05) Conclusion The above findings suggest that HNS display flexibility in their autonomic regulation during cognitive and emotional tasks. This characteristic is closely related to problem solving or adaptability skills. Additionally, HRV can be a promising clinical index regarding the assessment of psychophysiological resilience especially in the neurovisceral integration (NVI) model. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Region of Attica