RMSSD Values Research Articles

Utility Of Serial Short-time Indices Of HRV And Cardiac Dynamics Throughout The Day

Short-time indices of heart rate variability (HRV) and cardiac regulatory dynamics (CRD) throughout a 24-hr recording may provide an alternative to the collection of a full 24-hr recording, however, methodological approaches need to be further evaluated. PURPOSE: The purpose of this study was to examine the robustness of various methodological approaches of short-time indices of HRV and CRD throughout a 24-hr period. METHODS: Eight healthy males completed two 24-hr visits. R-R intervals were recorded continuously using a heart rate monitor. Measures of HRV include the root mean square of successive R-R intervals (rMSSD) and the standard deviation of R-R intervals (SDNN), while CRD was assessed using sample entropy (SampEn). Each 24-hr recording was separated into 145 epochs to create a new time-series (HRVEP). Length and position of these epochs were varied around every 10th-min: the 3-min before every 10th-min (B3), the 3-min following every 10th-min (A3), the 3-min splitting every 10th-min (S3), and the 5-min splitting every 10th-min (S5). The dimensionality and complexity of each of these epoched profiles were subsequently analyzed. Tests of equivalence (TOST) were used to compare the raw values of rMSSD, SDNN, and SampEn between epoching methods at the individual level while paired TOST tests were used to examine the dynamics of these epoched profiles between epoching methods. RESULTS: TOST test between epoching methods of the raw values for rMSSDEPand SDNNEPat the individual level were equivocal (p≥0.05), whereas SampEnEPshowed equality (p≤0.05). Further analysis of paired TOST test comparing the embedding dimension and complexity of HRVEPshowed inequality in the optimal embedding dimension of these time-series and statistical equality (p≤0.01) between the complexity of these time-series. CONCLUSIONS: Epoch-by-epoch analysis of rMSSDEP and SDNNEP were not equal whereas SampEnEPwas equivalent across epoching methods. Although the optimal embedding dimension of these time-series varied between epoching methods, the complexity of these time-series were similar between methods for all indices of HRVEP.

Cognitive performance and Heart rate variability: The influence of menstrual cycle in young subjects

Menstrual cycle characterized by various dynamic alterations in sex steroidal hormones not only alters the reproductive organs but also various systemic organs and hence higher functions are one among them. This study is an attempt to determine the influence of various hormones on cognitive function using short term heart rate variability analysis in different phases of menstrual cycle. Thirty participants were subjected for the baseline recording of HRV and psychomotor vigilance test and short term memory test along with HRV recording in three subsequent numbers of times to study variations in three different phases of menstrual cycle . Both time domain and frequency domain parameters were studied during resting state and while performing psychomotor vigilance test and short term memory test. The time domain and frequency domain parameters on comparison with resting state to during psychomotor vigilance test and short term memory test parameters were statistically insignificant in all three phases recorded. Unlikely on comparison of heart rate variability parameters both times domain and frequency domain values of RRI, RMSSD and LF (nu) values were statistically significant across the different phases suggesting upper hand of sympathetic tone. The present study indicated increased sympathetic discharge during follicular phase on comparison to luteal and menstrual phase. The results also indicated a change in cognitive functioning during different phases due to hormonal variations.

Involvement of Autonomic Nervous System in New-Onset Atrial Fibrillation during Acute Myocardial Infarction.

Background: Atrial fibrillation (AF) is common after acute myocardial infarction (AMI) and associated with in-hospital and long-term mortality. However, the pathophysiology of AF in AMI is poorly understood. Heart rate variability (HRV), measured by Holter-ECG, reflects cardiovascular response to the autonomic nervous system and altered (reduced or enhanced) HRV may have a major role in the onset of AF in AMI patients. Objective: We investigated the relationship between autonomic dysregulation and new-onset AF during AMI. Methods: As part of the RICO survey, all consecutive patients hospitalized for AMI at Dijon (France) university hospital between June 2001 and November 2014 were analyzed by Holter-ECG <24 h following admission. HRV was measured using temporal and spectral analysis. Results: Among the 2040 included patients, 168 (8.2%) developed AF during AMI. Compared to the sinus-rhythm (SR) group, AF patients were older, had more frequent hypertension and lower left ventricular ejection fraction LVEF. On the Holter parameters, AF patients had higher pNN50 values (11% vs. 4%, p < 0.001) and median LH/HF ratio, a reflection of sympathovagal balance, was significantly lower in the AF group (0.88 vs 2.75 p < 0.001). The optimal LF/HF cut-off for AF prediction was 1.735. In multivariate analyses, low LF/HF <1.735 (OR(95%CI) = 3.377 (2.047–5.572)) was strongly associated with AF, ahead of age (OR(95%CI) = 1.04(1.01–1.06)), mean sinus-rhythm rate (OR(95%CI) = 1.03(1.02–1.05)) and log NT-proBNP (OR(95%CI) = 1.38(1.01–1.90). Conclusion: Our study strongly suggests that new-onset AF in AMI mainly occurs in a dysregulated autonomic nervous system, as suggested by low LF/HF, and higher PNN50 and RMSSD values.

A Contact-Free, Ballistocardiography-Based Monitoring System (Emfit QS) for Measuring Nocturnal Heart Rate and Heart Rate Variability: Validation Study

Background Heart rate (HR) and heart rate variability (HRV) measurements are widely used to monitor stress and recovery status in sedentary people and athletes. However, effective HRV monitoring should occur on a daily basis because sparse measurements do not allow for a complete view of the stress-recovery balance. Morning electrocardiography (ECG) measurements with HR straps are time-consuming and arduous to perform every day, and thus compliance with regular measurements is poor. Contact-free, ballistocardiography (BCG)-based Emfit QS is effortless for daily monitoring. However, to the best of our knowledge, there is no study on the accuracy of nocturnal HR and HRV measured via BCG under real-life conditions. Objective The aim of this study was to evaluate the accuracy of Emfit QS in measuring nocturnal HR and HRV. Methods Healthy participants (n=20) completed nocturnal HR and HRV recordings at home using Emfit QS and an ECG-based reference device (Firstbeat BG2) during sleep. Emfit QS measures BCG by a ferroelectret sensor installed under a bed mattress. HR and the root mean square of successive differences between RR intervals (RMSSD) were determined for 3-minute epochs and the sleep period mean. Results A trivial mean bias was observed in the mean HR (mean –0.8 bpm [beats per minute], SD 2.3 bpm, P=.15) and Ln (natural logarithm) RMSSD (mean –0.05 ms, SD 0.25 ms, P=.33) between Emfit QS and ECG. In addition, very large correlations were found in the mean values of HR (r=0.90, P&lt;.001) and Ln RMSSD (r=0.89, P&lt;.001) between the devices. A greater amount of erroneous or missing data (P&lt;.001) was observed in the Emfit QS measurements (28.3%, SD 14.4%) compared with the reference device (1.1%, SD 2.3%). The results showed that 5.0% of the mean HR and Ln RMSSD values were outside the limits of agreement. Conclusions Based on the present results, Emfit QS provides nocturnal HR and HRV data with an acceptable, small mean bias when calculating the mean of the sleep period. Thus, Emfit QS has the potential to be used for the long-term monitoring of nocturnal HR and HRV. However, further research is needed to assess reliability in HR and HRV detection.

Decreased Task-Related HRV Is Associated With Inhibitory Dysfunction Through Functional Inter-Region Connectivity of PFC in Major Depressive Disorder.

The regulation of the autonomic nervous system (ANS) can improve cognitive function in major depressive disorders (MDD). Heart rate variability (HRV) derives from the dynamic control of the ANS and reflects the balance between the activities of the sympathetic and parasympathetic nervous systems by measuring tiny changes in adjacent heart beats. Task-related HRV may reflect the association between the flexibility of cognition and ANS function. The study was to investigate the neural mechanism of interactions between ANS and cognitive function in MDD with Magnetoencephalography (MEG) measurements. Participants included 20 MDD patients and 18 healthy controls (HCs). All participants were measured with a go/no-go task MEG. HRV indices, the standard deviation of the average normal-to-normal (NN) interval calculated over short periods (SDANN) and the square root of the mean squared differences of successive NN intervals (RMSSD), were derived from the raw MEG data. Results showed that MDD patients showed decreased SDANN and RMSSD. In MDD patients, both resting-state and task-related RMSSD were related to inhibitory and control dysfunction. In the go/no-go task, many areas in the prefrontal cortex (PFC) are responsible for an individual’s inhibitory function. A brain MEG functional connectivity analysis revealed that there were significant differences in four brain regions within the prefrontal cortex (PFC) between MDD patients and HCs. Task-related RMSSD in HCs were related to the functional connectivity between the left middle frontal gyrus and the anterior cingulate cortex (ACC), while in MDD patients, these values were not related to the above functional connectivity but were related to the functional connectivity between the left middle frontal gyrus and insula. However, the resting-state RMSSD value was not related to these significant difference functional connectivity networks in all participants. It concludes that the decreased task-related HRV is associated with inhibitory dysfunction through functional inter-region connectivity in the PFC in MDD, and the task-related HRV can be used as an index of the association between MDD and autonomic dysregulation.

Heart rate variability in sick sinus syndrome: does it have a diagnostic role?

Hypothesis of our study was that the irregular rhythm of sick sinus syndrome (SSS) was characterized by an augmented HRV. Objective was to assess whether SSS patients had a typical HRV profile. We screened all 1947 consecutive Holter ECGs performed in our Units of Vascular Medicine and Internal Medicine and Cardioangiology at the University of Palermo (Italy) from April 2010 to September 2014. Among these, we selected 30 patients with ECG criteria of SSS. They were compared to 30 patients without SSS matched for age, sex and comorbidities. The SSS group had a lower mean heart rate (HR) (P=0.003), and a longer mean NN max-min longer (P<0.0005) compared to control group. SSS group had higher mean pNN50 (P=0.043), mean RMSSD (P=0.006), mean SDNN (P=0.021), and mean SDNNi (P=0.005) as compared with control group. Moreover, HR ≤64.5 bpm, NN max-min>1355 msec, pNN50>16.08, RMSSD>50.2, SDNN>151.94, and SDNNi>71.1 showed a predictive value for diagnosis of SSS. The positivity of all 6 variables according to the aforementioned cut-offs ensured a positive predictive value of 100% and the negativity of all 6 variables had a negative predictive value of 94% for diagnosis of SSS. Among SSS patients, we did not observe any correlation between HR and HRV variables. SSS patients have a HRV profile characterized by: low HR, long NN max-min interval, and elevated pNN50, RMSSD, SDNN and SDNNi values with specific diagnostic cut-offs for diagnosis of SSS. Moreover, we found the absence of correlation between HR and all time-domain HRV variables in SSS patients.

Cardiac biomarkers associated with epilepsy in a captive baboon pedigree.

The epileptic baboon provides a natural model of idiopathic generalized epilepsy and sudden unexpected death in epilepsy (SUDEP). This retrospective, case-controlled study aims to evaluate cardiac biomarkers of epilepsy, specifically QT-interval prolongation and heart rate variability (HRV), in pedigreed, captive baboons undergoing scalp electroencephalography (EEG). We retrospectively identified 21 epileptic (nine females, mean age = 11.4±5.4years) and 19 asymptomatic control (12 females, mean age = 10.5±6.3years) baboons, who had undergone scalp EEG studies with an artifact-free, 10-beat electrocardiogram sample. All baboons were sedated with subanesthetic doses of ketamine prior to electrode placement. PR, QT, and RR intervals were measured, and Fridericia-corrected QT duration (QTcF) and root mean square of successive differences between RR intervals (RMSSD; representative of HRV) values were compared between the groups. The epilepsy group had significantly prolonged QT and QTcF intervals (P=.005) compared to controls. RMSSD values were nonsignificantly decreased in epileptic baboons compared to the control group. This study demonstrates cardiac repolarization anomalies and reduction of HRV in epileptic baboons, providing new cardiac biomarkers in pedigreed baboons and potential risk factors for SUDEP.

Feasibility of pulse rate variability as feedback in closed-loop percutaneous auricular vagus nerve stimulation

Percutaneous auricular vagus nerve stimulation (pVNS) is a novel approach of treating cardiovascular and inflammatory diseases, as well as pain and neurological conditions. The treatment can be optimized by using biosignals as objective measures and feedback-control. One suitable biofeedback could be the use of pulse rate and pulse rate variability (PRV) derived from optical pulse plethysmography (PPG) instead of heart rate and heart rate variability (HRV) derived from electrocardiogram (ECG). For this purpose, a single-lead ECG on the thorax and a PPG on the earlobe were measured simultaneously on 10 healthy subjects for 420 s during three different respiratory phases. The data was analyzed and compared with scatterplots, the Pearson correlation coefficient and a Bland-Altman analysis. The outcomes show a very high correlation of heart rates from PPG and ECG (ri= 0.9663) and SDNN values (rsdnn= 0.9791). Comparison of RMSSD values showed a high positive correlation (rrmssd= 0.7963) but a mean overestimation of 10 ms in RMSSD values measured with the PPG. The results presented suggest that PRV could be and alternative biofeedback used in pVNS.

Heart Rate Variability and Vagus Nerve Stimulation in Epilepsy Patients.

BackgroundVagus nerve stimulation (VNS) exerts a cortical modulating effect through its diffuse projections, especially involving cerebral structures related to autonomic regulation. The influence of VNS on cardiovascular autonomic function in drug-resistant epilepsy patients is still debated. We aimed to evaluate the impact of VNS on cardiovascular autonomic function in drug-resistant epilepsy patients, after three months of neurostimulation, using the heart rate variability (HRV) analysis.MethodologyMultiple Trigonometric Regressive Spectral analysis enables a precise assessment of the autonomic control on the heart rate. We evaluated time and frequency-domain HRV parameters in resting condition and during sympathetic and parasympathetic activation tests in five epilepsy patients who underwent VNS procedure.ResultsWe found appropriate cardiac autonomic responses to sympathetic and parasympathetic activation tests, described by RMSSD, pNN50, HF and LF/HF dynamics after three months of VNS. ON period of the neurostimulation may generate a transient vagal activation reflected on heart rate and RMSSD values, as observed in one of our cases.ConclusionVNS therapy in epilepsy patients seems not to disrupt the cardiac autonomic function. HRV represents a useful tool in evaluating autonomic activity. More extensive studies are needed to further explore cardiac autonomic response after neurostimulation.

Portable health monitoring kit using photolethysmogram signal

&lt;p&gt;This study investigates the feasibility of photoplethysmogram (PPG) signals in monitoring health condition and designing a portable health monitoring kit which is suitable for home use. The aim of this study is to ease people in monitoring their health continuously without the need to go to the hospital which can save a lot of time. The focus of this study is to find heart rate and blood pressure recording. The type of PPG sensor used in this project is a non-invasive PPG which measures the blood volume changes in any part of the body. A total of 16 subjects consisting of male and female with age range of 20 to 60 years old were involved in this research. The heart rate and blood pressure for each subject were acquired and analyzed. Based on the result, it shows that higher heart rate reading is associated with female and younger age groups. Meanwhile, for blood pressure value, male subjects tend to have higher blood pressure as compared to female subjects. However, there is no specific pattern for blood pressure in terms of the age group. In the case of HRV analysis based on Kubios software, the SDNN value is higher for male and older age subjects. Meanwhile, the RMSSD value is lower for male and older age subjects. Therefore, PPG signal has the capability to monitor the health status of an individual, which acts as an alternative biological signal for the existing health monitoring systems.&lt;/p&gt;

Heart rate variability parameters as markers of the adaptation to a sealed environment (a hypoxic normobaric chamber) in the horse.

Simulated hypoxic normobaric devices have been used in human beings in order to enhance endurance capacity. These devices are sealed chambers where the athletes are supposed to stay for at least 6-8hr daily. The current research assesses the changes in time-domain, spectral and non-geometrical heart rate variability (HRV) parameters in 6 horses subjected to progressive duration periods inside of a hermetically sealed chamber. It was pursued, firstly to evaluate the intensity of the stress experienced by the animals and secondly to elucidate whether the horses might require an acclimation period before implementation of hypoxic conditions. HRV parameters were monitored for 6days: day 0 (6-hr duration; in paddocks; basal conditions), and days 1, 2, 3, 4 and 5 (1, 2, 3, 4 and 6hr inside the chamber every day respectively). During day 1 and during the first hours of days 2 and 3, compared to day 0, horses presented increased HR and SDHR values and decreased RR interval duration. SD1 values decreased on some hours of days 2 and 3, but differences with day 0 were not found on day 1. Increased SDNN, RMSSD, SD1 and SD2 values were observed on days 4 and 5. These results showed an activation of the sympathetic activity together with an attenuation of the parasympathetic activity during the days 1 to 3. Increased parasympathetic activity was found only during the first hours of days 4 and 5. Spectral parameters experienced minor variations, with increased LFpeak and LF% during some hours of days 4 and 5. In conclusion, at least 3days are needed to adapt the horse to a sealed environment before starting to subject the animals to hypoxic conditions. When the horses were acclimatized, however, a minor stress was detected with they spent more than 4hr inside of the chamber.

Heart Rate Variability Monitoring During Strength and High-Intensity Interval Training Overload Microcycles.

Objective: In two independent study arms, we determine the effects of strength training (ST) and high-intensity interval training (HIIT) overload on cardiac autonomic modulation by measuring heart rate (HR) and vagal heart rate variability (HRV).Methods: In the study, 37 well-trained athletes (ST: 7 female, 12 male; HIIT: 9 female, 9 male) were subjected to orthostatic tests (HR and HRV recordings) each day during a 4-day baseline period, a 6-day overload microcycle, and a 4-day recovery period. Discipline-specific performance was assessed before and 1 and 4 days after training.Results: Following ST overload, supine HR, and vagal HRV (Ln RMSSD) were clearly increased and decreased (small effects), respectively, and the standing recordings remained unchanged. In contrast, HIIT overload resulted in decreased HR and increased Ln RMSSD in the standing position (small effects), whereas supine recordings remained unaltered. During the recovery period, these responses were reversed (ST: small effects, HIIT: trivial to small effects). The correlations between changes in HR, vagal HRV measures, and performance were weak or inconsistent. At the group and individual levels, moderate to strong negative correlations were found between HR and Ln RMSSD when analyzing changes between testing days (ST: supine and standing position, HIIT: standing position) and individual time series, respectively. Use of rolling 2–4-day averages enabled more precise estimation of mean changes with smaller confidence intervals compared to single-day values of HR or Ln RMSSD. However, the use of averaged values displayed unclear effects for evaluating associations between HR, vagal HRV measures, and performance changes, and have the potential to be detrimental for classification of individual short-term responses.Conclusion: Measures of HR and Ln RMSSD during an orthostatic test could reveal different autonomic responses following ST or HIIT which may not be discovered by supine or standing measures alone. However, these autonomic changes were not consistently related to short-term changes in performance and the use of rolling averages may alter these relationships differently on group and individual level.

Maternal, fetal and neonatal heart rate and heart rate variability in Holstein cattle

ABSTRACT: The aim of this study was to describe the normal values for maternal, fetal and neonatal heart rate (HR) and heart rate variability (HRV) indexes in the time domain (standard deviation of beat-to-beat interval - SDNN; root mean square of successive beat-to-beat differences - RMSSD) and the frequency domain (low frequency - LF; high frequency - HF; relationship between low and high frequency - LF/HF) in 23 Holstein cows, 23 fetuses and 18 neonates during the perinatal period. HR and HRV were calculated by fetomaternal electrocardiography (ECG). Fetomaternal measurements were taken six times prepartum (between days 234 and 279 of pregnancy) and measurements were taken in neonates six times after calving (after birth and five times weekly). HR, time and frequency domain were analyzed. No significant changes in maternal, fetal beat-to-beat interval (RR interval) or HR were found. In maternal variables, SDNN decreased significantly from 38.08±2.6ms (day 14 before calving) to 23.7±2.5ms (day 1 after calving) (p&lt;0.05), but the RMSSD did not change significantly. HR and RR interval of calf differed statistically from the day before delivery (163±7.5bpm; 381±24.2ms) to the day after calving (131±5bpm; 472±16.2ms). Time variables (SDNN and RMSSD) and the frequency-domain variables (LF and HF) were significantly different (p&lt;0.05) between fetal and neonatal stages. Reductions in the values of SDNN and RMSSD can reflect a sympathetic dominance. After calving, the increase in HF and decrease in LF variables can indicate activation of the vagal nerve followed by heart and respiratory modulation.

(191) Stress Dysregulation in Temporomandibular Disorder: A Study on Autonomic Reactivity and Recovery

Mental stress is a common trigger for worsening pain symptoms in temporomandibular disorder (TMD) and related pain conditions. The cumulative effect from dysregulated stress response (reactivity) and stress recovery is a key factor that links stress to chronic diseases. Although dysregulations in major stress systems have been shown in TMD, little is known about physiological recovery after mental stress exposure in TMD. This pilot study aimed to systematically assess differences in heart rate variability (HRV), a physiological marker of stress reactivity and recovery to mental stress in TMD cases and controls. Based on the Diagnostic Criteria for TMD, 26 females (11 controls and 15 cases) were recruited. Participants completed the Trier Social Stress Test (TSST) which consisted of 3 phases: 1) 15 minutes baseline, 2) 15 minutes of stress exposure, and 3) a recovery period lasting up to 60-minute post stress exposure. Time and frequency domain HRV measures were assessed. Mixed-model ANOVA with repeated measure and Friedman test, along with a two-sample t-test and the Wilcoxon rank-sum test, were used when appropriate to test group (2), time (11 time points) and group x time effects on stress reactivity and recovery (alpha = 0.05). At baseline, a group main effect was noted with the control group showing greater values in SDNN, VLF, LF, TP, and LF/HF ratio HRV measures. During stress exposure and recovery phases, a group main effect was observed with the control group expressing greater SDNN, RMSSD, LF, HF, and TP HRV values compared to TMD participants. Post hoc analysis revealed that the largest group differences were observed in the recovery period during minutes 10 to 30. A group x time interaction was not observed for any HRV measure. These results indicated dysregulations in stress reactivity and recovery that both should be considered when develop TMD intervention strategies.

Cardiac autonomic function evaluation in pediatric and adult patients with congenital myasthenic syndromes

Cardiac autonomic dysfunction has been examined in myasthenia gravis but not in congenital myasthenic syndromes (CMS). We aimed to evaluate cardiac autonomic functions in genetically defined CMS. Patients diagnosed with and under treatment for CMS were reviewed for 24-hour cardiac rhythm monitoring. Heart rate variability (HRV) measures were defined as: SDNN, mean of the standard deviations for all R-R intervals; SDNNi, standard deviation of all R-R intervals in successive five-minute epochs; RMSSD, square root of the mean of squared differences between successive R-R intervals. Ten patients with mutations in the epsilon subunit of the acetylcholine receptor (AChRε) and five patients with mutations in the collagen-like tail of asymmetric acetylcholinesterase (ColQ) were included. Median age at evaluation was 17 (2.5–46) years. In the AChRε group, RMSSD values; and in the ColQ group, SDNN, SDNNi and RMSSD values were significantly lower than those of healthy subjects. This first extensive report examining HRV in CMS showed alterations in patients with ColQ mutations and, to a lesser extent, in the group with AChRε mutations. This might indicate an increased risk of cardiac arrhythmias. We suggest cardiological follow-up in CMS, and consideration of any potential cardiovascular effects of therapeutic agents used in management.

ACUTE EFFECTS OF COLD WATER IMMERSION ON CARDIOVASCULAR AND AUTONOMIC RESPONSES

Background: Immersion has been used for many years for therapeutic purposes, but more recently the cardiovascular and authonomic effects appear as an important change in the organism during immersion in the aquatic environment.Objectives: The aim of this study was to investigate the acute effect of water immersion (22.6 °C) on heart rate, heart rate variability, body temperature, oxygen saturation, diastolic blood pressure and systolic blood pressure in young apparently healthy men.Method: Nine apparently healthy males were randomly allocated to an experimental situation (SE) and one control (SC). The SE subjects had the variables measured after the 10 minutes immersion. The subject of the SC remained 10 minutes at rest in the terrestrial environment. After 48h, the procedures were performed the reverse manner to perform balanced input.Results: After 10 minutes of immersion in water was observed reduction in the values of heart rate, significant increases on the RR intervals. The values of RMSSD (ms) increased after immersion, as shown pNN50 (%) and HF index increased (p = 0.009). The ratio (LF / HF) decreased after immersion. Significant differences when comparing the SBP were observed.Conclusions: Thus, is concluded that the immersion in water (22.6º C) increases vagal activity and reduces modulation of the sympathetic branch of the autonomic nervous system.

A New Algorithm to Reduce and Individualize HRV Recording Time.

The aim of the present work was to propose a Smartphone algorithm to analyze, in real time, the evolution of Heart Rate Variability (HRV) in order to individualize and reduce the recording time according to the specificities of each user. During HRV recording, a new RMSSD value is calculated each time a new RR is captured. The recording process stops once an acceptable stability of HRV is reached. This new method was tested on 3 groups of 15 subjects (cardiac patients, sedentary employees and national-level athletes) and compared with the gold standard method (5min HRV recording time). The RMSSD indices provided by the short method and by the gold standard method (respectively 62.1 ± 43.7ms vs. 62.7 ± 44.1ms) showed no significant differences. In addition, a very strong correlation was observed between RMSSD values obtained by the 2 methods (n = 45; R = 0.998; p < 0.001). Routine duration of the new method was significantly shorter with a time-savings of 2min (178 ± 51s vs. 300s; p < 0.05). This new algorithm seems to adapt perfectly to each subject, and it can detect the stability phase for HRV measurements during the recording process. Algorithm provides an adapted and personal routine duration that can evolve each day depending on parameters such as fatigue or stress level that are known to influence HRV. This solution can be easily implemented in a smartphone application and seems particularly suitable for performing daily HRV monitoring in field conditions.

Food Cue Reactivity and the Brain-Heart Axis During Cognitive Stress Following Clinically Relevant Weight Loss

Successful weight loss maintainers are more vulnerable to stress induced eating. The aim of our study was to determine what effect an attention-demanding cognitive performance task had on brain-heart reactivity to visual food cues in women who maintained clinically relevant weight loss vs. women who had never weight cycled. A clinical weight loss group (CWL, n = 17) and a BMI-matched control group (CTL, n = 23) completed modified Stroop tasks that either included high calorie food pictures (Food Stroop) or excluded food cues (Office Stroop). ECG, breathing rate, and EEG were recorded. CWL participants: The Eating Restraint scores (Three Factor Eating Questionnaire) of the CWL participants correlated negatively with their heart rates recorded during the Food Stroop task (r = 0.62, p < 0.01). There was no such relationship in CTL participants. The P200 latencies in CWL participants evoked by the Stroop color-word cues at the C3 electrode were positively correlated to the log high frequency power in their cardiac spectrograms during the Food Stroop (r = 0.63, p < 0.02). There were no such relationships in the Office Stroop task nor in CTL participants. Combined Groups: Participants' heart rates were significantly lower (p < 0.05) and their RMSSD values and the log Total Power in their cardiac spectrograms were significantly greater during the Food Stroop vs. Office Stroop (p < 0.01, Bonferroni corrected). In conclusion Eating Restraint scores in CWL participants correlated with their Stroop heart rates, while the P200 latencies evoked by the Stroop cues correlated with the log high frequency power in their cardiac spectrograms (marker of cardiac vagal activation) during the Food Stroop task. This provides evidence that even 12 months after successful weight loss maintenance the cardiac ANS reactivity to food cues while completing a cognitive performance test was still different to that in individuals of normal weight who never weight cycled. Across all participants the cardiac ANS reactivity evoked by performing the Stroop task was lowered by food cues suggesting that the dampening effect of food cues on cardiac ANS reactivity may be one of the drivers of ‘stress induced' eating.

Efecto agudo de la inmersión en agua fría en las respuestas cardiovasculares y autonómicas

Background: Immersion has been used for many years for therapeutic purposes, but more recently the cardiovascular and authonomic effects appear as an important change in the organism during immersion in the aquatic environment.Objectives: The aim of this study was to investigate the acute effect of water immersion (22.6 °C) on heart rate, heart rate variability, body temperature, oxygen saturation, diastolic blood pressure and systolic blood pressure in young apparently healthy men.Method: Nine apparently healthy males were randomly allocated to an experimental situation (SE) and one control (SC). The SE subjects had the variables measured after the 10 minutes immersion. The subject of the SC remained 10 minutes at rest in the terrestrial environment. After 48h, the procedures were performed the reverse manner to perform balanced input.Results: After 10 minutes of immersion in water was observed reduction in the values of heart rate, significant increases on the RR intervals. The values of RMSSD (ms) increased after immersion, as shown pNN50 (%) and HF index increased (p = 0.009). The ratio (LF / HF) decreased after immersion. Significant differences when comparing the SBP were observed.Conclusions: Thus, is concluded that the immersion in water (22.6º C) increases vagal activity and reduces modulation of the sympathetic branch of the autonomic nervous system.

Recovery Slope of Heart Rate Variability as an Indicator of Internal Training Load

The way in which the Root Mean Square of the Successive Differences between adjacent RR intervals (RMSSD) recovers immediately after exercise could be a good indicator of internal training load (ITL). The aim of this study is to design a recovery index based on RMSSD. Forteen healthy men took part in this study. The experiment lasted 2 weeks, with 4 separate (48 - 72 h) sessions. First session was an incremental treadmill test to determine ventilatory thresholds (VT1 and VT2) and maximal aerobic speed (MAS). Each subject ran at VT1 speed (second day), VT2 speed (third day) and a time-to-exhaustion test at MAS (fourth day). The duration of VT1 and VT2 loads was selected in such a way that the product intensity-duration (training load) was the same. HRV was measured from 10’ prior to test (Rest) to 30’ after completed (Recovery). Recovery slopes were calculated from RMSSD values at 10 and 30 minutes. Borg scale was recorded at the end of every test and the Training Impulse (TRIMP) values were calculated using Banister equations. The RMSSD values dropped substantially regardless of the intensity and the duration of exercise (average 4 ms). The RMSSD recovery was linear during the 30 min and different depending on the intensity of exercise. To propose a recovery index, we calculated the slope of RMSDD over the 30 minutes (slope-30) and also the first 10 minutes (slope-10). Given that the slopes presented an exponential behavior in relation with effort intensity, three curves were obtained (average values, plus SD and minus SD) defining a nomogram. For practical application, we propose: 1) to measure RMSSD the last 5 minutes of exercise and any period of 5 minutes during the first 30 minutes recovery; 2) to calculate the slope of RMSSD between exercise and recovery; 3) to compare with the nomogram.