Is cardiac autonomic function associated with cardiorespiratory fitness and physical activity in children and adolescents? A systematic review of cross-sectional studies

Assessment of Cardiorespiratory Fitness in 8-to-15-Year-Old Children with Overweight/Obesity by Three-Minute Step Test: Association with Degree of Obesity, Blood Pressure, and Insulin Resistance

OBJECTIVE

To assess cardiorespiratory fitness in children and adolescents with overweight/obesity using the Kasch pulse recovery (KPR) test, and its correlation with severity of obesity, insulin resistance, and blood pressure (BP).

METHODS

This is a retrospective analysis of baseline data from a study evaluating the efficacy of yoga for reduction of body mass index (BMI) in children aged 8-15 y with overweight/obesity. KPR three-minute step test was done. Children were classified into cardiorespiratory fitness categories based on the post-KPR heart rate (HR); the maximal oxygen consumption (VO2 max) was calculated, and the correlation analysis was done.

RESULTS

One hundred fifty-five children with mean age of 11.6 ± 1.8 y and mean BMI of 26.2 ± 4.1 kg/m2 were included. Mean post-KPR-HR and calculated VO2 max were 119 ± 14 per minute and 48.7 ± 5.6 mL/kg/min, respectively. In children < 13 y, cardiorespiratory fitness was excellent or very good in 28%, good or sufficient in 58%, and poor or very poor in 14%. BMI, waist circumference (WC), resting HR, systolic BP, and homeostatic model of insulin resistance (HOMA-IR) were higher among those with poor/very poor fitness, with WC z score being statistically significant (p = 0.015). Post-KPR-HR showed positive correlation with BMI z score (r = 0.16, p = 0.044), WC z score (r = 0.21, p = 0.011), and HOMA-IR (r = 0.22, p = 0.012).

CONCLUSION

In children with overweight/obesity, 14% had poor cardiorespiratory fitness. Post-KPR-HR and calculated VO2 max had good correlation with measures of obesity and HOMA-IR. Further studies evaluating cardiorespiratory fitness and normative data of VO2 max for Indian children are warranted.

Trajectories of cardiorespiratory fitness from childhood to adolescence: Findings from the QUALITY cohort

Estimate the shape and number of cardiorespiratory fitness (CRF) trajectories from childhood to adolescence; and verify whether CRF trajectory membership can be predicted by sex, biological maturation, body weight, body composition and physical activity (PA) in childhood. Data from QUALITY were used. Participants attended baseline (8-10 y old, n = 630) and follow-ups 2 years (n = 564) and 7 years (n = 359) after baseline. Group-based trajectory analysis for relative peak oxygen consumption (VO2peak, ml·kg-1·min-1) was performed. A multinomial logistic regression model was used to estimate the associations between baseline predictors and trajectory membership. Mean age of the 454 participants was 9.7 ± 0.9 years at baseline. Three distinct VO2peak trajectories were identified and all tended to decrease. They were labelled according to the starting point and slope. High-Decreasers were mostly boys, had lower body weight and fat-free mass index and higher PA levels at baseline (p < 0.05). Female sex and higher weight were associated with higher odds of being classified in the Low-Decreaser trajectory (OR = 74.03, 95%CI = 27.06-202.54; OR = 1.48, 95%CI = 1.36-1.60). Those with higher PA were less likely to be Low-Decreasers (OR = 0.96, 95%CI = 0.94-0.97). Sex, body weight and PA in childhood are important influencing factors of VO2peak (ml·kg-1·min-1) trajectories across adolescence.

Heart Rate Variability and Cardiorespiratory Fitness in Youth Populations: The Impact of Heart Rate on Data Analysis

The positive association between heart rate variability and cardiorespiratory fitness in youth populations is unclear. In this regard, several methodological aspects related to heart rate variability analysis could partially explain the disagreement between studies. To the best of the authors’ knowledge, the influence of the heart rate on data analysis is unclear. In the present short communication, we discuss the impact of the heart rate on the associations between heart rate variability and cardiorespiratory fitness in youth. In addition, we proposed some aspects that should be considered for statistical analyses when the relationship between heart rate variability and cardiorespiratory fitness is studied. Finally, we should acknowledge that these recommendations may be applicable for other health-related outcomes different than cardiorespiratory fitness (e.g., inflammatory markers, cognition, cardiovascular disease status).

A Recreational Swimming Intervention during the Whole School Year Improves Fitness and Cardiometabolic Risk in Children and Adolescents with Overweight and Obesity

The benefits of swimming as a treatment for overweight children are undefined. We investigated the effects of recreational swimming on cardiometabolic risk in children/adolescents with normal and excess weight. Participants (n = 49, 26 girls, 10.3 ± 1.8 y) were grouped as 'eutrophic swimming' (EU-Swim, n = 14); 'excess weight swimming' (EW-Swim, n = 20) with an 'obese swimming' subgroup (OB-Swim, n = 10); and 'excess weight sedentary' (EW-Sed, n = 15) with an 'obese sedentary' subgroup (OB-Sed, n = 11). Swimming (50 min, twice/week, moderate-vigorous intensity) was an extra activity during the school year (6 + 3 months with a 3-month school break). Nutritional status, blood pressure (BP), physical activity, cardiorespiratory fitness, biochemical variables, autonomic modulation, endothelial function, abdominal fat, and carotid thickness were assessed at baseline, 6, and 12 months. Greater improvements (p < 0.05) occurred in EW-Swim vs. EW-Sed in body mass index (z-BMI, -16%, d+ 0.52), waist-to-height ratio (W/H, -8%, d+ 0.59-0.79), physical activity (37-53%, d+ 1.8-2.2), cardiorespiratory fitness (30-40%, d+ 0.94-1.41), systolic BP (SBP, -6-8%, d+ 0.88-1.17), diastolic BP (DBP, -9-10%, d+ 0.70-0.85), leptin (-14-18%, d+ 0.29-0.41), forearm blood flow (FBF, 26-41%, d+ 0.53-0.64), subcutaneous fat (SAT, -6%, d+ 0.18), and intra-abdominal fat (VAT, -16%, d+ 0.63). OB-Swim showed improvements vs. OB-Sed in TNFα (-17%, d+ 1.15) and adiponectin (22%, d+ 0.40). Swimming improved fitness and cardiometabolic risk in children/adolescents with overweight/obesity. (TCTR20220216001).

Effects of long-term exercise training on physiological signals and personality traits in women in law enforcement

Law enforcement teams across the globe experience the highest occupational stress and stress-related diseases. Physical exercise and an active lifestyle are recommended as part of their profession to equip them to fight stress and related health adversities. The research is carried out using objective measures of Heart Rate Variability (HRV), Electro Dermal Activity (EDA), Heart Rate Recovery (HRR), and subjective questionnaires. HRV was generated with an electrocardiogram (ECG) signal acquired using NI myRIO 1900 interfaced with the Vernier EKG sensor. HRR was acquired with the help of a Polar chest strap exercise heart rate monitor and EDA acquisition was carried out with Mindfield E-Sense electrodes. Then statistical features are extracted from the collected data, and feed to the AQCNN (Aquila convolution neural network) classifier to predict the stress. Signal analyses were done in Kubios 4.0, Ledalab V3.x in a MATLAB environment. The results pointed out that exercise training is effective in increasing the vagal tone of the Autonomic Nervous System (ANS) and hence improves the recovery potential of the cardiovascular system from stress. The proposed AQCNN method improves the accuracy of 95.12% which is 93.13%, 85.36% and 80.13% better than MANOVA technique, CNN and ML-SVM respectively. The findings have the potential to influence decision-making in the selection and training of recruits in high-stress positions, hence optimizing the cost and time of training by identifying maladaptive recruits early.

Comprehensive cardiac evaluation to maximal exercise in a contemporary population of prepubertal children

BACKGROUND

Heart rate (HR) is a biomarker used to measure physiological function, health status and cardiovascular autonomic function. The purpose of this study was to determine sex- and age-specific reference values for cardiac autonomic function at rest, during maximal exercise and the recovery phase in prepubertal children.

METHODS

Five hundred and twelve healthy children 7-11 years of age performed a Léger test. A heart RR-interval monitor recorded the heart data and a specific software analysed the cardiac autonomic response through HR and HR variability (HRV). It analysed HR before the test (resting HR, RHR), during the test (HR_peak) and HR recovery (HRR) in the first minute (HRR1) and the fifth minute (HRR5). The values are mean ± SD.

RESULTS

Collectively, 91.2% of girls and 92.3% of boys were within the recommended ranges regarding RHR. The average HR_peak was 199 ± 10.83 b.p.m. and 96.8% of girls and 95.3% of boys were within the minimum threshold value recommended (180 b.p.m.). Boys showed lower values of RHR than girls (p < 0.001) and larger values of HRR 1 and HRR5 (p < 0.001).

CONCLUSIONS

This study comprehensively provides a reference set of data for the most important HR variables that can be obtained during exercise testing in prepubertal children regarding age and sex and in a field setting.

IMPACT

This is the first study to provide reference values of autonomic cardiac function at rest, during maximal exercise and during the recovery period in prepubertal children aged 7-11 years. Despite the early age of participants, cardiorespiratory fitness, RHR and HRR are different according to sex. Aerobic performance and HR_peak have a negative correlation with body mass index and cardiometabolic risk.

Reading with induced worry: The role of physiological self-regulation and working memory updating in text comprehension

BACKGROUND

An interplay of emotional and cognitive aspects underlies academic performance. We focused on the contribution of such interplay to text comprehension.

AIMS

We investigated the effect of worry on comprehension and the role of two potential moderators of this effect: physiological self-regulation as resting heart rate variability (HRV) and working memory updating.

SAMPLE

Eighty-two seventh graders were involved in a quasi-experimental design.

METHODS

Students read an informational text in one of two reading conditions: to read for themselves to know more (n = 46; low-worry condition) or to gain the highest score in a ranking (n = 36; high-worry condition). Students' resting HRV was recorded while watching a video of a natural scenario. The executive function of working memory updating was also assessed. After reading, students completed a comprehension task.

RESULTS

Findings revealed the moderating role of HRV in the relationship between induced worry and text comprehension. In the high-worry condition, students with higher resting HRV performed better than students who read under the same instructions but had lower HRV. In contrast, in the low-worry condition, students with higher resting HRV showed a lower performance as compared to students with lower HRV. Finally, working memory updating was positively related to text comprehension.

CONCLUSIONS

Our findings indicate that the cognitive component of anxiety, that is, worry, plays a role in performing a fundamental learning activity like text comprehension. The importance of physiological self-regulation emerges clearly. In a condition of high worry, higher ability to regulate emotions and thoughts acts as a protective factor.

Using compositional analysis to explore the relationship between physical activity and cardiovascular health in children and adolescents with and without type 1 diabetes

OBJECTIVE

The aim of this study was to use a compositional analysis approach to account for the inherent co-dependencies between behaviors and to explore how daily movement behaviors influence cardiovascular health in children with and without T1D.

RESEARCH DESIGN AND METHODS

Augmentation index, pulse wave velocity (PWV) and heart rate variability were measured in 20 children with (11.9 ± 1.6 years) and 17 children without T1D (11.6 ± 2.2 years). Subsequently, physical activity and sleep were assessed at 20 Hz for 28 consecutive days using a wrist-worn accelerometer. Compositional analyses were utilized to explore the relative effects of each movement behavior and the overall movement complex on cardiovascular parameters, with predictive modeling used to explore the effects of reallocating 20 min between behaviors.

RESULTS

Arterial stiffness markers were most influenced by the total movement composition, whereas autonomic function was most influenced by sedentary time and sleep relative to all other behaviors. Reallocation of time from moderate-to-vigorous physical activity (MVPA) to any other behavior was predicted to negatively affect all cardiovascular measures, independent of disease status, whereas reallocating time to MVPA was consistently predicted to improve all outcome measures. Additionally, the same intensity of physical activity appeared to be more potent for cardiovascular health in T1D children compared to nondiabetic peers.

CONCLUSIONS

Intensity, rather than volume, of physical activity may be key in reducing risk of premature adverse changes in cardiovascular health, whereas increasing time in MVPA could potentially the slow progression of cardiovascular aging in children with diabetes.

Effects of Screen Time and Season on Cardiovascular System Indicators in Primary Schoolchildren

Indicators of the cardiovascular system, including heart rate (HR) and blood pressure (BP) variability parameters, were analyzed in primary school students with different computer screen times. The study included 4084 students of grades 1–4 (age 7–12 years) from 66 Moscow schools. The screen time at school and out of school was assessed by teachers, based on the national Sanitary Rules and Regulations: 0, no screen time; 1, screen time matching hygienic standards; 2, screen time at least twice greater than recommended. Physiological examinations were carried out by spiroarteriocardiorhythmography with a face mask, the conditions corresponding to the functional stress test (mild hypercapnia/hypoxia). Testing took place in spring and autumn (independent samples). Statistical data processing was performed using nonparametric criteria. It was revealed that the introduction of computer technologies in school lessons within the limits of hygienic standards was accompanied by an increase, within the normal range, of systolic BP in girls at the end of grade 2 and 4 and in boys at the beginning and end of grade 4. Screen time at least twice higher than the hygienic standard did not have an additional effect on BP, but provoked shifts in the function of autonomic regulation. Boys were more sensitive to the influence of this environmental factor. Their pattern of seasonal variability in total power (TP) of the HR variability spectrum was reversed compared to that of children who did not use computers at school; i.e., higher TP values were observed in spring. In grade 4, the process was accompanied by an increase in spontaneous arterial baroreflex sensitivity and a decrease in the relative power of the LF range in the variability spectrum of systolic BP. The changes were assumed to reflect the adaptive response to changes in educational environment.

Influence of Chronic Exposure to Exercise on Heart Rate Variability in Children and Adolescents Affected by Obesity: A Systematic Review and Meta-Analysis

Background: Sedentary lifestyles are increasingly common amongst children, and insufficient physical activity is a global epidemic estimated to contribute to future incapacities and potential deaths. Objective: We aimed to increase the amount of evidence concerning the effect of chronic exposure to exercise on heart rate variability in children and adolescents affected by obesity. Methods: A systematic review commenced following the PRISMA guidelines developed by Web of Science, Virtual Health Library, PubMed, Cochrane Library, Embase, Ovid, Medline Complete, and Scopus using keywords obtained from the Descriptors in Health Sciences and Medical Subject Headlines (MeSH) terms. We considered (1) Population: Pediatric individuals affected by obesity; (2) Intervention: Exercise; (3) Control: Pre-intervention and sedentary; (4) Outcomes: Clearly presented primary parameters; and (5) Studies: Clinical trials, case controls, case reports, and case series. Results: 11 articles were involved and predominantly included procedures observed during approximately 12 weeks with a distribution of three sessions per week, each session being 30–60 min of aerobic exercise; additionally, the exercise grades were typically completed at a percentage of subjects’ maximum heart rates. The meta-analyses displayed a significant effect on the domains of time (R-R interval, SDNN, rMSSD), frequency (HF ms², HF (n.u.), LF/HF), and the non-linear index (SD1). Conclusions: Chronic exposure to exercise influences heart rate variability in children and adolescents affected by obesity by elevating the variability and parasympathetic activity and improving the sympathetic-vagal balance. Exercises should be recommended for the improvement of cardiac autonomic modulation to prevent the likelihood of further chronic diseases.

Heart rate variability improves in 3-5-year-old children following a 6-month physical activity-based intervention: the Active Early Learning (AEL) cluster randomised controlled trial

Heart rate variability (HRV) measurement provides non-invasive assessment of autonomic stability and cardiometabolic disease risk. Insufficient physical activity in early childhood may contribute to negative cardiometabolic health. The Active Early Learning (AEL) study was a 6-month randomised controlled trial investigating the effects of a physical activity-based program incorporating movement within the daily curriculum of preschool children. The current study assessed the effects of the AEL intervention on HRV as a measure of cardiac vagal control. Children aged between 3-5 years and enrolled in a preschool with an attendance of ≥15 children were eligible. Physical activity was recorded using an Actigraph wGT3x accelerometer worn at the waist of participants over 3 consecutive days. A Polar H10 chest strap measured HRV with the HF-band and RMSSD representing cardiac vagal control. After 6 months of the AEL trial, linear mixed model analyses revealed a significant intervention effect for increased HF (p = 0.044). The control group did not demonstrate changes in cardiac vagal control after the intervention ceased. Independent of age, sex, physical activity and BMI, the AEL study elicited significant improvements in the cardiac vagal control of participants who received the intervention. Findings highlight the importance of investigating HRV for assessing the cardiometabolic health in young children. ANZCTR trial registration number: ACTRN12619000638134. Novelty: The AEL curriculum improved child HRV independent of age, sex, physical activity and BMI. Heart rate and RR intervals did not demonstrate changes for the intervention and control groups. Multivariate programs for developing physical competence, confidence, knowledge and motivation may improve child health.

Analysis of Gender Differences in HRV of Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Using Mobile-Health Technology

In a previous study using mobile-health technology (mHealth), we reported a robust association between chronic fatigue symptoms and heart rate variability (HRV) in female patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). This study explores HRV analysis as an objective, non-invasive and easy-to-apply marker of ME/CFS using mHealth technology, and evaluates differential gender effects on HRV and ME/CFS core symptoms. In our methodology, participants included 77 ME/CFS patients (32 men and 45 women) and 44 age-matched healthy controls (19 men and 25 women), all self-reporting subjective scores for fatigue, sleep quality, anxiety, and depression, and neurovegetative symptoms of autonomic dysfunction. The inter-beat cardiac intervals are continuously monitored/recorded over three 5-min periods, and HRV is analyzed using a custom-made application (iOS) on a mobile device connected via Bluetooth to a wearable cardiac chest band. Male ME/CFS patients show increased scores compared with control men in all symptoms and scores of fatigue, and autonomic dysfunction, as with women in the first study. No differences in any HRV parameter appear between male ME/CFS patients and controls, in contrast to our findings in women. However, we have found negative correlations of ME/CFS symptomatology with cardiac variability (SDNN, RMSSD, pNN50, LF) in men. We have also found a significant relationship between fatigue symptomatology and HRV parameters in ME/CFS patients, but not in healthy control men. Gender effects appear in HF, LF/HF, and HFnu HRV parameters. A MANOVA analysis shows differential gender effects depending on the experimental condition in autonomic dysfunction symptoms and HF and HFnu HRV parameters. A decreased HRV pattern in ME/CFS women compared to ME/CFS men may reflect a sex-related cardiac autonomic dysfunction in ME/CFS illness that could be used as a predictive marker of disease progression. In conclusion, we show that HRV analysis using mHealth technology is an objective, non-invasive tool that can be useful for clinical prediction of fatigue severity, especially in women with ME/CFS.

Daily physical activity, cardiorespiratory fitness, nutritional status, endothelial function, and autonomic modulation in school-age adolescents: A principal component analysis

PURPOSE

This study evaluated the association between cardiorespiratory fitness, abdominal obesity, blood pressure, endothelial function, and autonomic modulation in school-age adolescents exhibiting different levels of habitual physical activity and nutritional status, through a multivariate statistical approach.

METHODS

101 adolescents aged 15-18 years (54 females) underwent assessments of daily physical activity, body mass index, cardiorespiratory fitness, reactive hyperemia, and heart rate variability. Based on BMI adjusted for age and sex (z-BMI), 21 adolescents were classified as 'overweight' (9 girls), and 9 as 'obese' (4 girls). The common variation between those variables was assessed through Principal Component Analysis (PCA).

RESULTS

Main axis of common variation of outcomes analyzed defined four principal components (PCs) accounting for 69.7% of overall variance, related to 'abdominal obesity and blood pressure' (PC1; eigenvalue=2.76), 'cardiorespiratory fitness, endothelial function, and autonomic modulation' (PC2, eigenvalue=1.98), 'cardiorespiratory fitness' (PC3, eigenvalue=1.21), and 'sedentary behavior' (PC4, eigenvalue=1.02). Girls reported longer screen time and sedentary behavior than boys. Notwithstanding, in both sexes poorer cardiorespiratory fitness corresponded to lower reactive hyperemia and vagal modulation, irrespective of the nutritional status. Overall, adolescents classified as 'obese' and 'sedentary' exhibited poorer CRF concomitantly to autonomic and endothelial dysfunctions.

CONCLUSION

In school-age adolescents, endothelial and autonomic dysfunctions related to poor cardiorespiratory fitness, irrespective of the nutritional status and physical activity level. However, endothelial and autonomic dysfunctions were more prevalent among adolescents combining poor cardiorespiratory fitness, reduced levels of daily physical activity, and overweight/obesity.

Physical activity is associated with lower pulsatile stress but not carotid stiffness in children

The cardiovascular disease (CVD) process may begin early in life when accompanied by atherosclerotic risk factors. CVD risk factors in children are associated with stiffening of the large elastic arteries, a reflection of subclinical atherosclerosis. Physical activity is a preventative lifestyle strategy that may benefit arterial stiffness by attenuating the hemodynamic stress on the artery wall. This study examined the relations between physical activity, carotid pulsatile stress, and carotid stiffness in children. One hundred and forty children (9-11 yrs; 50.0% male, 57.9% African American, 42.10% Caucasian, body mass index (BMI) 20.1±4.7 kg/m²) participated in this study. Physical activity counts were measured using a wrist-worn accelerometer and averaged over 7 days. Carotid artery β-stiffness and pulse pressure (calibrated to brachial mean and diastolic pressure) were assessed as via ultrasound and tonometry, respectively. Pulsatile stress was calculated as the product of carotid pulse pressure and heart rate. Physical activity counts were correlated with pulsatile stress (r= -0.27), and BMI (r= -0.23), but were unrelated to carotid stiffness. In multivariate models, associations between physical activity counts and pulsatile stress remained (B= -1.3 [95%CI, -2.4, -0.2], β= -0.20, p<0.05) after covariate adjustment for age, race, sex, pubertal stage and BMI. Carotid pulsatile stress was related to regional carotid stiffness (r=0.45, p<0.05). These data suggest that higher levels of physical activity at young age are associated with lower hemodynamic stress in the carotid artery. Findings are discussed in the context of an inverse relationship between hemodynamic pulsatile stress and carotid stiffness in children.

Birth weight and heart rate autonomic recovery following exercise in healthy term-born adults

The impact of birth weight (BW) on adult health has been studied, related to the autonomic nervous system, and implicated in cardiovascular risk. We investigated cardiorespiratory and heart rate (HR) autonomic recovery after moderate effort in healthy term-born adults with different BWs. We studied 28 healthy physically active women aged between 18 to 30 years split equally into two groups according to BW: G1 (n = 14), BW between 2500 g and 3200 g and G2 (n = 14), BW > 3200 g. The groups remained seated at rest for 15 min, followed by aerobic exercise on a treadmill (five minutes at 50–55% of maximum HR and 25 min 60–65% of maximum HR) and then remained seated for 60 min during recovery from the exercise. Cardiorespiratory parameters and HR variability (HRV) [RMSSD, HF (ms²)] were assessed before and during recovery from exercise. In G1, HR was increased from 0 to 20 min after exercise whilst in G2 HR was higher from 0 to 7 min following exercise. In G1, short-term HRV was increased from 5 to 10 min after exercise but in G2 it recovered prior to 5 min following effort. In conclusion, healthy term-born women with low normal BW present slower HR autonomic recovery after exercise.

Effect of Equine-Assisted Activities on Cardiac Autonomic Function in Children with Cerebral Palsy: A Pilot Randomized-Controlled Trial

Objective: Children with cerebral palsy (CP) have an impaired cardiac autonomic function. Attenuated heart rate recovery (HRR), which is a valuable prognostic parameter for autonomic nervous system, is known to be associated with an increased risk of cardiovascular events and all-cause mortality. However, only few studies have observed the effects of exercise on the cardiac autonomic function in children with CP. The purpose of this pilot study was to examine the effects of equine-assisted activity (EAA) program on cardiac autonomic function in children with CP. Design: A single-blinded, parallel, two-arm pilot trial with 1:1 randomization to the EAA or control group. Setting: A tertiary university hospital and a local arena. Subjects: Twenty-six children with CP (Gross Motor Function Classification System Levels I-II). Intervention: Each lesson of the EAA program for the EAA group was conducted for 40 min twice a week, and the whole program duration was 16 weeks (a total of 32 sessions). Outcome measures: A graded exercise test was performed to measure the resting heart rate (RHR), HRR, and peak oxygen uptake (VO_2peak) on both groups before and after the 16-week period. Results: The autonomic nervous function measured by the response of HRR improved at 1 min (p < 0.009), 3 min (p < 0.001), and 5 min (p < 0.004) only in the EAA group. RHR significantly improved in the EAA group (p < 0.013), whereas the VO_2peak did not significantly differ between the two groups. Conclusion: The HRR and RHR of the children with CP improved after completing the 16-week EAA program. The results demonstrated that the program had a positive effect on the improvement of cardiac autonomic function in these patients. Clinical Trial Registration Number: NCT03870893.

The Impact of Thyroid Diseases on the Working Life of Patients: A Systematic Review

Thyroid diseases are characterized by a wide range of physical and mental symptoms that can affect biological function, emotional and social life of patients. However, their impact on work functioning is not yet fully understood. Therefore, this review aims to address the way in which thyroid diseases can affect occupational outcomes, i.e., the employment rate, sick leave, working capacity and work income of patients. A systematic review of Pubmed, Scopus and ISI Web of Knowledge databases has been performed. Although it is not possible to extrapolate precise data for benign pathologies, about a third of the survivors of thyroid cancer could be unemployed. Hyperthyroid and hypothyroid patients presented a greater risk of long-term sick leave than controls, depending on the severity of the disease. Hyperthyroidism impaired working ability in about a third of affected patients, particularly in cases complicated by orbitopathy with diplopia. A possible influence of thyroid diseases on various occupational outcomes emerged from our review, however further research seems necessary to understand the relationship between work problems, specific pathological characteristics over time and risk factors in the workplace. This may support a comprehensive, interdisciplinary management of thyroid disorders, with benefits for patients’ personal, social and professional life.

Role of Type and Volume of Recreational Physical Activity on Heart Rate Variability in Men

The aim of this study was to investigate the effect of recreational aerobic physical activity (PA) type and volume on heart rate variability (HRV) in Arab men. This was a retrospective, cross-sectional study, and included men (n = 75, age = 37.6 ± 7.1 years, body mass index (BMI) = 26.7 ± 3.1 kg/m²) who were members of a walking group, cycling group, or were inactive controls. Monthly distances from the past three months were obtained from walking and cycling groups, and the volume of PA was classified into three subgroups (high, moderate, low). HRV was measured using a computerized electrocardiographic data acquisition device. R–R interval recordings were performed while participants rested in a motionless supine position. RR intervals were recorded for 15 minutes, and a five-minute segment with minimal ectopic beats and artifacts was selected for HRV analysis. Time-domain parameters included the mean R–R interval, standard deviation of the mean R–R interval (SDNN), and root-mean-squared difference of successive RR intervals (RMSSD). The frequency-domain parameters included high-frequency power (HF), low-frequency power (LF), and LF to HF ratio (LF/HF). Results showed that there were no significant differences between walking, cycling, and control groups for all HRV parameters. Time-domain analyses based on PA volume showed that age-adjusted SDNN for the high-active group was greater than the low-active group (P = 0.03), and RMSSD for the moderate-active group was greater than the control group (P = 0.009). For the frequency domain, LF for the high-active group was greater than the low-active and control groups (P = 0.006), and HF for the moderate-active group was greater than the low-active group (P = 0.04). These data indicate that walking >150 km per month, or cycling >100 km per month at a speed >20 km/h may be necessary to derive cardiac autonomic benefits from PA among Arab men.

Associations of cardiometabolic risk factors with heart rate variability in 6- to 8-year-old children: The PANIC Study

BACKGROUND

Associations of cardiometabolic risk factors with heart rate variability (HRV) in children are unclear. We examined associations of cardiometabolic risk score (CRS) and individual cardiometabolic risk factors with HRV variables in 6- to 8-year-olds.

METHODS

The participants were a population-based sample of 443 children participating in baseline measurements of the Physical Activity and Nutrition in Children trial. Cardiometabolic risk factors included waist circumference (WC), insulin, glucose, triglycerides, HDL cholesterol, systolic blood pressure (SBP), and diastolic blood pressure (DBP). CRS was calculated as WC + insulin + glucose + triglycerides - HDL cholesterol + the mean of SBP and DBP. HRV variables (SDNN, RMSSD, HF, LF, LF/HF, Mean RR) were measured using 5-minute electrocardiography at rest and analyzed using the Kubios HRV software. In this cross-sectional study, associations of CRS and individual cardiometabolic risk factors with HRV were investigated using linear regression analyses adjusted for sex and peak height velocity.

RESULTS

CRS was negatively associated with RMSSD, HF, Mean RR (P value < .05) and positively with LF/HF (P value = .005). Insulin was negatively associated with SDNN, RMSSD, HF, LF, and Mean RR (P value < .05) and positively with LF/HF (P value = .008). SBP was negatively associated with SDNN, RMSSD, HF, LF, and Mean RR (P value < .05). DBP was negatively associated with SDNN, RMSSD, and Mean RR (P value < .05). WC, glucose, triglycerides, or HDL cholesterol were not associated with HRV variables.

CONCLUSIONS

Higher CRS, insulin, and blood pressure were associated with smaller HRV, mainly indicating lower parasympathetic activity, in young children. This knowledge may help improving the clinical management of metabolic syndrome and cardiovascular diseases since childhood.

The Impact of Shift-Work and Night Shift-Work on Thyroid: A Systematic Review

Thyroid hormones are regulated by the pituitary thyroid stimulating hormone (TSH), whose secretion presents a circadian rhythmicity. Indeed, it is conceivable that shift- and night shift-work, affecting sleep-wake rhythms, may impact thyroid functionality. Therefore, the aim of the present review was to provide an overview on the association between shift- and night shift-work and thyroid hormonal changes and disease development. A systematic review of studies available in PubMed, Scopus, and ISI Web of Science databases was performed. A positive association between night shift-work and increased TSH concentrations was reported by most of the reviewed investigations. Inconclusive evidence was available on thyroid diseases. However, the limited number of studies, the noticeable heterogeneity in the shift-work scheduling, in terms of amount, duration, type of shift- or night shift-work, prevents easily integrating findings and extrapolating definite conclusions. Further investigation seems necessary to better define the relationship between shift schedules and different thyroid outcomes, and possible long-term implications of early functional changes. Overall, this may support the adoption of advanced risk assessment and management strategies aimed to achieve a safer workplace organization and a timely, responsible realization of all the benefits of a 24-h economy.

Identifying poor cardiorespiratory fitness in overweight and obese children and adolescents by using heart rate variability analysis under resting conditions

Background: Childhood obesity, including overweight, continues increasing worldwide affecting health expectancy, quality of life and healthcare expenditure. These subjects have higher probability of suffering or developing cardio metabolic risk factors. Recent studies have revealed cardiorespiratory fitness (CRF) as a valuable clinical parameter to identify these subjects and have even suggested cut-off values. However, evaluating CRF in overweight and obese youth can be difficult to implement, unfriendly and expensive.Objective: Develop a screening tool to identify high-risk subjects in a representative population of those attending overweight/obesity assessment programmes without prior intervention. It will be based on heart rate variability parameters, which has strong association with CRF and cardio metabolic risk factors.Methods: Sixty-three subjects, overweight and obese, between 9 and 17 years of age, and of both sexes were enrolled. None of them had secondary obesity syndromes and/or suffered from acute or chronic disease. Anthropometric parameters, electrocardiogram signal recording under resting conditions and cardiorespiratory fitness - evaluated by oxygen consumption and time elapsed of cardiopulmonary exercise test - were measured.Results: Significant differences in the sympathetic nervous system activity - assessed by heart rate variability analysis - are observed when grouping by overweight and obesity degree as well as by CRF (poor/normal). Body mass index, puberty and sympathetic nervous system activity are the significant variables of a logistic regression model develop to identify poor CRF individuals. Its accuracy reaches 92%.Conclusions: A screening tool based on heart rate variability and anthropometric parameters was developed to identify subjects with higher probability of suffering or developing cardio metabolic risk factors.

Associations of physical activity, sedentary time, and cardiorespiratory fitness with heart rate variability in 6- to 9-year-old children: the PANIC study

Purpose

To study the associations of physical activity (PA), sedentary time (ST), and cardiorespiratory fitness (CRF) with heart rate variability (HRV) in children.

Methods

The participants were a population sample of 377 children aged 6–9 years (49% boys). ST, light PA (LPA), moderate PA (MPA), vigorous PA (VPA), and moderate-to-vigorous PA (MVPA), and PA energy expenditure (PAEE) were assessed using a combined heart rate and movement sensor, maximal power output per kilograms of lean body mass as a measure of CRF by maximal cycle ergometer exercise test, and HRV variables (SDNN, RMSSD, LF, and HF) using 5 min resting electrocardiography. Data were analysed by linear regression adjusted for years from peak height velocity.

Results

In boys, ST was inversely associated (β = − 0.185 to − 0.146, p ≤ 0.049) and MVPA, VPA, PAEE, and CRF were directly associated (β = 0.147 to 0.320, p ≤ 0.048) with HRV variables. CRF was directly associated with all HRV variables and PAEE was directly associated with RMSSD after mutual adjustment for ST, PAEE, and CRF (β = 0.169 to 0.270, p ≤ 0.046). In girls, ST was inversely associated (β = − 0.382 to − 0.294, p < 0.001) and LPA, MPA, VPA, MVPA, and PAEE were directly associated with HRV variables (β = 0.144 to 0.348, p ≤ 0.049). After mutual adjustment for ST, PAEE, and CRF, only the inverse associations of ST with HRV variables remained statistically significant.

Conclusions

Higher ST and lower PA and CRF were associated with poorer cardiac autonomic nervous system function in children. Lower CRF in boys and higher ST in girls were the strongest correlates of poorer cardiac autonomic function.

Electronic supplementary material

The online version of this article (10.1007/s00421-019-04231-5) contains supplementary material, which is available to authorized users.

Physical activity is associated with cardiac autonomic function in adolescent men

Introduction

Moderate to vigorous physical activity (MVPA) has been shown to be associated with autonomic regulation of the heart measured with heart rate variability (HRV). Only a limited amount of studies have examined this relationship among adolescents, and the effects of increasing PA on HRV is not well established. The aim of this study was to investigate how overall self-reported PA associates with HRV in a large population of adolescent men.

Methods

The study was part of the Finnish MOPO study consisting of 3629 young men (mean age 18, SD 1 years) enrolled for military call-ups in 2009–2013. Overall PA, including both the intensity and frequency of habitual exercise, was assessed by a questionnaire and the respondents categorized into four groups of PA (low, moderate, high and top). Short-term HRV, physical performance and body composition were measured.

Results

HRV, as indicated by mean ln rMSSD, increased according the PA categories as follows: low (3.65 ms (SD 0.7), p<0.001 vs. other groups), moderate (3.78 ms (0.6) p<0.001), high (3.85 ms (0.6) p<0.001) and top activity (3.93 ms (0.6) p<0.001) According to the multivariable linear regression analysis, a significant positive relationship (β = 0.129, p<0.05) was observed between self-reported PA and ln rMSSD independent of body mass index, waist circumference and fat percentage.

Conclusions

Physical activity was positively associated with cardiac autonomic regulation, in adolescent men. A linear increase in HRV according to PA was observed, suggesting that even slight increments in PA might be beneficial for cardiac autonomic regulation The results emphasize the importance of physical activity in improving cardiac health in young people.

Relationship Between Resting Heart Rate Variability and Intermittent Endurance Performance in Novice Soccer Players

Purpose: This study examined the relationships between the Yo-Yo Intermittent Recovery Test level 1 (Yo-Yo IR1) and resting heart rate variability (HRV) and submaximal 5'-5' test derived measures in novice male soccer players. Methods: Forty players (11.54 ± 0.58 years) from a soccer academy participated in this study, performing physical tests on two different days, separated by 48 h, as follows: (day 1) resting HRV and Yo-Yo IR1 test, and (day 2) anthropometric assessments (for peak height velocity assessment [PHV]) and the 5'-5' test. The Pearson product-moment correlation coefficient was used to determine the correlations between Yo-Yo IR1 performance and the remaining variables. A partial correlation analysis was further performed using age, stature, body mass, distance to PHV, and age at PHV as "confounders." Results: The highest correlation score was observed between Yo-Yo IR1 performance and resting HRV, when the absolute age was used as confounder (r = 0.72; p < .05). Conclusions: We observed that a practical measure of parasympathetic activity at rest is largely associated with performance obtained during a traditional intermittent endurance performance test.

Physical Activity and Trajectories of Cardiovascular Health Indicators During Early Childhood

OBJECTIVES

Cardiovascular disease prevention should begin in childhood. However, the influence of physical activity on cardiovascular health in early childhood is unknown. Our purpose in this study was to determine the effect of physical activity on trajectories of cardiovascular health indicators during early childhood.

METHODS

This prospective, observational cohort study (Health Outcomes and Physical Activity in Preschoolers) enrolled 418 3- to 5-year-olds with annual assessments for 3 years. Total physical activity (TPA) and moderate-to-vigorous physical activity (MVPA) were measured over 7 days via accelerometry. Cardiovascular health indicators included cardiovascular fitness (exercise time on a maximal treadmill test [treadmill time] and 1-minute heart rate recovery), resting arterial stiffness (whole-body pulse wave velocity and carotid β stiffness index), and seated systolic blood pressure. Data were analyzed by using linear mixed-effects modeling; effects are reported as unstandardized estimates (Est).

RESULTS

There were main effects of TPA and MVPA on treadmill time (Est = 0.004 [P = .005] and 0.008 [P = .001], respectively) and heart rate recovery (Est = 0.05 [P < .001] and 0.08 [P < .001], respectively). There was a main effect of TPA on pulse wave velocity (Est = -0.001; P = .02) and an MVPA × time interaction (Est = -0.002; P = .01). For carotid β stiffness index, the effect of a TPA × time interaction was not significant (Est = -0.002; P = .051); however, there was a significant MVPA × time interaction (Est = -0.003; P = .03). MVPA was associated with a slower rate of change in systolic blood pressure for girls (Est = 0.06; P = .009).

CONCLUSIONS

Children who engage in higher levels of physical activity during early childhood have better cardiovascular health indicators, with more intense physical activity (ie, MVPA) attenuating the stiffening of arteries.

Heart Rate Is a Better Predictor of Cardiorespiratory Fitness Than Heart Rate Variability in Overweight/Obese Children: The ActiveBrains Project

Cardiac autonomic function can be quantified through mean heart rate (HR) or heart rate variability (HRV). Numerous studies have supported the utility of different HRV parameters as indicators of cardiorespiratory fitness (CRF). However, HR has recently shown to be a stronger predictor of CRF than HRV in healthy young adults, yet these findings need to be replicated, in other age groups such as children. Therefore, this study aimed: (1) to study the associations between indicators of cardiac autonomic function (HR, standard and corrected HRV parameters) and CRF in overweight/obese children; and (2) to test which of the two indicators (i.e., HR or HRV) is a stronger predictor of CRF. This study used cross-sectional baseline data of 107 overweight/obese children (10.03 ± 1.13 years, 58% boys) from the ActiveBrains project. Cardiac autonomic indicators were measured with Polar RS800CX®. CRF was assessed using a gas analyzer while performing a maximal incremental treadmill test. Correlations and stepwise linear regressions were performed. Mean HR and standard HRV parameters (i.e., pNN50, RMSSD, and SDNN) were associated with CRF (r coefficients ranging from -0.333 to 0.268; all p ≤ 0.05). The association of HR with CRF persisted after adjusting for sex, peak height velocity (PHV), adiposity moderate-to-vigorous physical activity, energy intake and circadian-related variable intradaily variability of activity patterns whilst for HRV parameters (i.e., pNN50, RMSSD, and SDNN) disappeared. Stepwise linear regression models entering HR and all HRV parameters showed that mean HR was the strongest predictor of CRF (β = -0.333, R 2 = 0.111, p < 0.001). Standard and corrected HRV parameters did not provide additional value to the coefficient of determination (all p > 0.05). Our findings suggest that HR is the strongest indicator of CRF. It seems that quantification of HRV parameters in time and frequency domain do not add relevant clinical information about the cardiovascular health status (as measured by CRF) in overweight/obese children beyond the information already provided by the simple measure of HR.

Effects of exercise intensity on vascular and autonomic components of the baroreflex following glucose ingestion in adolescents

Purpose

To investigate the effects of an oral glucose tolerance test (OGTT) on baroreflex sensitivity (BRS) in a sample of healthy adolescents, and how acute exercise bouts of different intensities alter the effects of the OGTT on BRS.

Methods

Thirteen male adolescents (14.0 ± 0.5 years) completed three conditions on separate days in a counterbalanced order: (1) high-intensity interval exercise (HIIE); (2) moderate-intensity interval exercise (MIIE); and (3) resting control (CON). At ~ 90 min following the conditions, participants performed an OGTT. Supine heart rate and blood pressure were monitored continuously at baseline, 60 min following the conditions, and 60 min following the OGTT. A cross-spectral method (LFgain) was used to determine BRS gain. Arterial compliance (AC) was assessed as the BRS vascular component. LFgain divided by AC (LFgain/AC) was used as the autonomic component.

Results

Although non-significant, LFgain moderately decreased post-OGTT when no exercise was performed (pre-OGTT = 24.4 ± 8.2 ms mmHg^− 1; post-OGTT = 19.9 ± 5.6 ms mmHg^− 1; ES = 0.64, P > 0.05). This was attributed to the decrease in LFgain/AC (pre-OGTT = 1.19 ± 0.5 ms µm^− 1; post-OGTT = 0.92 ± 0.24 ms µm^− 1; ES = 0.69, P > 0.05). Compared to CON (Δ = − 4.4 ± 8.7 ms mmHg^− 1), there were no differences for the pre–post-OGTT delta changes in LF/gain for HIIE (Δ = − 3.5 ± 8.2 ms mmHg^− 1) and MIIE (Δ = 1.3 ± 9.9 ms mmHg^− 1) had no effects on BRS following the OGTT (all ES < 0.5). Similarly, compared to CON (Δ = − 0.23 ± 0.40 ms µm^− 1) there were no differences for the pre–post-OGTT delta changes in LF/gain for HIIE (Δ = − 0.22 ± 0.49 ms µm^− 1) and MIIE (Δ = 0.13 ± 0.36 ms µm^− 1).

Conclusion

A moderate non-significant decrease in BRS was observed in adolescents following a glucose challenge with no apparent effects of exercise.

Normative Values for Heart Rate Variability Parameters in School-Aged Children: Simple Approach Considering Differences in Average Heart Rate

Background: Heart rate variability (HRV) analysis is a clinical tool frequently used to characterize cardiac autonomic status. The aim of this study was to establish normative values for short-term HRV parameters by considering their main determinants in school-aged children.

Methods: Five-minute electrocardiograms were taken from 312 non-athlete children (153 boys) at age of 6 to 13 years for computation of conventional time- and frequency-domain HRV parameters. Heart rate (HR), respiratory rate, age, body mass index, and sex were considered as their potential determinants. Multiple regression analysis revealed that HR was the principal predictor of all standard HRV indices. To develop their universal normative limits, standard HRV parameters were corrected for prevailing HR.

Results: The HRV correction for HR yielded the parameters which became independent on both sex and HR, and only poorly dependent on age (with small effect size). Normal ranges were calculated for both time- and frequency-domain indices (the latter computed with either fast Fourier transform and autoregressive method). To facilitate recalculation of standard HRV parameters into corrected ones, a calculator was created and attached as a Supplementary Material that can be downloaded and used for both research and clinical purposes.

Conclusion: This study provides HRV normative values for school-aged children which have been developed independently of their major determinants. The calculator accessible in the Supplementary Material can considerably simplify determination if HRV parameters accommodate within normal limits.

Breath of Life: The Respiratory Vagal Stimulation Model of Contemplative Activity

Contemplative practices, such as meditation and yoga, are increasingly popular among the general public and as topics of research. Beneficial effects associated with these practices have been found on physical health, mental health and cognitive performance. However, studies and theories that clarify the underlying mechanisms are lacking or scarce. This theoretical review aims to address and compensate this scarcity. We will show that various contemplative activities have in common that breathing is regulated or attentively guided. This respiratory discipline in turn could parsimoniously explain the physical and mental benefits of contemplative activities through changes in autonomic balance. We propose a neurophysiological model that explains how these specific respiration styles could operate, by phasically and tonically stimulating the vagal nerve: respiratory vagal nerve stimulation (rVNS). The vagal nerve, as a proponent of the parasympathetic nervous system (PNS), is the prime candidate in explaining the effects of contemplative practices on health, mental health and cognition. We will discuss implications and limitations of our model.