MIND-BODY RESPONSE AND NEUROPHYSIOLOGICAL CHANGES DURING STRESS AND MEDITATION: CENTRAL ROLE OF HOMEOSTASIS

Stress profoundly impacts quality of life and may lead to various diseases and conditions. Understanding the underlying physiological and neurological processes that take place during stress and meditation techniques may be critical for effectively treating stress-related diseases. The article examines a hypothetical physiological homeostatic response that compares and contrasts changes in central and peripheral oscillations during stress and meditation, and relates these to changes in the autonomic system and neurological activity. The authors discuss how cardiorespiratory synchronization, which occurs during the parasympathetic response and meditation, influences and modulates activity and oscillations of the brain and autonomic nervous system. Evidence is presented on how synchronization of cardiac and respiratory rates during meditation may lead to a homeostatic increase in cellular membrane potentials in neurons and other cells throughout the body. These potential membrane changes may underlie the reduced activity in the amygdala, and other cortical areas during meditation, and research examining these changes may foster better understanding of the restorative properties and health benefits of meditation

Gender Differences in Heart Rate Variability Among Individuals Undergoing Regular Resistance Training : Preliminary observations

Objectives: Frequency-domain analysis of heart rate variability (HRV) is an effective tool to evaluate autonomic balance. This study aimed to investigate gender differences in HRV among individuals undergoing regular resistance training. Methods: This preliminary cross-sectional study was conducted from April to September 2016 in João Pessoa, Paraíba, Brazil. The low-frequency (LF), high-frequency (HF) and LF/HF ratio components of HRV spectral analysis were analysed among 22 men and 27 women undergoing regular resistance training. Results: Among the male participants, the LF component was significantly increased compared to females in both the supine (1,171 ± 192 versus 545 ± 74 ms2; P = 0.0067) and upright (1,824 ± 260 versus 738 ± 133; P = 0.0011) positions. The LF/HF ratio was also significantly increased in both positions among male participants (P <0.0500 each). Conclusion: These preliminary data suggest a possible gender difference in the HRV of individuals undergoing resistance training

Autonomic response to walk tests is useful for assessing outcome measures in people with multiple sclerosis

Objective: The aim of this study was to evaluate the association between changes in the autonomic control of cardiorespiratory system induced by walk tests and outcome measures in people with Multiple Sclerosis (pwMS). Methods: Electrocardiogram (ECG) recordings of 148 people with Relapsing-Remitting MS (RRMS) and 58 with Secondary Progressive MS (SPMS) were acquired using a wearable device before, during, and after walk test performance from a total of 386 periodical clinical visits. A subset of 90 participants repeated a walk test at home. Various MS-related symptoms, including fatigue, disability, and walking capacity were evaluated at each clinical visit, while heart rate variability (HRV) and ECG-derived respiration (EDR) were analyzed to assess autonomic nervous system (ANS) function. Statistical tests were conducted to assess differences in ANS control between pwMS grouped based on the phenotype or the severity of MS-related symptoms. Furthermore, correlation coefficients (r) were calculated to assess the association between the most significant ANS parameters and MS-outcome measures. Results: People with SPMS, compared to RRMS, reached higher mean heart rate (HRM) values during walk test, and larger sympathovagal balance after test performance. Furthermore, pwMS who were able to adjust their HRM and ventilatory values, such as respiratory rate and standard deviation of the ECG-derived respiration, were associated with better clinical outcomes. Correlation analyses showed weak associations between ANS parameters and clinical outcomes when the Multiple Sclerosis phenotype is not taken into account. Blunted autonomic response, in particular HRM reactivity, was related with worse walking capacity, yielding r = 0.36 r = 0.29 (RRMS) and r > 0.5 (SPMS). A positive strong correlation r > 0.7 r > 0.65 between cardiorespiratory parameters derived at hospital and at home was also found. Conclusion: Autonomic function, as measured by HRV, differs according to MS phenotype. Autonomic response to walk tests may be useful for assessing clinical outcomes, mainly in the progressive stage of MS. Participants with larger changes in HRM are able to walk longer distance, while reduced ventilatory function during and after walk test performance is associated with higher fatigue and disability severity scores. Monitoring of disorder severity could also be feasible using ECG-derived cardiac and respiratory parameters recorded with a wearable device at home

Effect of asthma and six-months high-intensity interval training on heart rate variability during exercise in adolescents

Little is known regarding the influence of asthma and exercise, and their interaction, on heart rate variability (HRV) in adolescents.Thirty-one adolescents with asthma (13.7±0.9 years; 21.9±3.9 kg·m−2; 19 boys, 12 girls) and thirty-three healthy adolescents (13.8±0.9 years; 20.3±3.2 kg·m−2; 16 boys, 17 girls) completed an incremental ramp test and three heavy-intensity constant-work-rate cycle tests. Thirteen adolescents (7 boys, 6 girls; 6 asthma, 7 control) completed six-months high-intensity interval training (HIIT) and were compared to age- and sex-matched controls. Standard time-domain, frequency-domain and non-linear indices of HRV were derived at baseline, three- and six-months.Asthma did not influence HRV at baseline or following HIIT. Total power, low frequency and normalised low frequency power, and sympathovagal balance increased at three-months in HIIT, subsequently declining towards baseline at six-months. Normalised high frequency power was reduced at three-months in both groups, which was sustained at six-months. No effects of HIIT were observed in the time-domain nor in the non-linear indices.HRV was not influenced by asthma, potentially because such derangements are a function of disease progression, severity or duration. HIIT may be associated with a short-term shift towards greater sympathetic predominance during exercise, perhaps caused by physiological overload and fatigue

Empirical mode decomposition analysis of HRV data from patients undergoing local anaesthesia (brachial plexus block)

Spectral analysis of heart rate variability (HRV) is used for the assessment of cardiovascular autonomic control. In this study, a data-driven adaptive technique called empirical mode decomposition (EMD) and the associated Hilbert spectrum has been used to evaluate the effect of local anaesthesia on HRV parameters in a group of 14 patients undergoing axillary brachial plexus block. The normalized amplitude Hilbert spectrum was used to calculate the error index associated with the instantaneous frequency. The amplitude and the frequency values were corrected in the region where the error was higher than twice standard deviation. The intrinsic mode function (IMF) components were assigned to the LF and the HF part of the signal by making use of the centre frequency and the standard deviation spectral extension estimated from the marginal spectrum of the IMF components. The optimal range of the stopping criterion was found to be between 4 and 9 for the HRV data. The statistical analysis showed that the LF/HF ratio decreased within an hour of the application of the brachial plexus block compared to the values at the start of the procedure. These changes were observed in 13 of the 14 patients included in this study

Sex Differences in Cardiac Autonomic Modulation and Baroreflex Sensitivity Following Differential Exercise Training

Maintained balance between sympathetic and parasympathetic tone within the cardiac autonomic systems is a vital component of cardiovascular regulation. The alteration of baroreflex function can contribute to chronic parasympathetic withdrawal and subsequent sympathetic dominance that is often seen in the development and progression of cardiovascular diseases. Heart rate variability (HRV) and baroreflex sensitivity (BRS) are non-invasive clinical measures utilized to assess baroreflex control and cardiac autonomic modulation, respectively. Aerobic exercise (AE) training has been shown to increase HRV and BRS; however, little is known concerning the response of HRV or baroreflex function to resistance exercise (RE) training. The purpose of this study was to assess the potential sex differences of short-term aerobic training versus resistance training on HRV and BRS in a hypertensive population. A 2x2x2 design was utilized to analyze mode (resistance vs. aerobic) x time (pre- versus post-training) x sex (male versus female). Forty pre- to stage-1 essential hypertensives between the ages of 33 and 60 years old (20 men, 20 women) underwent either AE training [30 minutes of treadmill exercise, 3 days per week at 65% of peak oxygen consumption (VO2 peak)] or RE training (3 sets of 10 repetitions for 9 major muscle groups, 3 days per week at 10 repetition maximum). Body mass index (BMI), body composition assessment, electrocardiogram (ECG) recordings, beat-to-beat blood pressure (BP), and heads up tilt tests were performed at baseline pre and post 4 week training period. An increase in BRS was seen in both sexes following AE training; however, RE training, showed decreases in BRS in males and no change in females. Following RE training decreases in HRV as indicated by the low frequency to high frequency (LF: HF) ratio were seen in males, and increases in HRV were observed within females. These data show that 4 weeks of moderate intensity aerobic training results in increases in BRS and HRV in both sexes. The decrease in BRS seen in males following 4 weeks of RE training may be related to an increase in arterial stiffness in hypertensive individuals

Slow breathing reduces sympathoexcitation in COPD

Neurohumoral activation has been shown to be present in hypoxic patients with chronic obstructive pulmonary disease (COPD). The aims of the present study were to investigate whether there is sympathetic activation in COPD patients in the absence of hypoxia and whether slow breathing has an impact on sympathoexcitation and baroreflex sensitivity. Efferent muscle sympathetic nerve activity, blood pressure, cardiac frequency and respiratory movements were continuously measured in 15 COPD patients and 15 healthy control subjects. Baroreflex sensitivity was analysed by autoregressive spectral analysis and the alpha-angle method. At baseline, sympathetic nerve activity was significantly elevated in COPD patients and baroreflex sensitivity was decreased (5.0+/-0.6 versus 8.9+/-0.8 ms.mmHg(-1)). Breathing at a rate of 6 breaths.min(-1) caused sympathetic activity to drop significantly in COPD patients (from 61.3+/-4.6 to 53.0+/-4.3 bursts per 100 heartbeats) but not in control subjects (39.2+/-3.2 versus 37.5+/-3.3 bursts per 100 heartbeats). In both groups, slow breathing significantly enhanced baroreflex sensitivity. In conclusion, sympathovagal imbalance is present in normoxic chronic obstructive pulmonary disease patients. The possibility of modifying these changes by slow breathing may help to better understand and influence this systemic disease