Effects of yogic breath regulation: A narrative review of scientific evidence

Sympathetic hyperactivity in patients with hypertension: pathogenesis and treatment. Part I

The article is devoted to the influence of sympathetic  nervous system (SNS) on the cardiovascular  system.  Influence of SNS activity on the blood pressure  level and the pathogenesis of hypertension  development, as well as the effect of SNS on many biochemical and metabolic parameters playing a key role in the development  of metabolic syndrome and hypertension  are considered. Possible mechanisms  of action of various methods that reduce  the SNS activity, restore  the function of autonomic nervous system  and normalize the cardiovascular system and blood pressure  are considered.

Beneficial Effects of Yoga Stretching on Salivary Stress Hormones and Parasympathetic Nerve Activity

This study aimed to determine the effect of yoga stretching on salivary stress hormones and cardiac autonomic nervous system. To our knowledge, this study is the first to investigate changes in cardiac autonomic nervous system after yoga stretching. In this crossover design study, 10 adult men (age, 26.3 ± 2.5 years) without yoga experience participated in the rest and yoga trials for 90 min. Measurements were carried out before (pre), immediately (post), 60 min, and 120 min after rest or yoga stretching. Saliva samples were collected by chewing a sterile cotton ball at a frequency of 60 cycles per minute. Salivary cortisol and testosterone concentrations were measured using an enzyme-linked immunosorbent assay. With the subjects in the sitting position, heart rate variability was measured using pulse analyzer plus for 150 seconds. As regards rate changes, salivary testosterone level tended to increase (p = 0.088), testosterone/cortisol ratio significantly increased (p < 0.05), and cortisol level significantly decreased (p < 0.05) at 120 min after yoga stretching. The square root of the mean-squared differences of successive normal-to-normal intervals and natural logarithm high-frequency component, which are indicators of parasympathetic nerve activity, increased at 60 min (p < 0.05) and 120 min (p < 0.05) in the yoga trial, respectively. In conclusion, yoga stretching can enhance parasympathetic nerve activity and improve stress hormones. Therefore, yoga stretching may be useful to compensate for physical inactivity and increase life expectancy in the general population.

Effect of Mind Sound Resonance Technique (MSRT - A yoga-based relaxation technique) on psychological variables and cognition in school children: A randomized controlled trial

OBJECTIVE

School children undergo stress, which could impact their psychological functions and cognitive abilities. Yoga practices have been found useful in enhancing psychological functions and performance. The current study was planned to evaluate a yoga-based relaxation technique's efficacy as an extracurricular activity on psychological state and cognitive function.

DESIGN AND SETTING

This study was a parallel-group randomized controlled trial conducted at a government school in south India.

PARTICIPANTS

Sixty students with age ranging between 14-16 years (mean age ± SD; 15.3 ± 0.71 years) satisfying the inclusion and exclusion criteria were randomized to experimental and control groups with an allocation ratio of 1:1.

INTERVENTION

Experimental group received Mind Sound Resonance Technique (MSRT), whereas the control group performed supine rest (SR) for two-weeks.

OUTCOME MEASURES

Participants were assessed with State trait anxiety inventory - short form, Mind Wandering Questionnaire, State Mindfulness Attention Awareness Scale, and Trail making task at baseline and post-intervention.

RESULTS

Experimental group showed a reduction in state anxiety and mind wandering with improvement in state mindfulness and performance in the Trail-making task compared to the control group.

CONCLUSION

Results of the current trial indicate the beneficial role of MSRT in enhancing psychological and cognitive functions in children. Further, large-scale trials are warranted to ascertain the usefulness of the technique.

Autonomic Tone and Baroreflex Sensitivity during 70° Head-up Tilt in Yoga Practitioners

Introduction:

The intervention of yoga was shown to improve the autonomic conditioning in humans evident from the enhancement of parasympathetic activity and baroreflex sensitivity (BRS). From the documented health benefits of yoga, we hypothesized that the experience of yoga may result in adaptation to the orthostatic stress due to enhanced BRS.

Aim:

To decipher the effects of yoga in the modulation of autonomic function during orthostatic challenge.

Materials and Methods:

This was a comparative study design conducted in autonomic function test lab, of the Department of Physiology, All India Institute of Medical Sciences, New Delhi, India. Heart rate variability (HRV), blood pressure variability, and BRS were analyzed on forty naïve to yoga (NY) subjects and forty yoga practitioners with an average age of 31.08 ± 7.31 years and 29.93 ± 7.57 years, respectively. All participants were healthy. Seventy degrees head up tilt (HUT) was used as an intervention to evaluate the cardiovascular variability during orthostatic challenge.

Results:

During HUT, the R-R interval (P = 0.042), root mean square of succesive R-R interval differences (RMSSD) (P = 0.039), standard deviation of instantaneous beat-to-beat R-R interval variability (SD1) (P = 0.039) of HRV, and sequence BRS (P = 0.017) and α low frequency of spectral BRS (P = 0.002) were higher in the yoga group. The delta decrease in RRI (P = 0.033) and BRS (P < 0.01) was higher in the yoga group than the NY group.

Conclusion:

The efferent vagal activity and BRS were higher in yoga practitioners. The delta change (decrease) in parasympathetic activity and BRS was higher, with relatively stable systolic blood pressure indicating an adaptive response to orthostatic challenge by the yoga practitioners compared to the NY group.

High-Frequency Cerebral Activation and Interhemispheric Synchronization Following Sudarshan Kriya Yoga as Global Brain Rhythms: The State Effects

Context:

Respiration is known to modulate neuronal oscillations in the brain and is measured by electroencephalogram (EEG). Sudarshan Kriya Yoga (SKY) is a popular breathing process and is established for its significant effects on the various aspects of physiology and psychology.

Aims:

This study aimed to observe neuronal oscillations in multifrequency bands and interhemispheric synchronization following SKY.

Settings and Design:

This study employed before- and after-study design.

Subjects and Methods:

Forty healthy volunteers (average age 25.45 ± 5.75, 23 males and 17 females) participated in the study. Nineteen-channel EEG was recorded and analyzed for 5 min each: before and after SKY. Spectral power for delta, theta, alpha, beta, and gamma frequency band was calculated using Multi-taper Fast Fourier Transform (Chronux toolbox). The Asymmetry Index was calculated by subtracting the natural log of powers of left (L) hemisphere from the right^® to show interhemispheric synchronization.

Statistical Analysis:

Paired t-test was used for statistical analysis.

Results:

Spectral power increased significantly in all frequency bands bilaterally in frontal, central, parietal, temporal, and occipital regions of the brain after long SKY. Electrical activity shifted from lower to higher frequency range with a significant rise in the gamma and beta powers following SKY. Asymmetry Index values tended toward 0 following SKY.

Conclusions:

A single session of SKY generates global brain rhythm dominantly with high-frequency cerebral activation and initiates appropriate interhemispheric synchronization in brain rhythms as state effects. This suggests that SKY leads to better attention, memory, and emotional and autonomic control along with enhanced cognitive functions, which finally improves physical and mental well-being.

A Perspective on Yoga as a Preventive Strategy for Coronavirus Disease 2019

The pandemic outbreak of coronavirus disease 2019 (COVID-19) infection caused by severe acute respiratory syndrome-coronavirus 2 has led to profound public health crisis. In particular, individuals with preexisting conditions of heart disease, diabetes, cerebrovascular diseases and the elderly are most vulnerable to succumb to this infection. The current COVID-19 emergency calls for rapid development of potential prevention and management strategies against this virus-mediated disease. There is a plethora of evidence that supports the add-on benefits of yoga in stress management, as well as prevention and management of chronic noncommunicable diseases. There are some studies on the effect of yoga in communicable diseases as well but very few for acute conditions and almost none for the rapidly spreading infections resulting in pandemics. Based on the available scientific evidences on yoga in improving respiratory and immune functions, we have formulated very simple doable integrated yoga modules in the form of videos to be practiced for prevention of the disease by children, adults, and the elderly.

Mindfulness with paced breathing reduces blood pressure

Elevated blood pressure (BP) is a major avoidable cause of premature morbidity and mortality in the United States (US) and worldwide, due primarily to increased risks of stroke as well as myocardial infarction. While there are therapeutic lifestyle changes and adjunctive pharmacologic medications of proven benefit, recent interest has increasingly focused on Complementary and Alternative Medicine, in particular, Mind-Body Interventions. With respect to BP, it is tempting to speculate that mindfulness with paced breathing will have beneficial effects in the short run that may translate into lowered risks of stroke in the long run. Paced breathing is deep diaphragmatic breathing with typical rates equal to or less than 5-7 breaths per minute compared with the usual rate of 12-14. One plausible mechanism of benefit is that paced breathing stimulates the parasympathetic nervous system which alters neuronal function in specific areas of the brain and reduces stress chemicals. The hypothesis that mindfulness with paced slow breathing reduces BP could be directly tested in randomized trials designed a priori to do so. Subsequently, a finding that mindfulness with paced breathing reduces BP would also lead to direct tests in randomized trials of reductions of carotid atherosclerosis and, if so, a larger scale trial to test whether there is a direct impact of mindfulness with paced breathing on reducing the risks of stroke and MI. If rigorous testing of this medical hypothesis led to positive results this would have large and important clinical and policy implications in the US and worldwide.

Brain and Physiological Markers of Autonomic Function Are Associated With Treatment-Related Improvements in Self-Reported Autonomic Dysfunction in Veterans With Gulf War Illness: An Exploratory Pilot Study

BACKGROUND

Gulf War Illness (GWI) is a poorly understood condition characterized by a constellation of mood, cognitive, and physical symptoms. A growing body of evidence demonstrates autonomic nervous system (ANS) dysfunction. Few published treatment studies exist for GWI.

METHOD

We recently completed a randomized controlled trial comparing a 10-week group yoga intervention to 10-week group cognitive behavioral therapy (CBT) for veterans with GWI. Here, we present exploratory data on ANS biomarkers of treatment response from a small pilot exploratory neurophysiological add-on study (n = 13) within that larger study.

RESULTS

Findings suggest that veterans with GWI receiving either yoga or CBT for pain improved following treatment and that changes in biological ANS-especially for the yoga group-moved in the direction of healthy profiles: lower heart rate, higher square root of the mean squared differences between successive R-R intervals (RMSSD), greater parasympathetic activation/dominance (increased high-frequency heart rate variability [HF-HRV], decreased low-frequency/high-frequency [LF/HF] ratio), reduced right amygdala volume, and stronger amygdala-default mode/amygdala-salience network connectivity, both immediately posttreatment and at 6-month follow-up. Biological mechanisms of CBT appeared to underlie improvements in more psychologically loaded symptoms such as self-reported fatigue and energy. Higher tonic arousal and/or more sympathetic dominance (higher skin conductance, lower RMSSD, lower HF-HRV, higher LF/HF ratio) pretreatment predicted greater treatment-related improvements in self-reported ANS for both the yoga and CBT group.

CONCLUSION

These exploratory pilot data provide preliminary support for the suggestion that treatment (yoga, CBT) is associated with improvements in both biological and self-reported ANS dysfunctions in GWI. The major limitation for these findings is the small sample size. Larger and more controlled studies are needed to replicate these findings and directly compare biomarkers of yoga versus CBT.

Effects of alternate nostril breathing exercise on respiratory functions in healthy young adults leading stressful lifestyle

Alternate nostril breathing (ANB) is one of the best and easiest breathing exercises (pranayama) of yoga that are good for health and physical fitness. ANB exercise has beneficial and therapeutic effects on respiratory function in both normal as well as diseased humans. This study was conducted with the objective of assessing the physiological effects of short-term ANB exercise on respiratory function in healthy adult individuals leading a stressful life. This prospective interventional study was conducted in the Department of Physiology, Chittagong Medical College (CMC), Chattogram, Bangladesh from July 2017 to June 2018. A total of 100 participants aged 18-20 years, studying in the first year in CMC, were included by using a simple random sampling method. Among them, 50 participants were enrolled in the experimental group. Age- and BMI-matched 50 participants constituted the control group. Height, weight were measured, and BMI was calculated. The participants of the experimental group performed ANB exercise over 4 weeks for 10 min/day. The control participants were neither trained nor allowed to practice nostril breathing during the whole study period. Respiratory parameters like forced vital capacity (FVC), forced expiratory volume in 1st second (FEV₁), and peak expiratory flow rate (PEFR) were measured by using a digital spirometer (Chest graph HI-101, Japan). Readings were taken in a healthy upright sitting posture in the control and experimental group initially and after 4 weeks. Student's t-test was conducted by using SPSS for windows version-23. The mean value of FVC, FEV₁, PEFR were significantly (P < 0.001) changed after the ANB exercise when compared to the values before breathing exercise. The results of this study suggest that respiratory function is significantly improved after the ANB exercise. Therefore, ANB can be recommended for increasing respiratory efficiency.

Immediate Effect of a Yoga Breathing Practice on Attention and Anxiety in Pre-Teen Children

Pre-teen children face stressors related to their transition from childhood to adolescence, with a simultaneous increase in academic pressure. The present study compared the immediate effects of 18 min of (i) high frequency yoga breathing with (ii) yoga-based breath awareness and (iii) sitting quietly, on (a) attention and (b) anxiety, in 61 pre-teen children (aged between 11 and 12 years; 25 girls). Attention was assessed using a six letter cancellation task and Spielberger’s State Trait Anxiety Inventory STAI-S was used to measure anxiety before and after the three practices, practiced on separate days. Repeated measures ANOVA, followed by Bonferroni adjusted post-hoc analyses showed an increase in total attempts and net scores after high frequency yoga breathing (p < 0.05), while wrong attempts increased after yoga based breath awareness (p < 0.05). Anxiety decreased comparably after all three interventions. The 25 girls in the group had the same trend of results as the whole group with respect to the attention-based cancellation task, while boys showed no, how since change. For both girls and boys, anxiety decreased after all three 18min interventions. The results suggest that high frequency yoga breathing could be a short, useful school based practice to improve attention and reduce anxiety.

How Breath-Control Can Change Your Life: A Systematic Review on Psycho-Physiological Correlates of Slow Breathing

Background: The psycho-physiological changes in brain-body interaction observed in most of meditative and relaxing practices rely on voluntary slowing down of breath frequency. However, the identification of mechanisms linking breath control to its psychophysiological effects is still under debate. This systematic review is aimed at unveiling psychophysiological mechanisms underlying slow breathing techniques (<10 breaths/minute) and their effects on healthy subjects.

Methods: A systematic search of MEDLINE and SCOPUS databases, using keywords related to both breathing techniques and to their psychophysiological outcomes, focusing on cardio-respiratory and central nervous system, has been conducted. From a pool of 2,461 abstracts only 15 articles met eligibility criteria and were included in the review. The present systematic review follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

Results: The main effects of slow breathing techniques cover autonomic and central nervous systems activities as well as the psychological status. Slow breathing techniques promote autonomic changes increasing Heart Rate Variability and Respiratory Sinus Arrhythmia paralleled by Central Nervous System (CNS) activity modifications. EEG studies show an increase in alpha and a decrease in theta power. Anatomically, the only available fMRI study highlights increased activity in cortical (e.g., prefrontal, motor, and parietal cortices) and subcortical (e.g., pons, thalamus, sub-parabrachial nucleus, periaqueductal gray, and hypothalamus) structures. Psychological/behavioral outputs related to the abovementioned changes are increased comfort, relaxation, pleasantness, vigor and alertness, and reduced symptoms of arousal, anxiety, depression, anger, and confusion.

Conclusions: Slow breathing techniques act enhancing autonomic, cerebral and psychological flexibility in a scenario of mutual interactions: we found evidence of links between parasympathetic activity (increased HRV and LF power), CNS activities (increased EEG alpha power and decreased EEG theta power) related to emotional control and psychological well-being in healthy subjects. Our hypothesis considers two different mechanisms for explaining psychophysiological changes induced by voluntary control of slow breathing: one is related to a voluntary regulation of internal bodily states (enteroception), the other is associated to the role of mechanoceptors within the nasal vault in translating slow breathing in a modulation of olfactory bulb activity, which in turn tunes the activity of the entire cortical mantle.