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1.  Changes in Autonomic Variables Following Two Meditative States Described in Yoga Texts 
In ancient yoga texts there are two meditative states described. One is dharana, which requires focusing, the second is dhyana, during which there is no focusing, but an expansive mental state is reached. While an earlier study did show improved performance in an attention task after dharana, the autonomic changes during these two states have not been studied.
Autonomic and respiratory variables were assessed in 30 healthy male volunteers (group mean age±SD, 29.1±5.1 years) during four mental states described in traditional yoga texts. These four mental states are random thinking (cancalata), nonmeditative focusing (ekagrata), meditative focusing (dharana), and effortless meditation (dhyana). Assessments were made before (5 minutes), during (20 minutes), and after (5 minutes), each of the four states, on four separate days.
During dhyana there was a significant increase in the skin resistance level (p<0.001; post hoc analysis following ANOVA, during compared to pre) and photo-plethysmogram amplitude (p<0.05), whereas there was a significant decrease in the heart rate (p<0.001) and breath rate (p<0.001). There was a significant decrease in the low frequency (LF) power (p<0.001) and increase in the high frequency (HF) power (p<0.001) in the frequency domain analysis of the heart rate variability (HRV) spectrum, on which HF power is associated with parasympathetic activity. There was also a significant increase in the NN50 count (the number of interval differences of successive NN intervals greater than 50 ms; p<0.001) and the pNN50 (the proportion derived by dividing NN50 by the total number of NN intervals; p<0.001) in time domain analysis of HRV, both indicative of parasympathetic activity.
Maximum changes were seen in autonomic variables and breath rate during the state of effortless meditation (dhyana). The changes were all suggestive of reduced sympathetic activity and/or increased vagal modulation. During dharana there was an increase in skin resistance. The changes in HRV during ekagrata and cancalata were inconclusive.
PMCID: PMC3546358  PMID: 22946453
2.  Blood pressure and purdue pegboard scores in individuals with hypertension after alternate nostril breathing, breath awareness, and no intervention 
Previously alternate nostril yoga breathing (anuloma-viloma pranayama) was shown to reduce the blood pressure (BP) in people with hypertension. An elevated BP has been associated with poor performance in certain tasks requiring attention and co-ordination. The Purdue pegboard task assesses manual dexterity and eye-hand co-ordination.
In the present study there were ninety participants with essential hypertension. Their ages ranged from 20 to 59 years (group average age ±S.D., 49.7±9.5 years; sixty males). Participants were randomized as three groups, with thirty participants in each group. One group practiced alternate nostril yoga breathing for 10 minutes, the second group practiced breath awareness for the same duration and the third group was given a control intervention (i.e., reading a magazine with neutral content). Assessments were taken before and after the interventions for participants of the three groups. Assessments included the blood pressure and performance in the Purdue pegboard task. Data were analyzed with a repeated measures ANOVA and post-hoc analyses were Bonferroni adjusted.
Following alternate nostril breathing (ANYB) there was a significant decrease in systolic and diastolic blood pressure (p<0.001 and p<0.05), and an improvement in Purdue pegboard task scores for both hands (p<0.05), and for the right hand (p<.001). Breath awareness (the control session) also showed a significant decrease in systolic blood pressure (p<0.05). The right hand scores improved in the group reading a magazine (p<0.05).
The results suggest that the immediate effect of ANYB is to reduce the BP while improving the performing in a task requiring attention, bimanual dexterity and visuo-motor co-ordination.
PMCID: PMC3628802  PMID: 23334063
hypertension; alternate nostril yoga breathing; blood pressure; Purdue pegboard task; attention; visuo-motor co-ordination; bi-manual dexterity
3.  Adaptation of Endurance Training with a Reduced Breathing Frequency 
The purpose of the study was to investigate the influence of training with reduced breathing frequency (RBF) on tidal volume during incremental exercise where breathing frequency was restricted and on ventilatory response during exercise when breathing a 3% CO2 mixture. Twelve male participants were divided into two groups: experimental (Group E) and control (Group C). Both groups participated three cycle ergometry interval training sessions per week for six weeks. Group E performed it with RBF i.e. 10 breaths per minute and group C with spontaneous breathing. After training Group E showed a higher vital capacity (+8 ± 8%; p = 0.02) and lower ventilatory response during exercise when breathing a 3% CO2 mixture (-45 ± 27%; p = 0.03) compared with pre-training. These parameters were unchanged in Group C. Post-training peak power output with RBF (PPORBF) was increased in both groups. The improvement was greater in Group E (+42 ± 11%; p < 0.01) than in Group C (+11 ± 9%; p = 0.03). Tidal volume at PPORBF was higher post-training in Group E (+41 ± 19%; p = 0.01). The results of the present study indicate that RBF training during cycle ergometry exercise increased tidal volume during incremental exercise where breathing frequency was restricted and decreased ventilatory sensitivity during exercise when breathing a 3% CO2 mixture.
Key PointsTraining with a reduced breathing frequency during exercise decreased ventilator sensitivity to carbon dioxide. In addition, it increased minute ventilation during exercise with imposed reduced breathing frequency.Training with reduced breathing frequency could not be realized at higher intensity of exercise due to the additional stress caused by such a breathing pattern. Therefore the improvement in aerobic endurance (considering peak oxygen uptake) could not be expected after this kind of training.
PMCID: PMC3873666  PMID: 24421735
Interval training; reduced breathing; incremental exercise
4.  Blood Pressure and Heart Rate Variability during Yoga-Based Alternate Nostril Breathing Practice and Breath Awareness 
Previous research has shown a reduction in blood pressure (BP) immediately after the practice of alternate nostril yoga breathing (ANYB) in normal healthy male volunteers and in hypertensive patients of both sexes. The BP during ANYB has not been recorded.
Participants were 26 male volunteers (group mean age ±SD, 23.8±3.5 years). We assessed (1) heart rate variability, (2) non-invasive arterial BP, and (3) respiration rate, during (a) ANYB and (b) breath awareness (BAW) sessions. Each session was 25 minutes. We performed assessments at 3 time points: Pre (5 minutes), during (15 minutes; for ANYB or BAW) and Post (5 minutes). A naïve-to-yoga control group (n=15 males, mean age ±SD 26.1±4.0 years) were assessed while seated quietly for 25 minutes.
During ANYB there was a significant decrease (repeated measures ANOVA) in systolic BP and respiration rate; while RMSSD (the square root of the mean of the sum of squares of differences between adjacent NN intervals) and NN50 (the number of interval differences of successive normal to normal intervals greater than 50 ms) significantly increased. During BAW respiration rate decreased. In contrast, respiration rate increased during the control state. ANYB and BAW were significantly different (2-factor ANOVA) in RMSSD and respiration rate. BAW and control were different with respect to respiration rate.
The results suggest that vagal activity increased during and after ANYB, which could have contributed to the decrease in BP and changes in the HRV.
PMCID: PMC4247229  PMID: 25408140
Arterial Pressure; Heart Rate; Yoga
5.  Finger dexterity and visual discrimination following two yoga breathing practices 
International Journal of Yoga  2012;5(1):37-41.
Practicing yoga has been shown to improve motor functions and attention. Though attention is required for fine motor and discrimination tasks, the effect of yoga breathing techniques on fine motor skills and visual discrimination has not been assessed.
To study the effect of yoga breathing techniques on finger dexterity and visual discrimination.
Materials and Methods:
The present study consisted of one hundred and forty subjects who had enrolled for stress management. They were randomly divided into two groups, one group practiced high frequency yoga breathing while the other group practiced breath awareness. High frequency yoga breathing (kapalabhati, breath rate 1.0 Hz) and breath awareness are two yoga practices which improve attention. The immediate effect of high frequency yoga breathing and breath awareness (i) were assessed on the performance on the O′Connor finger dexterity task and (ii) (in) a shape and size discrimination task.
There was a significant improvement in the finger dexterity task by 19% after kapalabhati and 9% after breath awareness (P<0.001 in both cases, repeated measures ANOVA and post-hoc analyses). There was a significant reduction (P<0.001) in error (41% after kapalabhati and 21% after breath awareness) as well as time taken to complete the shape and size discrimination test (15% after kapalabhati and 15% after breath awareness; P<0.001) was also observed.
Both kapalabahati and breath awareness can improve fine motor skills and visual discrimination, with a greater magnitude of change after kapalabhati.
PMCID: PMC3276931  PMID: 22346064
Finger dexterity; shape and size discrimination; yoga breathing
6.  Measurement of the effect of Isha Yoga on cardiac autonomic nervous system using short-term heart rate variability 
Beneficial effects of Yoga have been postulated to be due to modulation of the autonomic nervous system.
To assess the effect of Isha Yoga practices on cardiovascular autonomic nervous system through short-term heart rate variability (HRV).
Design of the Study:
Short-term HRV of long-term regular healthy 14 (12 males and 2 females) Isha Yoga practitioners was compared with that of age- and gender-matched 14 (12 males and 2 females) non-Yoga practitioners.
Methods and Materials:
ECG Lead II and respiratory movements were recorded in both groups using Polyrite during supine rest for 5 min and controlled deep breathing for 1 minute. Frequency domain analysis [RR interval is the mean of distance between subsequent R wave peaks in ECG], low frequency (LF) power, high frequency (HF) power, LF normalized units (nu), HF nu, LF/HF ratio] and time domain analysis [Standard Deviation of normal to normal interval (SDNN), square of mean squared difference of successive normal to normal intervals (RMSSD), normal to normal intervals which are differing by 50 ms (NN50), and percentage of NN50 (pNN50)] of HRV variables were analyzed for supine rest. Time domain analysis was recorded for deep breathing.
Results showed statistically significant differences between Isha Yoga practitioners and controls in both frequency and time domain analyses of HRV indices, with no difference in resting heart rate between the groups.
Practitioners of Isha Yoga showed well-balanced beneficial activity of vagal efferents, an overall increased HRV, and sympathovagal balance, compared to non-Yoga practitioners during supine rest and deep breathing.
PMCID: PMC3371565  PMID: 22707866
Cardiovascular ANS; heart rate variability; Isha Yoga
7.  Yoga respiratory training improves respiratory function and cardiac sympathovagal balance in elderly subjects: a randomised controlled trial 
BMJ Open  2011;1(1):e000085.
Since ageing is associated with a decline in pulmonary function, heart rate variability and spontaneous baroreflex, and recent studies suggest that yoga respiratory exercises may improve respiratory and cardiovascular function, we hypothesised that yoga respiratory training may improve respiratory function and cardiac autonomic modulation in healthy elderly subjects.
76 healthy elderly subjects were enrolled in a randomised control trial in Brazil and 29 completed the study (age 68±6 years, 34% males, body mass index 25±3 kg/m2). Subjects were randomised into a 4-month training program (2 classes/week plus home exercises) of either stretching (control, n=14) or respiratory exercises (yoga, n=15). Yoga respiratory exercises (Bhastrika) consisted of rapid forced expirations followed by inspiration through the right nostril, inspiratory apnoea with generation of intrathoracic negative pressure, and expiration through the left nostril. Pulmonary function, maximum expiratory and inspiratory pressures (PEmax and PImax, respectively), heart rate variability and blood pressure variability for spontaneous baroreflex determination were determined at baseline and after 4 months.
Subjects in both groups had similar demographic parameters. Physiological variables did not change after 4 months in the control group. However, in the yoga group, there were significant increases in PEmax (34%, p<0.0001) and PImax (26%, p<0.0001) and a significant decrease in the low frequency component (a marker of cardiac sympathetic modulation) and low frequency/high frequency ratio (marker of sympathovagal balance) of heart rate variability (40%, p<0.001). Spontaneous baroreflex did not change, and quality of life only marginally increased in the yoga group.
Respiratory yoga training may be beneficial for the elderly healthy population by improving respiratory function and sympathovagal balance.
Trial Registration identifier: NCT00969345; trial registry name: Effects of respiratory yoga training (Bhastrika) on heart rate variability and baroreflex, and quality of life of healthy elderly subjects.
Article summary
Article focus
Yoga respiratory training may improve respiratory function and cardiac autonomic modulation in healthy elderly subjects.
Key messages
Yoga respiratory training improves respiratory function by increasing PEmax and PImax.
Yoga respiratory training improves both cardiac autonomic modulation by lowering the low frequency component, and the sympathovagal balance evaluated by heart rate variability.
Strengths and limitations of this study
The study design allowed evaluation of heart rate variability without confounding by the effects of drugs, including β-blockers, that can interfere with autonomic modulation.
As the sample size was small and only included healthy elderly subjects, the results should be extrapolated with caution to elderly subjects with significant comorbidities.
The respiratory exercises were taught to highly motivated yoga practitioners, and so the general elderly population may find it difficult to learn them.
Paced breathing during the collection of heart rate variability measurements may influence autonomic variables but allowed the confounding effects of respiratory training on the pattern of breathing to be avoided.
PMCID: PMC3191432  PMID: 22021757
8.  Yoga breathing through a particular nostril is associated with contralateral event-related potential changes 
International Journal of Yoga  2012;5(2):102-107.
In earlier studies uninostril yoga breathing was shown to influence the activity of the cerebral hemispheres differently, based on (i) auditory evoked potentials recorded from bilateral scalp sites, and (ii) performance in hemisphere-specific tasks. But change in P300 (event-related potential generated when subjects attend to and discriminate between stimuli) from bilateral scalp sites when subjects were practicing uni- and alternate-nostril breathing are yet to be explored.
The present study was designed to determine whether or not immediately after uninostril or alternate nostril yoga breathing there would be a change in the ability to pay attention to a given stimulus.
Materials and Methods:
Twenty-nine healthy male volunteers, with ages between 20 and 45 years were randomly allocated to five sessions, viz., (i) right-, (ii) left-, (iii) alternate-nostril yoga breathing, (iv) breath awareness and (v) no intervention, each for 45 min on separate days. The P300 event related potential was recorded using an auditory oddball paradigm from sites on the left (C3) and right (C4), referenced to linked earlobes, before and after each session.
Post-hoc analysis with Bonferroni adjustment showed that the P300 peak latency was significantly lower at C3 compared to that at C4, following right nostril yoga breathing (P<0.05).
These results suggest that right nostril yoga breathing facilitates the activity of contralateral (left) hemisphere, in the performance of the P300 task.
PMCID: PMC3410187  PMID: 22869992
Contralateral changes; P300; uni-nostril yoga breathing
9.  Effect of an office worksite-based yoga program on heart rate variability: A randomized controlled trial 
BMC Public Health  2011;11:578.
Chronic work-related stress is a significant and independent risk factor for cardiovascular and metabolic diseases and associated mortality, particularly when compounded by a sedentary work environment. Heart rate variability (HRV) provides an estimate of parasympathetic and sympathetic autonomic control, and can serve as a marker of physiological stress. Hatha yoga is a physically demanding practice that can help to reduce stress; however, time constraints incurred by work and family life may limit participation. The purpose of the present study is to determine if a 10-week, worksite-based yoga program delivered during lunch hour can improve resting HRV and related physical and psychological parameters in sedentary office workers.
Methods and design
This is a parallel-arm RCT that will compare the outcomes of participants assigned to the experimental treatment group (yoga) to those assigned to a no-treatment control group. Participants randomized to the experimental condition will engage in a 10-week yoga program delivered at their place of work. The yoga sessions will be group-based, prescribed three times per week during lunch hour, and will be led by an experienced yoga instructor. The program will involve teaching beginner students safely and progressively over 10 weeks a yoga sequence that incorporates asanas (poses and postures), vinyasa (exercises), pranayama (breathing control) and meditation. The primary outcome of this study is the high frequency (HF) spectral power component of HRV (measured in absolute units; i.e. ms2), a measure of parasympathetic autonomic control. Secondary outcomes include additional frequency and time domains of HRV, and measures of physical functioning and psychological health status. Measures will be collected prior to and following the intervention period, and at 6 months follow-up to determine the effect of intervention withdrawal.
This study will determine the effect of worksite-based yoga practice on HRV and physical and psychological health status. The findings may assist in implementing practical interventions, such as yoga, into the workplace to mitigate stress, enhance health status and reduce the risk of cardiovascular and metabolic diseases.
Trial Registration
PMCID: PMC3154869  PMID: 21771340
exercise; training; insulin resistance; diabetes; obesity; cytokines
10.  Effect of yoga or physical exercise on physical, cognitive and emotional measures in children: a randomized controlled trial 
Previous studies have separately reported the effects of physical exercise and yoga in children, showing physical, cognitive and emotional benefits.
The present randomized controlled trial assessed the effects of yoga or physical exercise on physical fitness, cognitive performance, self-esteem, and teacher-rated behavior and performance, in school children.
98 school children between 8 to 13 years were randomized as yoga and physical exercise groups {n = 49 each; (yoga: 15 girls, group mean age 10.4 ± 1.2 years), (physical exercise: 23 girls, group mean age 10.5 ± 1.3 years)}. Both groups were blind assessed after allocation, using: (i) the Eurofit physical fitness test battery, (ii) Stroop color-word task for children, (iii) Battle’s self-esteem inventory and (iv) the teachers’ rating of the children’s obedience, academic performance, attention, punctuality, and behavior with friends and teachers. After assessments the yoga group practiced yoga (breathing techniques, postures, guided relaxation and chanting), 45 minutes each day, 5 days a week. During this time the physical exercise group had jogging-in-place, rapid repetitive movements and relay races or games. Both groups were assessed at the end of 3 months. Data were analyzed with RM ANOVA and post-hoc tests were Bonferroni adjusted.
There was one significant difference between groups. This was in social self-esteem which was higher after physical exercise compared to yoga (p < 0.05). All the changes reported below are based on after-before comparisons, within each group. Both groups showed an increase in BMI, and number of sit-ups (p < 0.001). Balance worsened in the physical exercise group, while plate tapping improved in the yoga group (p < 0.001). In the Stroop task both groups showed improved color, word- and color-word naming (p < 0.01), while the physical exercise group showed higher interference scores. Total, general and parental self-esteem improved in the yoga group (p < 0.05).
Yoga and physical exercise are useful additions to the school routine, with physical exercise improving social self-esteem.
Trial registration
The study was registered in the Clinical Trials Registry of India (CTRI/2012/11/003112).
PMCID: PMC3826528  PMID: 24199742
Yoga; Physical exercise; Physical fitness; Cognitive performance; Self-esteem; School children
11.  Sleep-Disordered Breathing and Mortality: A Prospective Cohort Study 
PLoS Medicine  2009;6(8):e1000132.
In a cohort of 6,441 volunteers followed over an average of 8.2 years, Naresh Punjabi and colleagues find sleep-disordered breathing to be independently associated with mortality and identify predictive characteristics.
Sleep-disordered breathing is a common condition associated with adverse health outcomes including hypertension and cardiovascular disease. The overall objective of this study was to determine whether sleep-disordered breathing and its sequelae of intermittent hypoxemia and recurrent arousals are associated with mortality in a community sample of adults aged 40 years or older.
Methods and Findings
We prospectively examined whether sleep-disordered breathing was associated with an increased risk of death from any cause in 6,441 men and women participating in the Sleep Heart Health Study. Sleep-disordered breathing was assessed with the apnea–hypopnea index (AHI) based on an in-home polysomnogram. Survival analysis and proportional hazards regression models were used to calculate hazard ratios for mortality after adjusting for age, sex, race, smoking status, body mass index, and prevalent medical conditions. The average follow-up period for the cohort was 8.2 y during which 1,047 participants (587 men and 460 women) died. Compared to those without sleep-disordered breathing (AHI: <5 events/h), the fully adjusted hazard ratios for all-cause mortality in those with mild (AHI: 5.0–14.9 events/h), moderate (AHI: 15.0–29.9 events/h), and severe (AHI: ≥30.0 events/h) sleep-disordered breathing were 0.93 (95% CI: 0.80–1.08), 1.17 (95% CI: 0.97–1.42), and 1.46 (95% CI: 1.14–1.86), respectively. Stratified analyses by sex and age showed that the increased risk of death associated with severe sleep-disordered breathing was statistically significant in men aged 40–70 y (hazard ratio: 2.09; 95% CI: 1.31–3.33). Measures of sleep-related intermittent hypoxemia, but not sleep fragmentation, were independently associated with all-cause mortality. Coronary artery disease–related mortality associated with sleep-disordered breathing showed a pattern of association similar to all-cause mortality.
Sleep-disordered breathing is associated with all-cause mortality and specifically that due to coronary artery disease, particularly in men aged 40–70 y with severe sleep-disordered breathing.
Please see later in the article for the Editors' Summary
Editors' Summary
About 1 in 10 women and 1 in 4 men have a chronic condition called sleep-disordered breathing although most are unaware of their problem. Sleep-disordered breathing, which is commonest in middle-aged and elderly people, is characterized by numerous, brief (10 second or so) interruptions of breathing during sleep. These interruptions, which usually occur when relaxation of the upper airway muscles decreases airflow, lower the level of oxygen in the blood and, as a result, affected individuals are frequently aroused from deep sleep as they struggle to breathe. Symptoms of sleep-disordered breathing include loud snoring and daytime sleepiness. Treatments include lifestyle changes such as losing weight (excess fat around the neck increases airway collapse) and smoking cessation. Affected people can also use special devices to prevent them sleeping on their backs, but for severe sleep-disordered breathing, doctors often recommend continuous positive airway pressure (CPAP), a machine that pressurizes the upper airway through a face mask to keep it open.
Why Was This Study Done?
Sleep-disordered breathing is a serious condition. It is associated with several adverse health conditions including coronary artery disease (narrowing of the blood vessels that supply the heart, a condition that can cause a heart attack) and daytime sleepiness that can affect an individual's driving ability. In addition, several clinic- and community-based studies suggest that sleep-disordered sleeping may increase a person's risk of dying. However, because these studies have been small and have often failed to allow for other conditions and characteristics that affect an individual's risk of dying (“confounding factors”), they provide inconsistent or incomplete information about the potential association between sleep-disordered breathing and the risk of death. In this prospective cohort study (part of the Sleep Heart Health Study, which is researching the effects of sleep-disordered breathing on cardiovascular health), the researchers examine whether sleep-disordered breathing is associated with all-cause mortality (death from any cause) in a large community sample of adults. A prospective cohort study is one in which a group of participants is enrolled and then followed forward in time (in this case for several years) to see what happens to them.
What Did the Researchers Do and Find?
At enrollment, the study participants—more than 6,000 people aged 40 years or older, none of whom were being treated for sleep-disordered breathing—had a health examination. Their night-time breathing, sleep patterns, and blood oxygen levels were also assessed and these data used to calculate each participant's apnea-hypopnea index (AHI)—the number of apneas and hypopneas per hour. During the study follow-up period, 1,047 participants died. Compared to participants without sleep-disordered sleeping, participants with severe sleep-disordered breathing (an AHI of ≥30) were about one and a half times as likely to die from any cause after adjustment for potential confounding factors. People with milder sleep-disordered breathing did not have a statistically significant increased risk of dying. After dividing the participants into subgroups according to their age and sex, men aged 40–70 years with severe sleep-disordered breathing had a statistically increased risk of dying from any cause (twice the risk of men of a similar age without sleep-disordered breathing). Finally, death from coronary artery disease was also associated with sleep-disordered breathing in men but not in women.
What Do These Findings Mean?
These findings indicate that sleep-disordered breathing is associated with an increased risk of all-cause mortality, particularly in men aged 40–70 years, even after allowing for known confounding factors. They also suggest that the increased risk of death is specifically associated with coronary artery disease although further studies are needed to confirm this finding because it was based on the analysis of a small subgroup of study participants. Although this study is much larger than previous investigations into the association between sleep-disordered breathing and all-cause mortality, it has several limitations including its reliance on a single night's measurements for the diagnosis of sleep-disordered breathing. Nevertheless, these findings suggest that clinical trials should now be started to assess whether treatment can reduce the increased risk of death that seems to be associated with this common disorder.
Additional Information
Please access these Web sites via the online version of this summary at
The US National Heart Lung and Blood Institute has information (including a video) about sleep-disordered breathing (sleep apnea) (in English and Spanish)
The UK National Heath Service also provides information for patients about sleep apnea
MedlinePlus provides links to further information and advice about sleep-disordered breathing (in English and Spanish)
More information on the Sleep Heart Health Study is available
PMCID: PMC2722083  PMID: 19688045
12.  An explorative study of metabolic responses to mental stress and yoga practices in yoga practitioners, non-yoga practitioners and individuals with metabolic syndrome 
Stress places a metabolic burden on homeostasis and is linked to heightened sympathetic activity, increased energy expenditure and pathology. The yogic state is a hypometabolic state that corresponds with mind-body coherence and reduced stress. This study aimed to investigate metabolic responses to stress and different yoga practices in regular yoga practitioners (YP), non-yoga practitioners (NY) and metabolic syndrome patients (MS).
YP (n = 16), NY (n = 15) and MS (n = 15) subjects underwent an experimental protocol that comprised of different 5-minute interventions including mental arithmetic stress test (MAST), alternate nostril breathing (ANB), Kapabhati breathing (KB) and meditation (Med) interspersed with 5 minutes of quiet resting (neutral condition (NC)). During the intervention periods continuous body weight adjusted oxygen consumption (VO2ml/min/kg) was measured using open circuit indirect calorimetry with a canopy hood.
This is the first study to report oxygen consumption (OC) in yoga practitioners during and after MAST and the first to report both within and between different populations. The results were analysed with SPSS 16 using 3X9 mixed factorial ANOVAs. The single between-subject factor was group (YP, NY and MS), the single within-subject factor was made up of the nine intervention phases (NC1, MAST, NC2, ANB, NC3, KB, NC4, Med, NC5). The results demonstrated that the regular YP group had significantly less OC and greater variability in their OC across all phases compared to the MS group (p = .003) and NY group (p = .01). All groups significantly raised their OC during the mental arithmetic stress, however the MS group had a significantly blunted post-stress recovery whereas the YP group rapidly recovered back to baseline levels with post stress recovery being greater than either the NY group or MS group.
Yoga practitioners have greater metabolic variability compared to non-yoga practitioners and metabolic syndrome patients with reduced oxygen requirements during resting conditions and more rapid post-stress recovery. OC in metabolic syndrome patients displays significantly blunted post-stress recovery demonstrating reduced metabolic resilience. Our results support the findings of previous randomised trials that suggest regular yoga practice may mitigate against the effects of metabolic syndrome.
Clinical trial number
ACTRN12614001075673; Date of Registration: 07/10/2014.
PMCID: PMC4247158  PMID: 25398263
Yoga; Meditation; Breathing; Metabolic syndrome; Oxygen consumption; Energy Expenditure; Metabolic rate; Stress reactivity; Stress recovery
13.  Atoh1-dependent rhombic lip neurons are required for temporal delay between independent respiratory oscillators in embryonic mice 
eLife  2014;3:e02265.
All motor behaviors require precise temporal coordination of different muscle groups. Breathing, for example, involves the sequential activation of numerous muscles hypothesized to be driven by a primary respiratory oscillator, the preBötzinger Complex, and at least one other as-yet unidentified rhythmogenic population. We tested the roles of Atoh1-, Phox2b-, and Dbx1-derived neurons (three groups that have known roles in respiration) in the generation and coordination of respiratory output. We found that Dbx1-derived neurons are necessary for all respiratory behaviors, whereas independent but coupled respiratory rhythms persist from at least three different motor pools after eliminating or silencing Phox2b- or Atoh1-expressing hindbrain neurons. Without Atoh1 neurons, however, the motor pools become temporally disorganized and coupling between independent respiratory oscillators decreases. We propose Atoh1 neurons tune the sequential activation of independent oscillators essential for the fine control of different muscles during breathing.
eLife digest
A healthy adult at rest will breathe in and out around 20 times per minute. Each breath requires a complex series of coordinated muscle activity. Inhalation begins with the opening of the airway followed by the contraction of the diaphragm and the intercostal muscles between the ribs, causing the chest cavity to expand. As the lungs increase in volume, the pressure inside them drops and air is drawn in. Relaxation of the diaphragm and intercostal muscles compresses the lungs, causing us to exhale.
Breathing is driven by the brainstem and it cannot be suppressed indefinitely: holding your breath eventually triggers a reflex that forces breathing to resume. The region of the brainstem that controls breathing is called the preBötzinger Complex. However, there is increasing evidence that a second region in the brainstem is also involved. This region, which is called the retrotrapezoid nucleus/parafacial respiratory group, consists of three types of excitatory neurons—Dbx1 neurons, Phox2b neurons, and Atoh1 neurons—but their roles had not been clear. Now, using multiple lines of genetically modified mice, Tupal et al. have teased apart the roles of these three cell types.
These experiments showed that the Dbx1 neurons—which are also found in the preBötzinger Complex—have an essential role in sending the signals from the brain that drive the different muscle activities needed to breathe. The Phox2b neurons modulate breathing based on the level of carbon dioxide in the blood. Atoh1 neurons help control the sequence of respiratory muscle activity during a breath, probably by selectively inhibiting different populations of Dbx1 neurons.
The work of Tupal et al. indicates that distinct populations of neurons within the brainstem independently control two different aspects of breathing: the generation of breathing rhythms, and the coordination of these rhythms. Given that many other physiological processes involve rhythmic activity patterns, this model may help us to understand how the brain generates and controls complex behaviors more generally.
PMCID: PMC4060005  PMID: 24842997
breathing; central pattern generator; PreBötzinger Complex; oscillator; transcription; mouse
14.  Effect of yogic bellows on cardiovascular autonomic reactivity 
Yoga is an ancient science, which originated in India. Pranayama has been assigned a very important role in yogic system of exercises. It is known that regular practice of breathing exercises (pranayama) increases parasympathetic tone, decreases sympathetic activity, and improves cardiovascular functions. Different types of breathing exercises alter autonomic balance for good by either decrease in sympathetic or increase in parasympathetic activity. Mukh Bhastrika (yogic bellows), a type of pranayama breathing when practiced alone, has demonstrated increase in sympathetic activity and load on heart, but when practiced along with other types of pranayama has showed improved cardiac performance.
The present study was conducted to evaluate the effect of long term practice of fast pranayama (Mukh Bhastrika) on autonomic balance on individuals with stable cardiac function.
Settings and Design:
This interventional study was conducted in the department of physiology.
Materials and Methods:
50 healthy male subjects of 18 - 25 years age group, fulfilling the inclusion and exclusion criteria underwent Mukh Bhastrika training for 12 weeks. Cardiovascular autonomic reactivity tests were performed before and after the training.
Statistical Analysis Used:
The parameters were analyzed by Student t test.
This study showed an increase in parasympathetic activity i.e., reduced basal heart rate, increase in valsalva ratio and deep breathing difference in heart rate; and reduction in sympathetic activity i.e., reduction in fall of systolic blood pressure on posture variation.
It can be concluded that Mukh Bhastrika has beneficial effect on cardiac autonomic reactivity, if practiced for a longer duration.
PMCID: PMC3224442  PMID: 22135480
Cardiovascular autonomic reactivity; Mukh Bhastrika; valsalva ratio; yogic bellows
15.  Effect of Yoga on Autonomic Functions and Psychological Status During Both Phases of Menstrual Cycle in Young Healthy Females 
Context: Premenstrual stress affects 75% of women of childbearing age and yoga has been found to be beneficial in many psycho-somatic disorders.
Aims: To investigate the effect of integrated yoga on autonomic parameters and psychological well-being during both pre and post phases of menstrual cycle in healthy young female subjects.
Settings and Design: Present study is a randomized control trial and was conducted in the Department of Physiology, Lady Hardinge Medical College, New Delhi, India.
Material and Methods: Fifty apparently healthy females in the age group of 18-20 years were randomized into two groups: Group I (n=25) consisted of subjects who practiced yoga 35-40 minutes per day, six times per week for the duration of three menstrual cycles. Training was given by qualified yoga instructor. Group II (n=25) subjects acted as controls. Following parameters were recorded at the beginning and after completion of three menstrual cycles in all the subjects: Height, weight (BW), Resting Heart Rate (HR), Resting Systolic (SBP) and Diastolic Blood Pressure (DBP), parasympathetic reactivity tests including Expiration-Inspiration Ratio (E: I ratio) and 30:15 ratio, sympathetic reactivity tests including BP changes due to Isometric Hand Grip (IHG) exercise, and Cold Pressor Test (CPT). Assessment of psychological status was done by administering DIPAS (Defense Institute of Physiology and Allied Sciences) inventories of Anger self report scale, Trait Anxiety, Sense of well-being and Depression scale.
Statistical Analysis: Intra-group comparison of physiological parameters was done by using paired ‘t’ test, whereas intra-group comparison of non-parameteric data such as scores of anxiety, depression, anger and sense of well-being was done by Wilcoxon signed-rank test. Inter-group comparison of parameters was done by Students ‘t’ test for parametric tests and Mann-Whitney ‘U’ test for non-parameteric tests.
Results: There was significantly higher BW, resting SBP, DBP, sympathetic activity and blunting of parasympathetic reactivity and also, significantly higher scores of anger, depression, anxiety and decreased score of well-being in premenstrual phase as compared to postmenstrual phase in both the groups in initial cycle. There was significantly higher percentage decrease in BW, HR, SBP & DBP in yoga group as compared to control group in both the phases from initial to second and onwards between second and third menstrual cycle. Also, decrease in anger, depression and anxiety and increase in well-being score was significant in yoga group as compared to control group from initial to second and third cycle in premenstrual phase while the change was significant only in depression score in postmenstrual phase.
Conclusion: Our study shows that there was significant alteration of autonomic functions and psychological status in premenstrual phase when compared with postmenstrual phase in young healthy females. Also, regular practice of yoga has beneficial effects on both phases of menstrual cycle by bringing parasympathodominance and psychological well-being probably by balancing neuro-endocrinal axis.
PMCID: PMC3843391  PMID: 24298457
Yoga; Premenstrual stress; Autonomic functions; Psychological status
16.  Effect of rosary prayer and yoga mantras on autonomic cardiovascular rhythms: comparative study 
BMJ : British Medical Journal  2001;323(7327):1446-1449.
To test whether rhythmic formulas such as the rosary and yoga mantras can synchronise and reinforce inherent cardiovascular rhythms and modify baroreflex sensitivity.
Comparison of effects of recitation of the Ave Maria (in Latin) or of a mantra, during spontaneous and metronome controlled breathing, on breathing rate and on spontaneous oscillations in RR interval, and on blood pressure and cerebral circulation.
Florence and Pavia, Italy.
23 healthy adults.
Main outcome measures
Breathing rate, regularity of breathing, baroreflex sensitivity, frequency of cardiovascular oscillations.
Both prayer and mantra caused striking, powerful, and synchronous increases in existing cardiovascular rhythms when recited six times a minute. Baroreflex sensitivity also increased significantly, from 9.5 (SD 4.6) to 11.5 (4.9) ms/mm Hg, P<0.05.
Rhythm formulas that involve breathing at six breaths per minute induce favourable psychological and possibly physiological effects.
What is already known on this topicReduced heart rate variability and baroreflex sensitivity are powerful and independent predictors of poor prognosis in heart diseaseSlow breathing enhances heart rate variability and baroreflex sensitivity by synchronising inherent cardiovascular rhythmsWhat this study addsRecitation of the rosary, and also of yoga mantras, slowed respiration to almost exactly 6/min, and enhanced heart rate variability and baroreflex sensitivityThe rosary might be viewed as a health practice as well as a religious practice
PMCID: PMC61046  PMID: 11751348
17.  Acute Application of Bilevel Positive Airway Pressure Influences the Cardiac Autonomic Nervous System 
Clinics (Sao Paulo, Brazil)  2009;64(11):1085-1092.
Noninvasive positive pressure has been used to treat several diseases. However, the physiological response of the cardiac autonomic system during bilevel positive airway pressure (Bilevel) remains unclear.
The aim of this study was to evaluate the heart rate variability (HRV) during Bilevel in young healthy subjects.
Twenty men underwent 10-minute R-R interval recordings during sham ventilation (SV), Bilevel of 8–15 cmH2O and Bilevel of 13–20 cmH2O. The HRV was analyzed by means of the parallel R-R interval (mean R-Ri), the standard deviation of all R-Ri (SDNN), the root mean square of the squares of the differences between successive R-Ri (rMSSD), the number of successive R-Ri pairs that differ by more than 50 milliseconds (NN50), the percentage of successive R-Ri that differ by more than 50 milliseconds (pNN50), the low frequency (LF), the high frequency (HF) and SD1 and SD2. Additionally, physiological variables, including blood pressure, breathing frequency and end tidal CO2, were collected. Repeated-measures ANOVA and Pearson correlation were used to assess the differences between the three studied conditions and the relationships between the delta of Bilevel at 13–20 cmH2O and sham ventilation of the HRV indexes and the physiological variables, respectively.
The R-Ri mean, rMSSD, NN50, pNN50 and SD1 were reduced during Bilevel of 13–20 cmH2O as compared to SV. An R-Ri mean reduction was also observed in Bilevel of 13–20 cmH2O compared to 8–15 cmH2O. Both the R-Ri mean and HF were reduced during Bilevel of 8–15 cmH2O as compared to SV, while the LF increased during application of Bilevel of 8–15 cmH2O as compared to SV. The delta (between Bilevel at 13–20 cmH2O and sham ventilation) of ETCO2 correlated positively with LF, HF, the LF/HF ratio, SDNN, rMSSD and SD1. Acute application of Bilevel was able to alter the cardiac autonomic nervous system, resulting in a reduction in parasympathetic activity and an increase in sympathetic activity and higher level of positive pressure can cause a greater influence on the cardiovascular and respiratory system.
PMCID: PMC2780525  PMID: 19936182
Heart rate; Neural control; Heart rate variability; Noninvasive positive pressure ventilation; Physiological responses
18.  Breathing exercises: influence on breathing patterns and thoracoabdominal motion in healthy subjects 
The mechanisms underlying breathing exercises have not been fully elucidated.
To evaluate the impact of four on breathing exercises (diaphragmatic breathing, inspiratory sighs, sustained maximal inspiration and intercostal exercise) the on breathing pattern and thoracoabdominal motion in healthy subjects.
Fifteen subjects of both sexes, aged 23±1.5 years old and with normal pulmonary function tests, participated in the study. The subjects were evaluated using the optoelectronic plethysmography system in a supine position with a trunk inclination of 45° during quiet breathing and the breathing exercises. The order of the breathing exercises was randomized. Statistical analysis was performed by the Friedman test and an ANOVA for repeated measures with one factor (breathing exercises), followed by preplanned contrasts and Bonferroni correction. A p<0.005 value was considered significant.
All breathing exercises significantly increased the tidal volume of the chest wall (Vcw) and reduced the respiratory rate (RR) in comparison to quiet breathing. The diaphragmatic breathing exercise was responsible for the lowest Vcw, the lowest contribution of the rib cage, and the highest contribution of the abdomen. The sustained maximal inspiration exercise promoted greater reduction in RR compared to the diaphragmatic and intercostal exercises. Inspiratory sighs and intercostal exercises were responsible for the highest values of minute ventilation. Thoracoabdominal asynchrony variables increased significantly during diaphragmatic breathing.
The results showed that the breathing exercises investigated in this study produced modifications in the breathing pattern (e.g., increase in tidal volume and decrease in RR) as well as in thoracoabdominal motion (e.g., increase in abdominal contribution during diaphragmatic breathing), among others.
PMCID: PMC4311599  PMID: 25590447
19.  Autonomic function in hypertrophic cardiomyopathy. 
British Heart Journal  1993;69(6):525-529.
BACKGROUND--Autonomic dysfunction has been found to be a powerful predictor of arrhythmic events and sudden death after myocardial infarction. Hypertrophic cardiomyopathy carries a risk of sudden death and this risk is increased by the occurrence of syncope. OBJECTIVES--To determine if autonomic dysfunction occurs in patients with hypertrophic cardiomyopathy and if it is associated with the occurrence of syncope. PATIENTS AND METHODS--Autonomic function was measured in 30 patients with hypertrophic cardiomyopathy, 15 with and 15 without a history of syncope, and in 28 healthy volunteers. RESULTS--Tests of parasympathetic activity showed that the mean (SD) variation in heart rate during deep breathing was reduced in patients compared with controls, 17 (9) v 22 (9) beats/min, p = 0.03, the Valsalva ratio was also reduced in patients, 1.52 (0.33) v 1.70 (0.36), p = 0.05 but the immediate heart rate response to standing, the 30:15 ratio, was similar in both groups. Tests of sympathetic activity--namely the diastolic blood pressure response to sustained handgrip and the change in systolic blood pressure on standing--did not differ between patients and controls. There was no significant difference in autonomic function between patients with and without a history of syncope. A secondary predetermined analysis showed that the degree of impairment in variation of heart rate with breathing was correlated with the severity of left ventricular hypertrophy, r = 0.39, p = 0.03. CONCLUSIONS--Patients with hypertrophic cardiomyopathy have a selective impairment of variability of heart rate with deep breathing and the Valsalva manoeuvre indicating decreased cardiac parasympathetic activity. The data suggest that the afferent limb of these reflexes is impaired and that the severity of impairment is related to the degree of left ventricular hypertrophy.
PMCID: PMC1025165  PMID: 8343320
20.  Changes in P300 following alternate nostril yoga breathing and breath awareness 
This study assessed the effect of alternate nostril yoga breathing (nadisuddhi pranayama) on P300 auditory evoked potentials compared to a session of breath awareness of equal duration, in 20 male adult volunteers who had an experience of yoga breathing practices for more than three months. Peak amplitudes and peak latencies of the P300 were assessed before and after the respective sessions. There was a significant increase in the P300 peak amplitudes at Fz, Cz, and Pz and a significant decrease in the peak latency at Fz alone following alternate nostril yoga breathing. Following breath awareness there was a significant increase in the peak amplitude of P300 at Cz. This suggests that alternate nostril yoga breathing positively influences cognitive processes which are required for sustained attention at different scalp sites (frontal, vertex and parietal), whereas breath awareness brings about changes at the vertex alone.
PMCID: PMC3679963  PMID: 23721252
Alternate nostril yoga breathing; P300; Breath awareness; Cognitive processes
21.  Cardiac autonomic function in patients with diabetes improves with practice of comprehensive yogic breathing program 
The aim of this study was to observe the effect comprehensive yogic breathing (Sudarshan Kriya Yoga [SKY] and Pranayam) had on cardiac autonomic functions in patients with diabetes.
Materials and Methods:
This is a prospective randomized controlled intervention trial. Cardiac autonomic functions were assessed in 64 diabetics. Patients were randomized into two groups, one group receiving standard therapy for diabetes and the other group receiving standard therapy for diabetes and comprehensive yogic breathing program. Standard therapy included dietary advice, brisk walking for 45 min daily, and administration of oral antidiabetic drugs. Comprehensive yogic breathing program was introduced to the participants through a course of 12 h spread over 3 days. It was an interactive session in which SKY, a rhythmic cyclical breathing, preceded by Pranayam is taught under the guidance of a certified teacher. Cardiac autonomic function tests were done before and after 6 months of intervention.
In the intervention group, after practicing the breathing techniques for 6 months, the improvement in sympathetic functions was statistically significant (P 0.04). The change in sympathetic functions in the standard therapy group was not significant (P 0.75). Parasympathetic functions did not show any significant change in either group. When both parasympathetic and sympathetic cardiac autonomic functions were considered, there was a trend toward improvement in patients following comprehensive yogic breathing program (P 0.06). In the standard therapy group, no change in cardiac autonomic functions was noted (P 0.99).
Cardiac autonomic functions improved in patients with diabetes on standard treatment who followed the comprehensive yogic breathing program compared to patients who were on standard therapy alone.
PMCID: PMC3712380  PMID: 23869306
Cardiac autonomic function; comprehensive yogic breathing; diabetes mellitus
22.  The Difference in Respiratory and Blood Gas Values During Recovery After Exercise With Spontaneous Versus Reduced Breathing Frequency 
Extrapolation from post-exercise measurements has been used to estimate respiratory and blood gas parameters during exercise. This may not be accurate in exercise with reduced breathing frequency (RBF), since spontaneous breathing usually follows exercise. This study was performed to ascertain whether measurement of oxygen saturation and blood gases immediately after exercise accurately reflected their values during exercise with RBF. Eight healthy male subjects performed an incremental cycling test with RBF at 10 breaths per minute. A constant load test with RBF (B10) was then performed to exhaustion at the peak power output obtained during the incremental test. Finally, the subjects repeated the constant load test with spontaneous breathing (SB) using the same protocol as B10. Pulmonary ventilation (VE), end-tidal oxygen (PETO2), and carbon dioxide pressures (PETCO2) and oxygen saturation (SaO2) were measured during both constant load tests. The partial pressures of oxygen (PO2) and carbon dioxide (PCO2) in capillary blood were measured during the last minute of exercise, immediately following exercise and during the third minute of recovery. At the end of exercise RBF resulted in lower PETO2, SaO2 and PO2, and higher PETCO2 and PCO2 when compared to spontaneous breathing during exercise. Lower SaO2 and PETO2 were detected only for the first 16s and 20s of recovery after B10 compared to the corresponding period in SB. There were no significant differences in PO2 between SB and B10 measured immediately after the exercise. During recovery from exercise, PETCO2 remained elevated for the first 120s in the B10 trial. There were also significant differences between SB and B10 in PCO2 immediately after exercise. We conclude that RBF during high intensity exercise results in hypoxia; however, due to post-exercise hyperpnoea, measurements of blood gas parameters taken 15s after cessation of exercise did not reflect the changes in PO2 and SaO2 seen during exercise.
Key pointsIn some sports, the environment is inappropriate for direct measurement of respiratory and blood gas parameters during exercise. To overcome this problem, extrapolation from post-exercise measurements has often been used to estimate changes in respiratory and blood gas parameters during exercise.The possibility of hypoxia and hypercapnia during exercise with reduced breathing frequency has been tested by measuring capillary blood sampled after the exercise.Reduced breathing frequency during high intensity exercise results in hypoxia; however, due to marked post-exercise hyperventilation, measurements of blood gas parameters taken 15 s after the cessation of exercise did not yield any changes in these parameters.Despite hyperventilation during recovery, hypercapnia could be detected by measuring blood gas parameters within 15 s after the exercise with reduced breathing frequency.
PMCID: PMC3763292  PMID: 24150010
Constant load test; reduced breathing frequency; recovery; respiratory parameters; oxygen saturation; blood gas
23.  Acute Auditory Stimulation with Different Styles of Music Influences Cardiac Autonomic Regulation in Men 
No clear evidence is available in the literature regarding the acute effect of different styles of music on cardiac autonomic control.
The present study aimed to evaluate the acute effects of classical baroque and heavy metal musical auditory stimulation on Heart Rate Variability (HRV) in healthy men.
Patients and Methods:
In this study, HRV was analyzed regarding time (SDNN, RMSSD, NN50, and pNN50) and frequency domain (LF, HF, and LF / HF) in 12 healthy men. HRV was recorded at seated rest for 10 minutes. Subsequently, the participants were exposed to classical baroque or heavy metal music for five minutes through an earphone at seated rest. After exposure to the first song, they remained at rest for five minutes and they were again exposed to classical baroque or heavy metal music. The music sequence was random for each individual. Standard statistical methods were used for calculation of means and standard deviations. Besides, ANOVA and Friedman test were used for parametric and non-parametric distributions, respectively.
While listening to heavy metal music, SDNN was reduced compared to the baseline (P = 0.023). In addition, the LF index (ms2 and nu) was reduced during exposure to both heavy metal and classical baroque musical auditory stimulation compared to the control condition (P = 0.010 and P = 0.048, respectively). However, the HF index (ms2) was reduced only during auditory stimulation with music heavy metal (P = 0.01). The LF/HF ratio on the other hand decreased during auditory stimulation with classical baroque music (P = 0.019).
Acute auditory stimulation with the selected heavy metal musical auditory stimulation decreased the sympathetic and parasympathetic modulation on the heart, while exposure to a selected classical baroque music reduced sympathetic regulation on the heart.
PMCID: PMC4109034  PMID: 25177673
Autonomic Nervous System; Cardiovascular System; Music; Auditory Stimulation
24.  Can Blood Gas and Acid-Base Parameters at Maximal 200 Meters Front Crawl Swimming be Different Between Former Competitive and Recreational Swimmers? 
The aim of the present study was to ascertain whether maximal 200 m front crawl swimming strategies and breathing patterns influenced blood gas and acid-base parameters in a manner which gives advantage to former competitive swimmers in comparison with their recreational colleagues. Twelve former competitive male swimmers (the CS group) and nine recreational male swimmers (the RS group) performed a maximal 200 m front crawl swimming with self- selected breathing pattern. Stroke rate (SR) and breathing frequency (BF) were measured during the swimming test. Measures also included blood lactate concentration ([LA]) and parameters of blood acid-base status before and during the first minute after the swimming test. The CS group swam faster then the RS group. Both groups have similar and steady SR throughout the swimming test. This was not matched by similar BF in the CS group but matched it very well in the RS group (r = 0.89). At the beginning of swimming test the CS group had low BF, but they increased it throughout the swimming test. The BF at the RS group remained constant with only mirror variations throughout the swimming test. Such difference in velocity and breathing resulted in maintaining of blood Po2 from hypoxia and Pco2 from hypercapnia. This was similar in both groups. [LA] increased faster in the CS group than in the RS group. On the contrary, the rate of pH decrease remained similar in both groups. The former competitive swimmers showed three possible advantages in comparison to recreational swimmers during maximal 200 m front crawl swimming: a more dynamic and precise regulation of breathing, more powerful bicarbonate buffering system and better synchronization between breathing needs and breathing response during swimming.
Key pointsTraining programs for competitive swimmers should promote adaptations to maximal efforts.Those adaptations should include high and maximal intensity swims with controlled breathing frequency (taking breath every fourth, fifth, sixth or eighth stroke cycle for front crawl swimming).Such training will improve breathing regulation in order to impose a better synchronization between breathing needs and breathing response during maximal swimming.
PMCID: PMC3763334  PMID: 24150142
Swimming; freestyle; breathing; blood gas; acid-base status
25.  Characterization of the Fetal Diaphragmatic Magnetomyogram and the Effect of Breathing Movements on Cardiac Metrics of Rate and Variability 
Early human development  2011;87(7):467-475.
Breathing movements are one of the earliest fetal motor behaviors to emerge andare ahallmark of fetal well-being. Fetal respiratory sinus arrhythmia (RSA) has been documented but efforts to quantify the influence of breathing on heart rate (HR) and heart rate variability (HRV) are difficult due to the episodic nature of fetal breathing activity. We used a dedicated fetal biomagnetometer to acquire the magnetocardiogram (MCG) between 36-38 weeks gestational age (GA). We identified and characterized a waveform observed in the raw data and independent component decomposition that we attribute to fetal diaphragmatic movements during breathing episodes. RSA and increased high frequency power in a time-frequency analysis of the IBI time-series was observed during fetal breathing periods. Using the diaphragmatic magnetomyogram (dMMG) as a marker, we compared time and frequency domain metrics of heartrate and heart rate variability between breathing and non-breathing epochs. Fetal breathing activity resulted in significantly lower HR, increased high frequency power, greater sympathovagal balance, increased short-term HRV andgreater parasympathetic input relative to non-breathing episodesconfirming the specificity of fetal breathing movements on parasympathetic cardiac influence. No significant differences between breathing and non-breathing epochs were found in two metrics reflecting total HRVor very low, low and intermediate frequency bands. Using the fetal dMMG as a marker, biomagnetometry can help to elucidate the electrophysiologic mechanisms associated with diaphragmatic motor function and may be used to study the longitudinal development of human fetal cardiac autonomic control and breathing activity.
PMCID: PMC3114157  PMID: 21497027
Autonomic Nervous System; Magnetocardiogram; Fetal Biomagnetometry; Diaphragm Activation

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