HRV

How Slow Deep Breathing Results in Positive Emotions and More Creativity

Key Points

  • Dominance of the calming parasympathetic nervous system is associated with positive emotions and can be evoked through slow breathing.

  • Slow breathing leads to “hyperpolarization,” which literally makes neurons less excitable.

  • Slow breathing reduces activity in the amygdala, which increases relaxation and boosts creativity.

The Breathing Diabetic Summary

You probably know by now that emotional states are linked to breathing.  When you’re stressed, you breathe faster.  When you’re calm, you breathe slower.  Intuitively, it makes sense.  But how exactly does it occur?  That’s what this current paper explores.  It’s a fascinating look at how cardiorespiratory coherence can potentially influence emotions.  Of course, what matters most is simply that it works.  But here, we learn how it might be working…and it’s pretty amazing.

 

Feedforward or Feedback?

The fundamental hypothesis is that cardiorespiratory coherence (which I’m going to refer to as slow breathing for simplicity, although that’s not 100% correct) can regulate the autonomic nervous system and brainstem.  This, in turn, modulates the emotional regions of the brain.

This is a unique hypothesis because we typically think of emotions through a “feedforward” lens.  An emotion arises in the brain and “feeds” its signal to the rest of the body.  But here, they’re saying feedbacks from slow breathing, namely the ones on the nervous system and brain, can elicit positive emotions.

That is, you might be able to breathe yourself into happiness.

 

How Emotional States Correspond to Autonomic Function

 The most important indicator that this is possible is the link between positive emotional states and higher levels of cardiorespiratory coherence.  Of course, correlation doesn’t mean causation.  Still, the general conclusion from most studies is that positive emotions are associated with parasympathetic (calming) dominance, and negative moods are associated with sympathetic (fight or flight) dominance.

 This supports their hypothesis.  If we simply induce relaxation and parasympathetic dominance through slow breathing, maybe positive emotions will follow.

 

Hyperpolarization might Explain the Calming Effects of Slow Breathing and Meditation

 One fascinating way they propose this feedback might occur is through neuronal “hyperpolarization.”   Hyperpolarization seems to be a fancy way of saying that the neurons are harder to “excite.”  Meaning it actually takes a lot more energy to fire the neurons that make you stressed or anxious.  This helps explain why we feel relaxed after we meditate or breathe slowly.  These practices actually change our cells, making it harder to feel stressed…pretty crazy.

As an aside, I know I feel most joyful and optimistic after my morning breathing practice.  It feels like magic, but I guess it’s just hyperpolarization at its finest : )

 

Inhibition of the Amygdala from Slow Breathing

And here is a critical implication of hyperpolarization: inhibition of the amygdala. 

When we meditate or practice slow breathing (~4-6 breaths/minute), the neuronal hyperpolarization reduces activity in our amygdala.  This turns down negative thinking and turns up creativity.

As Steven Kotler tells us in The Art of Impossible, ““Unfortunately, to keep us safe, the amygdala is strongly biased toward negative information. …This crushes optimism and squelches creativity. When tuned toward the negative, we miss the novel.

Perhaps this is why, after interviewing the most creative people on the planet, Tim Ferriss discovered that “More than 80% of the interviewees have some form of daily mindfulness or meditation practice.

These practices naturally lead to cardiorespiratory coherence, quieting the pessimistic amygdala, allowing us to see the novelty all around us.

A Summary of How Slow Breathing Modifies Emotions 

Let’s wrap it all together to see how slow breathing can improve our emotional state. 

Positive emotional states are associated with high levels of cardiorespiratory coherence.  These states induce hyperpolarization, which inhibits the excitability of neurons.  This then modifies regions of the brainstem and inhibits the action of the amygdala and other limbic areas.  However, the opposite might also be true: simply breathing slowly will inhibit amygdala activity, allowing us to experience positive emotions, less stress, and more creativity.

Abstract

The brain is considered to be the primary generator and regulator of emotions; however, afferent signals originating throughout the body are detected by the autonomic nervous system (ANS) and brainstem, and, in turn, can modulate emotional processes. During stress and negative emotional states, levels of cardiorespiratory coherence (CRC) decrease, and a shift occurs toward sympathetic dominance. In contrast, CRC levels increase during more positive emotional states, and a shift occurs toward parasympathetic dominance. The dynamic changes in CRC that accompany different emotions can provide insights into how the activity of the limbic system and afferent feedback manifest as emotions. The authors propose that the brainstem and CRC are involved in important feedback mechanisms that modulate emotions and higher cortical areas. That mechanism may be one of many mechanisms that underlie the physiological and neurological changes that are experienced during pranayama and meditation and may support the use of those techniques to treat various mood disorders and reduce stress.

 

 

Journal Reference:

Jerath R, Crawford MW. How Does the Body Affect the Mind? Role of Cardiorespiratory Coherence in the Spectrum of Emotions. Adv Mind Body Med. 2015 Fall;29(4):4-16. PMID: 26535473.

 

2020 Meta-Analysis: Slow Breathing Improves A Variety of Behavioral and Physiological Outcomes

Key Points

  • Across 58 studies and 2,485 patients, heart rate variability biofeedback (HRVB) and slow breathing improve a wide range of behavioral and physiological outcomes.

  • These methods provide a simple, safe, and effective complementary therapy that could be useful in a wide variety of settings.

  • Slow breathing (without biofeedback) is likely to be enough, requiring little more than a cellphone application to get started.

The Breathing Diabetic Summary

A hallmark of slow breathing is that it increases heart rate variability (HRV). It does this by increasing respiratory sinus arrhythmia (RSA), which synchronizes your heart rate with your breathing. When they match, your heart rate increases while you inhale and it decreases while you exhale.

Thus, RSA enhances the “peaks and troughs” of heart rate with each breath, which increases HRV. Because HRV is a robust indicator of overall health and wellness, this is one way in which slow breathing is so powerful. So much so, in fact, that HRV biofeedback (or HRVB) has become extremely popular to help with a variety of problems. 

With HRVB, a person’s “perfect” breathing rate is determined—that is, one that maximizes HRV. And because increases in RSA and HRV are driven by increases in the calming parasympathetic branch of the nervous system, this can reduce negative stress and increase overall resiliency. This has wide-reaching positive benefits.

We’ve covered many of them before. But here are some of the general benefits:

  • Reduced blood pressure.

  • Reduced stress and anxiety.

  • Improved emotional control.

  • Enhanced cognitive function.

  • Better cardio-autonomic function.

  • Improved gas exchange in the lungs.

In this meta-analysis, the authors performed an extensive literature review to examine these benefits of HRVB from a broader statistical perspective. They included papers spanning a wide range of settings, measuring a wide range of outcomes.

Note that, although HRVB sounds fancy (and it can be), many of the benefits are achieved by simply breathing at a rate of about 5-6 breaths per minute.

Therefore, this meta-analysis also included studies that used 6 breaths per minute because:

it is possible that simply doing paced breathing at about six breaths per minute would have the same salutary effects as breathing more exactly at resonance frequency. […] This can easily be taught by following a computer-generated pacing signal or a clock.

From a practical perspective, this might be the most important aspect of this meta-analysis.

After starting with more than 1,500 papers, they ended up with 58 studies having a total of 2,485 patients.

Their statistical analysis of all these studies revealed that HRVB and slow breathing both significantly improve many aspects of health and wellness.

The greatest benefits were for:

  • Athletic performance

  • Artistic performance

  • Depression

  • Gastrointestinal problems

  • Anxiety and anger

  • Respiratory disorders

  • Systolic blood pressure

  • Pain

Smaller, but still meaningful, benefits were found for:

  • Self-reported stress

  • Quality of life

  • Diastolic blood pressure

  • PTSD

  • General energy

  • Sleep

Interestingly, I would have expected several items on the second list to be on the first. But that’s why meta-analyses like this are so important : ) Also, note that measures like “self-reported stress” are harder to quantify. The authors even mention that these results might be the result of how the questionnaires were given.

In any case, the overall results of this meta-analysis are quite exceptional: HRVB and slow breathing both have wide-ranging benefits for overall health and wellness.

These two sentences from the paper sum it up better than I ever could:

These results suggest that HRVB might be a useful addition to the skill sets of clinicians working in a variety of settings, including mental health, behavioral medicine, sports psychology, and education. The method is easy to learn and can easily be used along with other forms of intervention, with rare side effects.

Abstract

We performed a systematic and meta analytic review of heart rate variability biofeedback (HRVB) for various symptoms and human functioning. We analyzed all problems addressed by HRVB and all outcome measures in all studies, whether or not relevant to the studied population, among randomly controlled studies. Targets included various biological and psychological problems and issues with athletic, cognitive, and artistic performance. Our initial review yielded 1868 papers, from which 58 met inclusion criteria. A significant small to moderate effect size was found favoring HRVB, which does not differ from that of other effective treatments. With a small number of studies for each, HRVB has the largest effect sizes for anxiety, depression, anger and athletic/artistic performance and the smallest effect sizes on PTSD, sleep and quality of life. We found no significant differences for number of treatment sessions or weeks between pretest and post-test, whether the outcome measure was targeted to the population, or year of publication. Effect sizes are larger in comparison to inactive than active control conditions although significant for both. HRVB improves symptoms and functioning in many areas, both in the normal and pathological ranges. It appears useful as a complementary treatment. Further research is needed to confirm its efficacy for particular applications.

 

 

Journal Reference:

Lehrer, P., Kaur, K., Sharma, A., Shah, K., Huseby, R., Bhavsar, J., & Zhang, Y. (2020). Heart Rate Variability Biofeedback Improves Emotional and Physical Health and Performance: A Systematic Review and Meta Analysis. Applied Psychophysiology and Biofeedback, 45(3), 109–129. https://doi.org/10.1007/s10484-020-09466-z

 

How slow breathing improves physiological and psychological well-being (hint: it might be in your nose)

Zaccaro_et_al-2018_WTG.JPG

Key Points

  • Slow breathing increases heart rate variability, respiratory sinus arrhythmia, and alpha brain wave activity

  • These physiological changes lead to improved behavioral outcomes

  • The nose links slow breathing to these positive physiological and psychological outcomes

The Breathing Diabetic Summary

I think this paper wins “Best Title Ever” award!

This was a review study that pulled together all of the scientific literature on slow breathing and psychological/behavioral outcomes.  They were trying to answer the following question: What physiological changes are common to all slow breathing studies that have shown improvements in stress and anxiety?

After using some rather rigorous criteria for their literature search, they reduced 158 potential papers down to only 15. 

The physiological outcome parameters they focused on were heart rate variability (HRV), respiratory sinus arrhythmia (RSA), and brain wave activity.  The studies they examined also used several different subjective questionnaires to assess stress, anxiety, depression, and well-being.

As it is with science, there was a lot of nuance and many contradictory findings.  However, several common results did emerge.

First, slow breathing was associated with increases in HRV, particularly in the low frequency (LF) band.  Second, it was associated with increases in RSA.  Finally, slow breathing was associated with increases in alpha brain wave activity (brain waves associated with “flow”) and decreases in theta brain wave activity. 

All of these common physiological changes observed during/after slow breathing were associated with improved psychological and behavioral outcomes.  For example, several studies showed reductions in anxiety, improvements with depression, reduced anger, and increased relaxation.

Thus, slow breathing consistently increases HRV, RSA, and alpha brain wave activity.  These physiological changes then improve psychological and behavioral outcomes.

From a practical perspective, all of the studies used breathing rates of 3-6 breaths/min.  With practice, we can use an app (such as Breathing Zone) to achieve these rates.

Lastly, they examined the importance of the nose.  They reviewed studies showing that nasal breathing has a direct relationship with brain activity, which goes away when the nasal cavity tissue is numbed.  Moreover, certain areas of the brain follow oscillations that match breathing…but only with nasal respiration.  In fact, simply puffing air into the nostrils activates the brain at those “puff” oscillations (independent of actually breathing).

The authors hypothesize that the nose is the link between slow breathing, brain and autonomic functioning, and positive emotional outcomes.

From all of this, we find that slow breathing through the nose at 3-6 breaths/min (Principle 1) has positive effects on HRV, RSA, and brain wave activity.  These benefits then lead to improved psychological and behavioral outcomes.

Abstract

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.

Journal Reference:

Zaccaro A, Piarulli A, Laurino M, et al.  How Breath-Control Can Change Your Life: A Systematic Review on Psycho Physiological Correlates of Slow Breathing.  Front Hum Neurosci.  2018;12:353.

Intermittent hypoxia is beneficial in sedentary, non-athletic, and clinical populations

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Key Points

  • Intermittent hypoxia improves cardio-autonomic function and exercise tolerance

  • There are several ways to achieve intermittent hypoxia and receive benefits, including prolonged hypoxic exposure, intermittent hypoxic exposure, and intermittent hypoxic training

  • Intermittent hypoxia is beneficial in sedentary and clinical populations

The Breathing Diabetic Summary

I love review papers because they summarize the key findings from the scientific literature in an easy to follow manner. Therefore, anytime I find a review study on a subject of interest, I dive right in.

This one was unique because it looked at the effects of simulated altitude on non-athletic, sedentary, and clinical populations. Most studies on simulated altitude involve elite performers, so it was interesting seeing a review paper focusing on more “everyday” people.

Using different search criteria, they identified 26 studies that have looked at intermittent hypoxia in the abovementioned populations. Within those 26 studies, they then identified 3 different methods of achieving intermittent hypoxia:

  1. Prolonged hypoxic exposure (PHE): Continuous hypoxic interval, such as “live high, train low”.

  2. Intermittent hypoxic exposure (IHE): Short intervals (5-10 min) of hypoxic:normoxic exposure.

  3. Intermittent hypoxic training (IHT): Exercising in hypoxia.

For our purposes, IHE and IHT are the only practical methods for achieving hypoxia via breath holds. However, the results for PHE will also be included for completeness (and, maybe one day altitude tents will be affordable!).

Here, I’ll summarize the benefits they found for each method of hypoxia.

IHE:

  • Reduced systemic stress

  • Improved heart rate variability

  • Improved autonomic balance

  • Reduced blood pressure

  • Greater exercise tolerance

  • Longer time to exhaustion while exercising

  • Hematological results were mixed. Some studies showed increased red blood cells, others didn’t.

PHE:

  • Improved lung ventilation

  • Improved submaximal exercise performance

  • Improved blood lipid profile

  • Improved blood flow to the heart

IHT:

  • Increased aerobic capacity

  • Increased fat burning

  • Increased mitochondrial density

  • Improved autonomic balance

With respect to PHE, the research suggested that at least 1 hour of 12% O2 for 2 weeks would provide the greatest benefits without side effects. They did not provide recommendations for IHE or IHT.

However, a 2014 review study showed that 3-15 episodes of 9-16% O2 is the therapeutic range for IHE. This corresponds to blood O2 saturations of approximately 82-95%.

Also, from a practical perspective, we know that we can perform walking breath holds to achieve mild IHT. Essentially, we combine the IHE protocol with walking.

Overall, this paper suggests that intermittent hypoxia has many benefits in sedentary, non-athletic, and clinical populations, including improved cardiovascular and autonomic function and increased exercise capacity.

It also showed that there are several ways to achieve those benefits: Prolonged exposure, intermittent exposure, or exposure during exercise.

I recommend that you find a modality that fits you or your client’s lifestyle that can be practiced consistently.

Abstract from Paper

BACKGROUND: The reportedly beneficial improvements in an athlete's physical performance following altitude training may have merit for individuals struggling to meet physical activity guidelines.

AIM: To review the effectiveness of simulated altitude training methodologies at improving cardiovascular health in sedentary and clinical cohorts.

METHODS: Articles were selected from Science Direct, PubMed, and Google Scholar databases using a combination of the following search terms anywhere in the article: "intermittent hypoxia," "intermittent hypoxic," "normobaric hypoxia," or "altitude," and a participant descriptor including the following: "sedentary," "untrained," or "inactive."

RESULTS: 1015 articles were returned, of which 26 studies were accepted (4 clinical cohorts, 22 studies used sedentary participants). Simulated altitude methodologies included prolonged hypoxic exposure (PHE: continuous hypoxic interval), intermittent hypoxic exposure (IHE: 5-10 minutes hypoxic:normoxic intervals), and intermittent hypoxic training (IHT: exercising in hypoxia).

CONCLUSIONS: In a clinical cohort, PHE for 3-4 hours at 2700-4200 m for 2-3 weeks may improve blood lipid profile, myocardial perfusion, and exercise capacity, while 3 weeks of IHE treatment may improve baroreflex sensitivity and heart rate variability. In the sedentary population, IHE was most likely to improve submaximal exercise tolerance, time to exhaustion, and heart rate variability. Hematological adaptations were unclear. Typically, a 4-week intervention of 1-hour-long PHE intervals 5 days a week, at a fraction of inspired oxygen (FIO2) of 0.15, was beneficial for pulmonary ventilation, submaximal exercise, and maximum oxygen consumption ([Formula: see text]O2max), but an FIO2 of 0.12 reduced hyperemic response and antioxidative capacity. While IHT may be beneficial for increased lipid metabolism in the short term, it is unlikely to confer any additional advantage over normoxic exercise over the long term. IHT may improve vascular health and autonomic balance.

Journal Reference:

Lizamore CA, Hamlin MJ.  The Use of Simulated Altitude Techniques for Beneficial Cardiovascular Health Outcomes in Nonathletic, Sedentary, and Clinical Populations: A Literature Review.  High Alt Med Biol.  2017;18(4):305-321.

Breathe slowly (and pause) to improve heart rate variability

Russell_et_al-2017_WTG.JPG

Key Points

  • Slow breathing at ~6 breaths/min increases heart rate variability (HRV)

  • Including a post-exhalation pause enhances relaxation and makes it easier to breathe slowly

  • A post-exhalation pause also enhances some HRV parameters more than continuous breathing

The Breathing Diabetic Summary

We don’t want our hearts to beat like a metronome, but to constantly be changing and adapting to the current conditions.  One way to measure this is through heart rate variability (HRV), which represents the changes in time between heartbeats.  HRV is a marker of overall health: Higher HRV is associated with better health. 

Many studies have shown that slow breathing can increase HRV.  Depending on the individual, it appears that breathing at a pace between 4 and 6 breaths/min maximizes HRV.  However, there are many ways to achieve a breathing rate of 4-6 breaths/min. 

For example, you can inhale for 5 sec, and exhale for 5 sec.  Inhale for 4 sec, exhale for 6 sec, etc.  But, these different methods might not necessarily be the best way to maximize HRV.  The current study set out to see if including a post-exhalation pause would increase HRV compared to continuous breathing with equal inhales and exhales.

Specifically, they tested two different methods for breathing at 5.5 breaths/min: 5-5 and 4-2-4.  The 5-5 protocol used a 5 sec inhale and 5 sec exhale.  The 4-2-4 protocol used a 4 sec inhale, 2 sec exhale, and 4 sec post-exhalation pause. 

Forty subjects performed the breathing protocols in a seated upright position.  They performed each breathing protocol for 6 min, followed by a 5 min rest period before starting the next one.  Along with measuring several different HRV parameters, the authors also evaluated which breathing protocol the subjects found more relaxing and easier to perform.

68% of the participants found the 4-2-4 cycle easier to follow and 63% found it more relaxing.  The authors suspect that this is a result of the shorter inhalation period, which caused less strain on the breathing muscles.  They also suspect that the post-exhalation rest period reduced the risk of hyperventilation.

There is no one single measurement for HRV.  There are high and low frequency bands, along with other parameters such as the standard deviation of the NN intervals.  In this study, they found that the 4-2-4 cycle significantly improved one aspect of HRV (high-frequency HRV), whereas the 5-5 cycle improved another (low-frequency HRV).  Thus, although the title of the paper suggests that the rest period is critical, it is important to note that both breathing protocols improved HRV in different ways.

Overall, this study shows that you can improve HRV by slowing down your breath.  Whether you adopt a post-exhalation rest or simply do slow continuous breathing is up to you. Either way, you can rest assurred you will be improving this critical indicator of overall health.

Let’s wrap up with a quote from the end of the paper that is one of my new favorites:

With breathing interventions being relatively rapid interventions to implement and also demonstrating a wide range of positive clinical outcomes, breathing interventions warrant closer consideration from healthcare professionals.

Abstract from Paper

Heart rate variability (HRV) is associated with positive physiological and psychological effects. HRV is affected by breathing parameters, yet debate remains regarding the best breathing interventions for strengthening HRV. The objective of the current study was to test whether the inclusion of a postexhalation rest period was effective at increasing HRV, while controlling for breathing rate. A within-subject crossover design was used with 40 participants who were assigned randomly to a breathing pattern including a postexhalation rest period or a breathing pattern that omitted the postexhalation rest period. Participants completed training on each breathing pattern, practiced for 6 min, and sat quietly during a 5-min washout period between practices. Participants were given instructions for diaphragmatic breathing at a pace of six breaths/minute with or without a postexhalation rest period. Recordings of heart rate, breathing rate, HF-HRV, RMSSD, LF-HRV, and SDNN were collected before and during each of the breathing trials. HRV indices were derived from Lead 1 ECG recordings. Pairwise contrasts showed that inclusion of a postexhalation rest period significantly decreased heart rate (p<.001) and increased HF-HRV (p<.05). No differences were found for breathing rates (p>.05), RMSSD (p>.05), and SDNN (p>.05). Results indicated that omission of the postexhalation rest period resulted in higher LF-HRV (p<.05). A postexhalation rest period improves HF-HRV, commonly associated with self-regulatory control, yet the importance of a postexhalation rest period requires further exploration.

Journal Reference:

Russell MEB, Scott AB, Boggero IA, Carlson CR. Inclusion of a rest period in diaphragmatic breathing increases high frequency heart rate variability: Implications for behavioral therapy. Psychophysiology, 2017;54:358 – 365.