In other words, exhalation is under the direct control of
the vagus nerve,47 while vagal activity is suppress ed during inhalation.48,49
By increasing the duration of the out breath, it may be possible to access the
vagus nerve’ s connection with the rest and digest state, stimu late the on-
demand release of ACh to calm the nerves, and shift the system out of its
primal fight-or -flight response by signaling a state of relaxation.The concept of slow breathing to restore and enhance healt h is not
new.27 A variety of breathing techniques have long been central to
contemplative practices such as yoga, martial arts, Tai Chi Chuan, and
meditation. The essential idea, encapsulated by the yogic practice of
Pranayama , is that the mind and the breath are inextricably linked. The
Sanskrit word Prana  means the body’ s vital energy, and yama  is contr ol or
mastery of that. Some practices that don’t consciously focus on breath can
also have an impact. For exam ple, in deep transcendental meditation, the
breath can gradu ally become so faint that it even stops for a while.50 What
most of these practices have in common is breathing through the nose. Numerous scientific studies back up the centuries of tradition and
experience. Research into the effects of slow breathing on the body shows
significant impa cts on the ANS  and on the functions of the cardiovascular
and respiratory systems, including baroreflex sensitivity , HRV, blood flow
dynamics, RSA, and the balancing of the two branches of the ANS. Controlled slow breathing and breath holding can be used to optimize the
very physical functions associated with health and longevity and which may
provide greater resilience against disease. Studies looking at the physical mechanisms of breathing indicate a
connection between breath, cognition, and emotion, which involves the
ANS.28 Breathing well contributes to emotional balance and social
adaptation. A 2017 review in the Journal of Yoga and Physiotherapy
explains that, since exhalation is the relaxation phase, holding the breath
after exhaling activates the PNS, increasing relaxation.18 The paper
suggests that to experience long-term benefits from breath-hold exercises,
we need to spend time daily in parasympathetic dominance. The best way to
do this is to develop a habit of controlling the breath most of the time in an
easy, spontaneou s way. Another study found that yogic breathing exercises
altered autonomic responses to breath holding by increasing vagal tone and
decreasing sympathetic activity .51
COLD W ATER RESILIENCE AND EXPRESSIVE F ACES
While direct stimulation of the vagus nerve is only possible using an
implanted device, diaphragm breathing, meditation, and singing can all beused to increase vagal tone. The popular breathwork guru, Wim Hof, uses a
combination of breathing techniques and cold water immersion  to activate
the vagus nerve. Scientists have proven that immersing the face in cold water or
splashing cold water on the back of the neck increases parasympathetic
activity .52,53 In fact, one study recomme nds the practice to moderate
sympathetic activation after exercise to relieve stress on the heart.52
However , full body cold water immersion can cause potentially fatal cardiac
arrhythmia due to autonomic conflict, where both parasympathetic and
sympathetic inputs to the heart are activated simultaneously .54 This is
because rapid submersion in water less than 59 ° Fahrenheit (15 ° Celsius)
with simultaneous breath-holding activates two powerful autonomic
responses: the cold shock response and the diving response. At the same time, empirical evidence indicates that stronger vagal tone
can make the body more resilient to cold. Magnus Appelber g has taught
Ashtanga Yoga for nearly 20 years in Helsinki. He also enjoys ice
swimming—an activity popular in Finland, in which bathers dive into holes
in the ice, the hard-core amon g them staying in the water for several
minutes. About four years ago, Appelber g met the long-time yoga
exponent, phys iotherapist, and research scientist Simon Borg-Olivier . Olivier ’s message boiled down to the simple principle: breathe less, stretch
less (while getting more flexible), eat less, and move from the core. He
taught Appelber g about the Bohr effect, the dilation of blood vessels, and
the body’ s response to CO2. In particular , Olivier explained  how to balance
the ANS  using the breath, stimulating the parasympathetic, vagal branch
with the exhalation. Appelber g decided to change his breathing practice to include a simple
prolonged exhal e and breath holding after exhalation. He had been a winter
swimmer for 20 years and his ability to adapt to the cold had never been
particularly great. That winter , having adjusted his breathing, ice swimming
was a little easier . The following year, he tried applying the slow  exhalation
in the water and discovered he could swim for 200 meters in freezing water
—four times farther than the previous winter . Still, this wasn’ t completely
out of the ordinary . In February 2019, he became a social media
phenomenon with videos that showed him dropping into the ice holedirectly from a yoga pose. He was interviewed on TV and radio, and this
propelled him to experiment further . Appelber g started using very long exhalations and breath holds,
practicing these for 15 minutes before entering the water . Remarkably , this
practice, using the breath to augment levels of CO2 in his blood, increased
the time he was able to stay in the cold water without pain or hypothermia
from 5 minutes to 30 minutes— within 2 months. Appelber g found he could
maintain his core temperature better by practicing breath holds in the water . He experienced none of the pain in his toes or fingers that would indicate
the usual constriction of blood vessels, and the controlled breath kept him
present in his body . In a June 2020 email to me, he wrote,
The greatest help has been my almost 20 years of Vipassana
meditation, after all cold is only a sensation . . . . Right now, I’m
trying to find sources that could actually explain what is going on in
the body . This adaptation is a fact and I’ve found the circumstances
that are necessa ry for that: the stimulation of the parasympath etic
nervous system and the higher levels of carbon dioxide to counteract
the vasoconstriction. The ef fect on life in general has been amazing. Few people have Appelber g’s curiosity , resilience, and ability to push the
boundaries. It is important to emphasize that the practice of breath holds in the water
is not recommended unless you are working under the supervision of a
qualified breathing coach. For the rest of us mere mortals, the good news is
that you can gain considerable benefits by practicing the breathing exercises
on dry land. Interestingly , research that demo nstrates that immersing the face in cold
water stimulates the vagus nerve is echoed in the work of behavioral
neuroscientist and psychiatry professor , Steven Porges. Porges put forward
a theory suggesting that the vagus nerve comprises three neural circuits, the
most primitive of which is related to evolutionary behavio rs like the
“freeze” response of extreme stress, while the newest is linked to social
communication and self-soothing. Porges says that one way that breathing
exercises produ ce vagal stimulation is via sensory and motor nerves that
regulate facial muscles.55 This is in line with studies that show babies withmore expressive faces have higher HRV56 and with Wim Hof’s assertion
that it is possibl e to stimulate the vagus nerve by activating the parts of the
body it innerva tes. The vagus nerve is responsible for speech, the gag
reflex, and many movements of the mouth.57 In fact, according to Porges,
the very process of using the muscles in the face and head to actively
interact changes our physiologi cal state by increasing vagal influences on
the heart and calming the sympathetic nervous system’ s fight-or -flight
response. Conv ersely , the cosmetic treatment Botox, which is used to
smooth away signs of aging by effectively paralyzing the face, actually
works by inhibiting the release of ACh. THE DIAPHRAGM
The diaphragm is the main muscle for the physical act of breathing. It, too,
is innerv ated by the vagus nerve .58 It shoul d therefore come as no surprise
that diaphragmatic or deep breathing is one of the most common and
ancient methods for body-mind training and holistic treatment of stress and
psychosomatic conditions.28 Inhaling and exhaling from the diaphragm
slows the breath  and maximizes the exchange of blood gases.28 In a study ,
healthy participa nts who were trained in diaphragm breathing had slower
rates of respiration and were more likely to achieve the goal of three to
seven breaths per minute than those who breathed normally .27
Studies of the function and movement of the diaphragm muscle show
that optimal breathing requires active diaphragm control. Ideally , during the
inhalation, the lower ribs stay low, expanding only laterally , with the
abdomen expanding instead of the chest. The amount of move ment in the
diaphragm correlates with changes in lung volume. The more the
diaphragm moves between the in and out breaths, the great er the tidal
volume (the amount of air breathed in with each normal breath). Inhalations and exhalations are driven by a group of muscles
collectively referred to as the respiratory pump, the largest of which is the
diaphragm. During the in breath, the diaphragm contracts and flattens.27 It
pushes on the abdomen, and the lower ribs move upward and outward. Coordinated contraction of various muscles expands the rib cage, and the
chest opens outward. The resul ting changes in pressure trigger ventilationand gas exchange in the lungs. The out breath is more passive. The
diaphragm returns to its dome-shaped resting position, the lungs deflate,
and air is expelled. Importantly , it is possible to support optimum gas exchange with
controlled slow respiration as long as it is paired with an increase in tidal
volume . Diaphragmatic breathing at a rate of six breaths per minute reduces
the chem oreflex response to both hyper capnia  (where CO2 levels are too
high) and hypoxia  (where oxygen levels are too low).59–61 Conversely ,
increasing the speed of the breath to a faster -than-normal rate does nothing
to improve its efficiency: less of the air reaches the alveoli due to increased
“dead space.” As we saw in Chapter Three , slower breathing is simply more
efficient. Air reaches and distends more of the alveoli in the lungs, so more
oxygen enters the bloodstream. In a study comparing oxygen levels in the
arteries during normal breathing  and at 15, 6, and 3 breaths per minute, the
rate of 6 breath s per minute was found to be the best for reducing dead
space in the airways, increa sing oxygen uptake, and for ease of
sustainability . A paper published in Frontiers in Psychology  found that diaphragmatic
breathing, which  itself naturally results in a slower respiration rate, has the
potential to reduce the impact of stress and improve cognitive performance
in otherwise healthy adults.28 The results suggested that this may be
because HRV increases during diaphragmatic breathing, indicating a better
balance of activity between the SNS and PNS. Scientists inferred that deep
breathing might impact cognitiv e performance by influencing the ANS, and
that breathing may link the mind and body together to regulate the
information processing necessary to maintain attention. A review  of the possible pain-re lieving effect of deep breathing further
underlines the mind-body-breath connection. Scientists found that the
perception of pain was reduced when participants held their breath after a
deep inhalation,  a position where the diaphragm is lowered. Notably , this
appeared to involve the interv ention of the baroreceptors.58 The study
suggested that the pain response is not simply a neural process but that a
close relationship exists between the breath, the emotions, and the working
of the barorecep tors. Stress can lead to anxiety and depression , which can
adversely affect the way the diaphragm works. Equally , changes inemotional state can cause a greater perception of pain. The study concluded
that the diaphragm influences the working of the barorecept ors and the
perception of pain, and vice versa. This may be because the movement of
the diaphragm changes the pressure within the body , and the resulting flow
of blood in the body determines the baroreceptor response, but there is not
yet clear research to confirm this.58
SIX BREA THS PER MINUTE
To recap what we have already learned, slow breathing causes the
oscillations in blood pressure to synchronize with the rhythm of the heart,
creating the conditions for optimum blood gas exchange. Remember , there’ s
a significant connection between RSA, HRV, baroreceptors, and the ANS. Scientists have shown that slow  breathing at a rate of six breath s a minute,
with increased tidal volume (achieved by activating the diaphragm), rather
than suppressing the fight-or -flight activity of the sympathetic nervous
system, appears  to optimize the balance between the sympathetic and
parasympathetic branches of the ANS and to enhance autonom ic reactivity
to both physical and mental stress.27
Breathing at six breaths per minute has a powerful effect on many body
systems. In the respiratory syste m, it increases air in the lungs, enhances the
function of the diaphragm, improves ventilation efficiency , pulls more
oxygen into the blood, and is thought to increase blood flow back to the
heart (venous return). This has been demonstrated in studies of athletes at
high altitude. Athletes climbing  to the peaks of Everest and K2 without
oxygen supplies were able to achieve similar oxygenation with slower
breathing rates after two week s of acclimatization in lower atmospheric
oxygen levels. It was concluded that efficiency of breathing is more
important than quantity .62
In the cardiovascular system, breathing at six breaths per minute
increases the filling of the right heart and the amount of blood pumped by
the heart per minute.27 It cause s blood pressure oscilla tions to synchronize
with the rhythm of the heartbea t, increases HRV, and potentially decreases
mean blood pressure. In the cardiorespiratory system, it increases baroreflex
sensitivity and HRV. In the ANS, it increases vagal tone, promotes a shifttoward PNS dominance, and improves the responsiveness of the ANS
toward physical movement. The rate of six breaths per minute optimizes the
release and meta bolism of acetylcholine, maximizing RSA.27 It is also the
threshold for triggering the baroreflex and is the respiration rate with the
highest increase of HR V.
For centuries, people have practiced techniques like meditation and
yoga for their positive effects on physical and mental health and cognition. What all these activities have in common is that breathing is attentively
guided or regulated. Even simple awareness of the breath can influence the
rate of respiration. This, in turn, explains the health benefits of such
practices throug h their impact on the balance of the ANS. The physical
functions underlying these breathing techniques have been studied to
explain the impact of respiratory vagal nerve stimulation on inflammation,
the working of the heart, gener al physical and mental health, stress relief,
and enhanced brain power , including a better working memory and greater
creativity . There has also been research into the way the body interprets the top-
down (brain to body) and bottom-up (body to brain) signals and into the
possibility of training the autonomic responses.25 It has been confirmed that
respiratory vagus nerve stimulation (rVNS) reduces stress and inflammation
long-term. While rVNS produces an immediate shift in PNS activity during
and after practic e, it also results  in a shift in autonomic balance, increasing
vagal dominance both in resting states and in those active states requiring
behavioral and cognitive flexibility . Evidence shows  that breathing exercises with a low respiration rate can
stimulate the vagus nerve. Though how this occurs is not proven, scientists
believe the baroreflex mechanism causes this stimulation. The health
benefits felt by people practicing slow and controlled breathing are due to a
prolonged incre ase in vagal tone. Dominance of the PNS depends on the
consistent ability of the body’ s systems to relax. This provides a release
from chronic stress and prevents stress-related illness. LONG EXHALA TIONSPracticing breath holds, in particular , provides a tool to control the ANS. Breath holding also helps the body adapt to higher blood CO 2 (hypercapnia)
and provides a direct way to hack the body’ s stress response. As one paper
puts it, by practicing breath holds, you will eventually be able to “maintain
self-control in most stressful settings.”18 Short term, the benefits include
stress reduction , better regulation of blood pressure, and more focused
attention. Prolo nged practice improves cognitive function and enhances
autonomic balance, improving your ability to come back to baseline and
respond to external and internal challenges from a balanced physical and
psychological perspective.18
Studies into the different systems, such as the PNS, respiratory
ventilation, and HRV, have settled on a rate of six breaths per minute as
optimal. Howev er, given that the vagus nerve is activated purely  during the
out breath, why isn’t there more exploration into inhalation/exhalation
ratios? Does the vagus nerve work even better when exhalations are longer
than inhalations? One study carried out by scientists in Taiwan looked at this idea in
detail by examining healthy college students to discover the differences in
breathing with longer exhalation s compared to breathing with equal in/out
ratios in the effect on subjective feelings of anxiety and physiologically on
HRV.63 Specifically , they explored two very similar breathing rates—6
breaths per minute and 5.5 breaths per minute—each with inhalation to
exhalation ratios of 5:5 (equal) and 4:6 (longer exhalation). They expected slow breathing with longer exhalations to create more
intense feelings of relaxation and higher HRV than an equal ratio pattern. Previous studies showing the beneficial effects of 6 breaths per minute for
heart and lung functions had already confirmed that inhaling quickly and
exhaling slowly (2:8 respectively) was more effective in reducing mental
and physical arousal in threatening or stressful situations than inhaling
slowly and exhaling quickly .63 There are also various breathing exercises,
for exam ple in yoga, where techniques such as 2:1 breathing, during which
exhalations are twice the length of inhalations, are recognized as
beneficial.64 However , contrary to expectations, the Taiwan study revealed
that a respiratio n rate of 5.5 breaths per minute with equal length in/out
breaths (5:5) significantly increased HRV.63 What’ s more, it increased vagalnerve/PNS activation and barore flex function more than the other breathing
patterns, meaning it has the potential to help patients with condi tions where
low HR V is a feature. Several papers point out that slow breathing can be uncomfortable. This
might explain why people are attracted to activities like yoga and
meditation where the focus is on the breath, but the practice is guided to
make breathing effortless. To comfortably breathe at a rate of 5.5 breaths
per minute with an equal inhalation and exhalation ratio, a BOL T score of at
least 15 seconds  is required. There are programs in Chapter Two designed
to improve the BOL T score to 15 seconds, making slow breath ing practice
more attainable. It is certainly worth your time and effort, given the indications that this
breathing pattern increases PNS and baroreflex function and simultaneously
enhances relaxation. SYNCHRONIZED BREA THING—MANTRAS AND MUSIC
The age-old breathing practices cultivated in Eastern traditions have
significant scientific basis in terms of physical and mental influence.65
However , vario us other customs and activities have also been found to
synchronize cardiovascular rhythms by reducing breathing to the optimum
rate. Recitation of both the yoga mantra “om-mani-padme-hum ” and the
rosary prayer in Latin, with one person reciting the priest’ s part: “Ave
Maria, gratia plena, Dominus tecum, benedicta tui mulieribus et benedictus
fructus ventris tui Jesus ,” and the other the response: “Sancta Maria, Mater
Dei, ora pro nobis peccatoribus, nunc et in hora mortis nostrae, Amen ,” has
been found to lower the respiratory rate to, you guessed it, around six
breaths per minute.65
This is no coincidence. Mantras, which are usually repeated in
sequences of more than 100, similar to the rosary , which is recited 150
times, may have evolved as a device to slow respiration, induc e relaxation
and enhance concentration.66 The length of time required to perform over
100 mantras or to get through 150 recitations of the rosary is significant,
suggesting that one of the aims might be to induce physical chan ges as well
as altering mental state.Given that many  of the physical aspects at play here are rhythmical, it is
also worth looking at the conne ction between music and the PNS. Humans
interact with music at behavioral, emotional, and physiological levels, both
consciously and unconsciously .67 Over 100 years ago, it was suggested that
the ANS forms a sort of “sounding board” that reverberates to changes in
consciousness.67 Many centuries earlier , classical Greek philosophers
believed music and sports to be the two fundamental aspects of well-being. Contemporary experiments have explored how elements of music such as
beat, tempo, and pitch trigger emotional and behavioral responses, as well
as reactions in the physical and nervous systems. Singing has been found to reduc e tension, increase energy, and improve
mood. It directly activates the vocal cords and the muscles at the back of the
throat—which are connected to the vagus nerve.68 Regular singing can even
increase vagal tone. However , the impact of singing on HRV was found to
be dependent on whether the singer experienced the task as stressful or not. A greater heart rate variable was found in professional singers after a
singing lesson, while amateurs showed lower HRV. Heart rate increased
after solo singing but decreased  after choral singing, indicating that when a
person is perform ing music, rather than just listening to it, the perception of
the task as safe or scary influe nces the resultant physical reaction. It has
also been found that trained musicians have a lower baseline breathing rate
than nonmusicians.69
One study into the physiological responses to music found that even a
short listening session could bring about measurable cardiovascular and
respiratory effects.69 The level of arousal or focused attention was largely
determined by the tempo (speed) of the music. Regardless of taste in music
or whether the listener was previously familiar with the piece, slow music
from a variety of genres reduced cardiorespiratory response. A pause or
period of silence in the music produced a higher level of relaxat ion than the
music itself, suggesting that music may give pleasure and potential health
benefits as a result of the controlled alternation of arousal and relaxation. It
was concluded that music can be used to induce relaxation and reduce SNS
activity and that it may be useful in the management of cardiovascular
disease.In a therapeutic setting, music has been used to enhance
parasympathetic activity and decrease congestive heart failure by reducing
levels of inflammatory cytokines.70 Patients under going a 14-day  music
therapy course exhibited change s in HRV patterns that indicated enhanced
activity of the cardiovascular system.71 One experiment into the impact of
music on the autonomic response compared healthy participants with
patients in a vegetative state or with unresponsive wakefulness syndrome. Those participa nts with disorders of consciousness showed  replicable
changes in the balance between the SNS and the vagal system after passive
listening to symphonic music.72
USING HR V IN THE REAL WORLD
As part of the training that I run for our Oxygen Advantage instructors, I
was fortunate enough to organize an online coaching webinar in August
2020 with Dr. Jay T. Wiles, a clinical health physiologist. Dr. Wiles
specializes in sports performance and holistic and integrative health, and he
is board certified in biofeedback and HR VB. Dr. Wiles came to HRV throu gh his clinical practice, working with
patients with clinical stress, PTSD, and anxiety . As he learned about HRV,
he becam e fasci nated by its implications not only for peak performance and
sporting excellence but also for its potential applications in a clinical
setting. He became determined to present information about HRV in a way
that is easy to access and practical in day-to-day life. The way you use HVR depends on your starting point and your goals. This is also true for the breathing exercises in this book. It’ s helpful to avoid
preconceptions about what is “good” or “bad.” For instance, it may surprise
you to know that elite athletes often have very poor vagal tone because they
have taxed their nervous systems through years of overtraining and
overreaching. These athletes often come to HRVB to find out what is
impeding their performance. If you want to understand how well your nervous system is functioning,
HRV provides the best inexpensive, noninvasive way to do this. It has a
wide-ranging and diverse clinic al utility , but as it increases in popularity
among fitness enthusiasts, its purpose and application are frequentlymisunderstood. In many cases, the readings that people get from their
consumer -based devices are useless because they lack the contextual
framework to understand or improve them. Dr. Wiles originally became interested in HRV through his work with
trauma patients. He wanted something that would allow him to objectively
quantify the stress response. In clinic, he found that most information came
from his patient s in the form of subjective, qualitative data about how they
were feeling. While this was valuable, HRV offered quantitative data that
helped him build a clearer pictu re of what was going on with those patients
so he could help them better . He began using HRVB with the chronic pain
population, with patients who often had a variety of conditions including
pain, depression, stress, and anxiety , all existing comorbidly . He began to
see improvemen ts in all these symptoms and syndromes as a direct result of
HRVB. Dr. Wiles explained to me that we have trillions of processes going on
in the body in any given second. As we go about our day, the heart has to
adjust to everything we encounter in our environment, and to all of the
processes in the body . For this reason, higher HRV, which signifies greater
adaptability , is normally preferable. The widely held belief that the processes of the ANS are entirely
involuntary is incorrect. We can control HRV very easily , but we lose
control due to stress. Dr. Wiles believes that, because HRV is data driven,
research-supported, and quantifiable, it is incredibly valuable in
breathwork. In a sense, it strengthens the scientific basis for the work
because results can be so clearly and accurately measured. As we already discovered, HRV is measured in time domains (the time
difference betw een each heartbeat). It is also measured in frequency
domains (the frequency or the individual components of each heartbeat). These two elements, time and frequency , are the two main aspects of HRV. While the time domain data gives an important baseline for our HR V at rest,
the frequ ency domain data gives us insight into our overall stress response. If you have high vagal tone and good HRV, you will see an increase in high
frequencies and a decrease in low frequencies. This is because the high
frequencies receive predominantly PNS contributions. Another common belief that confounds HRVB training is that “higher is
normally better”  in terms of HRV measurements. As we touche d on earlier ,this is not always the case. For this reason, a self-comparison strategy is
always more valuable than a comparison against some imagined “norm.”
HRV may become too high because you are too much in a parasympathetic
state. The aim is not to be in a parasympathetic state all of the time; rather
to modulate the ANS and to learn to control HR V.
There is no “good” or “bad” in terms of short-term readings, and the
“normal” measu rement range changes as we age, so the idea of an ideal or
goal HRV is somewhat irrelevant. It’s important to remember that HRVB
devices measure two different things: time (RSMMD) and frequency
(SDNN). Be careful not to confuse the two. In frequency readings over 24
hours, 100 is considered a healthy reading, between 50 and 100 is
“compromised,” and, if your reading is below 50, you may be at risk of a
heart attack. However , even if your reading is just 20, don’t worry . The
focus should always be on self-comparison, your ability to modulate HRV,
and progress in an upward direction. Dr. Wiles stressed that the purpose of HRVB is not necessarily to raise
your baseline reading. “The primary thing,” he said, “is to be able to
modulate HRV in acute situation s, to get you out of the stress state and help
you perform at your highest level.”
One useful side effect of HRVB is that you will start to becom e more
aware of your own stress response, both physically and mentally , thereby
increasing your ability to self-re gulate. The human brain doesn’ t distinguish
stress caused by physical danger from the stress caused by less life-
threatening situations, such as relationship problems or financial worries. That is why it is so easy to become conditioned to being in a state of
permanently high SNS activation. HRVB gives you the tools to take back
control, to change gear when you need to. One of the techniques used for
this is breathwork. Dr. Wiles explained that while the HRVB studies discussed earlier got
many things right (focusing on low, slow breathing, the mind-body
connection, data tracking, and replication), they overlooked some things. For insta nce, they failed to focus on biochemistry , the depth of breath, light
and quiet breathing rather than heavy loud breathing, nose breathing instead
of mouth breathing, and the importance of hypercapnia (high blood CO2)
for vagal tone.You can influence HR V by engaging:
• Nasal breathing
• Light breathing
• Slow breathing
• Deep breathing
In fact, even without biofeedbac k, by using the exercises in this book, you
are already training your HRV. Biofeedback tools come in useful when you
want to see exactly what is happening from a physiological standpoint. Nasal breathing can have a significant impact on HRV due to the
influence of the baroreflex system and increased vasodilation. According to
Dr. Wiles, this vasodilatory response sends a cascade of biochemical
messages through the baroreflex to stimulate the vagus nerve. Simply
switching to nasal breathing will influence HRV, whether or not you engage
in diaphragm breathing or work to slow the cadence of your breath. To
illustrate this, Dr. Wiles described how free divers need to be able to
activate both branches of the ANS. These divers will generally breathe
nasally , but just before a dive they inhale through the mouth. This increases
blood pressure, so that the diver’s blood pressure levels out as he or she
dives, rather than dropping below normal. Nasal breathing also promotes increased HRV due to hypercapnia (high
blood CO2). Be aware that when you practice breath holds or light
breathing with air hunger , HRV may dip initially . This is because the body
perceives stress and responds accordingly . As you practice, the body will
adapt. Interestin gly, what often happens after the practice is that, even when
HRV has dipped, when you resume normal breathing, it becomes
significantly higher . According to research, change s in CO2 that accompany conscious
manipulation of breathing patterns independently influence autonomic
control of the heart and modulate HRV. Increased CO2 in people who are
awake enhances  high and low frequency power , indicating better vagal
tone73. The connection between CO 2, HRV, and vagal tone is the reason you
feel relaxed when you engage in light, slow breathing. From a biochemical
perspective, light, slow breathing, and hypercapnia also result in a flood ofhormones, an increase in acetylcholine, an influx of dopamine, and a
reduction in adrenaline and inflammation. It is much easie r to use HRV than it is to explain it in a simple way. It
provides a really good way to not only subjectively feel better , but to
objectively see the change in the nervous system. This can be very
motivating. If you have the opportunity to do so, it can be immensely
valuable to work with a professional breathing instructo r who can
demonstrate how HRV changes as you alter the biochemistry ,
biomechanics, and cadence of your breath. You can also buy your own HRV measurement tools. Howe ver, Dr.
Wiles cautions that they are “not all created equal.” Devices in the $300
range, such as the Lief Therape utics wearable ECG, Oura Ring, WHOOP
Strap, BioStrap, HeartMath Inner Balance™ or emW ave2®, and the Polar
H10 Chest Strap with the Elite HR V app, are all reliable. SOME TIPS FOR TRAINING
If you have a serious health condition or suffer with anxiety and panic
symptoms, the same principle applies as for the breathing exercises—begin
any practice or training gently . Some people find the air hung er produced
by the Breathe Light  exercise (found in Chapter Two) can cause an intense
stress reaction. Adjust your training accordingly and work your way up
from just a few minutes’ practice. If you do experience a stress response,
this is not necessarily a bad thing or something to be conce rned about. However , too strong an activation of the SNS can put you off trying the
exercises altoget her. Be reassured that as you get into the rhyth m of HRVB
training, your nervous system response will begin to modulate. If, after exercise , your HRV drops by more than 20%, you have over-
trained; your nervous system has had enough. In sports performance, HRV
is one of the greatest predictors of future injury . Dr. Wiles uses overnight
readings with his clients. The differences between these readings dictate
how hard the athlete trains the following day. He explained, “You have a
much greater chance of a succes sful workout if your HRV has not dropped
too much.”One thing I like to mention is my 20% and 40% rule. If your
overnight HR V reading is 20% lower than your normal baseline, this
should indicate “caution.” This does not mean you should not train,
but you should be aware of a suppressed nervous system. When  this
happens, I tell athletes to do a lighter training day. When your HRV
drops below 40%, this should be a day off where the athlete should
utilize “strong caution” as they will be much more susceptible to
injury and overtraining. Dr. Wiles told me that teaching these athletes how to modulate HRV to get
themselves back  into flow is vital. They need enough stress that they can
perform but not so much that it impairs performance. This is fundamentally
true for anyone who needs to perform, whether in a sporting, Arts, or
corporate setting. And this is where HR VB training can be truly valuable. Mouth breathing during sleep (discussed in Chapter Seven ) is also a big
“no.” Many of the Oxygen Advantage instructors report that their HRV
improves just from nasal breathing during sleep. According to Dr. Wiles,
this is a “non-ne gotiable” for athletes in his care. He described the case of
an ATP top level tennis player in his early thirties who had very low HRV
when he first attended the clinic for training. After working on light, slow,
deep breathing  and taping his mouth at night, the player’s HRV
measurement increased markedly . His performance on the court improved,
and his risk of injury decreased. One more tip: if you engage in public speaking, big presentat ions, or
performance of any kind, when you are midperformance, your focus should
be on what you are doing, not on your HRV. The trick is to condition your
response before the event and then trust that you’ll experience a significant
change during the event. Focus on the task at hand and rely on your body to
kick into high gear because your ANS is in a better state. This is the power
of HR V.
OceanofPDF .comFCHAPTER FIVE
FUNCTIONAL BREATHING, THE SECRET OF
FUNCTIONAL MOVEMENT
rom birth, breathing is our first and most basic motor pattern .1 As
toddlers, we learn to stand up against gravity and control posture with
the support of the diaphragm. As we grow , breathing is central to
both posture and functional movement. Throughout our lives, breathing and
posture sustain each other . But if breathing pattern disorders are present,
this relationship becomes dysfunctional. The result is poor core muscle
function and the onset of disabling conditions, such as lower back pain. If
you want a simple reason to correct poor breathing patterns, it’s this: when
your breathing is less than optim al, it will adversely affect your freedom of
movement, eventually causing chronic pain. In 2017 , researchers at Evansville University , Indiana, demo nstrated
that dysfunctional breathing (DB) directly and adversely affects the
musculoskeletal system.2 The musculoskeletal system includes the bones of
the skeleton, muscles, joints, tendons, cartilage, ligaments, and other
connective tissue. If the function  of this system is compromised, it becomes
impossible for the core muscles to support the spine and pelvis properly . Research has linked DB to a host of conditions that limit movement and
cause pain, including lower back and neck problems, and it is now
acknowledged that core muscle dysfunction plays a role in a variety of
musculoskeletal disorders and an overall increased risk of injury . Dysfunctional breathing can be at the root of recurrent and chronic
symptoms including lumbopelvic, chest and neck pain, fatigue,  anxiety , an
irritable bowel or bladder , “brain -fog,” paresthesia, and cold hands, fingers,
feet, or toes.3 However , there is a gap betwee n research and practice. Coremuscle exercise s—such as pelvic tilts and exercises using a stability ball
and hip bridge (a strengthening posture that involves lying on the back and
lifting the hips off the floor while the shoulder blades and feet remain
lengthened into the ground) —are often prescribed durin g physical
rehabilitation,4 but breathwork is not. Despite the recognized links between
breathing function and postura l support and the known prevalence of
breathing pattern disorders, the connection is rarely made in therapy . In fact,
breathing is usually overlooked.2
However , underlying breathing pattern disorders are common enough to
warrant more attention. In the United States, as many as 10% of patients in
general internal medicine practices have hyperventilation syndrome as their
main diagnosis.5 Dysfunctional breathing is even more widespread.6
Everyday physical symptoms, such as headache, back pain, chest pain, and
abdominal pain, which account for half of all primary care visits in the
United States,7 can potentially be made worse by dysfunctional breathing.8
The good news is that dysfunctional breathing can usually be resolved by
practicing simple exercises like the ones in this book. While dysfunctional breathing often indicates poor health and goes
hand-in-hand with dysfunctional movement, it is not necessarily related to
cardiovascular fitness. It is surprisingly common to be incredibly fit and
still have symptoms of dysfunctional breathing. In fact, many of the clients
I work with to restore functional breathing are top-level athletes. Even
when high levels of fitness are achieved and maintained, DB can indicate
problems elsewhere in the body . Ultimately , poor breathing patterns will
have a significa nt and long-term impact on both mental and physical well-
being. Breathin g is one of the body’ s critical functions. When its
fundamental processes break down, the body will compensate, calling on
structures such as the core musc les to help maintain respiration. If breathing
is not efficient in a normal restful waking state, it is never going to be
optimal during physical exercise . It will also be dysfunctional during sleep,
when the body needs to restore, repair , and revitalize its systems. BREA THING, CORE ST ABILITY , AND BALANCEYour core connects and supports the movement of your upper and lower
body . Whether you are kicking a ball, rowing, cycling, or vacuuming the
floor , the action  originates in or moves through the core. Weak or unstable
core muscles will affect the functioning of the legs and arms and cause poor
balance and stability . This can lead to falls, injuries in sport, or ongoing
pain and discomfort. A stable  core is the foundation  of functional movement. It underpins
basic activities such as bending to put your socks on or pick up your child,
sitting or standin g, and the many day-to-day things we barely notice doing
until they become painful. Core  strength isn’t just needed for manual work. Even sedentary desk jobs requir e core muscle strength so that the muscles
of the back don’ t become strained. The common narrative is that back pain and poor core stability  can be
prevented by exercises that balance and strengthen the core muscles,
specifically the abdominal muscles. However , this conception of “core
strength” misses  the true foundation of core stability: the breath . According
to a 2013 review by physiotherapist Josephine Key, breathing is a root
mechanism for core control. Breathing is integral to postural stability and
vice versa. Functional breathing supports posture and functional movement
via the diaphragm muscle. How ever, if the spine and pelvis are not stable,
there will never be optimum space for the diaphragm to descend during
inhalation. Key remarks that “If the posture is ‘good’ so too is the breathing
pattern and conversely , if the breathing pattern is healthy , so is the
posture.”1 Howev er, according to Key, the concepts of core strength and
function are often misunderstood. She quotes the spine biomechanics
specialist, Stuart McGill, who said, “There’ s so much mythology out there
about the core. The idea has reached trainers and through them the public
that the core means only the abs. There’ s no science behind that.”9
Certainly , many  people still understand the core to mean only the
transversus abdo minis muscle. There’ s a widely held idea that this muscle
alone supports and stabilizes the spine and pelvis, but this is simply not the
case. The core can be described anatomically as a box, with the diaphragm
on the top, the abdominals at the front, the gluteal and spinal muscles at the
back, and the pelvic floor and hip muscles at the base.10 Notice that the
mechanisms of core stability include both breathing and postural control.Core stability , breathing, and posture are inextricably linked  by the
pressure generated in the abdominal cavity by the movement of the
diaphragm. This is called intra-abdominal pressure (IAP). Intra-abdominal
pressure fluctuates through the breathing cycle. When you breathe in, your
diaphragm moves downward, producing positive pressure in the abdominal
cavity . This pressure works a bit like an inflating balloon. It has a
stabilizing effect, supporting the spine and pelvis. When breathing is fully
functional, the diaphragm is better able to generate optimal IAP— and better
spinal stability . This affects balance, as well as posture and movement. One small 2017
study explored the connection between diaphragm breathing training and
static and dynamic balance. Thirteen participants practiced breathing
exercises over eight weeks. Balance and breathing were assessed every
week. Researchers found that each week, as breathing scores improved,
participants showed fewer errors in single-leg balancing.11 This suggests
that diaphragm breathing may help improve balance. The stability of the trunk and pelvis is essential for athletic performance
and injury prevention,12 but it is also important for anyone who wants to
enjoy a good quality of life, pain free. Instability around the pelvis can
cause excess movement in other joints. That is why an athlete with poor
gluteal control may experience knee and foot pain. Instability in the lumbar
spine can cause stiffness in the thoracic spine, leading to compensating
movements in the shoulder and pain or tears in the rotator cuff tendon12. Likewise, people with back pain tend to brace the superficial muscles of the
abdomen and diaphragm. This, combined with poor core muscle activation,
inhibits normal functioning of the diaphragm and encourages upper chest
breathing.13,14 These problems are not confined to sports. Between 50% and
80% of adults suffer lower back pain at some point in their lives, and it is
the most common cause of disability among working age people
worldwide.15
A stable spine supports the body during movement. You may have seen
weightlifters breathe in before a lift and hold their breath during the lift. The breath hold on the inhalation is intended to generate high levels of
intra-abdominal pressure and “stiffen the spine.” Instead, Josephine Key
argues that if the weightlifter maintained a regular breathing pattern whenlifting, IAP levels would actually be better and the risk of spinal
compression less. In other words, a weightlifter with functional breathing
would be better able to generate adequate levels of IAP during a lift. Instead
of the lift relyin g on a breath hold, the weightlifter could actually generate
greater IAP as the diaphragm moves downward. It has been know n for some time that IAP increases during many tasks
that load the spine—for example, static and dynamic tasks such as walking,
lifting, and jumping. However , it had been argued that the pressure
generated during these basic movements isn’t enough to significantly
increase spinal stability . Studies failed to identify whether mechanical
support of the spine was provided by IAP or by the abdomin al muscles. However , one 2005 paper did find that IAP increases stiffness of the lumbar
spine without any concurr ent activity  from the abs and back extensor
muscles.16
When breathing is shallow and confined to the upper chest, it is difficult
to build up IAP. Instead, the body must rely on the back and neck muscles
for support. Proper movement  of the diaphragm prevents upper chest
breathing. When the diaphragm moves freely , the lower rib cage expands
laterally . The diaphragm must be unrestricted, because this expansion, with
the lower rib cage opening out to the front, back, and sides, only occurs if
the movement of the diaphragm creates sufficient pressure to push the ribs
outward1. This outward movement provides enough space between the
thorax and pelvis for the diaphragm to descend, and this helps keep the
posture balance d. (You will find an exercise to develop this lateral
expansion of the ribs in Chapter T wo.) According to a 2018 study , the diaphragm plays another role in the
stability of the trunk. When the diaphragm contracts, it minimizes the
displacement of the abdominal contents, such as the digestive organs, into
the chest, maintaining the hoop- like shape of the abdominal muscles.17 This
increases spinal stability throug h tension in the connective tissue or fascia
that covers the thoracic spine and the deep muscles under the back. The
thoracic spine is the longest part of the spine, from the lower neck to the
abdomen, and is the part connected to the rib cage. The study found that the
two functions of the diaphragm—breathing and postural stabilization—
operate independently of whether we are breathing in or out. Thisobservation led researchers to conclude that the diaphragm’ s response may
be regulated by the central nervous system17. This would make sense since
the diaphragm is also responsib le for the pain threshold and plays a role in
the perception of pain.17
The focus of that 2018 study was to determine whether a relationship
existed between  the health of the diaphragm muscle and mainta ining static
balance. Scientists found that balance was better , both with eyes open or
closed, when the diaphragm was thicker and moved more freely during
quiet and deep breathing. The diaphragm is a striated muscle—the same
type that moves the joints.18 A thicker diaphragm indica tes better
respiratory muscle strength,19 which goes hand in hand with functional
breathing. A diaphragm ultrasound (an easy-to-perform, easily
reproducible, noninvasive diagnostic tool) can determine the thickness and
excursion of the diaphragm. An ultrasound is a good supplemen t to (but not
a replacement for) respiratory muscle strength testing. In the 2018 static balance study , the same results were demonstrated in
patients diagnos ed with lung cancer , those under going lung resection, and
healthy people. It also showed that deterioration in diaphragm function after
chest surgery closely correlated with worsening balance. Proble ms with the
diaphragm, such as atrophy , paralysis, and reduced muscle thickness, were
clearly linked to the development of static balance disorders. It confirmed
that stable balance depends on the diaphragm’ s ability to generate optimal
IAP. The study concluded that balance is “inextricably linked to
breathing.”17
In an article in the 2017 Journal of Yoga and Physical Therapy
(exploring the subject of reduc ed blood carbon dioxide and vagus nerve
stimulation), U. P. Singh talks about the connection between the body and
breath and its importance to properly aligned posture and a well-balanced
outlook. Describing the concep t of “grounding” as a sure sense of reality
and self, with an openness and responsiveness to new ideas and input, he
argues that this “sense of self” is achieved by restoring appropriate patterns
of posture and breathing.20
This concept is integral to conte mplative practices the world over. Even
the word yoga , from the Sansk rit root “yuj (
),” means union—between
body and breath  and, in spiritu al terms, between the self and the higherconsciousness or divine. At the heart of this body-breath connection is the
ability to perform a full, relaxed exhalation, allowing the diaphragm to
achieve a natural domed position, in contact with the internal rib cage. Singh points out that, when it comes to functional movement, “We are
always under the influence of gravity .” Holding the breath after exhaling is
an excellent exercise to rehabilitate and strengthen the core muscles. Once
this skill is perfected, “it becomes a natural self-care; an invisible, but vital
skill.”20
Athletes also need to consider the role of normal breathing mechanics in
posture and spinal stabilization. Studies have shown that breathing pattern
disorders can lead to increased pain and contribute to problems  with motor
control, causing or contributing to dysfunctional patterns of movement.21
The diaphragm performs the dual functions of respiration and postural
support, but when all the body’ s systems are challenged, breathing always
takes precedence and wins.22
BREA THING AND EXERCISE: FUNCTIONAL
MOVEMENT AND INJUR Y
When athletes are physically active, dysfunctional breathing can manifest
as premature breathlessness or muscle fatigue, inevitably resulting in
suboptimal performance23. A combinatio n of upper chest breathing and
overbreathing can cause significant changes in respiratory chemistry . In
particular , dysfunctional breathing can decrease carbon dioxide (CO 2)
levels in the blood. When CO2 is depleted, blood pH increases, triggering
respiratory alkal osis—the blood becomes too alkaline. Respiratory alkalosis
can trigg er chan ges in the nervo us system and in physical and mental states
that can have a detrimental effect on the musculoskeletal syste m21 as well
as on general levels of health and performance. Respiratory alkalosis produces an array of symptoms, such as
exhaustion, headaches, dizzines s, light sensitivity , trouble sleeping, chest
pain, cramps, and feelings of breathlessness. The common maxim, “no pain,
no gain,” impli es that stressing the body to let it recover is a helpful
strategy , when in fact, forcing yourself past the point of discomfort canaffect mind-body coordination24 and create a negative experience that does
little to boost health and fitness. Studies by Dr. John Douillard  into an exercise technique that uses
5,000-year -old Vedic concepts of integrating mind, body , and environment
to achieve flow and requires the athlete to practice a form of deep nasal
breathing called ujjayi  (the same form of breathing used in yoga practices
like Ashtanga), found that the technique produced less feelings  of exertion
and greater comfort during high-intensity training than did normal aerobic
exercise.24 This breathing  practice contributes to a feeling of deep calm
during exercise and to increased respiratory sinus arrhythmia, helping
promote fitness, endurance, strength, and better mind-body coordination
with less ef fort, strain, and fatigue.24
Exercise increases demands on the respiratory , cardiovascular , and
muscular system s and requires the body to adapt to biomechanical,
biochemical, and psychological changes through the breath. Even top-level
athletes can succumb to injury if their breathing is dysfunction al. Rates of
musculoskeletal injury are relatively high among physically active people. One review in the Journal of Athletic Training  cites an average of 13.79
injuries per 1,000 athletic “exposures” during competition.25 Outside of
sport, across a variety of professions, the breath may be at the root of
repetitive strain injury (RSI).26
Since breathing pattern disorders are common in the general population
—one study states that “norm al patterns of breathing are the exception
rather than the rule”27—prevalence will be similar in the athletic
population. However , the effects of dysfunctional breathing may be
amplified due to the extra physiological and biomechanical demands of
exercise. Whatev er the task, if the body is not able to recruit the appropriate
muscles, the result will be compensatory patterns of movement. In 2014,  sport scientists Helen Bradley and Dr. Joseph Esformes studied
the relationship  between breathing pattern disorders and functional
movement. Functional movement was defined as the “ability to produce and
maintain sufficient mobility and stability along the kinetic chain while
accurately and efficiently completing fundamental movement patterns.”
More simply, that just means all systems work in harmony to ensure healthy
movement of the limbs. Thirty- four healthy men and women participated.The results showed that the most sensitive measures of breathing pattern
disorders were resting end-tidal carbon dioxide  (ETCO 2) and resting
respiratory rate. In total, 70% of subjects were identified as having
disordered breathing.21
In addition to end-tidal CO2, they used the Nijmegen Questionnair e
(NQ) and the Functional Movement Screening ™ test (both also used in
Kiesel’ s study discussed later in this chapter). Participants  with poor
breathing pattern s scored lower on the FMS test, while 87.5% of those who
passed were classified as diaphragmatic breathers. Functional breathing and
functional move ment were found to go hand in hand. The FMS test was
also shown to accurately predict injury in people with suboptimal patterns
of movement. Participants who returned a higher NQ score had a higher respiratory
rate and a lower ETCO 2 during the FMS  test. In other words, those with a
fast breathing rate had lower ETCO 2. In contrast, ETCO 2 reading s at rest
were significantly higher in diaphragm breathers than they were in chest
breathers. The research also revealed a clear link between a high ETCO 2
and a better FMS score. Thes e results unequivocally demonstrated the
importance of functional breathing patterns for functional movement.21
According to a 2016 paper published in the International Journal of
Sports Physical Therapy , it is possible to correct or reeducate disorderedbreathing.23 Fresh neural connections can restore the central nervous
system’ s normal motor control patterns. The paper suggests that breathing
pattern disorde rs should be the starting point for all orthopedic
investigations, stating, “If breat hing is not normalized, no other movement
pattern can be.”
The adequate oxygenation of muscles during exercise is also worth
looking at. Exercise, by its nature, is associated with a variety of
corresponding cardiovascular and respiratory responses.28 These generate
the effort necessary for the orderly recruitment of motor units that cause the
muscles to contract. A motor unit is the motor neuron (or messenger cell)
and the muscle fibers activated by that neuron. The muscles of most
mammals, inclu ding humans, store very little oxygen. In contrast, diving
mammals like whales, seals, and otters have an oxygen-binding protein
called myoglobin in their muscles.29
In Chapter One, we discussed how the extra resistance created by nasal
breathing signifi cantly increases  the oxygenation of the blood. Oxygen gets
from the air to the exercising muscles via the cardiovascular system. At
rest, a young, healthy person weighing between 50 and 100 kilograms
consumes between 0.15 and 0.4 liters of oxygen per minute. Around 80% of
this oxygen is used by the brain, heart, liver, and kidneys.28 Skeletal muscle
does not generally use much oxygen unless those muscles are contracting. During exercise, a young, untrained person can consume 10 or 15 times
as much oxygen. In elite endurance athletes, it can be 20 times more,
provided that they train with sufficient duration and intensity . According to
a 2015 paper , this maximal oxygen uptake, or VO 2 max (first observed in
the 1930 s in Donald Lash, the first man to break nine minutes for two
miles), is similar to that estimated for male hunter -gatherers and sheep or
cattle farmers in nonmechanize d societies. Values for women are around
10% or 15% lower due to lesser muscle mass, hematocrit, and
hemoglobin.28 Hemato crit is the volume percentage of red blood cells in the
blood. Hemoglobin is the protein in the red blood cells that carries oxygen
to the body’ s organs and tissues and transports CO2 back to the lungs to be
expelled during exhalation. Oxygen consumption is driven by cardiac output, which increases from
four to eight times during exerc ise, due to the faster heart rate and greaterstroke volume. Cardiac output is the amount of blood the heart pumps
through the circulatory system in one minute. Stroke volume is the amount
of blood pumped from the left ventricle of the heart per beat. In elite
athletes, stroke volume is enhanced by structural changes in the left
ventricle.28
Exercise also prompts a two- or threefold increase in whole-body
oxygen extractio n. This is cause d by differences in oxygen level s within the
arteries and blood vessels, and by reduced blood flow to the less active
skeletal muscles, kidneys, gastrointestinal tract, liver, spleen, and pancreas. The ability of exercising muscles to extract oxygen is also improved by
increased capilla ry density . The muscles of trained athletes actually grow
more blood vessels in response to regular exercise, which contri butes to the
rise in VO 2 max with traini ng.28 It has been known as far back as the late
1700s that “bloo d goes to where  it is needed.” This simple statement, made
by the Scottish surgeon Hunter , underlines the fundamental idea that under
most circumstances, metabolic demand (how much oxygen the muscles
need) and the blood flow to the contracting muscles are well matched.28
It’s also interesting to look at what happens when muscles become
injured. When an injury occur s, the rupture of blood vessels results in
ischemia (reduced blood flow) and hypoxia  (lack of oxygen) at the site of
the injury . One 2015 study explored the differing impacts of transient and
prolonged oxygen deficiency on the regeneration of muscle tissue. Researchers found that short-term hypoxia stimulates “productive
proliferation and differentiation” of satellite cells.30 Satellite cells are
muscle stem cells that can form  new muscle fibers and differentiate and
fuse to existing muscle.31 These cells are involved in the normal growth of
muscle and its regeneration after injury or disease. The study demonstrated that while transient hypoxia is essential for the
formation of muscle tissue and the stimulation of muscle stem cells, and is
beneficial to recovery ,30 prolonged hypoxia is detrimental to muscle repair ,
inhibiting the ability of the satellite cells to differentiate. Differentiation is
the important process by which cells change to perform a specific function. Muscle injury is a difficult subject to study because, while injuries of
this type are common, they are not reproducible in either severity or
location in a trial situation, especially as they always, by nature, occur byaccident. However , while the injuries of elite athletes may receive a high
proportion of attention from a rehabilitative standpoint, muscle and tendon
problems can af fect anyone. That study leaves open the question as to whether intermittent hypoxia
achieved by breath holding could have therapeutic applications in muscle
repair . Research is limited, but one master ’s study examined the curative
use of intermittent hypoxia to repair induced muscle injuries in rats. It
concluded that there was “absol utely no doubt” that the treatme nt would be
beneficial to athletes.32
During breath holding following normal breathing patterns, levels of
oxygen drop and CO2 increas e. This causes acidosis in humans through
increased blood CO2, decreased blood pH, and a reduced affinity for
oxygen—which facilitates oxygen delivery to the tissues—known as the
Bohr effect . The higher level of CO2 causes the bond  between hemoglobin
and oxygen to weaken. This makes more oxygen available to the tissues. Therefore, it may be possible that breath holding could improve  recovery of
injured or fatigued skeletal muscles. The increased oxygenation of the tissues seen after CO2 therapy
operates on the same principle. In 2011, scientists in Japan investigated
whether absorpt ion of CO2 and the Bohr effect could be induced in humans
by applying pure CO2 directly to the skin. They found that 10 minutes after
the gas was applied, the pH in the cells of the subject’ s calf muscle had
decreased significantly . Four minutes after CO2 was applied, there was a
marked drop in oxy-hemoglobi n concentrations, indicating better delivery
of oxyg en. The researchers concluded that CO2, when applied directly to
the skin, facilitates the absorption of CO2 in humans and causes greater
oxygenation of the tissues. This proved that the Bohr ef fect can be produced
artificially in the laboratory . This has potential benefits for people with
injuries or other disorders that can be treated with high levels of localized
oxygen in the tissues.33
In 2017, scientists tested 27 rats to find out whether transcutaneous CO2
(CO 2 applied directly to the skin) could speed up muscle repair . Each  of the
rats had an injury inflicted on a leg muscle—the equivalent muscle runs
down the front of the human shin—and each rat was assigned to one of twogroups. One group of rats was treated with transcutaneous CO2, while the
other group was untreated. In the rats treated with CO2, the muscle injury
had completely healed by the sixth week. In the untreated group , the injury
was only partially repaired after six weeks.34
Endurance exercise produces CO2 in the body through the aerobic
metabolic processes. However , the full role of CO2 is not yet clear . It has
been established that external application of CO2 to the skin promotes
changes in the muscles and that these changes are linke d to better
endurance and greater power in the skeletal muscles. The 2017 study
concluded that these changes also allow the muscles to heal more quickly . Scientists observ ed an increase in the number of small blood vessels in the
muscles of the CO2 group. This further confirms that CO2 is benef icial for
muscle development and performance in endurance sports and indicates that
it may enhance oxygenation of the skeletal muscles and recovery from
muscle fatigue. IMPROVING RESPIRA TORY MUSCLE STRENGTH
Breathing patterns will change during intense physical exercise . When the
system is under strain, respirat ion becomes the body’ s main concern. If
push comes to shove, the system needs oxygen to survi ve, and so
respiration will always be given  priority over postural control. This is the
underlying reason that while athletes might train to improve sports
performance and while regular  aerobic training improves cardiovascular
and skeletal muscle function, physical training does not strengthen the
breathing muscles.
_OceanofPDF.com_The_Breathing_Cure_-_Patrick_McKeown.txt
Summarize the following text section accurately and concisely. Maintain specific details and numerical information, and use anti-repetition mechanisms:

        In other words, exhalation is under the direct control of
the vagus nerve,47 while vagal activity is suppress ed during inhalation. 48,49
By increasing the duration of the out breath, it may be possible to access the
vagus nerve’ s connection with the rest and digest state, stimu late the on-
demand release of ACh to calm the nerves, and shift the system out of its
primal fight-or -flight response by signaling a state of relaxation. The concept of slow breathing to restore and enhance healt h is not
new. 27 A variety of breathing techniques have long been central to
contemplative practices such as yoga, martial arts, Tai Chi Chuan, and
meditation. The essential idea, encapsulated by the yogic practice of
Pranayama, is that the mind and the breath are inextricably linked. The
Sanskrit word Prana  means the body’ s vital energy, and yama  is contr ol or
mastery of that. Some practices that don’t consciously focus on breath can
also have an impact. For exam ple, in deep transcendental meditation, the
breath can gradu ally become so faint that it even stops for a while. 50 What
most of these practices have in common is breathing through the nose. Numerous scientific studies back up the centuries of tradition and
experience. Research into the effects of slow breathing on the body shows
significant impa cts on the ANS  and on the functions of the cardiovascular
and respiratory systems, including baroreflex sensitivity, HRV, blood flow
dynamics, RSA, and the balancing of the two branches of the ANS. Controlled slow breathing and breath holding can be used to optimize the
very physical functions associated with health and longevity and which may
provide greater resilience against disease. Studies looking at the physical mechanisms of breathing indicate a
connection between breath, cognition, and emotion, which involves the
ANS. 28 Breathing well contributes to emotional balance and social
adaptation. A 2017 review in the Journal of Yoga and Physiotherapy
explains that, since exhalation is the relaxation phase, holding the breath
after exhaling activates the PNS, increasing relaxation. 18 The paper
suggests that to experience long-term benefits from breath-hold exercises,
we need to spend time daily in parasympathetic dominance. The best way to
do this is to develop a habit of controlling the breath most of the time in an
easy, spontaneou s way. Another study found that yogic breathing exercises
altered autonomic responses to breath holding by increasing vagal tone and
decreasing sympathetic activity. 51
COLD W ATER RESILIENCE AND EXPRESSIVE F ACES
While direct stimulation of the vagus nerve is only possible using an
implanted device, diaphragm breathing, meditation, and singing can all beused to increase vagal tone. The popular breathwork guru, Wim Hof, uses a
combination of breathing techniques and cold water immersion  to activate
the vagus nerve. Scientists have proven that immersing the face in cold water or
splashing cold water on the back of the neck increases parasympathetic
activity. 52,53 In fact, one study recomme nds the practice to moderate
sympathetic activation after exercise to relieve stress on the heart. 52
However, full body cold water immersion can cause potentially fatal cardiac
arrhythmia due to autonomic conflict, where both parasympathetic and
sympathetic inputs to the heart are activated simultaneously. 54 This is
because rapid submersion in water less than 59 ° Fahrenheit (15 ° Celsius)
with simultaneous breath-holding activates two powerful autonomic
responses: the cold shock response and the diving response. At the same time, empirical evidence indicates that stronger vagal tone
can make the body more resilient to cold. Magnus Appelber g has taught
Ashtanga Yoga for nearly 20 years in Helsinki. He also enjoys ice
swimming—an activity popular in Finland, in which bathers dive into holes
in the ice, the hard-core amon g them staying in the water for several
minutes. About four years ago, Appelber g met the long-time yoga
exponent, phys iotherapist, and research scientist Simon Borg-Olivier. Olivier ’s message boiled down to the simple principle: breathe less, stretch
less (while getting more flexible), eat less, and move from the core. He
taught Appelber g about the Bohr effect, the dilation of blood vessels, and
the body’ s response to CO2. In particular, Olivier explained  how to balance
the ANS  using the breath, stimulating the parasympathetic, vagal branch
with the exhalation. Appelber g decided to change his breathing practice to include a simple
prolonged exhal e and breath holding after exhalation. He had been a winter
swimmer for 20 years and his ability to adapt to the cold had never been
particularly great. That winter, having adjusted his breathing, ice swimming
was a little easier. The following year, he tried applying the slow  exhalation
in the water and discovered he could swim for 200 meters in freezing water
—four times farther than the previous winter. Still, this wasn’ t completely
out of the ordinary. In February 2019, he became a social media
phenomenon with videos that showed him dropping into the ice holedirectly from a yoga pose. He was interviewed on TV and radio, and this
propelled him to experiment further. Appelber g started using very long exhalations and breath holds,
practicing these for 15 minutes before entering the water. Remarkably, this
practice, using the breath to augment levels of CO2 in his blood, increased
the time he was able to stay in the cold water without pain or hypothermia
from 5 minutes to 30 minutes— within 2 months. Appelber g found he could
maintain his core temperature better by practicing breath holds in the water. He experienced none of the pain in his toes or fingers that would indicate
the usual constriction of blood vessels, and the controlled breath kept him
present in his body. In a June 2020 email to me, he wrote,
The greatest help has been my almost 20 years of Vipassana
meditation, after all cold is only a sensation. Right now, I’m
trying to find sources that could actually explain what is going on in
the body. This adaptation is a fact and I’ve found the circumstances
that are necessa ry for that: the stimulation of the parasympath etic
nervous system and the higher levels of carbon dioxide to counteract
the vasoconstriction. The ef fect on life in general has been amazing. Few people have Appelber g’s curiosity, resilience, and ability to push the
boundaries. It is important to emphasize that the practice of breath holds in the water
is not recommended unless you are working under the supervision of a
qualified breathing coach. For the rest of us mere mortals, the good news is
that you can gain considerable benefits by practicing the breathing exercises
on dry land. Interestingly, research that demo nstrates that immersing the face in cold
water stimulates the vagus nerve is echoed in the work of behavioral
neuroscientist and psychiatry professor, Steven Porges. Porges put forward
a theory suggesting that the vagus nerve comprises three neural circuits, the
most primitive of which is related to evolutionary behavio rs like the
“freeze” response of extreme stress, while the newest is linked to social
communication and self-soothing. Porges says that one way that breathing
exercises produ ce vagal stimulation is via sensory and motor nerves that
regulate facial muscles. 55 This is in line with studies that show babies withmore expressive faces have higher HRV56 and with Wim Hof’s assertion
that it is possibl e to stimulate the vagus nerve by activating the parts of the
body it innerva tes. The vagus nerve is responsible for speech, the gag
reflex, and many movements of the mouth. 57 In fact, according to Porges,
the very process of using the muscles in the face and head to actively
interact changes our physiologi cal state by increasing vagal influences on
the heart and calming the sympathetic nervous system’ s fight-or -flight
response. Conv ersely, the cosmetic treatment Botox, which is used to
smooth away signs of aging by effectively paralyzing the face, actually
works by inhibiting the release of ACh. THE DIAPHRAGM
The diaphragm is the main muscle for the physical act of breathing. It, too,
is innerv ated by the vagus nerve. 58 It shoul d therefore come as no surprise
that diaphragmatic or deep breathing is one of the most common and
ancient methods for body-mind training and holistic treatment of stress and
psychosomatic conditions. 28 Inhaling and exhaling from the diaphragm
slows the breath  and maximizes the exchange of blood gases. 28 In a study,
healthy participa nts who were trained in diaphragm breathing had slower
rates of respiration and were more likely to achieve the goal of three to
seven breaths per minute than those who breathed normally. 27
Studies of the function and movement of the diaphragm muscle show
that optimal breathing requires active diaphragm control. Ideally, during the
inhalation, the lower ribs stay low, expanding only laterally, with the
abdomen expanding instead of the chest. The amount of move ment in the
diaphragm correlates with changes in lung volume. The more the
diaphragm moves between the in and out breaths, the great er the tidal
volume (the amount of air breathed in with each normal breath). Inhalations and exhalations are driven by a group of muscles
collectively referred to as the respiratory pump, the largest of which is the
diaphragm. During the in breath, the diaphragm contracts and flattens. 27 It
pushes on the abdomen, and the lower ribs move upward and outward. Coordinated contraction of various muscles expands the rib cage, and the
chest opens outward. The resul ting changes in pressure trigger ventilationand gas exchange in the lungs. The out breath is more passive. The
diaphragm returns to its dome-shaped resting position, the lungs deflate,
and air is expelled. Importantly, it is possible to support optimum gas exchange with
controlled slow respiration as long as it is paired with an increase in tidal
volume. Diaphragmatic breathing at a rate of six breaths per minute reduces
the chem oreflex response to both hyper capnia  (where CO2 levels are too
high) and hypoxia  (where oxygen levels are too low). 59–61 Conversely,
increasing the speed of the breath to a faster -than-normal rate does nothing
to improve its efficiency: less of the air reaches the alveoli due to increased
“dead space. ” As we saw in Chapter Three, slower breathing is simply more
efficient. Air reaches and distends more of the alveoli in the lungs, so more
oxygen enters the bloodstream. In a study comparing oxygen levels in the
arteries during normal breathing  and at 15, 6, and 3 breaths per minute, the
rate of 6 breath s per minute was found to be the best for reducing dead
space in the airways, increa sing oxygen uptake, and for ease of
sustainability. A paper published in Frontiers in Psychology  found that diaphragmatic
breathing, which  itself naturally results in a slower respiration rate, has the
potential to reduce the impact of stress and improve cognitive performance
in otherwise healthy adults. 28 The results suggested that this may be
because HRV increases during diaphragmatic breathing, indicating a better
balance of activity between the SNS and PNS. Scientists inferred that deep
breathing might impact cognitiv e performance by influencing the ANS, and
that breathing may link the mind and body together to regulate the
information processing necessary to maintain attention. A review  of the possible pain-re lieving effect of deep breathing further
underlines the mind-body-breath connection. Scientists found that the
perception of pain was reduced when participants held their breath after a
deep inhalation,  a position where the diaphragm is lowered. Notably, this
appeared to involve the interv ention of the baroreceptors. 58 The study
suggested that the pain response is not simply a neural process but that a
close relationship exists between the breath, the emotions, and the working
of the barorecep tors. Stress can lead to anxiety and depression, which can
adversely affect the way the diaphragm works. Equally, changes inemotional state can cause a greater perception of pain. The study concluded
that the diaphragm influences the working of the barorecept ors and the
perception of pain, and vice versa. This may be because the movement of
the diaphragm changes the pressure within the body, and the resulting flow
of blood in the body determines the baroreceptor response, but there is not
yet clear research to confirm this. 58
SIX BREA THS PER MINUTE
To recap what we have already learned, slow breathing causes the
oscillations in blood pressure to synchronize with the rhythm of the heart,
creating the conditions for optimum blood gas exchange. Remember, there’ s
a significant connection between RSA, HRV, baroreceptors, and the ANS. Scientists have shown that slow  breathing at a rate of six breath s a minute,
with increased tidal volume (achieved by activating the diaphragm), rather
than suppressing the fight-or -flight activity of the sympathetic nervous
system, appears  to optimize the balance between the sympathetic and
parasympathetic branches of the ANS and to enhance autonom ic reactivity
to both physical and mental stress. 27
Breathing at six breaths per minute has a powerful effect on many body
systems. In the respiratory syste m, it increases air in the lungs, enhances the
function of the diaphragm, improves ventilation efficiency, pulls more
oxygen into the blood, and is thought to increase blood flow back to the
heart (venous return). This has been demonstrated in studies of athletes at
high altitude. Athletes climbing  to the peaks of Everest and K2 without
oxygen supplies were able to achieve similar oxygenation with slower
breathing rates after two week s of acclimatization in lower atmospheric
oxygen levels. It was concluded that efficiency of breathing is more
important than quantity. 62
In the cardiovascular system, breathing at six breaths per minute
increases the filling of the right heart and the amount of blood pumped by
the heart per minute. 27 It cause s blood pressure oscilla tions to synchronize
with the rhythm of the heartbea t, increases HRV, and potentially decreases
mean blood pressure. In the cardiorespiratory system, it increases baroreflex
sensitivity and HRV. In the ANS, it increases vagal tone, promotes a shifttoward PNS dominance, and improves the responsiveness of the ANS
toward physical movement. The rate of six breaths per minute optimizes the
release and meta bolism of acetylcholine, maximizing RSA. 27 It is also the
threshold for triggering the baroreflex and is the respiration rate with the
highest increase of HR V. For centuries, people have practiced techniques like meditation and
yoga for their positive effects on physical and mental health and cognition. What all these activities have in common is that breathing is attentively
guided or regulated. Even simple awareness of the breath can influence the
rate of respiration. This, in turn, explains the health benefits of such
practices throug h their impact on the balance of the ANS. The physical
functions underlying these breathing techniques have been studied to
explain the impact of respiratory vagal nerve stimulation on inflammation,
the working of the heart, gener al physical and mental health, stress relief,
and enhanced brain power, including a better working memory and greater
creativity. There has also been research into the way the body interprets the top-
down (brain to body) and bottom-up (body to brain) signals and into the
possibility of training the autonomic responses. 25 It has been confirmed that
respiratory vagus nerve stimulation (rVNS) reduces stress and inflammation
long-term. While rVNS produces an immediate shift in PNS activity during
and after practic e, it also results  in a shift in autonomic balance, increasing
vagal dominance both in resting states and in those active states requiring
behavioral and cognitive flexibility. Evidence shows  that breathing exercises with a low respiration rate can
stimulate the vagus nerve. Though how this occurs is not proven, scientists
believe the baroreflex mechanism causes this stimulation. The health
benefits felt by people practicing slow and controlled breathing are due to a
prolonged incre ase in vagal tone. Dominance of the PNS depends on the
consistent ability of the body’ s systems to relax. This provides a release
from chronic stress and prevents stress-related illness. LONG EXHALA TIONSPracticing breath holds, in particular, provides a tool to control the ANS. Breath holding also helps the body adapt to higher blood CO 2 (hypercapnia)
and provides a direct way to hack the body’ s stress response. As one paper
puts it, by practicing breath holds, you will eventually be able to “maintain
self-control in most stressful settings. ”18 Short term, the benefits include
stress reduction, better regulation of blood pressure, and more focused
attention. Prolo nged practice improves cognitive function and enhances
autonomic balance, improving your ability to come back to baseline and
respond to external and internal challenges from a balanced physical and
psychological perspective. 18
Studies into the different systems, such as the PNS, respiratory
ventilation, and HRV, have settled on a rate of six breaths per minute as
optimal. Howev er, given that the vagus nerve is activated purely  during the
out breath, why isn’t there more exploration into inhalation/exhalation
ratios. Does the vagus nerve work even better when exhalations are longer
than inhalations. One study carried out by scientists in Taiwan looked at this idea in
detail by examining healthy college students to discover the differences in
breathing with longer exhalation s compared to breathing with equal in/out
ratios in the effect on subjective feelings of anxiety and physiologically on
HRV. 63 Specifically, they explored two very similar breathing rates—6
breaths per minute and 5. 5 breaths per minute—each with inhalation to
exhalation ratios of 5:5 (equal) and 4:6 (longer exhalation). They expected slow breathing with longer exhalations to create more
intense feelings of relaxation and higher HRV than an equal ratio pattern. Previous studies showing the beneficial effects of 6 breaths per minute for
heart and lung functions had already confirmed that inhaling quickly and
exhaling slowly (2:8 respectively) was more effective in reducing mental
and physical arousal in threatening or stressful situations than inhaling
slowly and exhaling quickly. 63 There are also various breathing exercises,
for exam ple in yoga, where techniques such as 2:1 breathing, during which
exhalations are twice the length of inhalations, are recognized as
beneficial. 64 However, contrary to expectations, the Taiwan study revealed
that a respiratio n rate of 5. 5 breaths per minute with equal length in/out
breaths (5:5) significantly increased HRV. 63 What’ s more, it increased vagalnerve/PNS activation and barore flex function more than the other breathing
patterns, meaning it has the potential to help patients with condi tions where
low HR V is a feature. Several papers point out that slow breathing can be uncomfortable. This
might explain why people are attracted to activities like yoga and
meditation where the focus is on the breath, but the practice is guided to
make breathing effortless. To comfortably breathe at a rate of 5. 5 breaths
per minute with an equal inhalation and exhalation ratio, a BOL T score of at
least 15 seconds  is required. There are programs in Chapter Two designed
to improve the BOL T score to 15 seconds, making slow breath ing practice
more attainable. It is certainly worth your time and effort, given the indications that this
breathing pattern increases PNS and baroreflex function and simultaneously
enhances relaxation. SYNCHRONIZED BREA THING—MANTRAS AND MUSIC
The age-old breathing practices cultivated in Eastern traditions have
significant scientific basis in terms of physical and mental influence. 65
However, vario us other customs and activities have also been found to
synchronize cardiovascular rhythms by reducing breathing to the optimum
rate. Recitation of both the yoga mantra “om-mani-padme-hum ” and the
rosary prayer in Latin, with one person reciting the priest’ s part: “Ave
Maria, gratia plena, Dominus tecum, benedicta tui mulieribus et benedictus
fructus ventris tui Jesus,” and the other the response: “Sancta Maria, Mater
Dei, ora pro nobis peccatoribus, nunc et in hora mortis nostrae, Amen,” has
been found to lower the respiratory rate to, you guessed it, around six
breaths per minute. 65
This is no coincidence. Mantras, which are usually repeated in
sequences of more than 100, similar to the rosary, which is recited 150
times, may have evolved as a device to slow respiration, induc e relaxation
and enhance concentration. 66 The length of time required to perform over
100 mantras or to get through 150 recitations of the rosary is significant,
suggesting that one of the aims might be to induce physical chan ges as well
as altering mental state. Given that many  of the physical aspects at play here are rhythmical, it is
also worth looking at the conne ction between music and the PNS. Humans
interact with music at behavioral, emotional, and physiological levels, both
consciously and unconsciously. 67 Over 100 years ago, it was suggested that
the ANS forms a sort of “sounding board” that reverberates to changes in
consciousness. 67 Many centuries earlier, classical Greek philosophers
believed music and sports to be the two fundamental aspects of well-being. Contemporary experiments have explored how elements of music such as
beat, tempo, and pitch trigger emotional and behavioral responses, as well
as reactions in the physical and nervous systems. Singing has been found to reduc e tension, increase energy, and improve
mood. It directly activates the vocal cords and the muscles at the back of the
throat—which are connected to the vagus nerve. 68 Regular singing can even
increase vagal tone. However, the impact of singing on HRV was found to
be dependent on whether the singer experienced the task as stressful or not. A greater heart rate variable was found in professional singers after a
singing lesson, while amateurs showed lower HRV. Heart rate increased
after solo singing but decreased  after choral singing, indicating that when a
person is perform ing music, rather than just listening to it, the perception of
the task as safe or scary influe nces the resultant physical reaction. It has
also been found that trained musicians have a lower baseline breathing rate
than nonmusicians. 69
One study into the physiological responses to music found that even a
short listening session could bring about measurable cardiovascular and
respiratory effects. 69 The level of arousal or focused attention was largely
determined by the tempo (speed) of the music. Regardless of taste in music
or whether the listener was previously familiar with the piece, slow music
from a variety of genres reduced cardiorespiratory response. A pause or
period of silence in the music produced a higher level of relaxat ion than the
music itself, suggesting that music may give pleasure and potential health
benefits as a result of the controlled alternation of arousal and relaxation. It
was concluded that music can be used to induce relaxation and reduce SNS
activity and that it may be useful in the management of cardiovascular
disease. In a therapeutic setting, music has been used to enhance
parasympathetic activity and decrease congestive heart failure by reducing
levels of inflammatory cytokines. 70 Patients under going a 14-day  music
therapy course exhibited change s in HRV patterns that indicated enhanced
activity of the cardiovascular system. 71 One experiment into the impact of
music on the autonomic response compared healthy participants with
patients in a vegetative state or with unresponsive wakefulness syndrome. Those participa nts with disorders of consciousness showed  replicable
changes in the balance between the SNS and the vagal system after passive
listening to symphonic music. 72
USING HR V IN THE REAL WORLD
As part of the training that I run for our Oxygen Advantage instructors, I
was fortunate enough to organize an online coaching webinar in August
2020 with Dr. Jay T. Wiles, a clinical health physiologist. Dr. Wiles
specializes in sports performance and holistic and integrative health, and he
is board certified in biofeedback and HR VB.
The vagus nerve is not directly controlled during inhalation, but is under direct control during exhalation.
What is controlled by the vagus nerve during exhalation?
The study aimed to explore the connection between diaphragmatic breathing and athletic performance, but not specifically to improve sports performance.
What is the primary focus of the study on the relationship between diaphragmatic breathing and athletic performance?
The diaphragm is the main muscle for physical act of breathing.
What is the main function of the diaphragm?
The primary goal of HRV training is not to increase the reading, but to modulate and improve the autonomic nervous system.
What is the primary goal of HRV training, as emphasized by Dr. Wiles?
The recommended rate for slow breathing is six breaths per minute.
What is the recommended rate for slow breathing?