Science of the Heart, Volume 2 Exploring the Role of the Heart in Human Performance An Overview of Research Conducted by the HeartMath Institute

Abstract

This insightful and comprehensive monograph provides fundamental and detailed summaries of HeartMath Institute’s many years of innovative research. It presents brief overviews of heart rate variability, resilience, coherence, heart-brain interactions,intuition and the scientific discoveries that shaped techniques developed to increase fulfillment and effectiveness. Included are summary reports of research conducted in the business, education, health and first responder fields. Both the layperson and science professional will appreciate its simplicity and thoroughness.

Full text

of the
HEART
SCIENCE
Exploring the Role of the
Heart in Human Performance
An overview of research conducted by HeartMath Institute
Volume 2

SCIENCE OF THE HEART
Exploring the Role of the Heart in Human Performance
Volume 2
Authored by Rollin McCraty, Ph.D.
Director of Research, HeartMath Research Center
Phone: (831) 338-8500
Email: info@heartmath.org
Visit our website at https://www.heartmath.org
Published by: HeartMath Institute
HeartMath Institute
14700 West Park Ave.
P.O. Box 1463
Boulder Creek, CA 95006
Distributed in USA by HeartMath Institute
Copyright © 2015 by HeartMath Institute
Cover and layout design by Sandy Royall
Volume 1 2001
Volume 2 2015
ISBN 978-1-5136-0636-1 Paperback
All rights reserved. No part of this book may be translated or reproduced in any form
without the written permission of HeartMath Institute.
HeartMath®, Freeze Frame®, Heart Lock-In®, Cut-Thru®, Inner Quality Management® (IQM)
are registered trademarks of HeartMath Institute.
10 9 8 7 6 5 4 3 2 1
First printing, November 2015
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© Copyright 2015 HeartMath Institute

Table of Contents
About HeartMath Institute ............................................................................................................ iii
Introduction .....................................................................................................................................1
Chapter 1: Heart-brain Communication ......................................................................................... 3
Chapter 2: Resilience, Stress and Emotions .................................................................................8
Chapter 3: Heart Rate Variability: An Indicator of Self-Regulatory Capacity,
Autonomic Function and Health ..................................................................................................13
Chapter 4: Coherence ...................................................................................................................24
Chapter 5: Establishing a New Baseline ......................................................................................29
Chapter 6: Energetic Communication ..........................................................................................36
Chapter 7: Intuition Research: Coherence and the Surprising Role of the Heart ......................45
Chapter 8: Health Outcome Studies ............................................................................................53
Chapter 9: Outcome Studies in Education ..................................................................................66
Chapter 10: Social Coherence: Outcome Studies in Organizations ...........................................81
Chapter 11: Global Coherence Research: Human-Earth Interconnectivity ................................89
Bibliography ................................................................................................................................100
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© Copyright 2015 HeartMath Institute

HeartMath Institute (HMI) is an innovative nonprot research and education or-
ganization that provides simple, user-friendly mental and emotion self-regulation
tools and techniques that people of all ages and cultures can use in the moment
to relieve stress and break through to greater levels of personal balance, stability,
creativity, intuitive insight and fulllment.
HMI research has formed the foundation for training programs conducted
around the world in many different types of populations, including major cor-
porations, government and social-service agencies, all branches of the Armed
Forces, schools and universities, hospitals and a wide range of health-care
professionals. The tools and technologies developed at HMI offer hope for
new, effective solutions to the many daunting problems that society currently
faces, beginning with restoring balance and maximizing the potential within
each of us.
HeartMath Institute’s Mission (HMI)
The mission of HeartMath Institute is to help people bring their physical, men-
tal and emotional systems into balanced alignment with their heart’s intuitive
guidance. This unfolds the path for becoming heart-empowered individuals who
choose the way of love, which they demonstrate through compassionate care
for the well-being of themselves, others and Planet Earth.
About HeartMath Institute
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© Copyright 2015 HeartMath Institute

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© Copyright 2015 HeartMath Institute
Introduction
New research shows the human heart is much more than an ecient pump that sustains life.
Our research suggests the heart also is an access point to a source of wisdom and intelligence
that we can call upon to live our lives with more balance, greater creativity and enhanced in-
tuitive capacities. All of these are important for increasing personal effectiveness, improving
health and relationships and achieving greater fulllment.
This overview will explore intriguing aspects of the science of the heart, much of which is still
relatively not well known outside the elds of psychophysiology and neurocardiology. We will
highlight research that bridges the science of the heart and the highly practical, research-based
skill set known as the HeartMath System.
The heart has been considered the source of emotion, courage and wisdom for centuries. For more than 25
years, the HeartMath Institute Research Center has explored the physiological mechanisms by which the
heart and brain communicate and how the activity of the heart inuences our perceptions, emotions, intuition
and health. Early on in our research we asked, among other questions, why people experience the feeling or
sensation of love and other regenerative emotions as well as heartache in the physical area of the heart. In the
early 1990s, we were among the rst to conduct research that not only looked at how stressful emotions affect
the activity in the autonomic nervous system (ANS) and the hormonal and immune systems, but also at the
effects of emotions such as appreciation, compassion and care. Over the years, we have conducted many studies
that have utilized many different physiological measures such as EEG (brain waves), SCL (skin conductance),
ECG (heart), BP (blood pressure) and hormone levels, etc. Consistently, however, it was heart rate variability,
or heart rhythms that stood out as the most dynamic and reective indicator of one’s emotional states and,
therefore, current stress and cognitive processes. It became clear that stressful or depleting emotions such as
frustration and overwhelm lead to increased disorder in the higher-level brain centers and autonomic nervous
system and which are reected in the heart rhythms and adversely affects the functioning of virtually all bodily
systems. This eventually led to a much deeper understanding of the neural and other communication pathways
between the heart and brain. We also observed that the heart acted as though it had a mind of its own and could
signicantly inuence the way we perceive and respond in our daily interactions. In essence, it appeared that
the heart could affect our awareness, perceptions and intelligence. Numerous studies have since shown that
heart coherence is an optimal physiological state associated with increased cognitive function, self-regulatory
capacity, emotional stability and resilience.
We now have a much deeper scientic understanding of many of our original questions that explains how and
why heart activity affects mental clarity, creativity, emotional balance, intuition and personal effectiveness. Our
and others’ research indicates the heart is far more than a simple pump. The heart is, in fact, a highly complex
Introduction

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Science of the Heart
information-processing center with its own functional brain, commonly called the heart brain, that communicates
with and inuences the cranial brain via the nervous system, hormonal system and other pathways. These
inuences affect brain function and most of the body’s major organs and play an important role in mental and
emotional experience and the quality of our lives.
In recent years, we have conducted a number of research studies that have explored topics such as the elec-
trophysiology of intuition and the degree to which the heart’s magnetic eld, which radiates outside the body,
carries information that affects other people and even our pets, and links people together in surprising ways.
We also launched the Global Coherence Initiative (GCI), which explores the interconnectivity of humanity with
Earth’s magnetic elds.
This overview discusses the main ndings of our research and the fascinating and important role the heart
plays in our personal coherence and the positive changes that occur in health, mental functions, perception,
happiness and energy levels as people practice the HeartMath techniques. Practicing the techniques increases
heart coherence and one’s ability to self-regulate emotions from a more intuitive, intelligent and balanced inner
reference. This also explains how coherence is reected in our physiology and can be objectively measured.
The discussion then expands from physiological coherence to coherence in the context of families, workplaces
and communities. Science of the Heart concludes with the perspective that being responsible for and increasing
our personal coherence not only improves personal health and happiness, but also feeds into and inuences
a global eld environment. It is postulated that as increasing numbers of people add coherent energy to the
global eld, it helps strengthen and stabilize mutually benecial feedback loops between human beings and
Earth’s magnetic elds.

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Heart-Brain Communication
The heart communicates with the brain and body in four ways:
• Neurological communication (nervous system)
• Biochemical communication (hormones)
• Biophysical communication (pulse wave)
• Energetic communication (electromagnetic elds)
Traditionally, the study of communication pathways between the head and heart has been approached from
a rather one-sided perspective, with scientists focusing primarily on the heart’s responses to the brain’s
commands. We have learned, however, that communication between the heart and brain actually is a dynamic,
ongoing, two-way dialogue, with each organ continuously inuencing the other’s function. Research has shown
that the heart communicates to the brain in four major ways: neurologically (through the transmission of nerve
impulses), biochemically (via hormones and neurotransmitters), biophysically (through pressure waves) and
energetically (through electromagnetic eld interactions). Communication along all these conduits signicantly
affects the brain’s activity. Moreover, our research shows that messages the heart sends to the brain also can
affect performance.
Some of the rst researchers in the eld of psycho-
physiology to examine the interactions between the
heart and brain were John and Beatrice Lacey. During
20 years of research throughout the 1960s and ’70s,
they observed that the heart communicates with the
brain in ways that signicantly affect how we perceive
and react to the world.
In physiologist and researcher Walter Bradford Can-
non’s view, when we are aroused, the mobilizing part
of the nervous system (sympathetic) energizes us for
ght or ight, which is indicated by an increase in heart
rate, and in more quiescent moments, the calming
part of the nervous system (parasympathetic) calms
us down and slows the heart rate. Cannon believed
the autonomic nervous system and all of the related
physiological responses moved in concert with the
brain’s response to any given stimulus or challenge.
Presumably, all of our inner systems are activated to-
gether when we are aroused and calm down together
when we are at rest and the brain is in control of the
entire process. Cannon also introduced the concept
of homeostasis. Since then, the study of physiology
has been based on the principle that all cells, tissues
and organs strive to maintain a static or constant
steady-state condition. However, with the introduc-
tion of signal-processing technologies that can ac-
quire continuous data over time from physiological
processes such as heart rate (HR), blood pressure
(BP) and nerve activity, it has become abundantly ap-
parent that biological processes vary in complex and
nonlinear ways, even during so-called steady-state
conditions. These observations have led to the under-
standing that healthy, optimal function is a result of
continuous, dynamic, bidirectional interactions among
multiple neural, hormonal and mechanical control
systems at both local and central levels. In concert,
these dynamic and interconnected physiological and
psychological regulatory systems are never truly at
rest and are certainly never static.
Heart-Brain Communication
CHAPTER 1

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Science of the Heart
For example, we now know that the normal resting rhythm of the heart is highly variable rather than monoto-
nously regular, which was the widespread notion for many years. This will be discussed further in the section
on heart rate variability (HRV).
Figure 1.1 Innervation of the major organs by the autonomic nervous system (ANS). Parasympathetic bers are primarily in the
vagus nerves, but some that regulate subdiaphragmatic organs travel through the spinal cord. The sympathetic bers also travel
through the spinal cord. A number of health problems can arise in part because of improper function of the ANS. Emotions can
affect activity in both branches of the ANS. For example, anger causes increased sympathetic activity while many relaxation
techniques increase parasympathetic activity.
The Laceys noticed that the model proposed by Can-
non only partially matched actual physiological be-
havior. As their research evolved, they found that the
heart in particular seemed to have its own logic that
frequently diverged from the direction of autonomic
nervous system activity. The heart was behaving as
though it had a mind of its own. Furthermore, the
heart appeared to be sending meaningful messages
to the brain that the brain not only understood, but
also obeyed. Even more intriguing was that it looked
as though these messages could affect a person’s
perceptions, behavior and performance. The Laceys
identied a neural pathway and mechanism whereby
input from the heart to the brain could inhibit or fa-
cilitate the brain’s electrical activity. Then in 1974,
French researchers stimulated the vagus nerve (which
carries many of the signals from the heart to the brain)
in cats and found that the brain’s electrical response
was reduced to about half its normal rate.[1] This sug-
gested that the heart and nervous system were not
simply following the brain’s directions, as Cannon had
thought. Rather, the autonomic nervous system and
the communication between the heart and brain were
much more complex, and the heart seemed to have
its own type of logic and acted independently of the
signals sent from the brain.
While the Laceys research focused on activity occur-
ring within a single cardiac cycle, they also were able
to conrm that cardiovascular activity inuences
perception and cognitive performance, but there were
still some inconsistencies in the results. These in-
consistencies were resolved in Germany by Velden
and Wölk, who later demonstrated that cognitive
performance uctuated at a rhythm around 10 hertz
throughout the cardiac cycle. They showed that the
modulation of cortical function resulted from ascend-
ing cardiovascular inputs on neurons in the thalamus,
which globally synchronizes cortical activity.[2, 3] An
important aspect of their work was the nding that

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© Copyright 2015 HeartMath Institute
it is the pattern and stability of the heart’s rhythm of
the afferent (ascending) inputs, rather than the num-
ber of neural bursts within the cardiac cycle, that are
important in modulating thalamic activity, which in
turn has global effects on brain function. There has
since been a growing body of research indicating that
afferent information processed by the intrinsic cardiac
nervous system (heart-brain) can inuence activity
in the frontocortical areas[4-6] and motor cortex,[7] af-
fecting psychological factors such as attention level,
motivation,[8] perceptual sensitivity[9] and emotional
processing.[10]
Neurocardiology: The Brain On the Heart
While the Laceys were conducting their research in
psychophysiology, a small group of cardiologists
joined forces with a group of neurophysiologists and
neuroanatomists to explore areas of mutual interest.
This represented the beginning of the new discipline
now called neurocardiology. One of their early ndings
is that the heart has a complex neural network that is
suciently extensive to be characterized as a brain on
the heart (Figure 1.2).[11, 12] The heart-brain, as it is com-
monly called, or intrinsic cardiac nervous system, is an
intricate network of complex ganglia, neurotransmit-
ters, proteins and support cells, the same as those of
the brain in the head. The heart-brain’s neural circuitry
enables it to act independently of the cranial brain to
learn, remember, make decisions and even feel and
sense. Descending activity from the brain in the head
via the sympathetic and parasympathetic branches
of the ANS is integrated into the heart’s intrinsic ner-
vous system along with signals arising from sensory
neurons in the heart that detect pressure, heart rate,
heart rhythm and hormones.
The anatomy and functions of the intrinsic cardiac ner-
vous system and its connections with the brain have
been explored extensively by neurocardiologists.[13, 14]
In terms of heart-brain communication, it is generally
well-known that the efferent (descending) pathways
in the autonomic nervous system are involved in the
regulation of the heart. However, it is less appreciated
that the majority of bers in the vagus nerves are
afferent (ascending) in nature. Furthermore, more of
these ascending neural pathways are related to the
heart (and cardiovascular system) than to any other
organ.[15] This means the heart sends more information
to the brain than the brain sends to the heart. More
recent research shows that the neural interactions
between the heart and brain are more complex than
previously thought. In addition, the intrinsic cardiac
nervous system has both short-term and long-term
memory functions and can operate independently of
central neuronal command.
Figure 1.2. Microscopic image of interconnected intrinsic
cardiac ganglia in the human heart. The thin, light-blue
structures are multiple axons that connect the ganglia.
Courtesy of Dr. J. Andrew Armour.
Once information has been processed by the heart’s
intrinsic nervous system, the appropriate signals are
sent to the heart’s sinoatrial node and to other tis-
sues in the heart. Thus, under normal physiological
conditions, the heart’s intrinsic nervous system plays
an important role in much of the routine control of
cardiac function, independent of the central nervous
system. The heart’s intrinsic nervous system is vital
for the maintenance of cardiovascular stability and
eciency and without it, the heart cannot function
properly. The neural output, or messages from the
intrinsic cardiac nervous system travels to the brain
via ascending pathways in the both the spinal column
and vagus nerves, where it travels to the medulla, hy-
pothalamus, thalamus and amygdala and then to the
cerebral cortex.[5, 16, 17] The nervous-system pathways
between the heart and brain are shown in Figure 1.3
and the primary afferent pathways in the brain are
shown in Figure 1.4.
Chapter 1: Heart-Brain Communication

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© Copyright 2015 HeartMath Institute
Science of the Heart
Had the existence of the intrinsic cardiac nervous
system and the complexity of the neural communica-
tion between the heart and brain been known while
the Laceys were conducting their paradigm-shifting
research, their theories and data likely would have
been accepted far sooner. Their insight, rigorous ex-
perimentation and courage to follow where the data
led them, even though it did not t the well-entrenched
beliefs of the scientic community of their day, were
pivotal in the understanding of the heart-brain con-
nection. Their research played an important role in
elucidating the basic physiological and psychologi-
cal processes that connect the heart and brain and
the mind and body. In 1977, Dr. Francis Waldropin,
director of the National Institute of Mental Health,
stated in a review article of the Laceys’ work, “Their
intricate and careful procedures, combined with their
daring theories, have produced work that has stirred
controversy as well as promise. In the long run, their
research may tell us much about what makes each of
us a whole person and may suggest techniques that
can restore a distressed person to health.”
Cortex
Subcortical Areas
Medulla
Spinal Cord
(Sympathetic)
Dorsal Root
Ganglion
Nodose Ganglion
Intrinsic Nervous System
SA Node
Chemosensory Neurons
Sympathetic & parasympathetic outputs to
muscles throughout the heart
Sympathetic
Parasympathetic
Afferent Pathways
Vagus Nerves
(Parasympathetic)
Mechanosensory Neurons
AV Node
Extrinsic Cardiac Ganglia
(Thoracic Cavity)
Heart-Brain
Communication Pathways
Brain
Heart
Figure 1.3. The neural communication pathways interacting between the heart and brain are responsible for the generation of HRV.
The intrinsic cardiac nervous system integrates information from the extrinsic nervous system and the sensory neurites within the
heart. The extrinsic cardiac ganglia located in the thoracic cavity have connections to the lungs and esophagus and are indirectly
connected via the spinal cord to many other organs, including the skin and arteries. The vagus nerve (parasympathetic) primarily
consists of afferent (owing to the brain) bers that connect to the medulla. The sympathetic afferent nerves rst connect to the
extrinsic cardiac ganglia (also a processing center), then to the dorsal root ganglion and the spinal cord. Once afferent signals
reach the medulla, they travel to the subcortical areas (thalamus, amygdala, etc.) and then the higher cortical areas.

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© Copyright 2015 HeartMath Institute
Figure 1.4. Diagram of the currently known afferent pathways by which information from the heart and cardiovascular system
modulates brain activity. Note the direct connections from the NTS to the amygdala, hypothalamus and thalamus. Although not
shown, there also is evidence emerging that there is a pathway from the dorsal vagal complex that travels directly to the frontal
cortex.
The Heart as a Hormonal Gland
In addition to its extensive neurological interactions,
the heart also communicates with the brain and body
biochemically by way of the hormones it produces.
Although not typically thought of as an endocrine
gland, the heart actually manufactures and secretes
a number of hormones and neurotransmitters that
have a wide-ranging impact on the body as a whole.
The heart was reclassied as part of the hormonal
system in 1983, when a new hormone produced and
secreted by the atria of the heart was discovered. This
hormone has been called by several different names
– atrial natriuretic factor (ANF), atrial natriuretic pep-
tide (ANP) and atrial peptide. Nicknamed the balance
hormone, it plays an important role in uid and elec-
trolyte balance and helps regulate the blood vessels,
kidneys, adrenal glands and many regulatory centers
in the brain.[18] Increased atrial peptide inhibits the
release of stress hormones,[19] reduces sympathetic
outow[20] and appears to interact with the immune
system.[21] Even more intriguing, experiments suggest
atrial peptide can inuence motivation and behavior.[22]
It was later discovered the heart contains cells that
synthesize and release catecholamines (norepi-
nephrine, epinephrine and dopamine), which are
neurotransmitters once thought to be produced only
by neurons in the brain and ganglia.[23] More recently,
it was discovered the heart also manufactures and
secretes oxytocin, which can act as a neurotransmit-
ter and commonly is referred to as the love or social-
bonding hormone. Beyond its well-known functions
in childbirth and lactation, oxytocin also has been
shown to be involved in cognition, tolerance, trust
and friendship and the establishment of enduring
pair-bonds. Remarkably, concentrations of oxytocin
produced in the heart are in the same range as those
produced in the brain.[24]
Chapter 1: Heart-Brain Communication

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© Copyright 2015 HeartMath Institute
Science of the Heart
An early editorial on the relationships between stress
and the heart accepted the proposition that in about
half of patients, strong emotional upsets precipitated
heart failure. Unspecied negative emotional arousal,
often described as stress, distress or upset, has been
associated with a variety of pathological conditions,
including hypertension,[26, 27] silent myocardial isch-
emia,[28] sudden cardiac death,[29] coronary disease,[30-32]
cardiac arrhythmia,[33] sleep disorders,[34] metabolic
syndrome,[35] diabetes,[36, 37] neurodegenerative diseas-
es,[38] fatigue[39, 40] and many other disorders.[41] Stress
and negative emotions have been shown to increase
disease severity and worsen prognosis for individuals
suffering from a number of different pathologies.[42, 43]
On the other hand, positive emotions and effective
emotion self-regulation skills have been shown to
prolong health and signicantly reduce premature
mortality.[44-49] From a psychophysiological perspec-
tive, emotions are central to the experience of stress.
It is the feelings of anxiety, irritation, frustration, lack
of control, and hopelessness that are actually what we
experience when we describe ourselves as stressed.
Whether it’s a minor inconvenience or a major life
change, situations are experienced as stressful to the
extent that they trigger emotions such as annoyance,
irritation, anxiety and overwhelm.[50]
In essence, stress is emotional unease, the experience
of which ranges from low-grade feelings of emotional
unrest to intense inner turmoil. Stressful emotions
clearly can arise in response to external challenges
or events, and also from ongoing internal dialogs and
attitudes. Recurring feelings of worry, anxiety, anger,
judgment, resentment, impatience, overwhelm and
self-doubt often consume a large part of our energy
and dull our day-to-day life experiences.
Resilience, Stress and Emotions
As far back as the middle of the last century, it was recognized that the heart, overtaxed by constant emo-
tional inuences or excessive physical effort and thus deprived of its appropriate rest, suffers disorders of
function and becomes vulnerable to disease.[25]
Additionally, emotions, much more so than thoughts
alone, activate the physiological changes compris-
ing the stress response. Our research shows a purely
mental activity such as cognitively recalling a past
situation that provoked anger does not produce nearly
as profound an effect on physiological processes as
actually engaging the emotion associated with that
memory. In other words, reexperiencing the feeling of
anger provoked by the memory has a greater effect
than thinking about it.[51, 52]
Resilience and Emotion Self-Regulation
Our emotions infuse life with a rich texture and trans-
form our conscious experience into a meaningful
living experience. Emotions determine what we care
about and what motivates us. They connect us to
others and give us the courage to do what needs to
be done, to appreciate our successes, to protect and
support the people we love and have compassion and
kindness for those who are in need of our help. Emo-
tions are also what allow us to experience the pain
and grief of loss. Without emotions, life would lack
meaning and purpose.
Emotions and resilience are closely related because
emotions are the primary drivers of many key physi-
ological processes involved in energy regulation. We
dene resilience as the capacity to prepare for, recover
from and adapt in the face of stress, adversity, trauma or
challenge.[53] Therefore, it follows that a key to sustain-
ing good health, optimal function and resilience is the
ability to manage one’s emotions.
It has been suggested that resilience should be
considered as a state rather than a trait and that a
person’s resilience can vary over time as demands,
CHAPTER 2

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© Copyright 2015 HeartMath Institute
circumstances and level of maturity change.[54] In
our resilience training programs, we suggest that
the ability to build and sustain resilience is related to
self-management and ecient utilization of energy
resources across four domains: physical, emotional,
mental and spiritual (Figure 2.1). Physical resilience
is basically reected in physical exibility, endurance
and strength, while emotional resilience is reected in
the ability to self-regulate, degree of emotional ex-
ibility, positive outlook and supportive relationships.
Mental resilience is reected in the ability to sustain
focus and attention, mental exibility and the capac-
ity for integrating multiple points of view. Spiritual
resilience is typically associated with commitment to
core values, intuition and tolerance of others’ values
and beliefs.
Figure 2.1. Domains of Resilience.
By learning self-regulation techniques that allow us
to shift our physiology into a more coherent state,
the increased physiological eciency and alignment
of the mental and emotional systems accumulates
resilience (energy) across all four energetic domains.
Having a high level of resilience is important not only
for bouncing back from challenging situations, but
also for preventing unnecessary stress reactions
(frustration, impatience, anxiety), which often lead to
further energy and time waste and deplete our physi-
cal and psychological resources.
Most people would agree it is the ability to adjust and
self-regulate one’s responses and behavior that is
most important in building and maintaining support-
ive, loving relationships and effectively meeting life’s
demands with composure, consistency and integrity.
Chapter 2: Resilience, Stress and Emotions
The ability to adjust and self-regulate also is central to
resilience, good health and effective decision-making.
[55] It is a key for success in living life with greater kind-
ness and compassion in all relationships. If people’s
capacity for intelligent, self-directed regulation is
strong enough, then regardless of inclinations, past
experiences or personality traits, they usually can do
the adaptive or right thing in most situations.[56]
___________________________
We are coming to understand health not as the
absence of disease, but rather as the process by
which individuals maintain their sense of coher-
ence (i.e. sense that life is comprehensible, man-
ageable, and meaningful) and ability to function
in the face of changes in themselves and their
relationships with their environment.[57]
___________________________
It has been shown that our efforts to self-regulate emo-
tions can produce broad improvements in increasing
or strengthening self-regulatory capacity, similar to
the process of strengthening a muscle, making us
less vulnerable to depletion of our internal reserves.[56]
When internal energy reserves are depleted, normal
capacity to maintain self-control is weakened, which
can lead to increased stress, inappropriate behaviors,
lost opportunities, poor communication and damaged
relationships. Despite the importance of self-directed
control, many people’s ability to self-regulate is far less
than ideal. In fact, failures in self-regulation, especially
of emotions and attitudes, arguably are central to the
vast majority of personal and social problems that
plague modern societies. For some, the lack of self-
regulatory capacity can be attributed to immaturity or
failure to acquire skills while for others it can be the
result of trauma or impairment in the neural systems
that underlie one’s ability to self-regulate.[58] Therefore,
we submit the most important skill the majority of
people need to learn is how to increase their capacity
to self-regulate emotions, attitudes and behaviors.
Self-regulation enables people to mature and meet
the challenges and stresses of everyday life with re-
silience so they can make more intelligent decisions
by aligning with their innate higher-order wisdom and

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Science of the Heart
expression of care and compassion, elements we often
associate with living a more conscientious life.
Our research suggests a new inner baseline reference
can be established by using the HeartMath (HM)
self-regulation techniques that help people replace
depleting emotional undercurrents with more posi-
tive, regenerative attitudes, feelings and perceptions.
A growing body of compelling scientific evidence is demonstrating a link between mental and
emotional attitudes, physiological health and long-term well-being:
60% to 80% of primary care doctor visits are related
to stress, yet only 3% of patients receive stress
management help.
[60-62]
In a study of 5,716 middle-aged people, those with the
highest self-regulation abilities were over 50 times more
likely to be alive and without chronic disease 15 years
later than those with the lowest self-regulation scores.
[63]
Positive emotions are a reliable predictor of better
health, even for those without food or shelter while
negative emotions are a reliable predictor of worse
health even when basic needs like food, shelter and
safety are met.
[64]
A Harvard Medical School Study of 1,623 heart attack
survivors found that when subjects became angry
during emotional conflicts, their risk of subsequent
heart attacks was more than double that of those who
remained calm.
[65]
A review of 225 studies concluded that positive
emotions promote and foster sociability and activity,
altruism, strong bodies and immune systems, effective
conflict resolution skills, success and thriving.
[66]
A study of elderly nuns found that those who expressed
the most positive emotions in early adulthood lived an
average of 10 years longer.
[67]
Men who complain of high anxiety are up to six times
more likely than calmer men to suffer sudden cardiac
death.
[68]
In a groundbreaking study of 1,200 people at high risk of
poor health, those who learned to alter unhealthy mental
and emotional attitudes through self-regulation training
were over four times more likely to be alive 13 years later
This new baseline, which will be summarized in a
later section, can be thought of as a type of implicit
memory that organizes perception, feelings and be-
havior.[5, 59] The process of establishing a new base-
line takes place at the physiological level, which is
imperative for sustained and lasting change to occur.
than an equal-sized control group.
[69]
A 20-year study of over 1,700 older men conducted by
the Harvard School of Public Health found that worry
about social conditions, health and personal nances
all signicantly increased the risk of coronary heart
disease.
[70]
Over one-half of heart disease cases are not explained
by the standard risk factors such as high cholesterol,
smoking or sedentary lifestyle.
[71]
An international study of 2,829 people ages 55 to 85
found that individuals who reported the highest levels
of personal mastery – feelings of control over life
events – had a nearly 60% lower risk of than those who
felt relatively helpless in the face of life’s challenges.
[72]
According to a Mayo Clinic study of individuals with
heart disease, psychological stress was the strongest
predictor of future cardiac events such as cardiac death,
cardiac arrest and heart attacks.
[73]
Three 10-year studies concluded that emotional
stress was more predictive of death from cancer and
cardiovascular disease than from smoking; people who
were unable to effectively manage their stress had a
40% higher death rate than nonstressed individuals.
[74]
A study of heart attack survivors showed that patients’
emotional states and relationships in the period after
myocardial infarction were as important as the disease
severity in determining their prognosis.
[75]
Separate studies showed that the risk of developing
heart disease is signicantly increased for people who
impulsively vent their anger as well as for those who
tend to repress angry feelings.
[76, 77]

11
© Copyright 2015 HeartMath Institute
Cognitive and Emotional System Integration
Dating back to the ancient Greeks, human thinking and
feeling, intellect and emotion have been considered
separate functions. These contrasting aspects of
the soul, as the Greeks called them, often have been
portrayed as being engaged in a constant battle for
control of the human psyche. In Plato’s view, emotions
were like wild horses that had to be reined in by the
intellect and willpower.
Research in neuroscience conrms that emotion and
cognition can best be thought of as separate but in-
teracting functions and systems that communicate
via bidirectional neural connections between the
neocortex, the body and emotional centers such as
the amygdala and body.[78] These connections allow
emotion-related input to modulate cortical activity
while cognitive input from the cortex modulates emo-
tional processing. However, the neural connections
that transmit information from the emotional centers
to the cognitive centers in the brain are stronger and
more numerous than those that convey information
from the cognitive to the emotional centers. This fun-
damental asymmetry accounts for the powerful inu-
ence of input from the emotional system on cognitive
functions such as attention, perception and memory
as well as higher-order thought processes. Conversely,
the comparatively limited inuence of input from the
cognitive system on emotional processing helps ex-
plain why it is generally dicult to willfully modulate
emotions through thought alone.
There can be differences from one individual to the
next in these reciprocal connections and interactions
between the cognitive and emotional systems that
affect the way we perceive, experience and eventually
remember our emotional experiences, and how we
respond to emotionally challenging situations. Unbal-
anced interactions between the emotional and cog-
nitive systems can lead to devastating effects such
as those observed in mood and anxiety disorders.[78]
Although there has been a historical bias favoring
the viewpoint that emotions interfere with and can
be at odds with rational thinking, which of course can
occur in some cases, emotions have their own type
of rationality and have been shown to be critical in
decision-making.[79] For example, Damasio points out,
patients with damage in areas of the brain that inte-
grate the emotional and cognitive systems can no lon-
ger effectively function in the day-to-day world, even
though their mental abilities are perfectly normal. In
the mid-1990s, the concept of emotional intelligence
was introduced, precipitating persuasive arguments
that the viewpoint of human intelligence being es-
sentially mind intellect was far too narrow. This was
because it ignored a range of human capacities that
bear equal if not greater weight in determining our
successes in life. Qualities such as self-awareness,
motivation, altruism and compassion, but especially
one’s ability to self-regulate and control impulses and
self-direct emotions were found to be as important or
more important than a high IQ. Those qualities, more
so than IQ, enable people to excel in the face of life’s
challenges.[80]
It is our experience that the degree of alignment be-
tween the mind and emotions can vary considerably.
When they are out of sync, it can result in radical
behavior changes that cause us to feel like there are
two different people inside the same body. It can also
result in confusion, diculty in making decisions,
anxiety and a lack of alignment with our deeper core
values. Conversely, when the mind and emotions are
in sync, we are more self-secure and aligned with our
deeper core values and respond to stressful situations
with increased resilience and inner balance.
Our research indicates that the key to the successful
integration of the mind and emotions lies in increasing
one’s emotional self-awareness and the coherence of,
or harmonious function and interaction among, the
neural systems that underlie cognitive and emotional
experience.[5, 58, 81]
As will be discussed in more detail in a later section,
we use the terms cardiac coherence, physiological
coherence and heart coherence interchangeably to
describe the measurement of the order, stability and
harmony in the oscillatory outputs of the body’s regu-
latory systems during any period of time.
Chapter 2: Resilience, Stress and Emotions

12
© Copyright 2015 HeartMath Institute
Science of the Heart
An important aspect of understanding how to in-
crease self-regulatory capacity and the balance
between the cognitive and emotional systems is the
inclusion of the heart’s ascending neuronal inputs
on subcortical (emotional) and cortical (cognitive)
structures which, as discussed above, can have
signicant inuences on cognitive resources and
emotions. Information is conveyed in the patterns
of the heart’s rhythms (HRV), that reects current
emotional states. The patterns of afferent neural
input (coherence and incoherence) to the brain af-
fect emotional experience and modulate cortical
function and self-regulatory capacity. We have found
that intentional activation of positive emotions plays
an important role in increasing cardiac coherence
and thus self-regulatory capacity.[5] These ndings
expand on a large body of research into the ways
positive emotional states can benet physical, men-
tal and emotional health.[44-49]
Because emotions exert such a powerful inuence on
cognitive activity, intervening at the emotional level
is often the most ecient way to initiate change in
mental patterns and processes. Our research demon-
strates that the application of emotion self-regulation
techniques along with the use of facilitative technol-
ogy (emWave®, Inner Balance™) can help people bring
the heart, mind and emotions into greater alignment.
Greater alignment is associated with improved deci-
sion-making, creativity, listening ability, reaction times
and coordination and mental clarity.[81]

13
© Copyright 2015 HeartMath Institute
Heart Rate Variability: An Indicator of Self-Regulatory
Capacity, Autonomic Function and Health
The autonomic nervous system (ANS) (Figure 1.1) is the part of the nervous system that controls the body’s
internal functions, including heart rate, gastrointestinal tract and secretions of many glands. The ANS also
controls many other vital activities such as respiration, and it interacts with immune and hormonal system
functions. It is well known that mental and emotional states directly affect activity in the ANS.
The autonomic nervous system must be considered
as a complex system in which both efferent (descend-
ing) and afferent (ascending) vagal (parasympathetic)
neurons regulate adaptive responses. Considerable
evidence suggests evolution of the ANS, specically
the vagus nerves, was central to development of emo-
tional experience, the ability to self-regulate emotional
processes and social behavior and that it underlies
the social engagement system. As human beings,
we are not limited to ght, ight, or freeze responses.
We can self-regulate and initiate pro-social behaviors
when we encounter challenges, disagreements and
stressors. The healthy function of the social engage-
ment system depends upon the proper functioning
of the vagus nerves, which act as a vagal brake. This
system underlies one’s ability to self-regulate and
calm oneself by inhibiting sympathetic outow to
targets like the heart and adrenal glands. This implies
that measurements of vagal activity could serve as a
marker for one’s ability to self-regulate. This also sug-
gests that the evolution and healthy function of the
ANS determines the boundaries for the range of one’s
emotional expression, quality of communication and
the ability to self-regulate emotions and behaviors.[82]
Many of HMI’s research studies have examined the
inuence of emotions on the ANS utilizing analysis
of heart rate variability/heart rhythms, which reects
heart-brain interactions and autonomic nervous sys-
tem dynamics.[5, 83]
The investigation of the heart’s complex rhythms,
or HRV began with the emergence of modern signal
processing in the 1960s and 1970s and has rap-
idly expanded in more recent times.[84] The irregular
HRV: An Indicator of Self-Regulatory Capacity, Autonomic Function and Health
behavior of the heartbeat is readily apparent when
heart rate is examined on a beat-to-beat basis, but is
overlooked when a mean value over time is calculated.
These uctuations in heart rate result from complex,
nonlinear interactions among a number of different
physiological systems (Figure 3.1).
Figure 3.1. Heart rate variability is a measure of the
normally occurring beat-to-beat changes in heart rate. The
electrocardiogram (ECG) is shown on the bottom and the
instantaneous heart rate is shown by the blue line. The time
between each of the heartbeats (blue line) between 0 and
approximately 13 seconds becomes progressively shorter and
heart rate accelerates and then starts to decelerate around
13 seconds. This pattern of heart-rate accelerations and
decelerations is the basis of the heart’s rhythms.
An optimal level of HRV within an organism reects
healthy function and an inherent self-regulatory ca-
pacity, adaptability, and resilience.[5, 58, 59, 85-88] While
too much instability, such as arrhythmias or nervous
system chaos, is detrimental to ecient physiological
functioning and energy utilization, too little variation
indicates age-related system depletion, chronic stress,
pathology or inadequate functioning in various levels
of self-regulatory control systems.[84, 89, 90]
CHAPTER 3

14
© Copyright 2015 HeartMath Institute
Science of the Heart
The importance of HRV as an index of the functional
status of physiological control systems was noted as
far back as 1965, when it was found that fetal distress
was preceded by reductions in HRV before any changes
occurred in heart rate.[91] In the 1970s, reduced HRV
was shown to predict autonomic neuropathy in diabetic
patients before the onset of symptoms.[92-94] Reduced
HRV also was found to be a higher risk factor of death
post-myocardial infarction than other known risk fac-
tors.[95] It has been shown that HRV declines with age
and that age-adjusted values should be used in the
context of risk prediction.[96] Age-adjusted HRV that is
low has been conrmed as a strong, independent pre-
dictor of future health problems in both healthy people
and in patients with known coronary artery disease and
correlates with all-cause mortality.[97, 98]
Based on indirect evidence, reduced HRV may cor-
relate with disease and mortality because it reects
reduced regulatory capacity and ability to adapt/
respond to physiological challenges such as exercise.
For example, in the Chicago Health, Aging and Social
Relations Study, separate metrics for the assessment
of autonomic balance and overall cardiac autonomic
regulation were developed and tested in a sample
of 229 participants. In this study, overall regulatory
capacity was a signicant predictor of overall health
status, but autonomic balance was not. In addition,
cardiac regulatory capacity was negatively associ-
ated with the prior incidence of myocardial infarc-
tions. The authors suggest that cardiac regulatory
capacity reects a physiological state that is more
relevant to health than the independent sympathetic
or parasympathetic controls, or the autonomic bal-
ance between these controls as indexed by different
measures of HRV.[99]
Heart rate variability also indicates psychological
resiliency and behavioral exibility, reecting an indi-
vidual’s capacity to self-regulate and effectively adapt
to changing social or environmental demands.[99, 100]
A growing number of studies have specically linked
vagally mediated HRV to self-regulatory capacity,[87, 88,
101] emotional regulation,[102, 103] social interactions,[86, 104]
one’s sense of coherence[105] and the personality charac-
ter traits of self-directedness[106] and coping styles.[107]
More recently, several studies have shown an associa-
tion between higher levels of resting HRV and perfor-
mance on cognitive performance tasks requiring the
use of executive functions.[89] HRV coherence (described
later) can be increased in order to improve cognitive
function[5, 108-110] as well as a wide range of clinical out-
comes, including reduced health-care costs.[59, 111-116]
Self-Regulation: Cortical Systems
Considerable evidence from clinical, physiological and
anatomical research has identied cortical, subcorti-
cal and medulla oblongata structures involved in car-
diac regulation. Oppenheimer and Hopkins mapped a
detailed hierarchy of cardiac control structures among
the cortex, amygdala and other subcortical structures,
all of which can modify cardiovascular-related neurons
in the lower levels of the neuraxis (Figure 3.2).[117]
Figure 3.2. Schematic diagram showing the relationship of
the principal descending neural pathways from the insular and
prefrontal cortex to subcortical structures and the medulla
oblongata as outlined by Oppenheimer and Hopkins.
[117]
The insular and prefrontal cortexes are key sites involved in
modulating the heart’s rhythm, particularly during emotionally
charged circumstances. These structures along with other
centers such as the orbitofrontal cortex and cingulate gyrus
can inhibit or enhance emotional responses. The amygdala
is involved with refined integration of emotional content
in higher centers to produce cardiovascular responses
that are appropriate for the emotional aspects of current
circumstances. Imbalances between the neurons in the insula,
amygdala and hypothalamus may initiate cardiac rhythm
disturbances and arrhythmias. The structures in the medulla
represent an interface between incoming afferent information
from the heart, lungs and other bodily systems and outgoing
efferent neuronal activity.
[117]

15
© Copyright 2015 HeartMath Institute
They suggest that the amygdala is involved with rened
integration of emotional content in higher centers
to produce cardiovascular responses that are ap-
propriate for the emotional aspects of the current
circumstances. The insular cortex and other centers
such as the orbitofrontal cortex and cingulate gyrus
can overcome (self-regulate) emotionally entrained
responses by inhibiting or enhancing them. They
also point out that imbalances between the neurons
in the insula, amygdala and hypothalamus may initi-
ate cardiac rhythm disturbances and arrhythmias.
The data suggests that the insular and medial pre-
frontal cortexes are key sites involved in modulating
the heart’s rhythm, particularly during emotionally
charged circumstances.
Thayer and Lane also have described the same set of
neural structures outlined by Oppenheimer and Hop-
kins, which they call the central autonomic network
(CAN). The CAN is involved in cognitive, emotional
and autonomic regulation, which they linked directly
to HRV and cognitive performance. In their model, the
CAN links the nucleus of tractus solitarius in the me-
dulla with the insula, prefrontal cortex, amygdala and
hypothalamus through a series of feedback and feed-
forward loops. They also propose that this network is
an integrated system for internal self-regulation by
which the brain controls the heart and other internal
organs, neuroendocrine and behavioral responses that
are critical for goal-directed behavior, adaptability and
sustained health. They suggest that these dynamic
connections explain why parasympathetically (va-
gal) mediated HRV is linked to higher-level executive
functions and reects the functional capacity of the
brain structures that support working memory and
emotional and physiological self-regulation. They have
shown that higher levels of vagally mediated HRV are
correlated with prefrontal cortical performance and
the ability to inhibit unwanted memories and intrusive
thoughts. The prefrontal cortex can be taken oine
when individuals perceive that they are threatened,
and prolonged periods of prefrontal cortical inactiv-
ity can lead to hypervigilance, defensiveness and
social isolation. During these decreases in prefrontal
cortical activation, heart rate (HR) increases and HRV
decreases.[89]
• Thoughts and even subtle emotions influence
the activity in the autonomic nervous system.
• The ANS interacts with our digestive, cardio-
vascular, immune, hormonal and many other
bodily systems.
• Negative emotions/feelings create disorder in
the brain’s regulatory systems and ANS.
• Feelings such as appreciation create increased
order in the brain’s regulatory systems and ANS,
resulting in improved hormonal- and immune-sys-
tem function and enhanced cognitive function.
The nucleus of tractus in the medulla oblongata inte-
grates afferent sensory information from propriocep-
tors (body position), chemoreceptors (blood chemis-
try) and mechanoreceptors, also called baroreceptors,
(pressure or distortion) from the heart, lungs and face.
The nucleus of tractus connects to the dorsal motor
nucleus of the vagus nerve and the nucleus ambiguus.
Neurocardiology research indicates that the descend-
ing vagal bers that innervate the heart are primarily
A-bers, which are the largest and fastest conducting
axons that originate from nerve cells located primarily
in the nucleus ambiguus. The nucleus ambiguus also
receives and integrates information from the cortical
and subcortical systems described above.[118] Thus,
the vagal regulatory centers respond to peripheral sen-
sory (afferent) inputs and higher brain-center inputs to
adjust neuronal outows, which results in the vagally
mediated beat-to-beat changes in HR.
Increased efferent activity in the vagal nerves (also
called the 10th cranial nerve) slows HR and increases
bronchial tone. The vagus nerves are the primary
nerves for the parasympathetic system and they in-
nervate the intrinsic cardiac nervous system. A few of
these connections synapse on motor neurons in the
intrinsic cardiac nervous system and these neurons
project directly to the SA node (and other tissues in
the heart), where they trigger acetylcholine release
to slow HR.[11] However, the majority of the efferent
preganglionic vagal neurons (~80%) connect to lo-
cal circuitry neurons in the intrinsic cardiac nervous
system, where motor information is integrated with
Chapter 3: HRV: An Indicator of Self-Regulatory Capacity, Autonomic Function and Health

16
© Copyright 2015 HeartMath Institute
Science of the Heart
inputs from mechanosensory and chemosensory
neurons in the heart.[119] Thus, efferent sympathetic
and parasympathetic activity is integrated in and with
the activity occurring in the heart’s intrinsic nervous
system, including the input signals from the mecha-
nosensory and chemosensory neurons within the
heart, all of which ultimately contribute to beat-to-beat
cardiac functional changes.[17]
In summary, the cardiorespiratory control system is
complex and information from many inputs is inte-
grated at multiple levels of the system, all of which
are important for the generation of normal beat-to-
beat variability in HR and BP. The medulla oblongata
is the major structure integrating incoming afferent
information from the heart, lungs and face with inputs
from cortical and subcortical structures and is the
source of the respiratory modulation of the activity
patterns in sympathetic and parasympathetic out-
ow. The intrinsic cardiac nervous system integrates
mechanosensitive and chemosensitive neuron inputs
with efferent information from both the sympathetic
and parasympathetic inputs from the brain, and as a
complete system affects HRV, vasoconstriction and
cardiac contractility in order to regulate HR and blood
pressure.[120]
HRV and Analysis Methods
The normal variability in heart rate results from the
descending (efferent) and the ascending (afferent)
activity occurring in the two branches of the ANS,
which act in concert, along with mechanical, hormonal
and other physiological mechanisms to maintain car-
diovascular parameters in their optimal ranges and to
permit appropriate adjustments to changing external
and internal conditions and challenges (Figure 1.3).
At rest, both sympathetic and parasympathetic nerves
are tonically active, with the vagal effects predomi-
nant. Therefore, heart rate best reects the relative
balance between the sympathetic and parasympa-
thetic systems. When speaking of autonomic bal-
ance, it should be kept in mind that a healthy system
is constantly and dynamically changing. Therefore,
an important indicator of the health status of the
regulatory systems is that they have the capacity to
respond to and adjust the relative autonomic balance,
as reected in heart rate, to the appropriate state for
whatever a person is engaged in at any given moment.
In other words, does the HR dynamically respond
and is it higher in the daytime or when dealing with
challenging tasks and lower when at rest or during
sleep? Inability of the physiological self-regulatory
systems to adapt to the current context and situation
is associated with numerous clinical conditions.[121]
Also, distinct, altered, circadian patterns in 24-hour
heart rates are associated with different and specic
psychiatric disorders, particularly during sleep.[122, 123]
Heart rate estimated at any given time represents the
net effect of the neural output of the parasympathetic
(vagus) nerves, which slows HR and the sympathetic
nerves, which accelerate it. In a denervated human
heart in which there are no connections from the ANS
to the heart following its transplantation, the intrinsic
rate generated by a pacemaker (SA node) is about
100 BPM.[124] Parasympathetic activity predominates
when HR is below this intrinsic rate during normal
daily activities and when at rest or sleep. When HR
is above ~100 BPM, the relative balance shifts and
sympathetic activity predominates. The average 24-
hour HR in healthy people is ~73 BPM. Higher HRs are
independent markers of mortality in a wide spectrum
of conditions.[121]
It is important to note the natural relationship between
HR and amount of HRV. As HR increases there is less
time between heartbeats for variability to occur, so
HRV decreases, while at lower HRs there is more time
between heartbeats, so variability naturally increases.
This is called cycle length dependence, and it persists
in the healthy elderly to a variable degree, even at
very advanced ages. However, elderly patients with
ischemic heart disease or other pathologies increas-
ingly have less variability as HRs decrease, ultimately
losing the relationship between HR and variability – to
the point that variability does not increase at all with
reductions in HR.[125] Even in healthy subjects, the
effects of cycle length dependence should be taken
into account when assessing HRV, and HR values
should always be reported, especially when HRs are
increased because of factors such as stress reactions,
medications and physical activity.

17
© Copyright 2015 HeartMath Institute
An increase in sympathetic activity is the principal
method used to increase HR above the intrinsic level
generated by the SA node. Activation of this branch
of the ANS, in concert with the activation of the en-
docrine system, facilitates the ability to respond to
challenges, stressors or threats by increasing the
mobilization of energy resources.
Following the onset of sympathetic stimulation, there
is a delay of up to 5 seconds before the stimulation
induces a progressive increase in HR, which reaches
a steady level in 20 to 30 seconds if the stimulus
is continuous.[120] The relatively slow response to
sympathetic stimulation is in direct contrast to vagal
stimulation, which is almost instantaneous. However,
the effect of sympathetic stimulation on HR is longer-
lasting and even a brief stimulus can affect HR for 5
to 10 seconds. Efferent (descending) sympathetic
nerves target the SA node via the intrinsic cardiac
nervous system and the bulk of the myocardium
(heart muscle). Action potentials conducted by these
motor neurons trigger norepinephrine and epinephrine
release, which increases HR and strengthens the
contractility of the atria and ventricles.
HRV can be assessed with various analytical ap-
proaches, although the most commonly used are
frequency domain (power spectral density) analysis
and time domain analysis. In both methods, the
time intervals between each successive normal QRS
complex are rst determined. All abnormal beats not
generated by the sinus node are eliminated from the
record. The interactions between autonomic neural
activity, BP, respiratory and higher-level control sys-
tems produce both short- and long-term rhythms in
HRV measurements.[5, 126, 127] The most common form
for observing these changes is the heart-rate tacho-
gram, a plot of the sequence of time intervals between
heartbeats (Figure 3.3).
Chapter 3: HRV: An Indicator of Self-Regulatory Capacity, Autonomic Function and Health
Figure 3.3. An example of the heart-rate tachogram, a plot of the sequence of time intervals between heartbeats over an 8-hour
period in ambulatory recording taken from a 36-year-old male. Each of the traces is one hour long, with the starting time of the
hour on the left-hand side of the gure. The time between each vertical line is 5 minutes. The vertical axis within each of the hourly
tracings is the time between heartbeats (interbeat intervals) ranging from 400 tp 1,200 milliseconds (label shown on second
row). A 15-minute period of HRV coherence can be seen in the latter part of the hour, starting at 19:30 when this man practiced
HeartMath’s Heart Lock-In
®
Technique. The latter part of the hour, starting at 23:30, is typical of restful sleep.

18
© Copyright 2015 HeartMath Institute
Science of the Heart
Power spectral analysis is used to separate the com-
plex HRV waveform into its component rhythms (Fig-
ure 3.4). Spectral analysis provides information about
how power is distributed (the variance and amplitude
of a given rhythm) as a function of frequency (the
time period of a given rhythm). The main advantages
of spectral analysis over the time domain measures
are that it supplies both frequency and amplitude
information on the specic rhythms that exist in the
HRV waveform, providing a means to quantify these
oscillations over any given period. The values are
expressed as the power spectral density, which is the
area under the curve (peak) in a given bandwidth of the
spectrum. The power or height of the peak at any given
frequency indicates the amplitude and stability of the
rhythm. The frequency reects the period of time over
which the rhythm occurs. For example, a 0.1 hertz fre-
quency has a period of 10 seconds. In order to under-
stand how power spectral analysis distinguishes the
various underlying physiological mechanisms re-
ected in the heart’s rhythm, a brief discussion of
the underlying physiological mechanisms is helpful.
The power spectrum is divided into three main fre-
quency ranges.
High-Frequency Band
The high-frequency (HF) spectrum is the power in the
range from 0.15 to 0.4 hertz, which equates to rhythms
with periods that occur between 2.5 and 7 seconds.
This band reects parasympathetic or vagal activity
and is frequently called the respiratory band because
it corresponds to the HR variations related to the
respiratory cycle known as respiratory sinus arrhyth-
mia. The mechanisms linking the variability of HR to
respiration are complex and involve both central and
reex interactions.[118] During inhalation, the cardio-
respiratory center inhibits vagal outow, resulting in
speeding up HR. Conversely, during exhalation, vagal
outow is restored, resulting in slowing HR.[128] The
magnitude of the oscillation is variable, but in healthy
people, it can be increased by slow, deep breathing.
Figure 3.4. This gure shows a typical HRV recording over a 15-minute period during resting conditions in a healthy individual.
The top trace shows the original HRV waveform. Filtering techniques were used to separate the original waveform into VLF, LF,
and HF bands as shown in the lower traces. The bottom of the gure shows the power spectra (left) and the percentage of power
(right) in each band.

19
© Copyright 2015 HeartMath Institute
Reduced parasympathetic (HF) activity has been
found in a number of cardiac pathologies as discussed
earlier. In terms of psychological regulation, reduced
vagally mediated HRV has been linked to reduced
self-regulatory capacity and cognitive functions that
involve the executive centers of the prefrontal cortex.
This is consistent with the nding that lower HF power
is associated with stress, panic and anxiety/worry.
Lower parasympathetic activity, rather than reduced
sympathetic functioning, appears to account for a
higher ratio of the reduced HRV in aging.[96]
Low-Frequency Band
The low-frequency (LF) band ranges between 0.04 and
0.15 hertz, which equates to rhythms or modulations
with periods that occur between 7 and 25 seconds.
This region was previously called the baroreceptor
range or midfrequency band by many researchers
because it primarily reects baroreceptor activity
while at rest.[129] As discussed previously, the vagus
nerves are a major conduit through which afferent
neurological signals from the heart are relayed to the
brain, including baroreex signals. Baroreceptors are
stretch-sensitive mechanoreceptors located in the
chambers of the heart and vena cavae, carotid sinuses
(which contain the most sensitive mechanoreceptors)
and the aortic arch. Baroreex gain is commonly cal-
culated as the beat-to-beat change in HR per unit of
change in BP. Decreased baroreex gain is related to
aging and impaired regulatory capacity.
The existence of a cardiovascular system resonance
frequency, which is caused by the delay in the feed-
back loops in the baroreex system, has long been
established. When the cardiovascular system oscil-
lates at this frequency, there is a distinctive high-
amplitude peak in the HRV power spectrum around
0.1 hertz. Most mathematical models show that the
resonance frequency of the human cardiovascular
system is determined by the feedback loops between
the heart and brain.[130, 131] In humans and many other
mammals, the resonance frequency of the system is
approximately 0.1 hertz, equivalent to a 10-second
rhythm, which is also characteristic of the coherent
state described earlier.
Chapter 3: HRV: An Indicator of Self-Regulatory Capacity, Autonomic Function and Health
The sympathetic nervous system does not appear
to have much inuence in rhythms above 0.1 hertz,
while the parasympathetic system can be observed to
affect heart rhythms down to 0.05 hertz (20-second
rhythm). Therefore, during periods of slow respira-
tion rates, vagal activity can easily generate oscil-
lations in the heart rhythms that cross over into the
LF band.[111, 132, 133] Thus, respiratory-related efferent
vagally mediated inuences are particularly present
in the LF band when respiration rates are below 8.5
breaths per minute/7-second periods or when an in-
dividual sighs or takes a deep breath.[133, 134]
In ambulatory 24-hour HRV recordings, it has been
suggested that the LF band reects sympathetic
activity and the LF/HF ratio has been used, contro-
versially so, to assess the balance between sympa-
thetic and parasympathetic activity.[135-137] A number
of researchers have challenged this perspective and
have persuasively argued that in resting conditions,
the LF band reects baroreex activity and not cardiac
sympathetic innervation.[40, 71, 96, 105-107]
The perspective that the LF band reects sympathetic
activity comes from observations of 24-hour ambula-
tory recordings in which there are frequent sympa-
thetic activations primarily resulting from physical
activity, but also emotional reactions, which can create
oscillations in the heart rhythms that cross over from
the VLF band into the lower region of the LF band. In
long-term ambulatory recordings, the LF band fairly
approximates sympathetic activity when increased
sympathetic activity occurs.[138] Unfortunately, some
authors have assumed that this interpretation also is
true of short-term resting recordings and have con-
fused slower breathing-related increases in LF power
with sympathetic activity, when in reality it is almost
entirely vagally mediated.
Very-Low-Frequency Band
The very-low-frequency band (VLF) is the power in
the HRV power spectrum range between 0.0033 and
0.04 hertz which equates to rhythms or modulations
with periods that occur between 25 and 300 seconds.
Although all 24-hour clinical measures of HRV reect-
ing low HRV are linked with increased risk of adverse

20
© Copyright 2015 HeartMath Institute
Science of the Heart
outcomes, the VLF band has stronger associations
with all-cause mortality than LF and HF bands.[98, 139-141]
Low VLF power has been shown to be associated
with arrhythmic death[142] and PTSD.[143] Additionally,
low power in this band has been associated with high
inammation[144, 145] in a number of studies and has
been correlated with low levels of testosterone, while
other biochemical markers, such as those mediated
by the HPA axis (e.g., cortisol), have not.[146] Longer
time periods using 24-hour HRV recordings should
be obtained to provide comprehensive assessment
of VLF and ULF uctuations.[147]
Historically, the physiological explanation and
mechanisms involved in the generation of the VLF
component have not been as well dened as the LF
and HF components. This region has been largely
ignored even though it is the most predictive of ad-
verse outcomes. Long-term regulation mechanisms
and ANS activity related to thermoregulation, the
renin-angiotensin system and other hormonal factors
appear to contribute to this band.[148, 149] Recent work
by Dr. J. Andrew Armour has shed new light on the
mechanisms underlying the VLF rhythm and suggests
that we have to reconsider both the mechanisms and
importance of this band.
This line of research began after some surprising
results from a study looking at HRV in autotrans-
planted hearts in dogs. In autotransplants, the heart
is removed and placed back in the same animal, so
there is no need for anti-rejection medications. The
primary purpose of the study was to determine if
the autonomic nerves reinnervated the heart post-
transplant. Monthly 24-hour HRV recordings were
done over a one-year period on all of the dogs with
autotransplanted hearts as well as control dogs. It
turned out that the nerves did reinnervate, but in a
way that was not accurately reected in HRV. It was
shown that the intrinsic cardiac nervous system had
neuroplasticity and restructured its neural connec-
tions. The truly surprising result was that these de-
innervated hearts had higher levels of HRV than the
control dogs immediately post-transplant and these
levels were sustained over a one-year period, includ-
ing HRV, which typically is associated with respiration
(Figure 3.5).[150] This was unexpected because in hu-
man transplant recipients, there is very little HRV.[151]
Autotransplant
Figure 3.5. Heart Rhythms Generated by a Transplanted Heart: At top left is the heart-rate tachogram of a dog after undergoing
cardiac autotransplantation, with the accompanying top-right graph showing the HRV power spectrum. For comparison, the
bottom graphs show the heart-rate tachogram and HRV power spectrum of a normal dog. Note the similarity between the two.

21
© Copyright 2015 HeartMath Institute
Following up on these results, Armour and colleagues
developed methods for obtaining long-term single-
neuron recordings from a beating heart and, simulta-
neously, from extrinsic cardiac neurons.[13] This work,
combined with later ndings by Kember and Armour,
implies that the VLF rhythm is generated by the
stimulation of afferent sensory neurons in the heart,
which in turn activates various levels of the feedback
and feed-forward loops in the heart’s intrinsic cardiac
nervous system, as well as between the heart and
neurons in the extrinsic cardiac ganglia and spinal
column.[152, 153] Thus, the VLF rhythm appears to be
produced by the heart itself and is an intrinsic rhythm
that appears to be fundamental to health and well-
being. Armour has observed that when the amplitude
of the VLF rhythm at the neural level is diminished in
an animal research subject, the animal is in danger and
will expire shortly if the research procedures proceed.
This cardiac origin of the VLF rhythm also is supported
by studies showing that sympathetic blockade does
not affect VLF power and VLF activity remains in
tetraplegics, whose sympathetic innervation of the
heart and lungs is disrupted.[154]
Circadian rhythms, core body temperature, metabo-
lism, hormones and intrinsic rhythms generated by the
heart all contribute to lower-frequency rhythms (e.g.,
very-low-frequency and ultra-low-frequency rhythms)
that extend below 0.04 hertz. In healthy individuals,
there is an increase in VLF power that occurs during
the night and peaks before waking.[155,156] This increase
in autonomic activity appears to correlate with the
morning cortisol peak.
To summarize, experimental evidence suggests the
VLF rhythm is intrinsically generated by the heart and
the amplitude and frequency of these oscillations are
modulated by efferent sympathetic activity. Normal
VLF power appears to indicate healthy function, and
increases in resting VLF power and/or shifting of fre-
quency can reect efferent sympathetic activity. The
modulation of the frequency of this rhythm resulting
from physical activity,[157] stress responses and other
factors that increase efferent sympathetic activation
can cause it to cross over into the lower region of the
LF band during ambulatory monitoring or during short-
Chapter 3: HRV: An Indicator of Self-Regulatory Capacity, Autonomic Function and Health
term recordings when there is a signicant emotional
stressor.[5]
Time Domain Measurements of HRV
Time domain indices quantify the amount of vari-
ance in the interbeat interval (IBI) using statistical
measures. Time domain measures are the simplest
to calculate. Time domain measures do not provide
a means to adequately quantify autonomic dynam-
ics or determine the rhythmic or oscillatory activity
generated by the different physiological control sys-
tems. However, since they are always calculated the
same way, data collected by different researchers are
comparable, but only if the recordings are exactly the
same length of time and the data are collected under
the same conditions. The three most important and
commonly reported time domain measures are the
SDNN, the SDNN index, and the RMSSD.
SDNN
The SDNN is the standard deviation of the normal-
to-normal (NN) sinus-initiated interbeat-intervals
measured in milliseconds. This measure reects the
ebb and ow of all the factors that contribute to HRV.
In 24-hour recordings, the SDNN is highly correlated
with ULF and total power.[96] In short-term resting
recordings, the primary source of the variation is
parasympathetically mediated, especially with slow,
deep-breathing protocols. However, in ambulatory and
longer-term recordings the SDNN values are highly
correlated with lower-frequency rhythms.[83] Thus, low
age-adjusted values predict morbidity and mortality.
For example, patients with moderate SDNN values
(50-100 milliseconds) have a 400% lower risk of mor-
tality than those with low values (0-50 milliseconds)
in 24-hour recordings.[158, 159]
SDNN Index
The SDNN index is the mean of the standard devia-
tions of all the NN intervals for each 5-minute seg-
ment. Therefore, this measurement only estimates
variability due to the factors affecting HRV within
a 5-minute period. In 24-hour HRV recordings, it is
calculated by rst dividing the 24-hour record into
288 ve-minute segments and then calculating the

22
© Copyright 2015 HeartMath Institute
Science of the Heart
standard deviation of all NN intervals contained
within each segment. The SDNN Index is the average
of these 288 values.[90] The SDNN index is believed to
primarily measure autonomic inuence on HRV. This
measure tends to correlate with VLF power over a
24-hour period.[83]
RMSSD
The RMSSD is the root mean square of successive
differences between normal heartbeats. This value
is obtained by rst calculating each successive time
difference between heartbeats in milliseconds. Each
of the values is then squared and the result is aver-
aged before the square root of the total is obtained.
The RMSSD reects the beat-to-beat variance in heart
rate and is the primary time domain measure used to
estimate the vagally mediated changes reected in
HRV. [90] The RMSSD is correlated with HF power and
therefore also reects self-regulatory capacity, as
discussed earlier.[83]
HRV Assessment Services
The Autonomic Assessment Report, (AAR), developed
by the HeartMath Research Center, provides physi-
cians, researchers and mental health-care profession-
als with a diagnostic tool to detect abnormalities and
imbalances in the autonomic nervous system and
predict those at increased risk of developing various
pathologies often before symptoms become mani-
fest. The HeartMath Research Center provides this
analysis service to physicians and medical institutions
throughout the U.S. and abroad.
The Autonomic Assessment Report is a powerful tool
for quantifying autonomic function. The AAR provides
health-care professionals and researchers with a non-
invasive test that quanties autonomic function and
relative balance and risk stratication, and assesses
the effects of interventions on autonomic function.
The AAR is derived from 24-hour am bulatory ECG
recordings, typically obtained with an “HRV” recorder,
which is inexpensive, lightweight and comfortable
to wear. The AAR is based on analysis of heart rate
variability, which provides a unique window into the
interactions of sympathetic and parasympathetic
control of the heart. The report includes time domain,
frequency domain and circadian rhythm analysis,
which together constitute a comprehensive analysis
of autonomic activity, relative balance and rhythms.
Time domain measures include the mean normal-
to-normal (NN) intervals during a 24-hour recording
and statistical measures of the variance between
NN intervals. Power spectral density analysis is used
to assess how power is distributed as a function of
frequency, providing a means to quantify autonomic
balance at any given point in the 24-hour period, as
well as to chart the circadian rhythms of activity in
the two branches of the autonomic nervous system.
HMI has established and maintains an extensive HRV
database of healthy individuals that greatly increases
the AAR’s value as a diagnostic and risk-assessment
tool. Additionally, the age and gender normative val-
ues are provided for each time and frequency domain
HRV value.
HRV is useful for monitoring autonomic function and
assessing ANS involvement in a number of clinical
conditions. Importantly, low HRV has been found to be
predictive of increased risk of heart disease, sudden
cardiac death as well as all-cause mortality.
Autonomic Function Imbalances Are
Associated With:
• Depression • Irritable Bowel
• Hypoglycemia • Fibromyalgia
• Panic Disorder • Hypertension
• Sleep Disorder • Chemical Sensitivity
• Asthma • Premenstrual Syndrome
• Fatigue • Anxiety
• Dizziness • Migraine
• Nausea • Arrhythmia
Autonomic imbalances have been implicated in a wide
variety of pathologies, including depression, fatigue,
premenstrual syndrome, hypertension, diabetes mel-
litus, ischemic heart disease, coronary heart disease
and environmental sensitivity. Stress and emotional
states have been shown to dramatically affect auto-
nomic function. Self-regulation techniques, which en-
able individuals to gain greater control of their mental
and emotional stress and improve their autonomic

23
© Copyright 2015 HeartMath Institute
functioning, can signicantly affect a wide variety
of disorders in which autonomic imbalance plays a
role. The AAR analysis is highly useful for the quan-
titative demonstration of the effects of HeartMath
interventions in restoring healthy autonomic function
in many patients who have been able to signicantly
improve their symptomatology and psychological
well-being through practice of these techniques.
Figure 3.6. Sample pages from the HeartMath Autonomic Assessment Report. Shown from top left to right are: (1) Summary
page with normative reference ranges. (2) 24-Hour Heart Rate Prole and Heart Rate Variability Index plot. (3) Autonomic Balance
Prole and frequency domain analysis summary. (4) Circadian Rhythm Analysis page and bottom graph. (5) One page of the three
heart-rate tachogram pages showing HRV from the full 24-hours.
Chapter 3: HRV: An Indicator of Self-Regulatory Capacity, Autonomic Function and Health
The Autonomic Assessment Report Interpretation Guide
and Instructions booklet, available from HMI, provides
clinicians with understandable descriptions of HRV
measures used in the report and how to interpret them
in clinical applications. It includes a number of case
histories and clinical examples.

24
© Copyright 2015 HeartMath Institute
Science of the Heart
Coherence
Denitions of Coherence
Clarity of thought, speech and emotional composure
The quality of being orderly, consistent and intelligible (e.g. a coherent sentence).
Synchronization or entrainment between multiple waveforms
A constructive waveform produced by two or more waves that are phase- or frequency-locked.
Order within a singular oscillatory waveform
An ordered or constructive distribution of power content within a single waveform; autocoherence (e.g. sine wave).
The various concepts and measurements embraced
under the term coherence have become central to elds
as diverse as quantum physics, cosmology, physiology
and brain and consciousness research.[59] Coherence
has several related denitions, all of which are ap-
plicable to the study of human physiology, social
interactions and global affairs. The most common
dictionary denition is the quality of being logically
integrated, consistent and intelligible, as in a coherent
statement.[159] A related meaning is the logical, orderly
and aesthetically consistent relationship among parts.
[159] Coherence always implies correlations, connect-
edness, consistency and ecient energy utilization.
Thus, coherence refers to wholeness and global
order, where the whole is greater than the sum of its
individual parts.
In physics, coherence also is used to describe the
coupling and degree of synchronization between
different oscillating systems. In some cases, when
two or more oscillatory systems operate at the same
basic frequency, they can become either phase- or
frequency-locked, as occurs between the photons
in a laser.[160] This type of coherence is called cross-
coherence and is the type of coherence that most
scientists think of when they use the term. In physiol-
ogy, cross-coherence occurs when two or more of the
body’s oscillatory systems, such as respiration and
heart rhythms, become entrained and operate at the
same frequency.
Another aspect of coherence relates to the dynamic
rhythms produced by a single oscillatory system.
The term autocoherence describes coherent activity
within a single system. An ideal example is a system
that exhibits sine-wavelike oscillations; the more
stable the frequency, amplitude and shape, the higher
the degree of coherence. When coherence is increased
in a system that is coupled to other systems, it can
pull the other systems into increased synchronization
and more ecient function.
Many contemporary scientists believe it is the underlying state of our physiological processes that de-
termines the quality and stability of the feelings and emotions we experience. The feelings we label as
positive actually reect body states that are coherent, meaning “the regulation of life processes becomes ef-
cient, or even optimal, free-owing and easy,”[160] and the feelings we label as “negative,” such as anger, anxiety
and frustration are examples of incoherent states. It is important to note, however, these associations are not
merely metaphorical. For the brain and nervous system to function optimally, the neural activity, which encodes
and distributes information, must be stable and function in a coordinated and balanced manner. The various
centers within the brain also must be able to dynamically synchronize their activity in order for information to
be smoothly processed and perceived. Thus, the concept of coherence is vitally important for understanding
optimal function.
CHAPTER 4

25
© Copyright 2015 HeartMath Institute
Figure 4.1. The top graphs show an individual’s heart rate variability, pulse transit time and respiration patterns for 10 minutes.
At the 300-second mark, the individual did HeartMath’s Freeze Frame Technique and all three systems came into entrainment,
meaning the patterns were harmonious instead of scattered and out of sync. The bottom graphs show the spectrum analysis view
of the same data. The left-hand side is the spectral analysis before Freeze-Framing. Notice how each pattern looks quite different
from the others. The graphs on the right show how all three systems are entrained at the same frequency after Freeze-Framing.
Chapter 4: Coherence
Global Coherence
For any system to produce a meaningful function, it
must have the property of global coherence. In hu-
mans, this includes our physical, mental, emotional
and social systems. However, the energy eciency
and degree of coordinated action of any given system
can vary widely and does not necessarily result in a
coherent output or ow of behavior. Global coherence
does not mean everyone or all parts of a system are
doing the same thing simultaneously. In complex glob-
ally coherent systems, such as human beings, there is
a vast amount of activity at every level of magnica-
tion or scale that spans more than two-thirds of the 73
known octaves of the electromagnetic spectrum.[165]
It can appear at one level of scale that a given system
is operating autonomously, yet it is perfectly coordi-
nated within the whole. In living systems, there are
microlevel systems, molecular machines, protons
and electrons, organs and glands, each functioning
autonomously, doing very different things at different
rates, yet all working together in a complex harmoni-
ously coordinated and synchronized manner. If this
were not happening, it would be a free-for-all among
For example, frequency pulling and entrainment can easily be seen between the heart, respiratory and blood-
pressure rhythms as well as between very-low-frequency brain rhythms, craniosacral rhythms and electrical
potentials measured across the skin.[142, 143]

26
© Copyright 2015 HeartMath Institute
Science of the Heart
the body’s independent systems, rather than a coor-
dinated federation of interdependent systems and
functions. Biologist Mae-Won Ho has suggested that
coherence is the dening quality of living systems
and accounts for their most characteristic properties,
such as long-range order and coordination, rapid and
ecient energy transfer and extreme sensitivity to
specic signals.[165]
We introduced the term physiological coherence to
describe the degree of order, harmony and stability in
the various rhythmic activities within living systems
over any given time period.[163] This harmonious order
signies a coherent system, whose ecient or optimal
function is directly related to the ease and ow in life
processes. In contrast, an erratic, discordant pattern
of activity denotes an incoherent system whose func-
tion reects stress and inecient utilization of energy
in life processes. Specically, heart coherence (also
referred to as cardiac coherence or resonance) can be
measured by HRV analysis wherein a person’s heart-
rhythm pattern becomes more ordered and sine wave-
like at a frequency of around 0.1 hertz (10 seconds).
When a person is in a more coherent state there
is a shift in the relative autonomic balance toward
increased parasympathetic activity (vagal tone),
increased heart-brain synchronization and entrain-
ment between diverse physiological systems. In this
mode, the body’s systems function with a high degree
of eciency and harmony and natural regenerative
processes are facilitated. Although physiological
coherence is a natural human state that can occur
spontaneously, sustained episodes generally are
rare. While some rhythmic-breathing methods may
induce coherence for brief periods, our research in-
dicates that people can achieve extended periods of
physiological coherence by actively self-generating
positive emotions.
When functioning in a coherent mode, the heart pulls
other biological oscillators into synchronization with
its rhythms, thus leading to entrainment of these
systems (Figure 4.1). Entrainment is an example of a
physiological state in which there is increased coher-
ence between multiple oscillating systems and also
within each system. Thus, our ndings essentially
underscore what people have intuitively known for
some time: Positive emotions not only “feel better,”
they actually tend to increase synchronization of
the body’s systems, thereby enhancing energy and
enabling us to function with greater eciency and
effectiveness.
The coherence model takes a dynamic systems ap-
proach that focuses on increasing people’s self-regu-
latory capacity through self-management techniques
that induce a physiological shift, which is reected in
the heart’s rhythms. We also suggest that rhythmic
activity in living systems reects the regulation of
interconnected biological, social and environmental
networks and that important biologically relevant
information is encoded in the dynamic patterns of
physiological activity. For example, information is
encoded in the time interval between action potentials
in the nervous system and patterns in the pulsatile
release of hormones. Our research also suggests
that the time intervals between heartbeats (HRV)
also encode information, which is communicated
across multiple systems and helps synchronize the
system as whole. The afferent pathways from the
heart and blood vessels are given more relevance
in this model because of the signicant degree of
afferent cardiovascular input to the brain and the
consistent generation of dynamic patterns gener-
ated by the heart. Our perspective is that positive
emotions in general, including self-induced positive
emotions, shift the entire system into a more globally
coherent and harmonious physiological mode,
one that is associated with improved system per-
formance, ability to self-regulate and overall well-
being. The coherence model predicts that different
emotions are reected in state-specic patterns in
the heart’s rhythms[5] independent of the amount
of HRV/HR (Figure 4.2). Recent independent work
has veried this by demonstrating a 75% accuracy
rate in detection of discrete emotional states from
the HRV signal using a neural network approach for
pattern recognition.[164] In a study of the effects of
playing violent and nonviolent video games, it was
found that when playing violent video games, the
players had lower cardiac coherence levels and
higher aggression levels than did nonviolent game

27
© Copyright 2015 HeartMath Institute
Chapter 4: Coherence
players and that higher levels of coherence were
negatively related to aggression.[165]
Figure 4.2. Heart-rhythm patterns.
The coherent state has been correlated with a general
sense of well-being and improvements in cognitive,
social and physical performance. We have observed
this association between emotions and heart-rhythm
patterns in studies conducted in both laboratory and
natural settings and for both spontaneous and inten-
tionally generated emotions.[163, 168]
Several studies in healthy subjects, which helped
inform the model, show that during the experience of
positive emotions, a sine-wavelike pattern naturally
emerges in the heart’s rhythms without any conscious
changes in breathing.[51, 133] This is likely because of
more organized outputs of the subcortical structures
involved in processing emotional information, as
described by Pribram,[169] Porges,[82] Oppenheimer
and Hopkins[117] and Thayer,[89] in which the subcor-
tical structures inuence the oscillatory output of
the cardiorespiratory control system in the medulla
oblongata.
A brief summary of the psychophysiological coher-
ence model is provided below. A detailed discussion
on the nature of coherence can be found in two semi-
nal articles.[5, 59]
The Coherence Model Postulates:
1. The functional status of the underlying psycho-
physiological system determines the range of
one’s ability to adapt to challenges, self-regulate
and engage in harmonious social relationships.
Healthy physiological variability, feedback sys-
tems and inhibition are key elements of the com-
plex system for maintaining stability and capacity
to appropriately respond to and adapt to changing
environments and social demands.
2. The oscillatory activity in the heart’s rhythms
reects the status of a network of exible relation-
ships among dynamic interconnected neural struc-
tures in the central and autonomic nervous systems.
3. State-specic emotions are reected in the pat-
terns of the heart’s rhythms independent of
changes in the amount of heart rate variability.
4. Subcortical structures constantly compare infor-
mation from internal and external sensory systems
via a match/mismatch process that evaluates
current inputs against past experience to appraise
the environment for risk or comfort and safety.
5. Physiological or cardiac coherence is reected in
a more ordered sine-wavelike heart-rhythm pattern
associated with increased vagally mediated HRV,
entrainment between respiration, blood pressure
and heart rhythms and increased synchronization
between various rhythms in the EEG and cardiac
cycle.
6. Vagally mediated efferent HRV provides an index
of the cognitive and emotional resources needed
for ecient functioning in challenging environ-
ments in which delayed responding and behavioral
inhibition are critical.
7. Information is encoded in the time between
intervals (action potentials, pulsatile release of
hormones, etc.). The information contained in the
interbeat intervals in the heart’s activity is com-
municated across multiple systems and helps
synchronize the system as a whole.
8. Patterns in the activity of cardiovascular afferent
neuronal trac can signicantly inuence cogni-
tive performance, emotional experience and self-
regulatory capacity via inputs to the thalamus,
amygdala and other subcortical structures.

28
© Copyright 2015 HeartMath Institute
Science of the Heart
9. Increased “rate of change” in cardiac sensory
neurons (transducing BP, rhythm, etc.) during co-
herent states increases vagal afferent neuronal
trac, which inhibits thalamic pain pathways at
the level of the spinal cord.
10. Self-induced positive emotions can shift psycho-
physiological systems into more globally coherent
and harmonious orders that are associated with
improved performance and overall well-being.
The coherence model includes specic approaches
for quantifying the various types of physiological
coherence measures, such as cross-coherence (fre-
quency entrainment between respiration, BP and
heart rhythms), or synchronization among systems
(e.g., synchronization between various EEG rhythms
and the cardiac cycle), autocoherence (stability of a
single waveform such as respiration or HRV patterns)
and system resonance.[5] A coherent heart rhythm is
dened as a relatively harmonic, sine-wavelike signal
with a very narrow, high-amplitude peak in the low-
frequency (LF) region of the HRV power spectrum
with no major peaks in the very-low-frequency (VLF)
or high-frequency (HF) regions. Physiological coher-
ence is assessed by identifying the maximum peak
in the 0.04 to 0.26 hertz range of the HRV power
spectrum, calculating the integral in a window 0.030
hertzwide, centered on the highest peak in that re-
gion and then calculating the total power of the en-
tire spectrum. The coherence ratio is formulated as
(peak power/[total power – peak power]).[5]
Physiological Coherence
A state characterized by:
• High heart-rhythm coherence
(sine-wavelike rhythmic pattern).
• Increased parasympathetic activity.
• Increased entrainment and synchronization
between physiological systems.
• Ecient and harmonious functioning of
the cardiovascular, nervous, hormonal and
immune systems.
Social Coherence
Social coherence relates to pairs, family units, groups
or larger organizations in which a network of relation-
ships exists among individuals who share common
interests and objectives. Social coherence is reected
as a stable, harmonious alignment of relationships
that allow for the ecient ow and utilization of en-
ergy and communication required for optimal collec-
tive cohesion and action. There are, of course, cycles
and variations in the quality of family, team or group
coherence, similar to variations in an individual’s
coherence level. Coherence requires that group mem-
bers are attuned and emotionally aligned and that the
group’s energy is globally organized and regulated by
the group as a whole. Group coherence involves the
same principles of global coherence described earlier,
but in this context it refers to the synchronized and
harmonious order in the relationships between and
among the individuals rather than the systems within
the body. The principles, however, remain the same:
In a coherent team, there is freedom for the individual
members to do their part and thrive while maintain-
ing cohesion and resonance within the group’s intent
and goals. Anyone who has watched a championship
sports team or experienced an exceptional concert
knows that something special can happen in groups
that transcends their normal performance. It seems as
though the players are in sync and communicating on
an unseen energetic level. A growing body of evidence
suggests that an energetic eld is formed between
individuals in groups through which communication
among all the group members occurs simultane-
ously. In other words, there is a literal group “eld”
that connects all the members. Sociologist Raymond
Bradley, in collaboration with eminent brain researcher,
neurosurgeon and neuroscientist Dr. Karl Pribram,
developed a general theory of social communication
to explain the patterns of social organization com-
mon to most groups and independent of size, culture,
degree of formal organization, length of existence or
member characteristics. They found that most groups
have a global organization and coherent network of
emotional energetic relations interconnecting virtu-
ally all members into a single multilevel hierarchy.[170]

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Chapter 5: Establishing A New Baseline
Establishing a New Baseline
At the HMI Research Center, we have found that the heart plays a central role in the generation of emotional
experience and therefore, in the establishment of psychophysiological coherence. From a systems perspec-
tive, the human organism is truly a vast, multidimensional information network of communicating subsystems
in which mental processes, emotions and physiological systems are inextricably intertwined. Whereas our
perceptions and emotions were once believed to be dictated entirely by the brain’s responses to stimuli arising
from our external environment, the emerging perspectives in neuroscience more accurately describe perceptual
and emotional experience as the composite of stimuli the brain receives from the external environment and
the internal sensations or feedback transmitted to the brain from the bodily organs and systems.[5, 79] Thus, the
heart, brain, nervous, hormonal and immune systems must all be considered fundamental components of the
dynamic, interactive information network that determines our ongoing emotional experience.
Extensive work by Pribram has help