Polyvagal theory takes that nuance several steps further.

Developed by neuroscientist Stephen Porges in the 1990s, polyvagal theory proposes that the autonomic nervous system, and the vagus nerve in particular, operates not in two states but in three, organized in a hierarchy that reflects the evolutionary history of the nervous system itself. It has become a highly influential framework in trauma therapy, somatic practice, and increasingly, yoga teaching.

It has also generated genuine scientific debate, which we’ll touch on honestly. But as a clinical and pedagogical map, a way of understanding what you’re seeing in your students and what your classroom environment is actually doing, it is remarkably useful.

Two Vagal Pathways, Not One

Here is the core anatomical proposition of polyvagal theory, and the place where it meaningfully extends what we covered in the last post.

The vagus nerve is not a single, uniform pathway. It has two distinct branches, and according to Porges, they serve different functions and are activated under different conditions.

These two pathways are the ventral vagal complex and the dorsal vagal complex.

The ventral vagal complex is the newer, more evolutionarily recent branch. It originates in a specific region of the brainstem called the nucleus ambiguus and innervates the face, eyes, ears, larynx, and pharynx, including the muscles of facial expression, the middle ear, and the voice. It also connects to the heart and lungs. This is the branch associated with social engagement, connection, and felt safety. When it is online, the face is expressive, the voice has warmth and prosody, the eyes make contact, and the middle ear is tuned to the frequency range of human speech. The body is signaling and receiving the signal that the environment is safe.

The dorsal vagal complex is the older, more ancient branch. It originates in the dorsal motor nucleus of the vagus and descends primarily to the organs below the diaphragm, including the digestive tract, the heart at a deeper level, and the viscera. In its healthy, regulated expression, the dorsal vagal supports digestion, rest, and restoration. But under conditions of extreme or inescapable threat, it is the branch associated with the freeze response, the profound shutdown, immobilization, dissociation, or collapse we described in earlier posts. This is an ancient survival strategy, one that predates mammals: play dead, conserve resources, disappear. It is involuntary, it is not weakness, and it is important that yoga teachers understand it as a protective response rather than a behavioral choice.

The Three-State Hierarchy

Polyvagal theory organizes these pathways, along with the sympathetic branch, into a three-state hierarchy that the nervous system moves through in a predictable order based on its assessment of safety and threat.

At the top of the hierarchy is the ventral vagal state: social engagement, connection, regulated arousal. This is the state in which learning, creativity, intimacy, play, and genuine rest are all possible. It is not the absence of activation. You can be energized, focused, even challenged and still be operating from ventral vagal regulation. What characterizes it is the felt sense of safety and connection. This is the state most conducive to a meaningful yoga practice, and the state a well-held class can help cultivate.

When the nervous system determines that the environment is not safe, that a demand or threat is present and must be met, it moves down the hierarchy to sympathetic mobilization: fight or flight. Resources are redirected, the body prepares to act, and social engagement becomes secondary to survival. As we explored in the sympathetic branch post, this is not inherently pathological. Challenge, intensity, and even productive stress live here. The question is always whether the system can return to ventral vagal regulation once the demand has passed.

When the nervous system detects overwhelming or unresolved threat, especially when mobilization does not restore a sense of safety, it may shift toward dorsal vagal states of shutdown: freeze, collapse, dissociation, or immobilization. These responses reflect a move toward energy conservation and protection rather than active defense. In polyvagal theory, this state is often described as the most evolutionarily ancient pattern of response, emerging when the system no longer organizes primarily around fighting or fleeing.

This hierarchy is often described in polyvagal theory as the autonomic ladder. Regulation tends to move the system toward ventral vagal states of safety and connection, while dysregulation can shift the system toward sympathetic mobilization or dorsal withdrawal. In practice, the nervous system usually moves through these states gradually rather than instantly, which means that deep parasympathetic rest is often difficult to access when sympathetic activation is still high. You cannot simply will yourself into savasana from a threat state. The body typically needs time and supportive conditions to settle.

The Nervous System Is Always Listening

Here is something worth sitting with as a yoga teacher: your students’ nervous systems are making assessments about safety and threat constantly, almost entirely below the level of conscious awareness.

Porges gave this process a name: neuroception. It is the nervous system’s continuous, subconscious scanning of the environment for cues of safety or danger, reading facial expressions, voices, posture, proximity, and touch before the thinking brain has weighed in at all. We’ll explore neuroception in much greater depth in a future post, but it’s worth introducing here because it reframes something important about what happens in a yoga room.

According to the World Health Organization (WHO), around 70% of people globally will experience a potentially traumatic event during their lifetime. Not all of those people will develop PTSD or a clinical trauma response, but many will carry nervous systems that have been shaped by those experiences in ways that affect how safety is perceived, how touch is received, and how the body responds to a room full of strangers being asked to close their eyes and be still.

This is not cause for alarm. It is cause for awareness. Your students are not fragile, and your classroom is not a minefield. But the more you understand that a nervous system reading threat will respond from a very different place than one reading safety, the more intentional you can become about the environment you create before you’ve said a single word of instruction.

What This Looks Like in a Yoga Room

Think about what happens when a student walks into a yoga studio for the first time. Their nervous system is scanning, before their conscious mind has processed a single thought, for signals of safety or threat. Is the teacher’s voice warm or flat? Do people make eye contact or look through me? Does the room feel welcoming or evaluative?

These are not trivial aesthetic preferences. They are neurological inputs, processed in large part through the ventral vagal system, the ears tuned to vocal prosody, the eyes reading faces, and the body reading the social temperature of the room.

This is why the way you speak to your students matters at a level far deeper than content. A warm, regulated, melodic voice, the same quality Porges observed in mothers soothing infants, which he identified as a primary ventral vagal activator, literally helps move a student’s nervous system toward the state in which they can learn, integrate, and be present. A flat, clipped, or overly performance-focused delivery can do the opposite, even when the words themselves are perfectly correct.

It’s also why the arc of a well-structured class matters neurologically, not just aesthetically. Moving from dynamic activation into genuine stillness is not just good sequencing. It can help support a shift up the autonomic ladder, from sympathetic mobilization back toward ventral vagal regulation. Savasana at the end of that arc is not an add-on. It is the integration. It is where the nervous system consolidates the shift.

An Honest Note on the Science

Polyvagal theory is influential, clinically resonant, and widely applied, but it is not without its critics. Some neuroscientists have challenged aspects of Porges’ neuroanatomical claims, particularly around the strict separation of the ventral and dorsal vagal pathways and the proposed evolutionary timeline. The debate is ongoing and worth knowing about, especially as the theory continues to proliferate in wellness and therapeutic spaces, sometimes without that nuance.

What this means practically: polyvagal theory is best held as a map, not a complete and final territory. Maps are useful precisely because they simplify complex terrain into navigable form. This one has helped thousands of clinicians, somatic practitioners, and yoga teachers better understand what they were already observing in the bodies in front of them. That practical utility is real, even as the underlying science continues to be refined.

As yoga teachers, we are never diagnosing or treating. However, yoga is open to all, and that means we will encounter individuals at different places on the autonomic ladder, often without knowing it. Recognizing the cues creates space for compassion rather than judgment. We are using an understanding of the nervous system to inform how we hold space, how we speak, how we sequence, how we prioritize consent and offer touch. For that purpose, polyvagal theory offers a genuinely useful lens.

The Map Worth Carrying

The vagus nerve is not a single pathway but a layered system, and the states it mediates, social engagement, sympathetic mobilization, and dorsal vagal shutdown, form a hierarchy that the nervous system moves through in response to its assessment of safety and threat. Understanding this hierarchy doesn’t just change how you think about stress and relaxation. It changes how you think about your voice, your room, and the student in front of you who can’t quite seem to arrive.

In a future post, we’ll touch on neuroception—Porges’ term for the nervous system’s unconscious scanning for safety and threat. It’s present in every classroom, with every student, in every moment of every class. You’re already navigating it. Understanding it just makes you more intentional about how.

This is the fifth post in a foundational series on nervous system literacy for yoga teachers. Start from the beginning with post one, or subscribe to follow along as the series unfolds.

For teachers who incorporate touch, consent is the foundation. Learn how to approach it with clarity and confidence, and gain 16 foundational assist techniques inside the Rubber Band Method® Foundations course. 30 CEU hours available.

It’s a seductive framing. It’s also incomplete and, in some ways, just as misleading as calling the sympathetic nervous system the villain. In reality, sympathetic activation is not inherently stressful. It is the system that allows you to move, respond, and engage with your environment. In a yoga class, it supports your ability to move through vinyasas, transition between shapes like downward dog and warrior poses, and even come back to standing after savasana.

The parasympathetic nervous system is not the hero of this story. It is the moderator. Understanding the difference matters enormously for how you think about your students, your sequencing, and what you’re actually trying to cultivate in a yoga room.

The Architecture of the Parasympathetic Branch

Where the sympathetic nervous system originates in the thoracic and lumbar spine (the middle and lower back), the parasympathetic branch has two distinct points of origin: the brainstem and the sacrum (the triangular bone at the base of the spine, just above the tailbone).

From the brainstem, several cranial nerves carry parasympathetic fibers out to the head, neck, and organs of the chest and abdomen. The most significant of these, by a considerable margin, is the vagus nerve.

The word vagus is Latin for wandering, and the name is apt. The vagus nerve is the longest cranial nerve in the body. It exits the brainstem and passes through the neck alongside the carotid artery and jugular vein. Along the way, it innervates the ears and the throat, including the glottis, the part of the larynx that houses the vocal cords.

This is not a minor anatomical footnote. The vagus nerve innervates structures involved in vocalization and sensation in parts of the outer ear, which helps explain why a calm, warm voice can feel regulating and why humming, chanting or using ujjayi breathing may support parasympathetic activity. The sound environment you create in your classroom may be doing more nervous system work than you realized.

From the neck, the vagus continues its descent through the chest, branching extensively through the heart, lungs, and esophagus, before reaching the stomach, liver, pancreas, gallbladder, and intestines. It wanders, it branches, it listens, and it speaks, carrying information both from the body to the brain and from the brain to the body. We’ll explore that two-way conversation in depth in a future post.

From the sacrum, a second set of parasympathetic fibers extends downward to serve the lower digestive tract, bladder, and reproductive organs. These fibers govern the functions of elimination and, in states of genuine safety, sexual arousal and intimacy.

Acetylcholine: The Parasympathetic Messenger

Where the sympathetic nervous system communicates primarily through epinephrine and norepinephrine, the parasympathetic branch operates through a different neurochemical entirely: acetylcholine (ACh).

Acetylcholine is one of the oldest neurotransmitters in evolutionary terms. It predates the vertebrate nervous system and is found across a remarkable range of species. In the context of the parasympathetic branch, it acts as a broad moderating signal, modulating the systems that sympathetic activation has mobilized (including everyday actions, not just stress responses).

At the heart, acetylcholine slows the heart rate and reduces the force of contraction. This is the direct counterbalance to epinephrine’s acceleration. This is also the neurochemical basis of the slowdown you feel after a vigorous practice begins to wind down, or during a long, slow exhale. The vagus nerve’s influence on heart rate is so direct and measurable that it forms the basis of heart rate variability (HRV), a commonly used noninvasive marker of cardiac vagal regulation that we’ll explore in a future post.

In the brain, acetylcholine plays a central role in attention, learning, and memory consolidation. Parasympathetic states, meaning genuine rest and not just physical stillness, support the kind of diffuse, integrative cognition that allows new information to settle and connect. This is one reason insights often arrive in the shower, on a walk, or in savasana. The brain in a parasympathetically supported state is doing different and equally important work than the brain under sympathetic load.

In the digestive system, acetylcholine stimulates the entire process. It increases saliva production and activates gastric secretions, shifting the body back toward digestion after periods of activation, when resources were directed elsewhere to support mobilization.

This matters more than it might initially seem because the gut is not merely a digestive organ. It is home to the enteric nervous system (often referred to as the “second brain”) and produces the vast majority of the body’s serotonin.

Serotonin is commonly associated with mood and the brain, but approximately 90–95% of it is actually found in the gut, where it helps regulate intestinal movement and contributes to gut–brain signaling. This is one reason the gut is so central to nervous system health. Chronic stress can disrupt both digestion and this signaling pathway, influencing not only how the gut functions, but how we feel.

When the parasympathetic branch is chronically undertoned—when the body does not spend enough time in a well-perfused, digestive state—both serotonin activity and gut–brain communication can be affected. This is one of the more underappreciated ways chronic stress influences mood. It is not only a brain chemistry story; it is also a gut–brain story.

This relationship is reflected clinically. Medications that influence serotonin signaling are often prescribed for conditions like irritable bowel syndrome, highlighting the bidirectional nature of the gut–mood connection.

Parasympathetic Dominance: The Other Extreme

Here is where the wellness narrative around the parasympathetic branch tends to go quietly off the rails.

In a culture saturated with chronic stress, the parasympathetic branch is often framed as the destination, as though more is always better. But the nervous system does not work that way. Acute excessive vagal activation can create problems, including sudden drops in heart rate and blood pressure, as in vasovagal fainting. Some low-arousal or shutdown states can also look less like restoration and more like collapse. So while underactive parasympathetic regulation is common in modern life, parasympathetic activity itself is not inherently synonymous with health.

Acute excessive vagal activation, and certain low-arousal or shutdown states, can produce their own set of significant problems. Heart rate becomes too low. Blood pressure drops. Digestion becomes dysregulated in a different way, including dysmotility, bloating, and nausea. Fatigue can become profound and unresponsive to rest. Cognitive function may dull. Motivation and engagement can flatten. In acute form, excessive vagal activation produces the freeze and faint responses we described in the first post. This is the sudden parasympathetic override that drops heart rate and blood pressure dramatically, sometimes causing loss of consciousness.

At the extreme end of chronic parasympathetic dominance, what emerges looks less like relaxation and more like shutdown. This includes flat affect, profound fatigue, social withdrawal, and emotional numbness that can characterize certain presentations of trauma, depression, and chronic illness. This is a nervous system that has been pulled so far toward the brake that it can no longer find the accelerator.

No one would choose this state. It is a useful corrective to the idea that the parasympathetic branch is inherently the healthy one. Both branches are essential. Both require tone, responsiveness, and flexibility. The goal, as we established in the first post, is not calm. It is flexibility: the capacity to move fluidly between activation and recovery, mobilization and rest, engagement and ease.

The Undertoned Branch in an Overtaxed World

That said, there is an honest asymmetry worth naming.

We live in an environment of near-constant sympathetic provocation. Artificial light disrupts the diurnal cortisol curve. Screens deliver stimulating input at every idle moment. News cycles generate ambient threats. Work bleeds into evenings and weekends. Social comparison is built into the platforms most people spend hours on daily. The body rarely receives an unambiguous signal that it is genuinely safe, that demands have paused, and that it can fully release vigilance.

In this context, while neither branch is inherently superior, it is the parasympathetic branch that most commonly suffers from underuse. Not because relaxation is virtuous, but because the conditions that allow for genuine parasympathetic activation are increasingly rare in modern life. These conditions include felt safety, reduced input, rhythmic movement, connected relationship, and unhurried time.

This is why practices that support parasympathetic tone matter. Extended exhales activate the vagus nerve directly, slowing the heart through acetylcholine release. Humming, chanting, ujjayi breathing, and vocalization stimulate the vagal branches that innervate the larynx and glottis. Slow, rhythmic movement supports the transition between sympathetic mobilization and parasympathetic recovery. Skillful, purposeful touch, when it is consented to and received as safe, can signal to the nervous system that the environment is not threatening and support a downregulation that cognitive reassurance alone often cannot produce.

Your yoga class, when structured well, is an environment that helps tone and strengthen the parasympathetic branch. Not because it eliminates sympathetic activation, but because it moves through activation and back to recovery in a way modern life rarely structures. This is why we always allot time for savasana and cool down. That time at the end of class is not a reward for the hard work. It is the neurological point of the whole thing.

The Takeaway

The parasympathetic nervous system is vast, chemically rich, and critically important, not as a destination to reach, but as a dynamic counterpart to the sympathetic branch. Its primary messenger, acetylcholine, moderates the heart, supports cognition, restores digestion, and enables the gut conditions that underpin serotonin production and mood regulation. Its primary vehicle, the vagus nerve, is one of the most significant structures in the body for understanding why yoga, breath, sound, and touch produce the effects they do.

Neither branch is the hero. Both branches, working in flexible, responsive balance, are the point.

In the next post, we’ll expand this framework through the lens of polyvagal theory, Stephen Porges’ influential work that takes the vagus nerve as its centerpiece and offers a more nuanced map of how the nervous system navigates safety, threat, and connection. It’s a framework that has quietly reshaped trauma therapy, somatic practice, and yoga pedagogy alike, and it deserves a careful, honest look.

This is the fourth post in a foundational series on nervous system literacy for yoga teachers. Start from the beginning with post one, or subscribe to follow along as the series unfolds.

Explore: Hands-On Yoga Assists: A Teacher’s Guide to the Rubber Band Method®, which begins with The Science of Safe Touch and builds into practical, anatomically informed assists you can use in your classes.

But there’s a second stress system running alongside the sympathetic branch, one that operates on a slower timescale and has longer-lasting effects on virtually every system in the body. It doesn’t fire in seconds. It unfolds over minutes, hours, and in the case of chronic stress, years.

It’s called the HPA axis, and it’s one of the most important and most misunderstood systems in the biology of stress.

What the HPA Axis Actually Is

HPA stands for hypothalamic-pituitary-adrenal, three structures that form a hormonal relay system, each one triggering the next in a cascade.

It begins in the hypothalamus, that small master coordinator we met in the first post, nestled near the base of the brain just above the brainstem. When the hypothalamus perceives a stressor, it initiates the cascade. And it’s worth pausing here on the word perceives, because the hypothalamus does not distinguish between a real threat, an anticipated one, or an imagined one. If you vividly picture a stressful conversation you’re dreading, or replay an argument that happened three days ago, or lie awake catastrophizing about something that may never occur, the hypothalamus can read that as a live threat and trigger the same hormonal chain of events as if the danger were standing right in front of you. The nervous system, in this sense, does not always know the difference between what is happening and what you are thinking about.

From the hypothalamus, a signaling hormone is released that travels to the pituitary gland, a pea-sized structure at the base of the brain, often called the “master gland” for how many hormonal systems it governs. The pituitary responds by releasing its own hormone into the bloodstream, which then travels to the adrenal glands, the two small, triangular glands sitting atop each kidney, signaling them to release cortisol.

The whole cascade, from perception of a stressor to peak cortisol levels, unfolds over roughly 20–30 minutes. Which is why this system is slower than the immediate epinephrine spike of the sympathetic branch, but also why its effects are more sustained and why a stressful morning can still be chemically present in your student’s body when they arrive for an evening class if they’re still reliving that stressor.

Cortisol: Still Not the Villain

We touched on this in the last post, but it bears repeating here with more depth: cortisol is not a stress hormone in the pejorative sense. It is a survival hormone that also happens to be released under stress.

On a normal, unstressed day, cortisol follows a natural rhythm. It actually begins rising before you wake up, and that rising cortisol level is part of what causes you to wake up, providing the physiological readiness to meet the day. It peaks sharply in the first 30-45 minutes after waking, known as the cortisol awakening response, delivering energy, mental clarity, and alertness. It then gradually declines through the afternoon and evening, reaching its lowest point in the early hours of sleep. This rhythm, called the diurnal cortisol curve, is one of the markers clinicians use to assess overall stress system health.

Cortisol does essential work throughout this daily cycle. It regulates blood sugar by signaling the liver to release stored glucose for fuel, the same mechanism that kicks in during a challenging power yoga class or any sustained physical effort, giving your muscles the energy they need to keep going. It modulates immune function. Contrary to popular belief, cortisol doesn’t simply suppress immunity; it regulates it, preventing inflammatory responses from overshooting. It supports cardiovascular function, assists in memory consolidation, and plays a role in mood stability.

The issue, as always, is not the hormone itself. Like most things in the body, too much of it for too long stops being a resource and starts being a liability.

When the Cascade Doesn’t Turn Off

Under healthy conditions, the HPA axis has a built-in off switch. As cortisol rises in the bloodstream, it feeds back to the hypothalamus and pituitary, essentially signaling: message received, you can stand down. This negative feedback loop is what allows the stress response to be time-limited. Stressor arrives, cascade activates, cortisol rises, feedback signals resolution, and the system returns to baseline.

But this elegant mechanism has vulnerabilities.

When stressors are chronic, such as financial pressure, relationship conflict, caregiving demands, systemic inequity, trauma looping, or a nervous system that never fully learned to return to baseline, the feedback loop becomes dysregulated. The hypothalamus keeps signaling. The pituitary keeps responding. The adrenal glands keep producing. And the body stays in a prolonged state of cortisol elevation it was never designed to sustain.

Over time, this does measurable damage across multiple systems:

Sleep deteriorates. Cortisol and melatonin have an inverse relationship; as one rises, the other falls. Chronically elevated evening cortisol is associated with lower melatonin signaling and more fragmented sleep architecture, reducing the deep, restorative stages the nervous system most needs to recover.

Immune function is disrupted. Short-term cortisol elevation is anti-inflammatory. Chronic elevation does the opposite. It desensitizes immune cells to cortisol’s regulatory signal, which paradoxically leads to increased baseline inflammation. This is one of the mechanisms that can connect chronic stress to conditions like autoimmune disorders, cardiovascular disease, and accelerated cellular aging.

Memory and cognition are affected. The hippocampus, the brain region most central to memory formation and threat contextualization, is densely packed with cortisol receptors and highly sensitive to sustained cortisol exposure. Chronic stress can reduce hippocampal volume over time, which matters enormously for a very specific reason. A healthy hippocampus allows the nervous system to accurately assess whether something is actually a threat. It’s the part of the brain that looks at a stick on the ground and says that’s just a stick, after your amygdala, your threat-detection center, has already fired as if it were a snake. When the hippocampus is compromised by chronic stress load, that corrective signal weakens. The amygdala keeps firing. Threat responses become hair-trigger. The nervous system starts to lose its ability to distinguish between real danger and the memory or anticipation of it, which, as we noted earlier, the hypothalamus was never very good at distinguishing in the first place.

Mood dysregulation increases. Chronic HPA-axis disruption shows up frequently in depression research and anxiety-related conditions. The relationship is bidirectional. Stress dysregulates mood, and mood dysregulation sustains stress activation, creating feedback loops that can be genuinely difficult to interrupt through top-down means alone (more on this in a future post).

Over time, the stress response itself can become dysregulated. After sustained periods of high demand, cortisol rhythms may become altered, sometimes showing lower morning output or a flattened daily curve. This can show up as the flat, depleted, can’t-get-going feeling many people describe as burnout. Morning cortisol may fail to peak adequately, energy can feel low, and recovery may be slow. The diurnal rhythm that normally rises in the morning and falls through the day can lose its natural shape.

This cumulative toll is what we referred to in the first post as allostatic load, the physiological cost of sustained, unresolved adaptation. The HPA axis is one of its primary mechanisms.

What This Looks Like in Your Classroom

You cannot look at a student and know their HPA axis history. But you can develop an informed intuition for what chronic stress load looks like in a body.

The student who is perpetually exhausted but can’t relax. The one who moves through a vigorous practice without ever seeming to build heat, a nervous system so habituated to high activation that it barely registers the input. The one who bursts into tears in a hip opener, not because something dramatic happened, but because the body finally found enough safety to release what it had been holding. The one who falls asleep in every savasana, not from peace, but from a nervous system that collapses the moment vigilance is no longer required.

These can be outward patterns of chronic stress physiology. Not diagnoses; you are not your students’ clinician, but patterns worth recognizing and having compassion for.

What yoga offers these students is not a fix. Chronic HPA dysregulation is not resolved by a single class, a single workshop, or even a single year of consistent practice. But a well-held yoga class, one that builds activation and then guides genuine recovery, creates safety through consistency and predictability, and uses breath, movement, stillness, and consent-based touch as bottom-up regulatory tools, is a legitimate input into the system. Over time and with repetition, it can contribute to improving stress regulation, lowering baseline activation, and restoring some of the flexibility the system has lost.

This is not conjecture. There is a growing body of research suggesting that regular yoga practice can influence measurable markers of stress physiology, including cortisol levels, HPA axis reactivity, and inflammatory markers.

The Takeaway

The HPA axis is the body’s slow-burn stress system, powerful, essential, and vulnerable to the demands of modern life in ways the sympathetic nervous system alone doesn’t fully capture. Understanding it gives you a more complete picture of what chronic stress actually does to a human body and why so many of your students arrive carrying far more than their yoga mat.

In the next post, we turn to the other side of the autonomic nervous system, the parasympathetic branch, the vagus nerve, and the biology of genuine rest.

This is the third post in a foundational series on nervous system literacy for yoga teachers. Start from the beginning with post one, or subscribe to follow along as the series unfolds.

If this kind of science-meets-teaching thinking is useful to you, this is what I do. The Tissue Literacy for Yoga Teachers blog at rubberbandmethod.com goes deeper — same lens, applied directly to hands-on assists and adjustments.

Read Tissue Literacy for Yoga Teachers

You’re exploring the nervous system side of yoga teaching—
how safety, regulation, and perception shape the classroom.

But there’s another layer:
→ how those states are reflected in the body.

This is where Tissue Literacy for Yoga Teachers comes in.

While nervous system literacy helps you understand why the body responds the way it does…

Tissue literacy teaches you how to feel those responses as they take shape in the tissues—through tone, resistance, and receptivity.

If you’re ready to explore how this shows up in hands-on teaching:

Tissue Literacy for Yoga Teachers →

This is the applied side of the work—
where the nervous system becomes something you can feel, and respond to, through touch.

The sympathetic nervous system is not your enemy. It is one of the most elegant, finely calibrated systems in the human body. And without it, you wouldn’t just struggle to handle stress — you’d struggle to get out of bed in the morning.

More Than Fight or Flight

“Fight or flight” is the phrase most people reach for when describing the sympathetic nervous system, and it’s not wrong — but it frames the entire branch around threat, which misses most of what it actually does.

The sympathetic nervous system is your activation branch. It mobilizes energy, sharpens attention, increases physical capacity, and prepares you to engage with whatever is in front of you. That includes threats, yes — but it also includes a challenging yoga sequence, an exciting conversation, falling in love, teaching a class you’re passionate about, or simply standing up from your chair.

Every time you move through your day with energy and engagement, your sympathetic nervous system is involved. It is the neurological infrastructure of being alive and participating in life.

What It Actually Governs

The sympathetic nervous system originates in the thoracic and lumbar spine — the middle and lower portions of your back — where nerve fibers exit the spinal cord and branch outward to reach virtually every organ and tissue in the body. Its reach is broad and its effects are coordinated: when it activates, it doesn’t just do one thing. It does many things simultaneously, all in service of preparing the body to meet a demand.

Here’s what sympathetic activation looks like at the level of physiology — and how it shows up in real life and in the yoga room:

The heart rate increases and the heart contracts more forcefully. More blood moves through the body per minute, delivering oxygen and fuel to where it’s needed most. In your classroom, this is the student whose chest you can visibly see pounding after a vigorous vinyasa sequence.

The airways dilate. Bronchodilation, the widening of the airways in the lungs, allows more air to move in and out quickly. Breathing often becomes faster and may feel more chest-dominant, supporting rapid ventilation. Slow diaphragmatic breathing can feel counterintuitive when activation is high, as if you’re working against the sympathetic current.

Blood is redistributed. Vessels supplying the large skeletal muscles — legs, arms, back — dilate to increase flow. Circulation to digestion decreases, and in acute stress the skin may pale as vessels constrict. During heat or exertion, however, skin blood flow can increase to help regulate temperature. The body is triaging resources in real time.

The pupils dilate. Vision sharpens and widens. You become more alert to movement in your peripheral field. This is the body scanning for information.

Sweating increases. Particularly in the palms and soles, a detail that is both evolutionarily useful (better grip on surfaces) and immediately recognizable to anyone who has ever been nervous before teaching.

Digestion slows. Saliva production decreases, gut motility slows, and digestive secretions are reduced. The body has decided this is not the moment to process lunch.

Non-essential immune and reproductive functions are temporarily deprioritized. In the short term, this reallocation is adaptive. Sustained over time, however, chronic activation can begin to disrupt immune balance and reproductive regulation.

The Neurochemicals: Epinephrine, Norepinephrine, and Cortisol

The sympathetic nervous system communicates through a specific set of chemical messengers. Understanding what they are, and what they actually do, goes a long way toward dissolving the idea that stress chemistry is inherently harmful.

Epinephrine (you likely know it by its other name, adrenaline) is primarily a hormone, released rapidly from the adrenal medulla (the inner portion of the adrenal glands, which sit atop each kidney) in response to sympathetic activation. It acts fast, within seconds, and its effects are immediate and dramatic: heart rate surges, airways open, blood sugar rises as stored glucose is released for fuel. Epinephrine is the chemical of acute, intense activation. It’s what you feel when you get startling news, narrowly avoid a car accident, or step onto a stage. It is also what makes a challenging yoga class feel exhilarating rather than merely exhausting.

Epinephrine clears from the bloodstream relatively quickly, within minutes of the triggering stimulus ending, if the triggering stimulus ends. It is designed for short, sharp responses, not sustained states.

Norepinephrine (also called noradrenaline) is both a neurotransmitter and a hormone. It’s released at sympathetic nerve endings throughout the body and also from the adrenal medulla alongside epinephrine. Where epinephrine is the acute spike, norepinephrine provides more sustained sympathetic tone. It’s responsible for vasoconstriction (the narrowing of blood vessels to redirect blood flow), sustained alertness, and focused attention. Norepinephrine is also central to mood regulation, it’s one of the key neurochemicals targeted by some antidepressants, which speaks to how deeply our emotional states are rooted in sympathetic chemistry. It has a somewhat longer half-life than epinephrine, lingering in the system for mere minutes in acute release, though its effects can persist as long as sympathetic nerves continue signaling.

Cortisol is a hormone and the neurochemical that gets the worst press — and the most misunderstood reputation. Released from the adrenal cortex (the outer layer of the adrenal glands) via the HPA axis, cortisol is not a sympathetic neurotransmitter in the strict sense, but it works in close concert with the sympathetic branch and is worth addressing here directly.

Cortisol is vital. Without it, you cannot regulate blood sugar effectively, and you lose a key hormone for modulating inflammation and immune activity. Your cortisol levels naturally peak in the morning — this is called the cortisol awakening response — and supports morning energy and readiness to engage with the day.

Cortisol also has a much longer half-life (roughly an hour or more) than epinephrine or norepinephrine. It clears more slowly than adrenaline, and its physiological effects can persist long after the initial stressor has passed. This matters for yoga teachers: a stressful commute, an upsetting phone call, or a difficult interaction before class isn’t just emotional, it’s biochemical, with a measurable duration. Your student who arrived flustered may still be chemically mid–stress response when they roll out their mat.

The problem with cortisol is not the hormone itself. The problem is chronic, unrelenting release, which is a story about lifestyle, load, and the HPA axis. We’ll go there in full in the next post.

Sympathetic Activation Is Not Suffering

One of the most important reframes a yoga teacher can make is this: a student in sympathetic activation is not a student who is failing at yoga. They are a student whose nervous system is doing its job.

Sympathetic activation is appropriate during vigorous movement. It is appropriate during challenge, novelty, and intensity. A well-designed vinyasa class should produce sympathetic activation, that’s part of why it feels good. The satisfaction of a strong practice, the heat that builds in the body, the sense of having met something difficult and moved through it — these are, in part, sympathetic experiences.

What yoga offers, and what makes it genuinely therapeutic rather than merely athletic, is not the elimination of sympathetic activation but the practice of moving through it and back toward balance. The sequence arc from dynamic warm-up to cooling postures to savasana is, among other things, a guided tour of the nervous system: mobilize, challenge, recover. Do it repeatedly, over years of practice, and you are essentially training the ANS to be more flexible — to activate fully when needed, and to release that activation when the demand has passed.

That’s not just a metaphor, this is one way yoga can train autonomic flexibility over time.

A Note on What’s Coming

The sympathetic nervous system doesn’t operate in isolation. Its hormonal partner, the HPA axis, which governs the cortisol cascade, runs alongside it and deserves its own careful examination. In the next post, we’ll look at what happens when the sympathetic branch and the HPA axis are activated chronically, what that does to the body over time, and why so many of your students may be walking through your door already running on fumes.

This is the second post in a foundational series on nervous system literacy for yoga teachers. Start from the beginning with post one, or subscribe to follow along as the series unfolds.

If you want to go deeper on how the nervous system informs hands-on teaching, this series grew out of the research behind my book Hands-on Yoga Assists: A Teacher’s Guide to the Rubber Band Method® — a practical guide for yoga teachers on anatomy-informed assists and adjustments.

We notice these things. And if we’re honest, we sometimes wonder: is it me? Is it them? Are they checked out, resistant, or just not trying?

Here’s a more useful lens: it’s their nervous system.

What you’re witnessing in those moments isn’t effort or attitude or even personality — it’s autonomic state. A nervous system that is highly activated shows up differently on a yoga mat than one that is shut down, and differently again from one that is genuinely at ease. These states aren’t chosen consciously. They’re shaped by what happened that morning, that week, or in some cases, years and decades before your student ever walked through your door.

You may have experienced this in your own practice — arriving wound tight from the day and leaving somehow softer, more focused, more yourself. That shift is real, and it’s physiological. If you want to understand why yoga produces it — and I mean actually understand it, at the level of biology rather than belief — the autonomic nervous system is where you have to begin.

Automatic Doesn’t Mean Untouchable

The word autonomic comes from the same root as autonomous: self-governing. Your autonomic nervous system (ANS) manages heart rate, digestion, pupil dilation, modulates aspects of immune function, glandular secretion, vascular tone, and dozens of other processes that your conscious mind never has to think about. Your heart beats while you sleep. Your stomach churns through lunch while you teach. Your blood vessels constrict when you stand up too fast — and your ANS corrects it before you even notice.

For most of history, this system was considered essentially inaccessible to conscious influence. A background operating system you couldn’t reach from the front end. You were along for the ride.

That assumption has been significantly revised. Researchers have identified specific structures — including a small cluster of neurons in the brainstem called the pre-Bötzinger complex — that help explain why deliberate changes in breathing can influence autonomic state.

It’s one of the more exciting areas of current neuroscience, and we’ll dedicate a full post to it later in this series. For now, it’s enough to know that the old idea of the ANS as completely beyond our influence is no longer the consensus view.

The body, it turns out, has left some doors open.

The Architecture: Brain, Brainstem, and Two Branches

The autonomic nervous system is part of the broader peripheral nervous system — the vast network of nerves that extends from the brain and spinal cord out into every organ, gland, and tissue in the body. But its command center lives primarily in the brainstem and hypothalamus, ancient structures that sit below the cortex (our outermost layer of the brain — the wrinkled surface you picture when you picture a brain) and operate mostly outside conscious awareness.

Think of the brainstem as the building’s utility room: unglamorous, largely invisible, and absolutely critical. It regulates breathing rhythm, cardiovascular function, and basic arousal states. The hypothalamus — a small but powerful region nestled near the base of the brain, just above the brainstem — acts as a master coordinator between the nervous system and the hormonal system. Together, they are constantly receiving information from the body and the environment and making real-time adjustments.

From this central command, two branches extend outward to govern essentially everything:

The sympathetic nervous system and the parasympathetic nervous system.

These two branches reach the same organs — the heart, the lungs, the digestive tract, the blood vessels, the skin — and they generally have opposing effects on them. Where one accelerates, the other decelerates. Where one constricts, the other dilates. You’ve probably heard sympathetic described as “fight or flight” and parasympathetic as “rest and digest,” and while those shorthand labels are useful starting points, they’re incomplete in ways that matter for yoga teachers. Each branch is nuanced, layered, and physiologically rich — rich enough that we’ll give each one its own dedicated post in this series.

They Never Fully Turn Off

Here’s where a lot of wellness education goes sideways: the sympathetic and parasympathetic branches are not a light switch. They are not on or off. They are not enemies.

At every moment of your life, both branches of the autonomic nervous system are active simultaneously. What changes is the ratio — which branch is more dominant, and by how much. Even in deep, restorative sleep, your sympathetic nervous system maintains a baseline of tone. Even in an acute stress response — a fight-or-flight moment — your parasympathetic system doesn’t go completely silent.

In fact, the nervous system can produce responses beyond fighting or fleeing. Sometimes the body becomes still and immobilized — a state often described as freeze — while in other situations a vasovagal response can lead to lightheadedness or even fainting. These responses reflect shifting patterns of sympathetic and parasympathetic activity, and they are a reminder that the nervous system’s responses to threat are more varied and complex than the “fight or flight” shorthand suggests.

For a long time, physiologists described the ANS as pursuing homeostasis — the idea that the body maintains fixed, stable set points and that health means returning to them after any disruption. Blood pressure at X, temperature at Y, cortisol at Z. Deviate, correct, return. It’s a tidy model, and it’s not entirely wrong — but it’s incomplete.

The more accurate picture is allostasis: the body achieves stability not by returning to fixed points, but by continuously adjusting those set points based on what life is currently asking of it. It’s predictive and adaptive rather than reactive and rigid. And it involves real trade-offs, because resources are finite. When the ANS floods the muscles with blood during a stress response, it pulls from digestion. When it sustains elevated cortisol to manage ongoing demands, it borrows from immune function, sleep quality, and reproductive health. The body is always robbing Peter to pay Paul.

When life allows for recovery — when the borrowing gets repaid — the system remains resilient. But when the demands are chronic and the debts accumulate unpaid, the physiological cost of that sustained adaptation adds up. Researchers call this allostatic load, and it’s one of the central mechanisms behind the persistent nervous system patterns we’ll be returning to throughout this series.

That capacity for flexible, fluid movement between states — mobilizing and then returning to baseline, activating and then genuinely settling — is increasingly understood to be one of the central markers of physiological health. The goal isn’t calm. The goal is flexibility.

Why This Matters in a Yoga Room

Your students walk into class already in some autonomic state. It was shaped before they arrived — by their commute, their sleep, their last conversation, and patterns that may go back years or decades. They don’t check that state at the door.

Your class is an environment. The way you sequence, pace, cue, and — for those trained to offer it — touch, either works with the nervous system or against it. A student who arrives in a low-activation state — already sluggish, flat, or shut down — may struggle to meet the demands of a fast, intense flow, skipping every chaturanga and retreating to child’s pose not because they’re lazy or unwilling, but because their nervous system is operating in a low-activation state that makes mobilization harder. Conversely, a student who arrives in high-activation — wired, anxious, or still running on adrenaline from the day — may find it genuinely impossible to settle into a slow yin class, fidgeting through every long hold and lying in savasana with their eyes open and their mind reeling.

Neither student is doing yoga wrong. Their nervous systems are doing exactly what nervous systems do.

You don’t need a neuroscience degree to teach yoga well. But understanding the basic framework of the ANS — what it is, what it governs, how its two branches function in dynamic balance — gives you a lens that makes your existing intuitions more precise.

This series is about building that lens, one layer at a time. In the posts ahead, we’ll go deep into the sympathetic branch, the parasympathetic branch, and the emerging science around how bottom-up practices — movement, breath, touch, sound — can influence this system in ways we’re only beginning to measure and understand.

The nervous system is not background noise in your classroom. It’s the whole conversation.

This episode is essentially the science behind why RBM exists. Chapter 1 of Hands-On Yoga Assists — The Science of Safe Touch — picks up exactly where we left off today. [Start with the book.]

Before we explore the work, here’s how it came to be.

On paper, I’m a yoga teacher, massage therapist, somatic practitioner, author and founder.

But none of that is why this space exists.

This space exists because I once lived at the furthest end of the stress continuum — with misdiagnosed Complex Post-Traumatic Stress Disorder.

For nearly eight years, I cycled through medications at staggering doses, navigating side effects I never fathomed could happen to me. When I was eventually referred for electroconvulsive therapy, I sought a second opinion instead — a decision that changed the trajectory of my life.

Getting the correct diagnosis of CPTSD set me on a path toward body-based methods rather than pharmacological ones. If I was going to heal, I needed to understand what was happening inside my own body.

So I began studying the nervous system — not academically at first, but experientially. I applied every somatic tool I could find and that was available at the time. I learned to track regulation and dysregulation in real time:

In my thoughts, reactions, sleep, appetite, ability to sit still, illness, and energy.

It was everywhere.

That season of my life became a kind of self-directed doctorate in awareness. I started to recognize patterns. I began to understand stress not as a vague concept, but as a continuum — one I had personally inhabited at its most dysregulated end. And day by day, through working with my body, I slowly walked myself back toward regulation.

Healing made me curious. Curiosity made me study.

I immersed myself in anatomy, physiology, biomechanics, stress chemistry, neurobiology, somatics, and philosophy. I wanted to understand not just that the body changes under stress — but how and why. I wanted language for what I had lived. And as that language developed, I found myself doing something I hadn’t expected: I started seeing the stress continuum everywhere. In the people around me. In the yoga rooms I consistently inhabited. In the way a student’s shoulders carried their week, or the way certain bodies couldn’t soften no matter how beautiful the sequence.

What began as self study turned into a lens through which I started to see the world and hold compassion for it.

Yoga was one of the somatic tools that profoundly supported my healing. But what truly moved the needle for me wasn’t only movement or breath. It was skillful, contextual, consensual touch.

Touch was a huge part of my life growing up — my mother was a massage therapist and massage educator–but I never considered touch as a tool that could be applied to anything other than soft tissue therapy. When I encountered touch as a somatic mind-body tool — it was at first by accident, then with growing intention — and it did something nothing else had managed to achieve. It invited a felt sense of safety — one that arrived in the body first, and only then reached the mind. It didn’t require me to cognitively reframe or analyze. It bypassed the thinking mind and spoke directly to the nervous system in a language older than words.

I later came to understand this through the science of co-regulation, afferent signaling, the vagal pathway, and the neurochemistry of oxytocin and cortisol — mechanisms we’ll unpack together in future posts. But at the time, I felt it first. In my body. As the missing link.

So when I became a yoga teacher in 2011, my intention was simple: share what helped. That was a combination of many somatic tools — asana, breathwork, meditation, mantra, but most importantly, consensual, skillful touch.

When offered with precision and awareness, touch can organize tissue, communicate safety, refine proprioception, and support regulation in ways words cannot. That understanding, refined over years in real yoga classrooms, eventually became Rubber Band Method^® — a structured methodology for hands-on yoga assists grounded in consent, anatomy, and nervous system awareness.

But this Substack is not simply about a method. Yes, it’s a somatic tool we will explore here because I feel it’s greatly undervalued and underutilized, but it’s not the primary focus. This Substack is about the foundation underneath RBM — what led to its formation. That foundation is nervous system literacy.

I’m sharing this because I think you deserve to know who is asking for your attention and why. Everything I teach, I have lived. The stress continuum isn’t an academic framework to me — it’s a map I drew from the inside. The science of co-regulation isn’t abstract — it’s the explanation for why touch was my missing link when years of other interventions hadn’t been enough. Rubber Band Method® exists because what helped me heal is teachable. And this space exists because the foundation underneath that methodology deserves its own exploration.

What I hope to share here is my unique lens on the yoga space — colored by decades of healing from severe dysregulation and nearly another decade moving back towards regulation. It’s still a daily journey that insists I continue to explore my internal state and how my environment affects it.

Having been practicing yoga since 2002, most of my healing journey was performed inside the yoga classroom. This led me not only to see the nervous system and its scientific frame emerge on the mat — it led me to connect yogic philosophy with modern science. To recognize where others might be on the stress continuum. To understand yoga as a living, breathing space for regulation.

And so, it is my sankalpa, my intention to explore three pillars through the lens of the yoga classroom:

Science — anatomy, physiology, stress chemistry, biomechanics, and how regulation and dysregulation manifest in the body.

Philosophy — how awareness shapes perception, how compassion arises from understanding, and how ancient frameworks intersect with modern neuroscience in ways that are, frankly, astonishing.

Application — what this looks like in real rooms, with real students, on real days.

My hope is that these posts inspire in you a fascination in the nervous system like it has for me. This inquiry is where I get to grow and expand alongside you as I put fingers to keyboard and articulate the science as I see it showing up in my classrooms. My hope is that what you learn here helps you have compassion for yourself and your students — even the ones who skip or fall asleep in savasana, insist on doing a thousand chaturangas even when you haven’t guided them to do so or find stillness an incomprehensible thing.

I’m not an academic or a scientist. I’m more like a living case study — I’ve lived the spectrum of the stress continuum and can attest to what works. Or, at the very least, share information about the mechanisms behind yoga and other somatic tools. Here, our inquiry unfolds in the living laboratory of yoga, where the nervous system is toned — or triggered. Through science, philosophy, and embodied practice, we explore regulation on the path toward samadhi.

Welcome to Nervous System Literacy for Yoga Teachers.

Let’s begin.

This newsletter is the science behind the method. The method itself is in the book — Hands-On Yoga Assists (Human Kinetics, 2025). If you're a yoga teacher ready to transform how you offer touch, that's your next step.

This Substack — and its companion podcast — explores anatomy, physiology, somatics, and research as they meet the realities of a real yoga classroom.

We explore the autonomic nervous system, the vagus nerve, co-regulation, consent, hands-on touch, and the ways ancient yoga wisdom often describes patterns that modern science is now able to study and measure.

New posts come out about twice a month.

I’m Kiara Armstrong — yoga teacher, massage therapist, somatic practitioner, founder of Rubber Band Method®, and author of Hands-On Yoga Assists.

I’ve practiced yoga since 2002 and have been teaching since 2011. But my real education in the nervous system didn’t begin in a classroom. It began during my path of healing from complex post-traumatic stress disorder.

That journey took me deep into stress physiology, autonomic regulation, and somatics — and what I learned changed how I teach and how I understand every student who walks into a yoga room.

If you want to understand not just that yoga regulates the nervous system — but how and why — follow Nervous System Literacy for Yoga Teachers on Substack, or wherever you get your podcasts.