From Breath to Biology: Why the Vagus Nerve Matters and How To Track Vagal Tone

Functional medicine teaches us to look beneath symptoms—into the root causes that shape your body’s patterns over weeks, months, and years. And what is one of the most powerful places to begin that exploration? Your nervous system.

Many of us feel overwhelmed, stressed, or “out of balance,” but what we don’t realize is that our breathing patterns and recovery rhythms are silently shaping how our bodies respond to stress, sleep, digestion, mood, and immunity. This is where understanding the vagus nerve comes in.

The vagus nerve is one of the most important — and least talked about — parts of your nervous system. Think of it as a two-way communication line that runs from your brain down into your body, connecting to major organs like your heart, lungs, and digestive tract. It plays a key role in determining whether your body is in “stress mode” or “rest and repair mode.” When the vagus nerve is functioning well, your body can slow your heart rate, support healthy digestion, reduce inflammation, and help you feel calmer and more emotionally balanced. When it’s underactive or overwhelmed, your system may stay stuck in fight-or-flight, even when there’s no immediate threat — which can show up as poor sleep, gut issues, anxiety, fatigue, or hormonal imbalance.

What makes the vagus nerve especially powerful is that you can influence it intentionally. Unlike many automatic processes in the body, the vagus nerve responds to simple daily inputs ... particularly breathing! Slow, deep breathing with longer exhales sends a message of safety to your brain, which then signals the body to relax and heal. Over time, consistent practices like breath work, humming, and mindful pauses help improve what’s called vagal tone. This is essentially how flexible and resilient your nervous system is. A stronger vagal tone means your body can handle stress more efficiently and return to a calm state faster, creating the internal conditions needed for healing, balance, and long-term wellness.

I had the pleasure of recently reading The Vagus Nerve Solution, by Dr. Navaz Habib where she emphasizes that improving vagal tone can support better digestion, sleep, emotional regulation, and resilience to stress all without any fancy equipment. It starts with the breath!

Here are three breathing exercises from the book and related vagus-supportive techniques that you can easily add into your day:

1. Diaphragmatic Belly Breathing

   This is the foundational breath Dr. Habib highlights: slow inhalations that fill the belly, followed by longer exhales that tell your body it’s safe to rest.

   
   

   How to do it:

   • Place one hand on your belly and one on your chest.

   • Inhale through your nose slowly, letting the belly rise more than the chest.

     • inhale for a count of 4 seconds

   • Exhale slowly for longer than the inhale.

     • exhale for a count of 8 seconds

   • Repeat for 2–3 minutes.

     
     

   This style of breath helps massage your internal organs and stimulates the vagus nerve through the diaphragm.

   
   

2. 4-7-8 Breath (Relax & Reset)

   This rhythmical breath is similar to patterns discussed in the functional breathing world and supports deeper relaxation.

   
   

   Steps:

   • Inhale gently through your nose for 4 seconds.

   • Hold the breath for 7 seconds.

   • Exhale slowly through your mouth for 8 seconds.

   Repeat 3–5 cycles.

   
   

   This is a good one to do while in the shower warming up for the day or winding down before bed—pick a consistent daily cue to help this stick.

   
   

3.  Vocal Resonance / Humming Breath

   Humming or gentle vocalization on the exhale stimulates the vagus nerve by vibrating the throat muscles and calming the nervous system.

   
   

   How to do it:

   • Inhale comfortably through the nose.

   • Hum as you exhale, focusing on the vibration in your throat

     
     

   This exercise sounds silly but its easy to do and only takes 3-5 breaths/day to be effective! This can be added to your routine as you're making your morning coffee.

The key to seeing results isn’t perfection—it’s consistency. Pick small moments every day when you already pause and have a few moments to focus on yourself.

Some examples include:

• While you’re brushing your teeth

• As you’re waiting for your morning coffee

• While you're preparing a meal or warming up your lunch

• During traffic before your commute

• When you get into bed to start winding down

• In the shower while you're getting ready

These little windows are perfect opportunities to “anchor” your breath practice so it becomes part of your routine rather than another thing on your to-do list. Over time, the cumulative effect helps your nervous system shift into calmer, more regulated patterns.

Tracking Results and How to Measure Vagal Tone:

These habits are powerful, but pairing them with good data takes your self-care to the next level! A wearable device like the Oura Ring lets you see how your body responds to lifestyle changes rather than guessing.

Oura tracks metrics such as:

• 🌙 Sleep quality and stages

• 📈 Heart rate and heart rate variability (HRV) 

  • A key marker of vagal tone and recovery

• 🔥 Body temperature trends

• 💤 Readiness scores that help you decide whether to rest or push today

Seeing trends over time can be incredibly motivating! As you consistently practice vagus-nerve breath work and recovery strategies, your sleep may deepen, stress scores may decline, and your HRV may improve—all real, measurable signs that your nervous system is adapting and healing. This kind of biofeedback makes health feel less like guesswork and more like guidance, especially when you’re trying to break out of chronic stress patterns or persistent fatigue.

Heart Rate Variability (HRV): What Is It and What Should It Be?

Heart Rate Variability (HRV) refers to the small, natural variations in time between each heartbeat. Even if your heart rate is 60 beats per minute, those beats are not meant to be perfectly and evenly spaced ... and that’s a good thing! A healthy heart is responsive and adaptable, constantly adjusting to breathing, movement, stress, and rest.

HRV measures how flexible your nervous system is in real time. In functional medicine, HRV is often used as a window into how well your body is coping with stress and recovering from it.

HRV is closely linked to vagal tone because the vagus nerve is the primary driver of the parasympathetic (“rest and digest”) nervous system. When vagal tone is strong, the vagus nerve can effectively slow the heart rate during exhalation and relaxation. This creates greater variability between beats, resulting in higher HRV.

Higher HRV generally reflects better nervous system balance, stress resilience, and recovery capacity. Lower HRV, on the other hand, can indicate chronic stress, inflammation, poor sleep, overtraining, or nervous system dysregulation, where the body remains stuck in a sympathetic (“fight or flight”) state.

So why is this important to know? What makes HRV especially valuable is that it’s trainable. Practices that stimulate the vagus nerve—such as slow diaphragmatic breathing, extended exhales, meditation, quality sleep, and appropriate exercise—often lead to measurable improvements in HRV over time.

This is why tools like the Oura Ring are so helpful! They allow you to see how lifestyle choices and nervous system regulation practices are affecting your body beneath the surface. In essence, HRV acts as a real-time feedback loop, showing how well your vagus nerve is doing its job of helping your body shift into healing, repair, and balance.

What Should Your HRV Be?

A “normal” HRV can be a little tricky, because HRV is highly individual. There isn’t one perfect number that applies to everyone, but there are helpful ranges and patterns to understand. Most wearables (including Oura) report HRV using rMSSD, which is the most relevant metric for parasympathetic/vagal activity.

• Below 20 ms Very low — often associated with chronic stress, poor sleep, illness, or burnout

• 20–40 ms Lower range — common in people under ongoing stress or early in a healing journey

• 40–60 ms Moderate / average — reflects decent nervous system balance

• 60–100+ ms Higher HRV — often seen in well-recovered, resilient nervous systems

  
  

Many healthy adults fall somewhere between 30–70 ms, depending on age, fitness, genetics, and lifestyle.

In conclusion, functional wellness is ultimately about building bridges between how you live and how you feel. Breath work teaches your body that it can relax and recover. Wearables give you the data to guide intelligent choices. And thoughtful practices tied to your daily routine make consistency sustainable.

When you build health from the root—starting with nervous system regulation and supported by insight from your own metrics—that’s when transformation happens! And that’s what I'm here to help you with, every step of the way.

References:

• Shaffer, F., McCraty, R., & Zerr, C. L. (2014). A healthy heart is not a metronome: An integrative review of the heart's anatomy and heart rate variability. Frontiers in Psychology, 5, 1040. https://doi.org/10.3389/fpsyg.2014.01040

• Laborde, S., Mosley, E., & Thayer, J. F. (2017). Heart rate variability and cardiac vagal tone in psychophysiological research – Recommendations for experiment planning, data analysis, and data reporting. Frontiers in Psychology, 8, 213. https://doi.org/10.3389/fpsyg.2017.00213

• Laborde, S., Mosley, E., & Thayer, J. F. (2022). Heart rate variability and cardiac vagal tone: Theories, measurement, and implications for health and performance. Neuroscience & Biobehavioral Reviews, 142, 104896. https://doi.org/10.1016/j.neubiorev.2022.104896

• Clancy, J. A., Mary, D. A., Witte, K. K., Greenwood, J. P., Deuchars, S. A., & Deuchars, J. (2014). Non-invasive vagus nerve stimulation in healthy humans reduces sympathetic nerve activity. Brain Stimulation, 7(6), 871–877. https://doi.org/10.1016/j.brs.2014.07.031

• Lucas, L. (2024). The vagus nerve solution: Optimize total body health with simple techniques to reduce stress, soothe anxiety, improve digestion, and ease chronic pain. Everwell Publishing.