Activate the Vagus Nerve for Better HRV and Immunity

The vagus nerve is one of the most powerful levers you have for managing stress, improving recovery, and optimizing long-term health. It acts as the primary communication highway between your brain and your body's major organs, directly influencing your Heart Rate Variability (HRV), immune function, and ability to shift from a stressed state to a calm, restorative one. Understanding how to activate the vagus nerve gives you a practical, measurable way to improve your physiological resilience.

What is the vagus nerve and what does it do

The vagus nerve is the primary component of your parasympathetic nervous system, acting as the control center for your body's rest and digest functions. It originates in the brainstem and wanders through your neck, chest, and abdomen, connecting your brain to major organs like your heart, lungs, and gut. When stimulated, the vagus nerve sends a signal to your body that it is safe, which actively lowers your heart rate and reduces stress.

This pathway is directly responsible for controlling your Heart Rate Variability (HRV). A highly active vagus nerve leads to a higher HRV, indicating that your body is resilient, adaptable, and primed to perform.

Increasing vagal tone

The vagus nerve is analogous to a muscle; you can train it to get stronger. Increasing vagal tone (vagus nerve activity) and heart rate variability is one of the most practical ways to improve your overall wellness quickly. We can activate the vagus nerve, and hence influence parasympathetic tone (the deactivating branch of the autonomic nervous system), with breathing exercises, massage, intermittent fasting, taking omega-3 supplements, cold/heat thermogenesis, and exercise, among other things.

Behaviors like laughing, sex, chanting, gargling, and singing also activate the vagus nerve and in turn the parasympathetic nervous system.

Ways to improve vagus nerve function, increase HRV, and boost immunity

Diaphragmatic breathing

Voluntary regulation of internal bodily states (e.g., actively reducing your heart rate throughout the day with conscious breathwork) increases emotional control and psychological well-being. The working principle when thinking about calming the system is to limit the number of sensory inputs (i.e., sound, light, and potentially certain scents) and use conscious breath or body scanning (paying attention to parts of the body and bodily sensations in a gradual sequence from feet to head) as a mechanism to focus attention away from the mind. As little as 1 minute of diaphragmatic breathing a few times per day has been shown to have a beneficial effect on the cardiopulmonary system and enhance parasympathetic activation.

One of my favorite ways to activate vagal tone through breathwork is the following:

• breath in to the count of 5
• hold to the count of 5
• breath out to the count of 5
• wait to the count of 5 before breathing back in

This type of rhythmic breathing stimulates your parasympathetic nervous system and lowers stress levels while also increasing your vagal tone. There are a lot of great resources to tap to better understand various techniques. But overall, don't worry so much about how you are doing it, just do it.

The simple act of being still and consciously minding your breath and/or parts of your body can help you stay in the present moment, which is where "peace" lives. These small, mini moments of "peace" help to mitigate "negative stress accumulation," reduce anxiety, and as a result, can improve sleep onset latency and capacity to manage stress/control emotional response, promote autonomic balance, boost immunity and just generally make you more enjoyable to be around.

Cold thermogenesis

Cold thermogenesis (CT) is the practice of exposing yourself to cold temperatures. Research has shown that it has a positive influence on health and longevity by changing gene expression and fat cells. Cold adaptation offers a huge advantage in many different aspects of medicine, not only for obesity and diabetes, but for performance and longevity as well.

Acute cold exposure will activate the vagus nerve. Your sympathetic system (fight or flight) decreases when your body adjusts to cold, while your parasympathetic system (rest and digest) increases. There's actually a physiologic change that occurs that increases testosterone, growth hormone, and metabolic efficiency.

CT ignites your body's natural healing powers by providing long-lasting changes to the immune, lymphatic, circulatory, and digestive systems and generally enhances overall quality of life—all while leaving you feeling relaxed and refreshed. Do not start by jumping into a cold tub right away. You will torture yourself and leave behind a very unpleasant memory.

It is important to "cold adapt" first. I began by simply dunking my face into ice cold water. Later I upped my exposure by taking cold showers for 30 seconds, then slowly increased the time.

I also live in a cold climate, so for a good 6 months of the year I can take advantage of a nearby lake to help stimulate cold thermogenesis. Here are some useful CT protocols to start your path to cold adaptation (timing, duration, temperature, food, and other considerations).

Hydrating, eating, and fasting for gut health

Gut health is directly correlated to immune health immune health. One of the simplest things you can do to promote it is to drink water. Drinking lots of cool water (8, 9, 10 glasses a day), will activate the vagus nerve in your gut.

Probiotics are the "modulators of the microbiota"—they can improve the feedback loop of the vagus nerve and the gut/brain axis. Probiotic bacteria strains such as L Rhamnosus have been shown in studies to have antidepressant-like effects and influence GABA receptors (which are calming to the parasympathetic nervous system and are mediated by the vagus nerve). A study on Parmigiano Reggiano cheese showed that it can have up to 10 million CFU of viable lactic acid bacteria per gram when you eat it, a seemingly delicious way to get beneficial bacteria!

Bifidobacterium longum (found in yogurt) is another important bacteria that reduces anxiety by acting through the vagus nerve via the gut. Check out this great resource on friendly bacteria that can improve gut health.

Fasting is also a known contributor to a healthy gut. It's been shown to strengthen the immune system by giving your body the chance to rest and recover (since it's not busy digesting food or defending against inflammatory agents in food). This state of rest can be especially helpful for taming autoimmunity (i.e., misdirected immune responses that occur when the immune system goes awry and attacks the body itself) and improves neurological responses.

You might notice in your WHOOP data that when you stop eating 3-4 hours prior to bed and your sleep need is met (essentially creating a 12-hour "fast"), you will see a higher HRV (assuming your training and recovery are in proportion). Digestion is a parasympathetic activity, so it competes with recovery resource allocation. Therefore, periods of not eating can be beneficial as all resources can go toward recovery and rejuvenation.

James Clear has an excellent "beginners guide" for folks who are interested in testing intermittent fasting. My favorite resource for all things therapeutic fasting and other nutritional considerations is from Dr. Jason Fung.

Light exposure

Getting in at least 20 minutes of natural sunlight within half-an-hour of waking up in the morning (even if it is cloudy), as well as watching the sky transition from day to night in the evening, reinforces your natural circadian clock and has been shown to promote healthy cortisol and sleep patterns. In principle, we want to incorporate behaviors that help facilitate our body's natural cycles. There is significant science that supports the important connection between an "aligned circadian clock" and both psychological and physiological well-being (including immune health).

Morning light exposure and watching the sky change at night are simple habits that will optimally prompt biological processes associated with regulating sleep/wake times, appetite, energy levels, hormone production, and body temperature. Other benefits include improved mood and alertness, better heuristic processing, as well as increased vitamin D production (key for healthy immunity) and physical strength.

Exercise the right amount

When talking about immune health and functional adaptive response to exercise, the goal should be to optimize the interplay between the cardiovascular system and nervous system. "Under-training" (too little load relative to capacity) and "overtraining" (too much load relative to capacity) can not only make us more injury prone, but also compromise our defense system. WHOOP Strain and Recovery data can be extremely powerful in helping guide your workouts and give you insight into how you are coping and adapting to not just training demands, but also "life load" demands (i.e., everything else that is not exercise).

Journal of Sport and Health Science suggests that being physically active makes you less vulnerable to getting sick. According to David Nieman, director of the Appalachian State University Human Performance Lab, "Our data show that physically active people have a 40-50% reduction in the number of days they're ill with acute respiratory infections." In short, exercise is good for us, mentally, physically, and emotionally!

There is a sweet spot however, a balance that needs to be considered between both training volume and intensity and life load volume and intensity (stress, regular daily activities, etc.) with how much time you can devote to recovery and sleep. WHOOP quantifies this and gives you valuable insight into how your body is adapting to exercise stimulus and life load.

Singing, humming, and chanting

Your vocal cords connect directly to the vagus nerve. Because of this anatomical link, vocalizing is a highly effective way to stimulate a parasympathetic response. Activities like singing, humming, chanting, and even gargling water create vibrations in the back of the throat that activate the vagus nerve.

Incorporating a few minutes of humming or singing into your daily routine helps lower your heart rate and signals to your body that it is safe, improving your HRV over time.

How to measure vagus nerve activity with HRV

You cannot manage what you do not measure. While you can feel the immediate calming effects of vagus nerve stimulation, tracking your HRV provides objective data on your nervous system's health. HRV is a direct indicator of vagal tone.

When you consistently practice habits that activate the vagus nerve, like breathwork, cold exposure, or prioritizing sleep, you will typically see an upward trend in your HRV.

WHOOP measures your HRV every night during your deepest stages of sleep, giving you a clear picture of your baseline. By monitoring your daily Recovery, you can see exactly how your lifestyle choices impact your autonomic nervous system.

Frequently asked questions about the vagus nerve

How can you quickly activate your vagus nerve?

The fastest way to activate your vagus nerve is through physiological sighs or diaphragmatic breathing. Taking a deep inhale through the nose, followed by a long, slow exhale through the mouth immediately signals the parasympathetic nervous system to lower your heart rate. Splashing cold water on your face also triggers the mammalian dive reflex, providing rapid vagal stimulation.

What are the symptoms of a weak vagus nerve?

A weak vagus nerve, or low vagal tone, often presents as a low HRV, high resting heart rate, and difficulty recovering from stress. You may also experience poor digestion, chronic fatigue, anxiety, and disrupted sleep patterns. Monitoring your daily metrics helps you identify when your body is struggling to return to a restorative state.

What is the best point to stimulate the vagus nerve?

The vagus nerve runs from your brainstem down through your neck, chest, and abdomen. The most accessible points for stimulation are the back of the throat through humming or gargling, the face and neck through cold exposure, and the diaphragm through deep, rhythmic breathing.