Cold Plunge & Vagus Nerve Stimulation: How Ice Baths Trigger Parasympathetic Reset

Kotaro Kojima
Jul 9
4 min read

In the realm of wellness, few therapies are as jarring—and as powerfully transformative—as the cold plunge. The initial shock of icy water may seem uncomfortable, but beneath the surface lies a profound neurophysiological reset.

At Flōtstone, we integrate cold immersion not just as a tool for athletic recovery, but as a targeted method to engage one of the most critical elements of your nervous system: the vagus nerve. When stimulated properly, the vagus nerve activates the parasympathetic nervous system, shifting the body out of stress and into recovery mode.

In this post, we’ll dive deep into the science of vagal tone, explore the relationship between cold exposure and stress regulation, and explain how cold plunging can help you build mental resilience, emotional balance, and long-term nervous system health.

What Is the Vagus Nerve?

The vagus nerve is the tenth cranial nerve, and it plays a vital role in regulating the autonomic nervous system—specifically the parasympathetic branch, which is responsible for rest, digestion, and recovery.

It runs from the brainstem through the neck, heart, lungs, and digestive tract. Sometimes called the “wandering nerve,” it controls:

Heart rate and blood pressure
Respiration and lung function
Digestive function and gut-brain communication
Emotional regulation
Immune system modulation

In short, a well-functioning vagus nerve is essential to staying calm, healthy, and balanced.

Vagal Tone: Why It Matters

Vagal tone refers to the strength and responsiveness of the vagus nerve. Higher vagal tone means your body can rapidly:

Lower heart rate after a stress spike
Reduce inflammation
Calm the mind
Return to homeostasis

Low vagal tone is associated with:

Anxiety
Depression
Chronic inflammation
Heart rate irregularities
Poor digestion

Improving vagal tone is one of the most effective ways to build stress resilience—your body’s ability to recover quickly after a challenge.

The Cold Shock Response: A Gateway to the Vagus Nerve

When you immerse your body into cold water—especially below 50°F—your body initiates the cold shock response, which includes:

Rapid breathing or gasping
Initial spike in heart rate and blood pressure
Peripheral vasoconstriction (blood vessels narrow)

But this is only the beginning.

As your body adapts to the cold, the vagus nerve is stimulated, and the parasympathetic nervous system kicks in. Within minutes, your heart rate slows, your breathing deepens, and your internal stress dial turns down.

This shift is measurable. Heart rate variability (HRV), a key indicator of vagal tone, increases after cold immersion, indicating improved nervous system flexibility and resilience.

Cold Exposure & Parasympathetic Dominance: How It Works

Here’s how a cold plunge leads to a parasympathetic reset:

Initial Stress Spike The body reacts to cold with a fight-or-flight sympathetic response—this is natural and expected.
Rapid Adaptation As you consciously control your breath and remain still, the body shifts from sympathetic activation to parasympathetic dominance.
Vagal Activation Cold receptors in the face and neck trigger the vagus nerve through the diving reflex, a mammalian trait that slows heart rate and prioritizes oxygen conservation.
Nervous System Reset With regular exposure, this shift becomes more efficient. The body learns to exit stress faster—training your nervous system to be more resilient under pressure.

The Mental Benefits: Cold as Emotional Training

Regular cold plunging isn’t just physical—it’s mental conditioning. By willingly entering discomfort, you train your mind to stay calm under pressure.

This translates to real life:

Less reactivity during stress
Improved mood regulation
Greater tolerance for emotional triggers
Increased willpower and clarity

Research has found that cold showers and cold therapy can relieve symptoms of depression and anxiety, likely due to vagus nerve activation and endorphin release. Researchers have concluded that repeated cold exposure improves emotional resilience, cognitive control, and stress adaptation—all linked to improved vagal tone.

Physical Benefits: Beyond Mental Health

Cold plunging also supports the body in tangible, measurable ways:

Reduced inflammation Cold exposure suppresses pro-inflammatory cytokines, aiding recovery from workouts, injuries, or chronic pain.
Improved cardiovascular function Vasoconstriction and vasodilation cycles improve circulation and vascular health.
Boosted immune function Cold plunging may increase white blood cell count and enhance immune surveillance.
Better sleep Parasympathetic activation before bed can lead to deeper, more restorative sleep cycles.

How Flōtstone Elevates the Cold Plunge Experience

At Flōtstone, our temperature-controlled plunge suite is set between 37°F and 50°F and includes:

Private rooms for focused calm
Heated linens for post-plunge recovery
Dorai quick-dry stone flooring
Lounge and prep space to relax before or after
Optional contrast therapy combining infrared sauna and plunge to enhance the circulatory and lymphatic benefits

Our plunge sessions are designed to be safe, comfortable, and transformative, even for beginners. Staff are trained to help guide breathing, pacing, and mental readiness.

How Often Should You Cold Plunge?

We recommend starting with:

2–3 sessions per week
Duration: 2 to 5 minutes per plunge (build up gradually)

With consistency, clients often report:

Decreased baseline anxiety
Faster post-workout recovery
Greater mental clarity
Improved sleep patterns
Stronger emotional regulation

For those combining sauna + plunge in contrast therapy, alternating hot and cold for 2–3 rounds can supercharge lymphatic drainage, muscle recovery, and mental clarity.

Train the Nervous System, Transform Your Life

At Flōtstone, cold plunging is more than just a trend—it’s a tool for long-term transformation.

By targeting the vagus nerve and activating the parasympathetic nervous system, each session helps recalibrate your stress response, restore balance, and sharpen the mind.

Whether you’re an athlete, entrepreneur, busy parent, or wellness seeker, building vagal tone through cold exposure can help you move through life with greater calm, control, and clarity. Ready to reset your nervous system?

Book your Cold Plunge or Fire & Ice session today.

Sources

Tipton, M. J. (2003). Cold Stress. Best Practice & Research Clinical Anaesthesiology, 17(4), 551–568.

Rymaszewska, J., Ramsey, D., & Chładzińska-Kiejna, S. (2008). Whole-body cryotherapy as adjunct treatment of depressive and anxiety disorders. Medical Hypotheses, 71(5), 914–921.

Kreuzfeld, S., et al. (2020). Cold exposure and cognitive performance: A systematic review. Frontiers in Neuroscience, 14, 1221.

Bretherton, B. et al. (2019). Vagus nerve stimulation in psychiatry: A review of the evidence and future directions. Frontiers in Psychiatry, 10, 58.