What Is the Vagus Nerve, and What Does It Do?

A few days ago, we passed the 12,500 VNS sessions mark. That’s 12,500 pre-session face scans, 12,500 VNS sessions, and 12,500 post-session face scans. That is a lot of data. And here’s what it’s telling us so far.

30 minutes of yōjō = 90 minutes of meditation

A single yōjō vagus nerve stimulation (VNS) session lifts heart rate variability (HRV) by 3.76 ms on average. In a study published in 2025, 90 minutes of meditation lifted participants’ heart rate variability by 4.68 ms.

Both practices produce real physiological change. They share the same target: parasympathetic activation and increased vagal tone. We’re comparing them with sustainability in mind. For most working professionals, 30 minutes of hands-free VNS might be easier to manage than 90 minutes of meditation.

HRV improvement compounds

On average, yōjōers see a 1.5% improvement in HRV from established baselines after 1 month. That doesn’t sound like much, but the rate of change increases over time.

Month 1 — HRV up 1.5% from baselineMonth 3 — HRV up 4.7% from the baseline set in Month 2Month 6 — HRV up 16.5% from the baseline set in Month 5

Nervous systems respond better the more you train them.

yōjōers have a favorite mode

Of all these thousands of sessions, 49% were done in the Stress Mode. Sleep Mode came in second with 27%.

We’ve also seen a healthy spirit of exploration. Most of our members try all modes before eventually settling on one.

Why this matters

This shows that daily vagus nerve stimulation effectively supports nervous system health. It also proves that technology that was only a few years ago confined to the clinical setting can, in fact, fit into real life.

And it proves that yōjō’s device + human coaching + gentle data tracking boosts adherence, helping people stimulate their vagus nerve every day (more than once a day on average, based on the data).

Everything we’re learning — how our members yōjō, why they yōjō, what yōjōers need from their device, coach, or platform — is going into yōjō experience and making a bigger positive impact.

Much of it has already helped refine the yōjō Stone, our latest device, launching towards the end of the year.

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A few months ago, the gROW Atlantic Team, Vicki Anstey and Dr. Sophie Bostock, asked us a simple question: could yōjō help the team not only survive crossing the Atlantic in a row boat but make it across faster than any other female team?

We said we think so, let’s see.

This December, Vicki and Sophie will join the World's Toughest Row 2026: a 3,000-mile rowing race starting in San Sebastian, La Gomera, Canary Islands and ending at Nelson's Dockyard, Antigua. They're aiming to break the current world record for a female pair — 38 days and 12 hours — rowing two hours on, two hours off, for an estimated 1.5 million oar strokes.

They’ll face storms, salt, and silence. Sleep deprived and alone, they’ll have no support boat alongside them, no shore team, and no shortcuts — just two athletes, an ocean, and whatever they have brought with them, which happens to include their yōjōs, because peak performance, rapid recovery, and sustained endurance come from a well-regulated and flexible nervous system.

Meet the record-breakers

Vicki is a world record-breaking adventurer, TEDx speaker, and a leading expert on resilience, mindset, and human performance. She is a Certified Stress & Resilience Coach, UK Ambassador for Inspiring Girls, and one of the first women finalists on Channel 4's SAS: Who Dares Wins. She holds two world records for rowing the Pacific Ocean unaided in 2021 and for cycling 3,000 miles across America in the 2024 Race Across America.

Sophie is a sleep scientist with a PhD, the founder of The Sleep Scientist, and a national authority on sleep, recovery, and the nervous system. She has worked with elite athletes, surgeons, military personnel, and Olympians on the science of rest, alertness, and resilience under pressure.

Between them, they hold decades of expertise in the exact systems yōjō exists to support: rest, recovery, regulation. Which is what makes this partnership feel so natural.

No strangers to nervous system health, Vicki and Sophie have been thinking about, teaching, and living autonomic flexibility long before they ever set foot in an ocean rowing boat.

What their bodies will face out there

It’s called the World’s Toughest Row for a reason.

More people have climbed Everest than have rowed across an ocean. For a two-person crew, the load is particularly unforgiving. There is no third pair of hands. If one of you is sick, injured, or simply exhausted, the other one rows.

To understand why this matters to us, it helps to understand what around 38 days of that environment does to a human nervous system.

The autonomic nervous system has two branches that work in balance. The sympathetic branch drives action, picking up heart rate, quickening breathing, elevating cortisol levels, and narrowing attention. The parasympathetic branch, carried largely by the vagus nerve, does the opposite. It slows the heart, deepens the breath, and shifts the body into the state where repair, digestion, and recovery happen.

In healthy daily life, these two branches alternate fluidly. You activate when you need to act. You recover when you don't. That flexibility — the ability to shift between drive and recovery on demand — is what we mean by autonomic balance, and it shows up in measurable signals like heart rate variability (HRV).

Ocean rowing collapses that flexibility.

Sleep is fragmented into 90-minute windows (usually less!), never allowing a full recovery cycle. Rowing through the night completely disrupts circadian rhythms. Cortisol stays elevated. Cold and salt exposure keep the sympathetic system primed. Caloric deficit and dehydration add further stress signals. The body, in short, is held in a state of near-continuous sympathetic activation for six weeks. Unfaltering stress.

When the dominant state will be one of stress, could parasympathetic support give Vicki and Sophie the snatches of recovery they need precisely when they need it?

Where we come in

yōjō exists for one reason: to help people maintain autonomic flexibility — the ease with which the nervous system shifts between drive and recovery. We do that by supporting parasympathetic activity through daily vagus nerve stimulation, human coaching, and data-driven personalized programs.

For Vicki and Sophie, who are about to test their nervous systems under conditions that compress years’ worth of physiological stress into 6 weeks, yōjō will be providing on-the-go access to their parasympathetic systems and a way to boost nervous system recovery through the full arc of this journey.

That means yōjō devices on board, with daily vagus nerve stimulation built into their training and racing routines. It means personalized protocols, tuned to each athlete's physiology, training load, and recovery profile. It means ongoing science support, from prep to finish, our science team reviewing data, iterating protocols, and answering the questions that come up along the way.

This is the cleanest possible expression of the science we build around. Helping two of the most physiologically literate athletes access recovery under conditions designed to deny it to them is precisely what yōjō is here to do.

Follow along

This is the start of an eight-month journey that will end on a beach in Antigua in early 2027. Between now and then, we'll be sharing the science, the milestones, and the data from Sophie and Vicki’s first training rows to their return to life after the race, and will be digging much deeper for a three-part documentary series called Do you, better.

If you want to follow along on LinkedIn and Instagram, we'd love to have you.

As a GP, I understand the science behind vagus nerve stimulation. I know the vagus nerve is the body’s master regulator, that it connects the brain to the body, and that it governs that all-important shift from ‘fight-or-flight’ into ‘rest-and-digest’. I know the mechanism, but I don’t think I really expected the impact.

I definitely wasn’t prepared for how much of a difference I would feel.

How I yōjō

My routine is simple.

Every night, when I go to bed, I grab my yōjō. I apply the gel to the earpiece and pop it in my ear. I find a comfortable intensity and then just let the gentle electrical pulses do their thing.

I also use it during the day when I remember. This is becoming more frequent because the benefits have become harder to ignore.

The sensation took a little getting used to — little electrical zaps that you have to set to your comfort level — but it quickly became something I looked forward to rather than something I had to remind myself to do.

What surprised me most

Sleep. Sleep. Sleep.

I’ve always been someone who can lie awake, mind whirring, tossing and turning for hours before finally dropping off. In the first few days of using yōjō, I noticed I was falling asleep faster.

At first, I put this down to coincidence, a good few days, or a placebo effect. But now, several months in, I can say with confidence that it is none of these.

On the nights I use yōjō versus the nights I don’t, there is a noticeable difference.

My Garmin data backs this up, too: sleep quality has genuinely improved, not just my perception of it. And that matters to me as someone who values having objective data alongside improvements in how I feel.

Getting to sleep faster has been the biggest win.

Anyone who knows that particular frustration of lying in the dark, wide awake, brain refusing to switch off, will easily understand just how significant this has been.

A shift in how I think about my nervous system

Something I didn’t anticipate was how using yōjō would make me more intentional about my parasympathetic nervous system more broadly.

Understanding something intellectually and actively working on it are two different things. yōjō has brought vagal tone into my daily awareness in a way that’s spilled over into other habits.

I now use the physiological sigh regularly — a double inhale through the nose followed by a long exhale — which is one of the fastest ways to manually activate your parasympathetic nervous system. It’s the kind of technique I’ve always known about, but yōjō has made me more motivated to layer these practices together.

I feel more in control of my own nervous system regulation, and that feeling of agency is something I hadn’t expected to value as much as I do.

Would I recommend it?‍

I started this journey curious. I’m continuing it as a genuine convert.

Whether you’re someone who struggles to wind down at night, feels chronically overstimulated, or simply wants to feel more grounded in your own body, yōjō offers something that is both accessible and, in my experience, genuinely effective.

The science was always there. And now I’ve felt it for myself.

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