What Is Heart Rate Variability (HRV) and How Does the Vagus Nerve Control It?

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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You signed up for the gym. You bought the juicer. You downloaded the app, booked the class, and subscribed to the service. And then … life happened. Motivation dipped, the novelty wore off, and somehow three weeks passed without you doing the thing you genuinely, sincerely intended to do.

You are not alone. You are not lazy or lacking willpower. You are experiencing one of the most well-documented phenomena in health psychology: the intention-behavior gap.

What is the intention-behavior gap?

The intention-behavior gap describes the frustrating disconnect between wanting to do something and doing it consistently. While intentions are widely recognized as a direct determinant of behavior, they frequently fail to translate into action.

Just how big is this gap? Larger than most people expect.

Studies indicate that intentions account for 18 to 23% of the variance in behavior across a broad range of health contexts. Put another way: around 80% of our behavior is driven by factors other than our intentions. That is a sobering statistic, but understanding why it happens is the first step to doing something about it.

Motivation vs. volition

One of the most useful frameworks for understanding this process is the Health Action Process Approach (HAPA), developed by psychologist Ralf Schwarzer. HAPA proposes that the adoption, initiation, and maintenance of health behaviors involves a motivation phase and a volition phase. These are two genuinely different psychological processes, and they require different things from us.

In the motivation phase, something shifts in our thinking.

When we encounter external inputs — reading an article, receiving a medical diagnosis, or hearing about a friend’s experiences — our cognition changes. We form perceptions about our own personal risk of poor health, beliefs about the causes of illness or the effectiveness of different wellness strategies, and confidence in our ability to stop or start behaviors. These perceptions then form our intentions. And it often feels energizing, because this is the moment you decide to do something differently.

This motivational energy is also why the first actions feel relatively easy. Making a purchase or signing up for something are meaningful steps that require some motivation but relatively little ongoing effort. You do them once, they feel like progress, and that feeling is real.

But they are not the behavior itself.

The volition phase is where the real work begins. The adoption and maintenance of a behavior involves the development of self-regulatory skills and strategies. This is the phase most people underestimate and where most good intentions quietly expire.

Motivation gets you to the starting line, while volition gets you across it.

Why does volitional effort feel so hard?

The honest answer is that maintaining your new behavior competes with everything else in your life: habits that are already deeply embedded in your routine, the pull of immediate comfort, fluctuating energy and mood, and unexpected disruptions — not to mention the cognitive and physical effort it takes to remember the behavior and do it.

This is what is meant by self-regulation: your brain is having to override what it wants to do now in favor of what you planned to do.

Self-efficacy plays a central role here. When your belief in your own ability to carry out a behavior is low, you are more inclined to anticipate failure. This deepens your self-doubt and makes failure even more likely, in your mind. The effort and energy you were willing to put in to attempting the behavior dwindles.

The intention-behavior gap is not simply a matter of motivation running out. It is about whether you have the right tools to carry intention forward into consistent action, especially on the days when motivation is difficult to find.

Bridging the gap: what the science says actually works

1. Make a specific plan, not just a vague intention

One of the most robustly supported tools in behavior change science is implementation intention, a simple "if-then" plan developed by psychologist Peter Gollwitzer.

Rather than telling yourself "I'll do vagus nerve stimulation every day," you specify exactly when, where, and how: "If it's 9 pm and I'm sitting down to wind down, then I will use my yōjō vagus nerve stimulator for 30 minutes."

When you've made a specific if-then plan, your brain is essentially primed and ready. You notice the cue when it appears, and you already know exactly what to do next. No deliberating, no negotiating with yourself, no relying on willpower. The decision has already been made.

Essentially, you are outsourcing the decision to your environment rather than relying on in-the-moment willpower.

2. Plan for obstacles

Action planning is what you will do when things go smoothly. Coping planning prepares you for when they don't.

The idea is to imagine a scenario that will prevent you from performing your intended behavior and think of ways to cope with the situation so you still get to the behavior. Having a plan ready prevents a single disruption from derailing the whole effort.

For example: "If I work late and miss my exercise class, then I'll go for a walk before dinner."

3. Track your progress

Self-monitoring is one of the most consistently effective behavior change techniques identified in research. Interestingly, two things increase the likelihood of a person achieving a behavioral goal: being prompted to record behavior more frequently in a way others can see, and actively rather than passively tracking progress.

This doesn't need to be complicated. A simple habit tracker, a note in your phone, or the usage data in an app can all serve this purpose. What matters is creating a feedback loop: you see what you're doing (or not doing), and you can adjust accordingly.

4. Build self-efficacy by starting small

One of the most common reasons people abandon new behaviors is that they set themselves an unrealistically demanding starting point.

Every time we successfully perform a behavior, our confidence in our ability to do it again increases. Setting an easily achievable target to start sets us up for a series of small, early wins, giving us that “I got this” confidence that sustains effort over time.

Another way we can increase our self-efficacy is through positive self-talk. We are often our harshest critics, but the way we talk to ourselves about a behavior matters more than most people realize.

We believe what we hear ourselves say, so replacing “I always fail at this” with “I’m trying really hard and I know I can do it” directly strengthens self-efficacy, making you more likely to persist when things get difficult.

From effort to effortless — how behaviors become habits

Here is the genuinely good news: behaviors that currently require conscious effort do not have to stay that way.

With enough repetition in a consistent context, behaviors can become automatic. Your brain literally restructures itself to make the behavior less costly over time, gradually moving control from your conscious, decision-making mind to deeper, more automatic brain systems.

Early on, every repetition produces a noticeable gain in automaticity. Over time, these gains slow down until the behavior happens without much deliberate thought at all — like brushing your teeth.

Research by Phillippa Lally and colleagues at UCL found that this process takes an average of 66 days. Depending on the person and the behavior, it can take as few as 18 days to as many as 254.

The "21 days to build a habit" idea is a myth, but what isn’t is the fact that missing the occasional session doesn't derail the process. Automaticity resumes quickly after a slip.

If you can anchor your new behavior to an existing daily cue and make it something you have chosen for yourself rather than feel obliged to do, you are giving it the best possible conditions to stick.

Putting it all together

The intention-behavior gap is real, it's normal, and it affects almost everyone. But it is not insurmountable. The science points to a clear pathway.

1. Motivation sparks the intention.
2. Planning (both action planning and coping planning) bridges intention and behavior.
3. Self-monitoring keeps you honest and on track.
4. Self-efficacy — built through small, consistent wins — sustains effort.
5. And over weeks and months of repetition in a stable context, the behavior gradually shifts from something you have to consciously decide to do, to something that belongs to every day.

Whether it's daily vagus nerve stimulation, a new movement practice, or a dietary change, the right tools can help you turn your good intentions into a new habit.

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