The short answer: your nervous system has two sides: an accelerator that gets you going, and a brake that helps you rest and recover. The vagus nerve is a big part of that brake. It connects your brain to your heart, lungs and gut, and constantly tells your brain whether it's safe to slow down.
Your nervous system is everything. You experience life through it: every breath, every heartbeat, every moment of stress and every moment of calm. So it's worth understanding how it works.
The accelerator and the brake
Your nervous system has two sides.
The sympathetic side is your fight-or-flight mode. It's your gas pedal. It gets you up, gets you moving and gets you through the busy parts of the day.
The parasympathetic side is your rest-and-digest mode. It's your brake. It helps you slow down, digest your food, sleep and recover.
A healthy nervous system isn't sitting at 50/50. It moves freely between the two. You should be able to go from high stress to calm and collected in a reasonable amount of time. You get the school run done, then you can actually sit down with a cuppa. When the nervous system struggles to make that shift, that's when I start asking what's going on.
The Vagus nerve: your parasympathetic superhighway
The Vagus nerve is the longest nerve of its kind in your body. It runs from your brainstem down through your neck and into your chest and belly, connecting to your heart, lungs and gut along the way. It's a big part of your parasympathetic system, your brake.
Here's the part most people don't know: most of the vagus nerve's fibres carry information up to the brain, not down from it. Researchers estimate around 80% of its fibres are sensory.¹ So it's constantly sending messages from your body to your brain:
Am I safe?
Can I rest?
Can I sleep?
Can I breathe easy?
Your brain uses those answers to decide whether to keep the gas peda down or ease onto the brake.
When the nervous system gets stuck
The way I explain it in practice is like a car.
Stress, stuck on the accelerator. Life keeps the pedal down: work, kids, deadlines, broken sleep. The nervous system stays revved up. People in this place often tell me they're wired but tired. They're struggling to switch off at night, their mind's racing, and their shoulders are up around their ears.
Then the handbrake goes on. Nobody can run flat out forever. After long enough with the accelerator down, a lot of people hit a wall. They go from wired to completely flat, exhausted, foggy and running on empty, like the handbrake's been yanked on. That's not rest. It's the system running out of fuel.
I see this all the time in parents. Months of being on the go, then a crash. The tricky part is that both look like "stress", but they're very different states, and they need different things.
What the INSiGHT scan shows
Part of every first visit in our practice is an INSiGHT Neurological scan. One of the things it measures is heart rate variability (HRV): the tiny changes in time between your heartbeats.
HRV is widely used in research as a window into how your nervous system shifts between the accelerator and the brake.² I think of it as what's left in the tank: how much reserve your nervous system has to handle what life throws at it, and why some people struggle to bounce back on their own.
The scan doesn't diagnose anything. It gives us a clear picture of where your nervous system is at, and a baseline to track how things change over time.
Where chiropractic fits
This is where it gets interesting. Two people can walk in feeling "stressed" and need very different care.
If someone's nervous system is on edge, stuck on the accelerator, the last thing it needs is a lot of input at once. So we keep things gentle and specific.
If someone's running on empty with the handbrake on, the approach is different. Care is aimed at giving that nervous system a bit of a lift.
The scans let me tailor every adjustment to the nervous system in front of me, rather than doing the same thing for everyone. The goal of each adjustment is to support clear communication between body and brain. (More on that in What does a chiropractor actually do?)
Simple ways to help reset your nervous system
You don't need a scan to start looking after your nervous system. A wearable like a smartwatch or Oura ring can give you a rough picture of your HRV and sleep. Then try these:
If you're stuck on the accelerator (wired, can't switch off):
Breathe slowly. A few minutes of slow breathing, with the out-breath longer than the in-breath, is one of the simplest ways to ease onto the brake.
Protect your sleep. Put the phone away an extra hour before bed.
Give your brain a break. Put on a podcast or some music and do nothing else for 10 minutes.
Connect. A cuppa with a friend or a chat over the fence counts.
If the handbrake's on (flat, exhausted, foggy):
Move, gently. Wake up with movement, even a short stretch or walk.
Get outside. Take the kids for a 15-minute walk before school. Morning light and movement are a great combination.
Small and consistent beats big and occasional, every time.
Stressed parents, stressed kids: co-regulation
We talk about co-regulation in our practice all the time. It's the idea that our nervous systems pick up on each other's, especially between parents and kids.
Research has found that when mums were stressed, their babies' bodies showed signs of stress too, even after a short time together.³ Kids read our nervous systems before they read our words.
Think about school drop-off. When you're rushed, frazzled and running late, the kids tend to feel it, and the morning gets harder for everyone. That's not a parenting failure. It's just how nervous systems work together.
The flip side is good news: when your nervous system is in a better place, you're giving your kids a calmer one to borrow. That's why, when we look after families, it's normal for everyone to get a scan. Each nervous system gets care based on how it's presenting, and the whole family benefits from understanding each other a bit better.
Quick questions
What does the vagus nerve do? It connects your brain to your heart, lungs and gut, and is a big part of your rest-and-digest system. Most of its fibres carry information from your body up to your brain.
What does it mean to be stuck in fight or flight? Your nervous system stays on the accelerator longer than it should. People often feel wired but tired, with trouble switching off or sleeping.
What is heart rate variability? The small changes in time between your heartbeats. It's commonly used as a window into how well your nervous system shifts between stress and rest.
References
Breit S, Kupferberg A, Rogler G, Hasler G. Vagus nerve as modulator of the brain–gut axis in psychiatric and inflammatory disorders. Front Psychiatry. 2018;9:44.
Shaffer F, Ginsberg JP. An overview of heart rate variability metrics and norms. Front Public Health. 2017;5:258.
Waters SF, West TV, Mendes WB. Stress contagion: physiological covariation between mothers and infants. Psychol Sci. 2014;25(4):934–42.
