The short answer
Breathing is automatic, controlled by your brainstem, which mainly responds to the level of carbon dioxide in your blood. But unlike your heartbeat, you can also take control of it. That is what makes breathing exercises possible: by changing how fast, how deeply and through which route you breathe, you can change how your body and mind feel.
On this page
Why it helps to know how breathing works
Every breathing exercise on this site works through a handful of simple mechanisms. Understanding them makes the exercises easier to do well and easier to adapt: why a long out-breath calms you, why big fast breaths make you dizzy, why leaning forward eases breathlessness, and why breath-holding in water is dangerous.
The five things worth knowing
- Your lungs and diaphragm: the diaphragm does most of the work of breathing in; breathing out at rest is mostly passive. This is the basis of belly breathing and of the techniques for breathlessness.
- Normal breathing rate: 12 to 20 breaths a minute for an adult at rest. Calming exercises slow you to about five to seven.
- Nose breathing: your nose warms, moistens and filters air and slows the breath down. Some claims about it go well beyond the evidence.
- Carbon dioxide: the main driver of the urge to breathe. Over-breathing lowers it and causes tingling and dizziness.
- The vagus nerve: links breathing to your heart rate and to the calming side of your nervous system.
Automatic, but under your control
Most of the time you don’t think about breathing at all: your brainstem sets the rhythm, speeding it up when you exercise and slowing it when you sleep. But you can take over at any moment, slowing down, speeding up or holding your breath. Few other automatic body functions can be controlled so easily, and it is this overlap between automatic and voluntary control that gives breathing exercises their effects.
In this section
- How your lungs and diaphragm work, in plain English
How breathing in and out works, what the diaphragm and rib muscles do, why belly breathing moves your tummy, and why breathlessness uses neck muscles.
- What is a normal breathing rate? Adults and children
A normal breathing rate is 12 to 20 breaths a minute for an adult at rest. How to count it, the rates NHS staff look for, and children's rates.
- Nose breathing v mouth breathing: what the evidence says
What your nose does to the air you breathe, when mouth breathing is normal or a problem, what the evidence shows, and why mouth taping isn't advised.
- Carbon dioxide and over-breathing: why you feel dizzy
Why carbon dioxide drives your breathing, what over-breathing does to your blood, why it causes tingling and dizziness, and why the detox claims are wrong.
- The vagus nerve and breathing: what slow breathing does
What the vagus nerve is, how breathing affects it, why a long out-breath slows your heart, and which vagus nerve claims go beyond the evidence.
Common questions
What controls your breathing?
The brainstem, at the base of your brain, sets your breathing rhythm automatically. Sensors in the brainstem and in your neck arteries track carbon dioxide and oxygen in your blood, and adjust your breathing to keep them steady. You can override this for a while, but not indefinitely.
How many times a day do you breathe?
At a typical resting rate of 12 to 20 breaths a minute, an adult takes roughly 17,000 to 29,000 breaths a day, and more when active.
Why can breathing change how you feel?
Breathing is linked to the automatic nervous system that controls your heart rate and stress responses. Slow breathing, especially with a long out-breath, tends to shift that system towards a calmer state, partly through the vagus nerve.
References
- Asthma + Lung UK. How your lungs work.asthmaandlung.org.uk
- Zaccaro A et al. How breath-control can change your life: a systematic review on psycho-physiological correlates of slow breathing. Frontiers in Human Neuroscience, 2018.pubmed.ncbi.nlm.nih.gov
- Curley G, Laffey JG, Kavanagh BP. Bench-to-bedside review: carbon dioxide. Critical Care, 2010.pubmed.ncbi.nlm.nih.gov
First published 4 November 2026. Next review due November 2027. Spotted an error? Tell us and we'll correct it. Read our editorial policy.