Most runners breathe through the mouth without ever deciding to. Then someone suggests trying the nose, they last about ninety seconds, and they conclude it does not work for them. This post is about why those ninety seconds are so hard, why they are worth pushing through, and how to make the switch without wrecking your training.
Why is nasal breathing so hard when I run?
Because your nose is a smaller airway than your mouth, and running through it exposes how fast you were actually going. Mouth breathing lets you move a lot of air quickly, which means you can run above a truly sustainable effort and feel roughly fine. The nose does not allow that. Slightly too fast, and you feel an urgent need to open your mouth within a minute or two.
That urgency is not a lack of oxygen. It is carbon dioxide rising a little faster than your body is used to, and your body reacting strongly to it. Runners with low tolerance to carbon dioxide feel breathless early, even when their legs and lungs have plenty left. This is one of the central ideas in the Oxygen Advantage method taught by Patrick McKeown, and it is why nasal breathing is uncomfortable at first for almost everyone, including fit people.
The discomfort, in other words, is information. It tells you where your breathing sits today, not where it has to stay.
What does CO2 tolerance have to do with running?
Quite a lot, because carbon dioxide is the main trigger for the urge to breathe, and how you respond to it shapes how breathless you feel at any pace. If small rises in carbon dioxide make you feel desperate for air, you will breathe harder and faster than the effort requires, and running will feel harder than it needs to.
Training with nasal breathing, mostly on easy runs, gently and repeatedly exposes your body to slightly higher carbon dioxide. Over weeks, the panic signal quietens. The same pace starts to feel calmer. You can get a rough sense of your current tolerance in about a minute with the BOLT test, which is a simple seated measure. Many runners are surprised to find their score is lower than their fitness would suggest, and it often rises alongside nasal training.
Is nasal breathing honest pacing, then?
Yes, and this is probably its most immediate benefit. Nasal breathing acts like a built-in effort cap. If you can keep your mouth closed comfortably, you are at a genuinely easy effort. If you cannot, you are not, no matter what your watch or your ego says.
Most recreational runners run their easy days too hard. The easy runs drift toward the middle, the hard days suffer, and progress stalls. Nasal breathing fixes this mechanically. You simply cannot cheat it. Slow is slow, and slow is where aerobic fitness is mostly built.
There is also a nitric oxide angle. Research associates nasal breathing with the release of nitric oxide in the nasal passages, and nitric oxide plays a role in opening airways and blood vessels. That is worth knowing, but it is not a miracle, and I would not build your training around it. The pacing honesty and the carbon dioxide training are the parts you will actually feel.
How do I start nasal breathing on my runs?
Slow down first, then close your mouth, and accept that the first few weeks are an adjustment. Here is a plan that works for most people:
- Start with easy runs only. Keep your mouth closed for the whole run. If you cannot, the run is too fast, so slow down until you can. Walking breaks are fine and are not a failure.
- Expect to run slower for a while. Sometimes a lot slower. This is temporary, and it is the training working, not the training failing.
- Keep hard sessions as they are. Intervals and races can stay mouth breathing for now. You are changing your easy days, not your whole programme overnight.
- Give it four to eight weeks. Most runners find nasal-only easy pace creeps back toward their old easy pace within a couple of months. Patience is the entire method.
- If your nose feels blocked, slow down further and let it settle. Exercise usually opens the nose within a few minutes.
Nothing here should feel like strain. If you are dizzy or fighting for air, you are pushing too hard, and the fix is always the same: slower. If you have any condition listed on our safety page, keep everything gentle and speak to your doctor before changing how you train.
Does this connect to anything beyond running?
It does, and this is where it gets interesting. How you breathe on a run is a live readout of your state, and learning to keep it calm under effort is a form of self-regulation you can use anywhere. That is the heart of Mind Body Regulation: noticing what your body is doing and having practical tools to steady it. Runners often find that the calm they build on easy nasal runs shows up off the road too, in meetings, in traffic, in the evening wind-down.
If you would rather not figure this out alone, our group sessions go through the technique together, and it is easier to stay patient when other people are slowing down alongside you.
What should my first nasal run look like?
Short, slow, and slightly humbling. Pick an easy 20 to 30 minute run, close your mouth, and let your pace fall wherever it falls. Do not judge the number. Take your BOLT score before you start the block, note it, and check again in a month. The run will feel different by then, and you will have the number to prove it was not your imagination.
