Close Your Mouth. Then Look at the Data.
Nasal breathing during training has gone from fringe to mainstream. Some athletes swear by it. Some sports scientists roll their eyes.
Both camps are partly right. The research is real, but it is smaller and more specific than the hype suggests.
Here is what the studies actually measured, in whom, and what that means for your training week.
Why the Nose Matters
The nose is not just an air intake. Air breathed in through the nose carries nitric oxide produced in the nasal passages down to the lungs.
Lundberg and colleagues (1996) found that in healthy people, nasal breathing raised transcutaneous oxygen tension by about 10% compared with mouth breathing.
That is a resting finding in healthy adults, not an exercise performance result. It explains part of the mechanism. It does not prove a performance gain on its own.
Low Intensity Work: The Clearest Evidence
The best controlled study on nasal breathing during steady training comes from Rappelt and colleagues (2023).
Nineteen endurance trained adults, average VO2peak 53.4 mL/kg/min, rode 60 minutes at a self selected low intensity twice: once nasal only and once breathing freely. Power output was almost identical, about 145 to 147 W.
At the 60 minute mark, nasal only breathing produced:
Lower ventilation: 53.0 versus 60.0 litres per minute.
Lower breathing frequency: 27.3 versus 30.7 breaths per minute.
Lower oxygen uptake: 2.44 versus 2.61 litres per minute.
Lower blood lactate late in the session: about 1.2 versus 1.5 mmol/L.
Heart rate and perceived effort were the same in both conditions. Discomfort was marginally higher with nasal only breathing.
For a coach, that is a meaningful result. The same aerobic session was completed with less breathing work and no change in how hard it felt.
One more honest detail. Nasal breathing did not stop athletes drifting above the intended low intensity zone. And this was a single session with no familiarisation, so it tells us about acute responses, not long term adaptation.
Long Term Nasal Training
Dallam and colleagues (2018) followed recreational runners who trained with nasal only breathing for six months, then tested them at maximal effort breathing through the nose and through the mouth.
VO2max was about 7% lower with nasal breathing than with mouth breathing, but that difference was not statistically significant. Nasal breathing produced a lower breathing frequency, a lower respiratory exchange ratio and a lower ventilatory equivalent for oxygen.
In plain terms, the runners moved less air for the oxygen they used. That is a more economical breathing pattern.
The cautions matter. These were recreational runners, not elite athletes, and a 7% gap at maximal effort is not trivial even if it was not significant in a small study. Nobody should read this as nasal breathing raising VO2max.
The Counterpoint Sports Scientists Will Raise
Not every study favours the nose. LaComb and colleagues (2017) tested 19 people running at 50%, 65% and 80% of VO2max, breathing either through the nose or the mouth.
Mouth breathing produced higher breathing rate, ventilation, oxygen uptake and CO2 output at all three intensities. Nasal breathing was more efficient by ventilatory equivalents at 65% and 80% of VO2max. Even so, the authors concluded that mouth breathing was likely the more efficient mode overall, especially at higher intensities.
That is a fair reading of acute data in people who were not trained to nasal breathe. It is also why we never tell athletes to force nasal breathing through every session from day one.
Build it progressively. Start where the evidence is strongest, at low intensity, and extend the ceiling over weeks as the athlete adapts.
High Intensity Efforts: Performance Holds, Strain Shifts
Recinto and colleagues (2017) had nine people complete a 30 second Wingate sprint test twice, once breathing through the nose and once through the mouth.
Power output and performance did not differ between breathing modes. The respiratory exchange ratio was higher with mouth breathing, consistent with more overbreathing. Heart rate was higher with nasal breathing in the final seconds of the test.
So over a 30 second all out effort, closing the mouth did not cost power in this small sample. But it was not free either, and it is a long way from a full game.
At the top end of intensity in team sports, the mouth will open, and it should. Nasal breathing is a training tool, not a rule you obey when the game is on the line.
How We Use It at Vincere Protocol
Warm ups and low intensity aerobic work: nasal only. This is where the evidence is strongest, with lower ventilation and breathing frequency at the same workload.
Recovery between reps: return to the nose as fast as possible. It is a simple, visible marker of how quickly an athlete is regaining control.
Tempo and moderate work: nasal where possible, mouth when needed. Build the ceiling gradually across weeks.
Maximal efforts and match play: breathe however you need to. Then get back to the nose the moment the effort ends.
Monitor the athlete, not just the rule. If an athlete is visibly straining to keep the mouth closed, the intensity is too high for nasal work that day. Back off, return to the nose, and build again next session.
Light, slow, deep nasal breathing is the default we build. The research supports using it as an efficient pattern for the bulk of training volume, not as a replacement for maximal effort breathing.
FOR ELITE ATHLETES, THIS CAN HELP YOU
✔ Move less air for the same low intensity workload with nasal only breathing
✔ Lower breathing frequency and late session blood lactate during steady aerobic sessions
✔ Train a more economical breathing pattern over months of nasal training
✔ Use nasal recovery between reps as a clear marker of regaining control
Performance takeawayThe nose is your default for warm ups, aerobic volume and recovery. The mouth is there when maximal effort demands it.
Train the pattern in practice so it holds up under pressure.
Want this in your program? Enquire about Vincere Protocol for your team.
