Nasal breathing at high intensities

Training
1

Hi all, first post, I apologise if I’m doing this wrong. I did a search and didn’t find anything, hence new topic? Let me know if this is wrong.

Anyhow, I coach juniors on a local NICA MTB team. One of the other coaches (who presents himself as a training expert but who has no certifications) has been incessantly telling our inexperienced riders (13-17 year-old mid-level MTB riders) that they should be focused on breathing through their noses at all intensities. Specifically he is advocating for nasal in, mouth out breathing. I’m extremely sceptical and am actually worried about potential harm in this advice. It’s mid-season, right in the middle of our race schedule. He will prescribe this for intense intervals. All of the riders except 1 are using RPE only and frankly very few of them have much grasp on what ‘hard’ and ‘easy’ even mean. So RPE isn’t super reliable. In reality they are bottle rockets that go ‘hard’ and ‘harder’.They are very green.

His purported benefits are:

  1. ‘improved oxygen uptake’
  2. Nitric oxide (NO) production in the nose as a performance enhancer / bronchodilator

Now, I am very sceptical of these claims. Let’s start with Claim 2. My understanding is that while it is true that NO is introduced through nasal breathing, the ‘production’ of NO falls of significantly at high intensities and takes a long time to recover[1]. If anyone has any additional information to support or refute this, I’m all ears. So, based on this single study, it seems like the NO effect is pretty minimal once you have hit a high intensity. Additionally, breathing through both your nose and your mouth simultaneously still involves air in your nasal pathway and would therefore release the available NO into the lungs. Based on [1], there is a finite amount of NO that can be delivered, and breathing ‘normally’ doesn’t exclude this. I’ve never heard anyone encourage mouth only breathing.

So to Claim 1. What exactly he means by ‘improved oxygen uptake’ is unclear as it is quite vague and the pulmonary system is complex. I am a believer in controlled breathing/belly breathing. No arguments that shallow panting is ineffective. However, I think that the benefits that come from working on your breathing are mostly independent of which orifice(s) you breathe from. Hydraulics tells us that the minimum resistance will come from using both simultaneously, and for most riders this is the most natural. I’m not refuting other benefits of nasal breathing including filtering of particles and conditioning of the air. But at high intensities, I just feel like the nasal passageway is insufficient. In fact, from what I see VO2max and respiratory exchange ratio both decreased in supra threshold efforts when using nasal breathing in a short effort[2]. This in direct conflict with Claim 1. I tried to do some ergometer tests on myself and could barely manage sweet spot intervals when breathing through my own deviated septum that also suffers from allergies (N=1).

From what I can tell, there are a lot of trendy influencers right now extolling the virtues of nasal breathing, but I can find very little compelling evidence to back it up. I’m not sure why this is trending right now. I’m old enough to remember Breathe Right strip craze in the 90s, so it feels like the return of a fad to me. The studies that do show benefits of nasal breathing tend to be done at low intensities and to not account for the confounding factors of the implicit breathing control that comes from focusing on your breathing during a study like this. Am I missing something? Is there some seminal paper I’m not seeing?

I’m inclined to believe that there may be some benefits to working on controlled breathing with experienced athletes, particularly at low intensities and in the off season. This seems to be shared by Colby Pearce in this now somewhat dated Podcast (The Science of Breathing, with Dr. James Hull). I enjoy Dr. Hulls perspective on the subject as well in this episode. He basically dismisses the nasal breathing trend as fad and recommends healthy riders breathe naturally. His credentials are quite authoritative and it seems like a very balanced approach.

My concerns on our team is that the guidance for nasal breathing are being made on supra threshold intervals (Friel’s Zone 5c level) with relative beginners while the athletes are riding technical trails. Whether most these athletes should even be doing these types of intervals is another topic as well. For those familiar, I feel like the team has strayed from NICA principles.

Why am I concerned? 1) Fundamentally, I know that the athletes instincts will kick in and they will breathe as needed. But, having them focus on what is likely an impossible task introduces the possibility that they will worry that they are physiologically inferior to others. They may say to themselves “I’m supposed to be able to do this, but I can’t. What’s wrong with me.” 2) It’s a distraction. These riders should be worried about navigating terrain, gaining confidence, and having fun riding their bikes. Young healthy riders should be focused on the low hanging fruit in their training not chasing what are at best obscure marginal gains.

But, I’m curious to cast my net a little wider and see what some of the other opinions are on this subject. Thanks in advance. I’d love other papers and resources to review. Genuinely curious on this one.

[1] Lundberg JO, Rinder J, Weitzberg F, Alving K, Lundberg JM. Heavy physical exercise decreases nitric oxide levels in the nasal airways in humans. Acta Physiol Scand. 1997 Jan;159(1):51-7. doi: 10.1046/j.1365-201X.1997.68339000.x. PMID: 9124070.

[2] Recinto C, Efthemeou T, Boffelli PT, Navalta JW. Effects of Nasal or Oral Breathing on Anaerobic Power Output and Metabolic Responses. Int J Exerc Sci. 2017 Jul 1;10(4):506-514. doi: 10.70252/EHDR7442. PMID: 28674596; PMCID: PMC5466403.

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Not going to answer question directly. While running cross country in middle school and high school, I wish someone had taught me to breathe nasal first, then when that wasn’t sustainable nose in and mouth out, and then mouth only at the highest intensities. I’m now in my sixties and seeing health benefits and strength training gains with daily breath work (mostly box breathing at the moment). Started with StrongFirst (Simple&Sinister, then Second Wind Express course). Then last year with Coach Tim Cusick’s JoinBaseCamp, he calls it the gears of breathing (1st gear: nose only, 2nd gear: nose-in/mouth-out, and 3rd gear: mouth only). Its made a small but meaningful improvement on the bike. Your mileage may vary and all that.

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3

I’m a complete amateur and only ride for fun, so my statements aren’t scientific at all. I’m 68 and have been riding my road bike for 17 years, always with my mouth open. For me, nasal breathing increases concentration and tends to be a bit distracting. I also find that I can control my inhalation and exhalation better through my mouth. If I try nasal breathing, I automatically switch back after a few minutes. My open mouth also occasionally causes me to involuntarily get protein (flies) :wink:
For example, I see Nils Politt driving with his mouth open and he is certainly a great motor

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It becomes a habit rather quickly. On the condition that intensity is low enough to comfortably do it.

5

There is a saying in German: What little Hans doesn’t learn, big Hans will never learn. :rofl:
But I will try again with less effort and see if it helps me

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The way I see it, based on personal experience and thinking… the breathing topic seems incredibly over-hyped.

Sure, obviously nose breathing has benefits in freezing weather since the noise cavity warms up the air. In winter I run with a thin Buff over my mouth - even cloth so thin that I can easily breathe through it seems to fix the temperature problem immediately for me. Climbers on Mount Everest do the same.

I do use those nose plasters for easy running because it feels good, but when going past Z3 is not enough and of course I do mouth breathing. I ran without them, mouth breathing from Z1 onwards with no issues whatsoever for years, before.

I believe rhythm, cadence and deep belly breathing is much more important than which hole it goes through, but all of it can be just left up to nature. The importance of the first three is kind of obvious as if you do it wrong you notice yourself immediately for purely physical reasons. If it feels right it’s right.

Finally, if nose breathing was indeed so important, evolution would have selected for it anyways, and we would not be capable of mouth breathing anymore. It seems obvious that the mouth is absolutely intended to be used when you need high volumes of air.

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From the original question, teaching young people sports. Breathing is very important. Through your nose is better - but mine is generally full of snot. But, if you want to be good you need to concentrate on your breathing. Often we need to hold a pace for 10 minutes that our bodies only want to keep for 1 minute. You need to be in control, take full breathes in and out, and in control. Concentrating on that makes the pain more manageable, and increases the oxygen levels. If I am rowing I also need to concentrate on taking a good pull. On a MTB, taking good corners. It is an exercise for beginners, if they can not concentrate and control themselves then they can not get good results. When you are going full you need to concentrate on a lot more. Teaching simple breathing techniques when not going too hard is a good lead in to a lot more. In that respect it is a good exercise. People need to practice control and focus.

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I’m not doing it on higher intensities, at least not intentionally. But using it consciously on low intensities learned me to control rhythm and depth of breathing to become more efficient at it. I used to have a rather shallow breathing, now it just comes naturally.

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Thanks, to be clear the nasal breathing is being prescribed at high intensity, and without prior low intensity introduction.

Fundamentally, I’m hoping to see some papers and evidence for these nose breathing claims. I’m all about evidence-based approaches.

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Not every answer has a clear set of supporting studies. I’ve lowered my HR by about 3-5bpm at endurance and low tempo pace. No longer shallow mouth breathing in life and on the bike. Reduced nose congestion throughout the day. Better sleep at night. I have allergies and nose breathing on the bike is still challenging but with practice over a year it’s getting easier at low endurance. Then switch to nose in and mouth out until the intensity is so high I need all mouth breathing, but always in control.

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Hi, I agree with most of this. I think this claim of ‘3-5 bpm’ at low intensity should actually be really testable.

I’m not convinced whether it’s the nasal or intentional breathing that is having the most impact, that should be testable as well.

At high intensity, which is what my question is about. The data I’ve seen seems pretty clear that vo2 max is suppressed (obviously) with anything any kind of restrictive breathing. I’m looking for anything to the contrary, as this is what is being prescribed on our team.

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From 2017
(https://www.researchgate.net/publication/313090569_Oral_versus_Nasal_Breathing_during_Moderate_to_High_Intensity_Submaximal_Aerobic_Exercise)

"5. Conclusions Nasal breathing was more efficient strictly based on the ventilatory equivalents for oxygen and carbon dioxide. However when other variables are considered together, it is likely that oral breathing represents the more effective mode, particularly at higher exercise intensities. Anecdotally, most individuals prefer to breath through the mouth at moderate-to-high intensity exercise. Nasal breathing produced oxygen uptake values that were approximately 10% lower compared to oral breathing and there are a number of possible explanations. We propose that the greatest contributing factor is the inability to reach a steady state oxygen level, but also consider that increased anaerobic energy "

But there is an N of 1 of a high level triathlete increasing Vo2 max with nasal only breathing. Study participants did not appear to be highly trained, as this was not specified.

from 2025

" Conclusions

In young healthy subjects, an exclusively nasal respiration induces significant impairment on peak exercise capacity at CPET due to ventilatory limitation, with only minor effects on metabolic parameters at rest and in submaximal effort."

again, not elite or highly trained athletes, and they specifically say "Similarly, elite athletes may exhibit different behaviours under the same circumstances; future trials conducted on this population may be helpful.
"

I think as is frequently the case, one element that shows a benefit toward a particularly strategy is then extrapolated out, incorrectly. “Nose breathing increases NO which is a bronchodilator; therefore always mouth breathing will enhance performance”. While neglecting that nasal breathing will decrease oxygen intake, which will have a much larger negative performance impact than any marginal gains of increased NO.

I suspect breathing is a bit like cadence; generally the athletes self selected rate is optimal. BUT ALSO - every athlete is different and unique.

Personally, I nose breathe until I can’t. Mainly because nose breathing adds the extra filtering and humidifying, so it’s probably just generally healthier, and not for any specific performance reasons.

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You may not be able to achieve the same results as I saw. Also, in my testing it’s nasal (or nasal in, mouth out) and not intentional mouth only.

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For me its nasal only for recovery rides only. I’ll snot up too much and I don’t have large nostrils. LOL

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There is no definitive answer for all cases.

  1. It is better to breathe through your nose when you can.
  2. Say (example) that air from your nose is 5 % more efficient than though your mouth. If you can breath 10% more oxygen through your mouth, then that will give you more oxygen.

So, there is no rule. The reply depends on the size of your nasal passageways, and the sport. You can not give the same rules to someone with a large nasal passageway as someone with a small one. If you want references instead of experience then ChatGPT and Grok give better answers. It is impossible to always breathe though your nose. A question such as: are there studies showing that at high intensities nasal breathing is impossible? will give you your information.

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Say (example) that air from your nose is 5 % more efficient than though your mouth.

I’m looking for any kind of supporting evidence that a statement like this could be true. At very low intensity and for anaerobic weight lifting there have been a few studies. I’ve not seen anything remotely convincing that this is true for aerobic work anywhere near LT2 or even LT1 for that matter.

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In my second link from 2025. :slight_smile:

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You know what’s funny? I’m the opposite! The less I breathe through my nose, the more I snot up! When I’m going hard I’m still having to clear out my nose, which is a challenge when you’re in the middle of the field. I definitely see some pros on TV who have a disgusting string of snot hanging out their nose. This is me too!

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But that paper suggested nasal only breathing was suboptimal?

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I’m sorry, I somehow managed to turn around your question in my brain. You are right, they both are saying nasal breathing is less efficient at high intensity.

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