Study Busts Exercise Myth About Mouth Breathing - Conscious Breathing Institute

Study Busts Exercise Myth About Mouth Breathing

Most of us have been taught that we have to breathe through our mouth when we exert ourselves, but I argue that the belief that mouth breathing is necessary while engaging in physical activity, even when we exert ourselves at the top of our ability, to a large extent is a myth.

A horse weighing 500 kilo (80 stones) have no problems whatsoever to oxygenate it’s powerful muscles while running twice as fast as Usain Bolt and only breathing through the nose. Indeed, we are not a horse, but still, it is an interesting fact.

In a study recently completed with ten CrossFit athletes at a CrossFit-gym in Karlskrona, Sweden, the results confirm my claim. CrossFit is mainly known for two things: a) the wide variety of exercises, and b) the training is done with timed high-intensity workouts.

Three of the study subjects were men and seven were women, and on average they exercise approximately five times a week for a total of five hours a week. In other words, they are fit and are usually exercising at a high intensity level with the accompanying forceful breathing in and out through the mouth. On average the participants were 40-years old.

To only include CrossFit athletes in the study was a conscious choice, partly because they are used to performing heavy physical exertion while using a stopwatch and partly because they often exercise rigorously while breathing through their mouths in a highly intense fashion. In theory it should then be harder for them to participate in physical activity with their mouths closed, hence the myth-argument would be fully tested.

Physical tests with taped mouth

The study participants were given two separate physical exercise tests. In the first test, subjects exercised while breathing as they normally would. A week later, a second physical exercise test was administered, this time with participants’ mouths taped closed with Leukosilk tape so that only nasal breathing could occur.

Previous experience of training with only breathe through their nose was very limited, only 23.5 minutes per participant on average. Half of them had no experience whatsoever.

Number Minutes experience of taped mouth Intensity
5 participants 0 minutes
1 participant 35 minutes Low
2 participants 160 minutes Medium
2 participants 40 minutes High

Physical tests


  • 1. Push-ups. As many push-ups as possible. Metronome 60 bpm was used (30 push-ups/minute).
  • 2. Boxjump. Jump up on a box with both feet together and stretch out the hip. Walk down. As many jumps as possible during one minute.
  • 3. The plank. Lie in the plank position, with toes and elbows on the floor, as long as possible, for a maximum of three minutes.
  • 4. Dips. As many dips as possible. Metronome 60 bpm was used (30 dips/minute).
  • 5. Skipping rope. As many jump rope skips as possible in one minute.

Each activity was accompanied by two minutes of rest.


Two minutes after finishing skipping rope the CrossFit benchmarktest “Helen”, was started, which means three laps, on time, of the following: 400 meter run, 21 full kettle bell swings and 12 pull-ups.

Results: Could exert on the same level with nose breathing

In part I the results show that they could exert at almost exactly the same level – they managed to do a few more push-ups and dips (+6% resp. +12%), they managed to do the plank for exactly the same amount of time, while they were able to do slightly fewer box jumps and skipping rope (-4% resp. -6%).

In part II they were on average -2% or 13 seconds slower, with a time of 11 minutes and 27 seconds during mouth breathing compared to 11 minutes, 40 seconds during nasal breathing. This is an extremely small difference for such a tough test, given their minimal experience of doing high intense physical activity while only breathing through their noses.

According to the Borg scale, ranging from 6 (no exertion at all) to 20 (maximum exertion), they were able to exert themselves to the same level on both tests since they had on average 18,8 (extremely hard) during mouth breathing and 18,7 during nasal breathing.

Another confirmation of the fact that they managed to exert at the same level during nasal breathing is that their max pulse in both tests were 180.

I can readily admit that I was taken aback by their ability to perform while only breathing through their noses. If I had been asked before the test I would have answered with absolute certainty that several of the participants would be forced to either abort the test or start walking.

Activity Normal breathing Taped mouth Difference
Push-ups 35,3 38,3 +8%
Box jump 23,7 22,8 -4%
The Plank 2 min 50 sec 2 min 50 sec +-0
Dips 28,5 32,4 +12%
Skipping Rope 140,1 132,5 -6%
“Helen” 11,27 11,40 -13 sec (-2%)

Participants in action

Interesting about lactic acid and better recovery

The levels of lactic acid varied quite a bit amongst the participants. On average it was 11% lower during nasal breathing (12.8 mmol/L compared to 14.1 mmol/L). But it is the high levels of lactate that I find most interesting. Martin Söderberg, Elite Athlete Coordinator at Bleking Institure of Technology, was responsible for the measurements. Martin says:

I have measured the lactate levels on over 500 people and have never, neither before or after the nose breathing study, come across anyone with blood lactate levels above 20 mmol/liter. In this study, two out of nine, had above 20 mmol – 20,3 and 21,5 respectively.

This result is very interesting since most elite athletes can only tolerate 14-16 mmol/L. I would like to see more studies investigating if there is a connection between high levels of carbon dioxide and increased lactate tolerance.

White Blood cell Count was 24% lower during nasal breathing, which indicates that the immune system was not as stressed. White blood cells (WBC) are normally an indicator of the amount of inflammation in the body where high WBC levels point to high levels of inflammation.

The lower level of white blood cells could thereby serve as an explanation of the common recurring feedback of less muscle soreness after physical activity with nasal breathing.

Further, on average the participants slept 25 minutes longer after the physical test where they were breathing through their noses, 7 hours and 15 minutes total, which suggests that they were sleeping better.

Their own estimation of their nighttime sleep shows an improvement of 15% in their quality of sleep while their energy levels were 16% higher upon awakening. They were also taping their mouth at night after the nasal breathing only physical test.

Measuring the recovery

Good recovery is a prerequisite to be able to train and perform over time. In order to measure the participants ability to recover, a device from Firstbeat Technologies was used.

The equipment measure the bodys pulse variation, also called HRV=Heart Rate Variability, and it varies with each heartbeat and provides information about bodily functions. Measuring HRV reveals how the autonomic nervous system is operating and the physical and mental stress and the ability to recover after physical strain.

The participants used the Firstbeat equipment for approx. 36 hous in connection with each physical test, from the night before the physical test until the morning after the physical test. Through the analysis software it is possible to show the participants quality of recovery, measured in the standardized RMSSD (Root Mean Square of the Successive Differences). The higher RMSSD value, the better the quality of recovery.

According to the Firstbeat report, the quality of the recovery during sleep (pulse variation, RMSSD) was 10% better on the night after the physical test with nasal breathing.

Conclusion: The current views on mouth vs. nasal breathing needs to be revised

The current view that mouth breathing is necessary in order to be able to perform physically needs to be revised. I believe it to be mainly a limitation in our minds, similar to the Bannister effect.

Before Roger Bannister ran an English mile under four minutes in 1954, it was considered impossible. But once he made it, within just three years fifteen more runners succeeded in running faster than this “impossible” limit.

The current view can probably be derived from the fact that today’s sports coaches / researchers / physiotherapists / athletes have a minor, if any, focus on breathing, such as breathing rhythm, shallow vs. low breathing, nasal vs. mouth breathing, big vs. small breathing volume etc. It is surprising considering that efficient breathing lays the foundation for efficient oxygenation of the muscles and the nervous system so that strength, endurance and concentration can be maintained.

Frequently I hear from sports coaches and athletes that you don’t have to think about your breathing, it’s an automated process taking care of itself. I agree that it’s an automated process, but just as with most things in life, we can do it in an efficient way, and in a not so efficient way, and this goes for our breathing as well.

We all know that by doing push-ups we will become stronger and by jogging we will increase our fitness. There is no difference between doing those activities where we train to improve, than focusing to improve the way we move the air in and out of our lungs in order to breathe more efficiently.

Another argument I hear frequently is that if nasal breathing is so superior it would have been discovered many years ago and everyone at elite level would have done it. But just because something that appears to be as simple as nasal breathing during exercise seems to have been discovered more recently doesn’t negate its value.

New discoveries are made all the time. Just because everybody is doing or thinking in a certain way doesn’t mean it’s the best or correct way of doing it. With such a way of reasoning our planet would still have been considered to be flat, the high jumper Richard Fosbury would never have invented the Fosbury Flop, or high altitude training to improve our bloods oxygen carrying capacity would never have taken off.

Try for yourself

If you’re a sports coach, my advice to you is to try taping the mouth on your athletes during their next workout, or if you’re an athlete the advice is the same. Give mouth taping a chance during your next workout. Maybe you will, just as many people already have, experience increased strength, endurance and faster recovery.

At the same time or breathing habits outside the training arena is even more important since they lay the foundation for our breathing habits while exercising. A simple measure is to tape your mouth at night to ensure that your mouth stays closed and thereby improve oxygenation and recovery while asleep. Assess your breathing habits by answering the 20 simple questions in the Breathing Index.

Equipment used in the study

  • Scout lactate meter to measure lactate levels.
  • Hemocue WBC meter to measure white blood cell count.
  • Garmin heart rate monitor to measure the heart rate during the physical tests.
  • Firstbeat Lifestyle Assessment tool to measure max pulse and recovery during sleep, which is calculated by analyzing the HRV (Heart Rate Variability).
  • Leukosilk tape to keep the mouth closed during physical test #2.
  • Borg scale to measure perceived exertion.

What’s the point of breathing through your nose?

So what’s the point in breathing through your nose? The truth is that breathing through your mouth and breathing through your nose produce very different results. This is why many people who exercise are fit, but they may not be healthy. Good breathing habits are the foundation for lasting health, and the first step towards good breathing habits starts with nasal breathing.

In your nose, which is probably the most underestimated organ you have, the air you inhale is specially prepared for your lungs. Your nose acts like a filtering and heating system, warming and humidifying the air you are breathing in as well as trapping airborne particles and bacteria.

Plus, your nose is designed to drive the air down deep into your lungs when you breathe in, and maintain pressure in your lungs when you breathe out. This results in effective oxygenation, which in turn leads to slower and more rhythmical breathing.

When you breathe through your mouth the air that reaches your lungs is cold, dry and full of bacteria and other particles, which can make your airways irritated, inflamed and narrow. This in turn generates shallow, fast, non-rhythmical and inefficient breathing that leads to impaired oxygenation and increases the risk of nasal and upper respiratory infections.

Previous study confirm the result

A study I did a few years ago where ten participants biked with all their might is in line with the results from the study above. On one occasion they biked with their noses taped and in the other occasion they had their mouths taped. Some interesting results from this study:

  • Nasal breathing reduced lactic acid by 11% (8.0 mmol/L), compared to mouth breathing (9.0 mmol/L).
  • Participants took 22% fewer breaths during nasal breathing (31 breaths/minute) compared to mouth breathing (40).
  • The former Swedish triathlon IronMan record-holder (2005-2012) Clas Björling had 38% less lactic acid (295 Watts load) when using nasal breathing. Furthermore, Clas had a 10% lower heart rate, 139 compared to 155, with the same load.
  • Mattias Andersson, a former Nordic champion in Tae-Kwondo and an asthmatic, took 26% fewer breaths during nasal breathing. Mattias had an asthma attack after the test where he biked and only breathed through his mouth and had to take Bricanyl (terbutaline – a bronchodilator). However, after biking using nasal breathing, not only was he able to push back a looming asthma attack, he also managed to cycle for two minutes and fifteen seconds longer.
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