Breathing: does it really matter?


very Important. In any type of exertion or stressful situation, tactical breathing will allow your body to respond in a calmer state. It lowers your HR and clears your mind. This is common training practice for police, fire, military. Slowly breath in for 3 seconds(like you’re smelling a flower or bacon), pause, blow out for 3 seconds (like you’re blowing out a candle), pause, repeat.

Restricting the flow as you blow out is also supposed to expand your alveoli to allow for a better oxygen uptake.


If we want to get REALLY science-y and nerdy…regarding the sympathetic and parasympathetic nervous systems…it’s best to breath in through your nose – triggering the “calm” parasympathetic system – and exhale 1.5 times as long through your mouth; e.g inhale 2 seconds, exhale 3 seconds.

Just as inhalation through the nose triggers the PNS, exhalation is triggered by the PNS, thus consciously focusing on longer “forced” exhaling from the diaphragm will keep the PNS loop going and in dominance.

Nose breathing, utilizing the diaphragm, fills all 3 lobes of the lungs (vs upper-only via mouth breathing) leading to 10% higher oxidation of the blood. Yes, breathing matters.



Not that I don’t trust you, but do you have a source for this? More specifically, 10% higher oxidation of the blood how does that relate to performance (for any performance measure)? And what are the contributions of the individual components (Nose breathing, utilizing the diaphragm and filling all 3 lobes of the lungs)? I.e. if I only manage to do one of them how would that impact blood oxidation, and in the longer run performance?


Just looking at it from a mechanistic POV. When you breath during exercise the limiting factor is probably not oxygen uptake. There is still a big chunk of oxygen in your exhalations (13-16% Wikipedia). If oxygen uptake were a limiting factor there would be none. So the limiter from a cellular perspective is probably CO2 removal. If you don’t use full lung capacity during exercise you are off optimal on the CO2 expulsion. Belly breathing gets you to clear all the lungs of CO2.

Just to be clear 21% Oxygen would improve the gas exchange across the pulmonary membrane for sure and increase the blood oxygenation. But if those little red blood cells are full of carboxyhemaglobin then it won’t happen at all. So CO2 removal is the limiting factor hence the active breathing.

There is probably a thermal bonus too as expelled water vapor is bringing cooling to your core and blood more directly than skin evaporation. However that is probably overall more effective due to the area effect. MHO.


If you guys are interested in respiratory physiology I highly recommend Respiratory Physiology: the Essentials by John West.

It’s a fairly quick read and is a great start into hands down the most interesting topic in human physiology. (IMO)


Trying to locate the research…

Basically what happens is breathing via nose transports nitric oxide to the lungs thus allowing for greater CO2 exhalation.

Breathing via mouth utilizes mostly the upper lobes of the lungs which contain a high number of SNS receptors, which is why when you hit stressful times in training/racing, you’re more apt to take shallow mouth breaths, leaving the lungs under-utilized and filling with CO2. The opposite takes place with nose/diaphragm breathing.


Also from a simple mechanics standpoint, if you don’t exhale hard, you won’t be optimizing your new fresh breath in, since it’ll be only x% fresh air, with some of your CO2 still in there. I’m curious if CO2 will build up since it is more dense than O2 and N2


To further @Captain_Doughnutman “nerdy” talk on heart rate and breathing., it actually isn’t necessarily the breathing In through the nose that is the initiator of slowing down breathing or heart rate. It’s the exhaling that will have more control on the breathe rate and heart rate.

Heart rate is actually controlled by both the PNS AND the SNS. The SNS releases the hormones (catecholamines - epinephrine and norepinephrine) to accelerate the heart rate, while the PNS releases the hormone acetylcholine to slow the heart rate. This is regardless of breathing through the nose or mouth. What breathing through the nose does however, is slows the heart rate through inhibiting short fast breaths.

Breathing In is thought to control the the SNS side of things and the more deliberate and longer the exhale can initiate the PNS to slow things down when it comes to heart rate. They both also affects Heart Rate Variablility (HRV).

Below I will attach a segment of an hrv reading that I did to illustrate this. The first graph with nice uniform waves is when I am deliberately controlling heart rate and HRV through breathing and what’s called coherence. The second one is not trying to deliberately breathe in any particular way, not in coherence. Typically breathing around six breaths per minute will bring someone into coherence. More to it than that, but that is the largest factor. Again, regardless of through the nose or mouth in either instance. The nose breathing just slows the whole process down because it slows the process down where mouth breathing does not. Think, drinking a glass of water through a straw, as opposed to straight from the glass.

So… while this doesn’t give the answer you may be looking for, it illustrates how breathing and heart rate are interrelated. If you focus on the exhale, the inhale will take care of itself and the lungs will refill automatically. Discarding carbon dioxide is one part of the equation but focussing on the exhale also will help to decrease heart rate if you can get breathing under control, during high intensity OR low intensity. When you become proficient at this you can literally watch it take place if you are monitoring heart rate while working out.

Th same readings above could have been done while I was exercising and the outcomes will be similar to those graphs, albeit harder to control.

Now, as far as breathing, again, it is exhaling that is the biggest determinant of exhaustion of the diaphragm and breathing muscles. This can be strengthened (exhale) and has the greatest impact on performance in endurance events. Focussing on Strengthening the inhale musculature does not have significant changes or impact on performance whereas exhale strength and force does.

I won’t get into all the details but the evidence on all of this breathing information can be found in a good synopsis by Alison McConnell who is considered the leading authority on breathing muscle training. If you want a good read on the topic, see Breathe Strong Perform Better, as its is a good place to start on why all of this “breathing” has an impact and why breathing may matter, other than the obvious, to keep us alive😉


How many people have suggested to stop breathing and see what happens?


One other thing to consider is that when you burn fat, the byproducts are water and carbon dioxide. The water just enters your system and is used for whatever purpose, and the co2 is transported to the lungs to be exhaled. The fat residues are ~20% water and 80% fat.

So if you lose weight whilst cycling, about 80% of your weight loss leaves the body via exhaling. It’s your primary weight loss mechanism. So, good exhaling is how to physically remove the weight from your body!


If you stop breathing you can lower your HR to zero. :+1:


Double win!


Listened to the latest Sonya Looney podcast today, a lengthy discussion about breathing is on there if you’re interested


I did a VO2max vent test last year and the tester is huge on breathing. She explained it like this (I’m paraphrasing):

Because when blood CO2 levels increase blood pH decreases (leg burn). Deep controlled breathing (emphasis on the exhale) when on the rivet can help regulate CO2 and thus decrease the burn. Rate of breathing (hyperventilation) also reduces CO2 blood levels but, alkalosis will result which causes blood vessel constriction to the brain = feeling light headed. A compromise must be made.


Lots of great answers here but my VERY BASIC take on it is this…

We Exhale to get rid of Co2 (bad air if u like) and inhale to take in O2 (good air).
O2 is used by the body in various ways to help us exercise and produce that thing we are all trying to improve…power/watts.
The better and MORE EFFICIENTLY we can do this then I would suggest we have a better potential to produce more power…or as I have found, produce the same power with less effort (even if this is just a perception)

Think of it this way. (Hypothetically of course)
To produce 10w of power you need to take in 1 litre of O2.
However for every breath you take you loose 2w
Therefore I am thinking you would rather take just one deep efficient breath than 3 inefficient pants right?

Hope that made sense


I second this opinion … focus on the exhalation and get a big inhalation by reflex … see the distended bellies of the pros on long climbs as they belly breath … there diaphragm drops down low as they get the big reflex inhalation and the diaphragm pushes down on the belly pushing it out


on these Belly breaths (i just cant do them) that keeps coming up, I find this part very very hard, mainly as I do have difficulty inhaling properly through the nasal passages and hope that once this has been totally fixed then I might find I’m better than I am currently…but man when the work outs hit VO2max i really struggle with my breathing techniques but I push on and complete the workouts but just wish I can improve my O2 intake