Mouth Vs Nasal Breathing for Running
How does the way we breathe impact fat burning, blood lactate accumulation, and the end result of our cardiovascular endurance program?
To Health Advocates—
I hope you all are having an excellent week and enjoying the end of the year personally and professionally.
As I have hinted at in prior newsletters, I have always been an advocate for nasal breathing. I have seen positive effects in clients from developing this skill and just as many benefits for myself. Some of the benefits are noticeable on short time frames, while others build up over time.
I believe the benefits are physiological and physical. Physiological, for example, that recent research supports the idea that the gas exchange of oxygen and carbon dioxide is more efficient when nasal breathing vs mouth breathing (the purpose of today’s newsletter). The benefits can also be physical, as the respiratory process of these two different methods of respiration recruit different core musculature (we’ve discussed this in the past and will definitely come back to this). Physical also, in the sense that nasal vs mouth breathing can impact our facial structure, and development. A topic Andrew Huberman has covered extensively:
The purpose of today’s newsletter was to explore the difference in blood lactate accumulation during cardiovascular training, and whether mouth breathing or nasal breathing would impact this physiological outcome.
Below you will see an introduction to the contextual information you will need to understand why this experiment is significant, the details of the running test I performed, and then of course, how and why this impacts us and our own training.
I hope you enjoy!
P.S. Don’t have the time to read the full article? Skip to the bottom for a quick recap.
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How is burning fat calculated?
During metabolic tests, exercise physiologists can determine whether or not a client or patient is currently burning fat with a device that captures the gas exchange of respiration in a single person. Basically the device will measure the amount of oxygen being consumed, and the amount of carbon dioxide being expelled, among other measurements.
The formula for determining which fuel source (carbohydrates, fats, or proteins) are being used is this:
Respiratory Quotient = CO2 produced / O2 consumed
As long as more oxygen is being consumed, than carbon dioxide is being produced, our body will be burning fat to some degree, and the respiratory quotient would be less than 1.0. This number could drop as low as 0.7, as that would indicate that our body is predominately prioritizing fat burning at a the moment. As that number approaches 1.0 or even rises >1.0 then our body will be prioritizing carbohydrates as a fuel source.
A crash course explanation:
Scenario 1: If I was running as hard as I could for 5-10 straight minutes, my respiratory quotient would rise well above 1.0, as my body would be producing large amounts of carbon dioxide as a byproduct of the intensity that my body would be working at. During this effort, carbohydrates would be the main source of fuel that my body would be burning, and this would continue for a period of time afterwards.
Scenario 2: On the flipside, if I was jogging at a really easy, slow pace for 5-10 straight minutes, my RQ would potentially drop down towards 0.7 (the direction of RQ would be dependent on a person’s starting position in this case, but often times we see a drop during aerobic, easy efforts). During this run, since the intensity is low, more oxygen would be flooding my system than carbon dioxide is being expelled. Due to this, my body would be burning mostly fat as a fuel source, and little carbohydrates.
The takeaway: Our body’s respiration is significant when measuring whether or not someone is burning fat or carbohydrates at rest or during workouts. Is it then possible that our conscious focus of this physiological process can impact the outcome, and whether or not our body is favoring carbohydrates or fats?
What does blood lactate accumulation have to do with this?
During exercise (for this article, we are specifically referencing cardiovascular exercise, as discussing resistance training would then require even more context) our bodies create lactate as a byproduct of carbohydrate utilization by the muscles. As long as the intensity of exercise stays lows enough, our bodies can continue to keep up with clearing and recycling lactate to avoid the buildup of lactate in the bloodstream.
When lactate production becomes too overwhelming for our body’s ability to clear it, it is an indication that carbohydrate utilization is also increasing, and fat utilization as a fuel source, is decreasing.
This is why zone 2 training has become such a staple in today’s training world, as it is the most effective way to develop our body’s ability to clear lactate, and thus improve our body’s ability to continue to use fat as a fuel source during cardiovascular training.
Using fat as a fuel source during cardiovascular efforts is obviously helpful when trying to lose weight, maintain a healthy body weight, or develop our cardiovascular training skills. It is also relatively a low overall stressor on our body, and thus, can provide a very useful training stimulus without adding to levels of fatigue. This is useful information for any person who wants the health benefits from training or for any person interested in performance training for sport.
What you need to know about blood lactate accumulation:
Baseline levels of blood lactate should be between 1-2 mmol. This can be assessed using a simple blood lactate meter, where a single prick of blood provides blood lactate feedback in less than 15s.
During very easy aerobic efforts, e.g. walking, our blood lactate could drop even lower than baseline (potentially less than 1.0) as our body’s slow twitch fibers are doing an efficient job of clearing out lactate, thus providing a decrease in blood lactate accumulation.
During zone 2 efforts, we develop our body’s ability to clear lactate, as the demand of lactate clearance is just high enough, but not so overwhelming as to change our metabolic pathway. In this case, during zone 2 efforts, our body is being challenged to clear lactate, while still prioritizing a greater percentage of fat as its desirable fuel source. It is indicated that as this number approaches 2 mmol of blood lactate, then fat burning is waning, and carbohydrate utilization is beginning to be prioritized.
Once we rise over 2mmol of blood lactate, it is becoming more clear that our body is shifting away from fats as a fuel source and starting to favor carbohydrates as a fuel source.
What does blood lactate accumulation and respiration assessments have to do with each other?
Basically, as blood lactate is accumulating, we see a shift from fat utilization as a fuel source, towards carbohydrate utilization as a fuel source.
At the same time this is happening, carbon dioxide being produced and expelled is increasing as well. Once the amount of carbon dioxide being expelled is greater than the amount of oxygen being consumed, we are no longer using any fats as a fuel source. Remember our equation from above:
Respiratory Quotient = CO2 produced / O2 consumed
Now that brings me to the purpose for today’s newsletter. If nasal breathing is supposedly better at reducing hyperventilation, would nasal breathing provide a better training environment for aerobic efforts?
A simple comparison
On back to back days I ran a 2 mile, zone 2 paced run. I determined my zone 2 by using prior lactate measurements, and also compared it to a well known formula for determining training zones.
On day 1, I ran 2 miles at a 10:17 pace with an average heart rate of 135BPM, while NASAL breathing. You can see that run here:
On day 2, I ran 2 miles at a 10:11 pace with an average heart rate of 136BPM, while MOUTH breathing. That run:
The goal of the run was to maintain a heart rate as close to 135BPM as possible. The only variable I changed between each was my respiration. Day 1 was through my nose, day 2 was through my mouth.
Additionally, I measure blood lactate using the lactate plus meter. My baseline for the nasal breathing day is here:
My baseline for the mouth breathing day below. For context, prior to this second run, I had walked home from work (30 minutes), which potentially explains the difference in baseline.
Repeating one last time. The runs were identical in duration, distance, almost identical in pace (6s per mile difference), and heart rate was averaged at 135BPM one day, 136BPM the next day. My post nasal breathing run lactate:
This was my expectation, as a zone 2 run should prioritize low/close to baseline blood lactate levels. During this run, your body should be burning a high concentration of fat and oxygen consumption should still be larger than carbon dioxide output. These runs should be relatively easy on the body, good for the parasympathetic nervous system, great for recovery, overall health etc. For context, elite marathoners and triathletes spend greater than 50% of their time at these intensities, whereas a lay-person marathoner might not (and probably have less than ideal outcomes).
My second run, mouth breathing, post run blood lactate:
This is the one I was half surprised/ half not by. On one hand, you can feel that nasal breathing is more efficient when running. Subjectively I feel much better physically on the respiration side, and I also feel mentally better when doing so. This is part of the reason why I’ve been doing this for about 3 years now.
I was surprised, however, to see a not very subtle change in blood lactate. In theory, there shouldn’t be that much a difference metabolically to have two identical runs produce two very different outcomes in blood lactate.
I don’t have all the answers as to why this is, but can somewhat make an educated guess that nasal breathing leads to a better RQ, considering the fact that it directly impacts respiration.
Additionally, I think I may try to keep data on this for a few months to see if I continue to see a substantial change over time.
In the meantime, I have always been a proponent of nasal breathing, especially on low intensity, zone 1 and zone 2 work. I also feel that it leads to more efficient weight training sessions, from a physical standpoint. I haven’t posted much on that side of the equation but will prioritize that in the near future.
I hope this sheds some light on the nuance associated with respiration and endurance activities, and the need to further educate ourselves on the impact of this.
If you are interested in further reading on some of these topics, you can find the links below. I hope you all have a great weekend!
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Additional resources:
Nasal vs oral breathing on facial development
Nasal vs oral breathing on anaerobic ouput
The health benefits of nose breathing
The science of nose vs mouth breathing
Max oxygen consumption with nose vs mouth breathing
Lactate vs ventilatory threshold