How Should I Breathe When I Run?


“How should I breathe when I run?” 

I get asked this question all the time. We often take breathing for granted.

Many runners are told to “belly breathe,” to breathe from their diaphragm and take deeper breaths to take in more oxygen. However, the main stimulus to breathe, especially at sea-level, is to exhale carbon dioxide, as the partial pressure of CO2 rises in the blood from metabolism. At sea-level, your blood is nearly 100% saturated with oxygen, even while running a race, so it’s fruitless to take deeper breaths since what matters is how much oxygen is transported in your blood, not how much oxygen is in your lungs. The best distance runners in the world are small people, and so they have small lungs. When I measured total lung capacity of runners in the lab, I found that the smaller runners had smaller lung volumes, even though they were better runners. There is no relationship between your lung volume and how fast you run a 5K or marathon.

Since your diaphragm and other breathing muscles also use oxygen, the muscle contractions associated with deeper breaths can potentially “steal” some of the oxygen your leg muscles need to run. When you travel (or live) at higher altitude, you breathe more to compensate for the decreased partial pressure of oxygen in the environmental air. (Oxygen molecules travel from areas of higher pressure to areas of lower pressure, so the greater the difference in oxygen pressure between the environmental air and the air in our lungs, the greater the driving force for oxygen to travel from the environment into our lungs. The higher up in altitude you go, the less the pressure difference between the environmental air and the air in our lungs.)

While taking deeper breaths won’t help your running, coordinating your breathing to your stride rate can. Most animals, like the cheetah, coordinate their breathing patterns to their stride rates because of how the movement of their forelimbs assists the movement of their chest cavity. And so four-legged animals take a 1-to-1 step-to-breath ratio: For every step, they take one breath.

This coordination of breathing to stride rate, which is called “entrainment,” also happens in humans, although it is not as tightly coupled since humans have a greater anatomical separation between the movement of their legs and chest cavity. In humans, the entrainment of breathing to stride rate is linked to running experience, with more fit and experienced runners exhibiting greater entrainment. For my doctoral dissertation, I measured this entrainment of breathing and stride rate, and found that human runners take 3 or 4 steps per breath (inhalation + exhalation) when running at easy to moderate paces, and two steps per breath when running fast. With many miles of training, runners may learn how to most effectively ventilate their lungs and minimize the metabolic cost of breathing, which can improve running economy (the amount of oxygen you use to maintain a given submaximal pace).

Although the entrainment of breathing to stride rate seems to happen naturally with training, you can voluntarily coordinate the two rhythms. When you run, begin to exhale when either your right foot or left foot lands on the ground, and go through a complete breath (exhalation + inhalation) every 3 to 4 steps, always exhaling when your foot lands on the ground. When you run fast, try to take two steps per breath. 


5 Responses to How Should I Breathe When I Run?

  1. Thank you, Jason. I also find, especially with my XC runners, if they will focus on their breath (entrainment) when they are tired or want to stop, it will help them move past the feelings and run strong. So, focusing on breathing can also be a mental strategy to help all runners.

  2. Interesting read…

    Thanks for this Jason, and also the other things that you have sent. I am the coach who spoke to you about marathon running. I intend to look more into detail on the things you sent to me in regards to training programs, but just have not had the time to look at them yet. I realize that I will never be a sub 3:00 marathoner again. At this point and time, I just need to start with finishing a marathon! (Never thought that I would say that!). Then, eventually, I would, at least, like to be somewhat competitive in my age group category, again. I also am carrying at least an extra 40 pounds, that I will need to shed through changing some eating habits! I am also 59 years old now. Sometimes, I will get demotivated, in thinking that I am still I can remember running a 23:45, 5K, at the age of about 46, and was soooo disappointed that I didn’t break the 23:00 mark, that I was devastated enough to just basically quit running for a very long time. I had set my goal far too high… At one time, I was in the top 5% of elite distance runners in the state of Hawaii, and now would love to just get that LOVE for running back. Hard to believe that I lost it. I am running (jogging) now, and am staring to feel a little stronger though. Is there a particular book you have written, that would align to where I have been, and where I am at, at this point and time in my life. I will go back and take a look at your other emails, as soon as I can!! Any help you can give me, is greatly appreciated. Chuck Cisler

  3. Dr. Karp,

    Everything you have said about breathing makes clear sense. I have always talked to my runners about the rhythm of running, but this gives me a method to provide them.

    Thank you very much,

    Marty Makransky

  4. I find it fascinating how little research or writing there is on breathing patterns during exercise. A stark contrast to the amount of research done on many other components (heart rate, muscle type, stretching, etc etc etc). Didn’t recall that breath patterns were/are an interest area for you. Kudos on doing that work and on sharing it.

    I found that purposefully entraining was a good way to control effort (ie not go too hard). My endurance pace running seemed to fall into a 5 step pattern – one inhale/exhale for every 5 steps. Then again, I have large capacity lungs for my size (actually measured). Exhaling on a downstep seems to be natural to most runners. Self-observing, the diaphragm (etc) contraction along with a general tightening of the core helps to balance the tension of the foot placement and push off. However, most runners seem to be oblivious to this or to the pattern of their breathing. I observe that many runners seem to be breath limited. That is they have quite high heart rates even when they don’t seem to be breathing very hard. My conjecture is that if they breathed more forcefully, their performance at the same heart rate would improve.

    In case it’s of any interest:
    An average adult breathes about 0.5 L of air per breath at rest. Normal air contains ~ 0.03 % of CO2 which gets enriched to 4 % of exhaled air. The difference, 3.97 % is what you exhaled. One breath contains ~ 1 g of exhaled CO2

    A few references that you might find to be of interest:
    – Breathe Strong, Perform Better by Alison McConnell
    – Runner’s World Running on Air: The Revolutionary Way to Run Better by Breathing Smarter by Budd Coates

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