Diaphragmatic breathing & CO2 tolerance

By TWS resident Respiratory Physio Billie Woods


A Beginners Guide to a Sustainable Breathwork Practice- Part 2

If you haven't yet read Part 1 click HERE - you don't want to miss this!


The respiratory diaphragm is the body’s primary breathing muscle. Its function also impacts the digestive system, our posture and movement, pelvic floor function, breathing regulation, and fluid dynamics (venous return, cerebrospinal fluid, lymph circulation). The diaphragm affects how other respiratory muscles function, if our diaphragm is weak or under-used, we tend to rely on our accessory breathing muscles (muscles of our neck/shoulder region), creating an upper chest breathing pattern, which then leads to a vicious cycle of over-worked/tight/painful accessory muscles and increased diaphragm weakness and inactivity. When our diaphragm is not working well it can lead to issues with digestion, reflux, posture and stability, pelvic floor dysfunction, problems with lymphatic drainage, and an imbalance in our body’s physiology from dysfunctional breathing. Ahh sounds horrible!! The good news is, that just like any muscle in our body, the diaphragm can be strengthened and taught to work correctly.


In part 2 I will talk to you about the importance of using your diaphragm for breathing, the benefits of building up your tolerance to CO2 in the body, and I will give you some breathing techniques focusing on these, which you can add to your breathwork routine.


Diaphragmatic Breathing

The respiratory diaphragm is the body’s primary breathing muscle. Its function also impacts the digestive system, our posture and movement, pelvic floor function, breathing regulation, and fluid dynamics (venous return, cerebrospinal fluid, lymph circulation). The diaphragm affects how other respiratory muscles function, if our diaphragm is weak or under-used, we tend to rely on our accessory breathing muscles (muscles of our neck/shoulder region), creating an upper chest breathing pattern, which then leads to a vicious cycle of over-worked/tight/painful accessory muscles and increased diaphragm weakness and inactivity. When our diaphragm is not working well it can lead to issues with digestion, reflux, posture and stability, pelvic floor dysfunction, problems with lymphatic drainage, and an imbalance in our body’s physiology from dysfunctional breathing. Ahh sounds horrible!! The good news is, that just like any muscle in our body, the diaphragm can be strengthened and taught to work correctly.


So, let’s get started with just that, below is a technique for activating your diaphragm and creating a better breathing pattern.


Diaphragmatic Breathing


Breathwork on Sailboat deck

  1. Lying comfortably on your back, knees bent, feet flat on the floor.

  2. Breathe naturally to start, take a moment to fully relax (relax your pelvis, your shoulders, soften your jaw, let your tongue rest gently on the roof of your mouth)

  3. Now place one hand just above your belly button at the base of your ribs), and one hand on your chest.

  4. Start to breathe in through your nose (gentle, relaxed breath), direct the breath down low into the hand at the base of your ribs, keep your shoulders and chest relaxed, minimizing movement in your chest.

  5. Exhale gently and passively (not forced), try to make your exhale longer than your inhale, and gently pause at the end of the exhale, before breathing in again.

  6. Start to slow your breath down, try a ratio of 4:6, inhale for 4 counts, exhale for 6 counts (following the above procedure). If that is too difficult to bring the ratio down (maybe 3:5 works better), remember this is relaxed breathing, focusing on improving your breathing pattern, not pushing yourself to the max. on the other hand, if you are finding it too easy, then extend the ratio, maybe 6:8 or 8:10.

  7. Continue to check your body for any tension, particularly in the shoulder/neck region, allow yourself to relax.

  8. Enjoy 5-10 mins of this. This is you activating your parasympathetic nervous system!


Intro to CO2 Tolerance


We breathe in oxygen and breathe out carbon dioxide (CO2). The way we breathe, the rate, the volume, the rhythm, will all affect the delicate chemical balance in our bodies, which is always in search of homeostasis (balanced pH levels). Our pH will affect everybody's system and every organ in the body. If we over-breathe or hyper-ventilate, our bodies can become low in CO2, which increases our pH, and vice versa, if we under-breathe or hypo-ventilate, we increase our CO2 levels and therefore decrease our pH levels.


It is CO2 levels (not oxygen levels) in our body that will affect our breathing drive, if we have an increase in CO2 it increases our urge to breathe (not a lack of oxygen). So, if our tolerance to CO2 is low, even if we have a slight increase in our bodies CO2 levels, we want to breathe more, which leads to unnecessary over-breathing (Hyperventilation). If we increase our tolerance to CO2, we are then able to keep a calm, balanced state in situations where we may find ourselves getting anxious. And over time we create a larger window of tolerance, the window where we feel most comfortable and in control, it sits in between low CO2/hypo-arousal (feeling zoned out, disconnected, autopilot, shut down) and high CO2/hyper-arousal (feeling chaotic, out of control, anxious).


Breath-holds used intermittently during a breathing practice can be a useful tool for resetting CO2 tolerance. They can also be a good way to train tolerance for dyspnea (shortness of breath), and to relax and reset the nervous system.


The below technique is called Box Breathing, and it’s a really great way to start incorporating your nasal breathing, using your diaphragm, working on breath control, and starting with some basic breath-holding.



Box Breathing


  1. Start in a comfortable lying or sitting position (if in sitting making sure you can still maintain a good breathing pattern).

  2. Inhale through the nose, down into the base of your ribs for 4 seconds. Make sure you are keeping your shoulders/neck muscles relaxed.

  3. Hold your breath for 4 seconds.

  4. Gently (not forced) exhale through the nose for 4 seconds.

  5. Hold your breath for 4 seconds.

  6. Continue to repeat this sequence for 3-5 minutes.

  7. Remember, you can always change the time, if 4 seconds feels too hard, then reduce it, or if it feels too easy then you can increase the time.


Breathwork on Boat deck

If you add these exercises to the breath awareness and nasal breathing practices from Part 1, you will have a very well-rounded breathing practice to start forming some really great habits.


Please don’t hesitate to reach out if you have any questions or would like to learn more, I’m always happy to chat.


Breathe well salty souls!

(Disclaimer: This is a generalized program/generalized advice. If you have any medical conditions where you are unsure if breathwork will be suitable, please seek medical advice prior to starting this program. If you start to feel any adverse effects from these exercises, please stop and seek medical advice. I cannot take any responsibility for any adverse effects from this program.)



Billie Woods


Born and raised on the wild coastlines of New Zealand, Billie grew up with a unique connection with all things outdoors, but it was the ocean that really made her spirit soar! Surfing was her first love and then came sailing. Together with her husband (then fresh new boyfriend) they purchased a regal old sailing vessel, Jandu 42ft Swanson. They live aboard in Albany, Western Australia with their young daughter but are eager to set sail for distant oceans soon.

Billie is a qualified Yoga & Pilates teacher and a professional physiotherapist, with a passion for integrated breathing therapy techniques. Over the past 7 years, She has taken a more holistic approach to what she offers, whilst also considering the biomechanics, psychological & physiological aspects of breathing dysfunction in her patients. Together with her Survival Apnea/Ocean Confidence Instructor certification is a wealth of knowledge in this field and is passionate to share the power of the breath with the conscious sailing community.


To check out Billie's services see https://www.instagram.com/entirebreath/ https://www.entirebreath.com/



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