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Breathing: Autonomic Control vs. Choice.

"I believe the brain stem of the runner is better equipped than the cerebral cortex of a coach to determine breathing pattern."

Over the last 10 years, specifically since the book "The Oxygen Advantage" was published in 2015, there has been a bucket load of information on breath work. Namely, how breathing can impact performance and health. This brought some awareness and some much needed love to the respiratory system, one that is often overlooked in it's role in performance. It has also done wonders in helping manage stress and anxiety. There is some pretty clear evidence that specific breathing strategies can help 'activate a parasympathetic state'. In simple terms, it can help get you out of a 'fight, freeze or flight state' and calm you down. However, one solution to a very specific set of circumstances is exactly that... A solution to a very specific set of circumstances. This has led to pulmonary specialist and exercise physiologist Dr. Jerome Dempsey to state the above.

.... All the Wim Hoffers' and ice bath enthusiasts, don't worry, I'm not coming for you. I'm more directing this at those who implement specific breathing strategies in every context, specifically during exercise. Which I find rather ironic; S&C coaches often talk about "the task dictates the strategy" with movement, but when it comes to breathing (the very thing that is keeping you alive) apparently we know better, and we're all missing out on 'the key to elite endurance'.

Now, hyperventilation is definitely one of the more common things I see when people undergo physiological testing (RMR & VO2). And this is where a lot of breath work . Hyperventilation is defined as "breathing more than necessary for the given demand". For these individuals who hyperventilate at rest (>16 breaths per minute), and at low intensity exercise, there is a good deal of value in just slowing things down. The prescription of nose breathing for example at rest can help slow down your frequency, shift larger volumes of air and improve respiratory co-ordination. However, it still should be noted, the reason why hyperventilation occurs needs further investigation, typically via spirometry for any real understanding of why.

Because of this inefficient breathing strategy at rest, it has led lots of breathing gurus to talk about the benefits of nose breathing and 'diaphragmatic breathing' (whatever that is, usually it just means breathing slower with deeper breaths, but you always use your diaphragm to breathe). Regardless, both bring about the same response, and like i said, there is some value in the right context.

What is important to remember though, and unfortunately often skimmed over in prescription, is that there is no one best breathing strategy all of the time. In fact your breathing strategy should be incredibly diverse and respond to different environments and tasks. Importantly, just because we have the ability to somewhat override our autonomic nervous system by selecting a specific breathing strategy doesn't mean we should. Our chemoreceptors and mechanoreceptors (and other systems that interact) are there for a reason, and they do a pretty good job of keeping you alive! Exercise is a great example of this. Essentially exercise poses a different set of conditions than when at rest, and so your breathing should adjust appropriately to the demands.

A simplification: As exercise intensity increases, CO2 levels rise, causing a drop in pH (acidosis). When this occurs chemoreceptors (chemical messengers) notify the brain to command an increase in breathing frequency to off load the increased CO2. This occurs because the body needs to find homeostasis. If, however, you attempt to continue to nose breathe, or breathe in conjunction with cadence for example when running, simply because you think it is a better strategy / superior for performance, then all that will happen is for you to fatigue faster. The reason being, if you are breathing too slowly you are not ridding your body of CO2 fast enough, thus causing an increase in fatiguing byproducts.

If you have a look at the image, this is me performing some walking lunges with the metabolic analyser. To begin, I was breathing normally and allowing my body to respond how it should. As you can see when I start exercising there is a demand for more oxygen. Because bodyweight walking lunges are pretty comfortable, my O2 consumption was higher than my CO2 out as expected. When ample O2 is available and exercise intensity is comfortable, we derive energy through predominately oxidation of fat (this corresponds to something called an RER of 0.75/8 - which is roughly 75-80% fat and 25-20% carbohydrate utilisation). I then decided, whilst continuing with walking lunges, to purposefully slow my breathing and at times hold my breath. Almost instantaneously you can see when I do this, a chain of events occur...

1) Total of values of O2 consumption and CO2 expiration drop (as expected because I’m holding my breath / breathing less frequently).

2) The red line (CO2) and the blue line (O2) essentially come together like train tracks, and then the red line goes slightly above the blue line. This corresponds to an RER value of >1 (acidosis) aka my legs are screaming at me!

3) This essentially means there is no longer ample O2 available because I’m not allowing myself to breathe appropriately for the demands of exercise. Because of this, I need to find energy from somewhere to continue. That energy is produced via mitochondrial, cytosolic ATP turnover and via a continual depletion of glycogen and the phosphocreatine stores. The breakdown of which creates an acidic environment / lowers pH. This then causes a ‘respiratory drive’, meaning chemoreceptors send messages telling you ‘'breathe faster now, so you can expel CO2 quickly, otherwise i'm going to shut you down'". You can literally feel this respiratory drive when you hold your breath. Swimmers and divers perform something called hypoxic training. Essentially, what they are trying to do is desensitise this ‘respiratory drive’, trying to build tolerance to CO2 in the body so they can ‘function/or survive’ in a chaotic biological environment for longer. This is what I’m doing here in this example.

Whilst this is an extreme example, we see the consequence of not breathing adequately and appropriately for the set of conditions I'm faced with. Sometimes we see this profile in endurance athletes, but obviously to a much lesser degree, and for different reasons. It typically happens because athletes choose to nose breathe and slow their breath purposefully because they believe it is a good idea, which at rest and very low intensities it can be. But as stated, general prescription in every context is not helpful. Like with most things, the conversation is lost in the extremes. If this breathing strategy is continued and you are not breathing adequately for the demands, you will just fatigue faster.

Primarily, nose breathing or slow deep breathing can be used as an intervention to reduce hyperventilation at rest and during low intensity activities for those who perhaps struggle with respiratory issues/co-ordination. It can also be used to help regulate intensity for zone 1 rides for example. But moderate - high intensity exercise, that gets progressively more challenging and poses a different set of conditions? No, you should get out of the way and let the body do its thing.


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