Baby (and Adult) Humans cannot breathe underwater

This is a response to a forum post over on Beginner Triathlete about so-called “Hypoxic Breathing” swim drills, and originally appeared on my retired blog, exercisephysiologymd.com on January 17th, 2007

I’m a huge proponent of using terms that accurately reflect the underlying physical changes that occur on a biochemical level when training for triathlon swimming. The words I use as a coach transmit meaning to the athlete that may help reinforce what the benefit is.

That’s why the term “Hypoxic Breathing” does not belong in a swim or triathlon coach’s lexicon. If you ask swimmers, triathletes and many coaches what hypoxic breathing drills are, they’ll respond with answers like:

  • Holding your breath
  • Swimming Underwater (as far as you can)
  • Swimming a length while minimizing breathing
  • Swimming with increasing time between breaths, eg. every 3, every 5 or every 7 strokes

I want to address the first two responses primarily, but principals apply to the latter 2 answers as well.

Firstly, holding your breath prevents CO2 from escaping your lungs. Our body is constantly consuming oxygen and producing CO2 as a waste product. The CO2 builds up much faster than the oxygen is consumed, and needs to be released through the lungs. Holding your breathing causes the CO2 level to build up in your bloodstream. So these sets should really be called “Hypercarbic” sets. “Hyper-” meaning elevated and “-carbic” relating to the carbon dioxide level.

The build-up of Co2 in the lungs while holding your breath stimulates the brainstem and diaphragm to breath. This is the sensation you feel when you hold your breath without exhaling. The lungs start to burn and the urge to breath is irresistible. Breathing is usually involuntary, meaning we don’t think about it and when not thinking about it, don’t have control over it. Our brainstem, spinal cord, and diaphragm will keep the bellows moving no matter what.

But when we voluntarily decide to hold our breath, we are overriding the built-in mechanisms. We can continue to override those mechanisms even when the urge to breath crops up. When trying to stay under the water for a long time, some swimmers and divers will hyperventilate first, in order to lower the CO2 level and delay the urge to breathe. This means that the oxygen in your bloodstream drops lower and lower while the CO2 level takes longer to build up.

However, people have died doing these drills. There is no physiologic benefit from doing them. The name is a misnomer. If you want to swim uninterrupted without worrying about breathing, use a snorkel. The benefit of using a snorkel is that you don’t have to break form when breathing, and can focus on other parts of your swim stroke comes from not having your form break down when you roll (or don’t roll, or lift your head, or claw your way to the surface) to take a breath.

A far, far better solution is to have someone work with you to learn how to breathe properly. The number of strokes you take per breath is irrelevant. There is no right number. You need what you need. The body’s need for oxygen consumption and getting rid of carbon dioxide is dependent upon how much energy you are using and in what form you are using it (aerobic/anaerobic, etc). When I start my swim warmup, I will frequently swim 7 to 9 strokes without breathing only because I am swimming smoothly, I have not gotten my oxygen consumption up by working hard, I am not generating a lot of waste products due to the low effort. When I have the urge to breathe, I breathe. When I am doing long endurance sprints, I may breathe every 2 strokes. When I am rested and doing a single 25-yard sprint, yes, I can do it with no breaths. But not because I am forcing myself to do it. It is because 15-20 seconds of maximum effort requires little oxygen.

A novice swimmer who uses all the energy they have just to stay on the surface of the water will need to breathe every stroke because of the amount of energy they are using.

Do not play with the basic needs of your body.

There is a mantra in Emergency Medical Services:

Air goes in and out,
Blood goes round and round
Pink is good and blue is bad.

That’s all an EMT, Paramedic or Emergency Medicine nurse or physician needs to know in order to resuscitate a patient. If it’s good enough for these professionals, it’s good enough for the recreational swimmer.

Air goes in and out.

Don’t forget it.

Practice it daily. Frequently. You’ll get really good at it.

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