Is Hypoxic Training Good, Bad or The Wrong Terminology?

Courtesy of Paul Newsome, Smooth Swim Head Coach, and VASA, a SwimSwam Partner.

You may have heard swim coaches use the term Hypoxic Training and wondered exactly what it meant. The literal definition means to swim with fewer breaths per length and so limit the supply of oxygen to your body. The traditional thinking was that oxygen deprivation helps promote your aerobic development – a theory we don’t subscribe to at Swim Smooth.

If you have tried a hypoxic set yourself (e.g. breathing every 5, 7 or 9 strokes) you will know that after a short distance you become quite desperate for air and things rapidly become a battle to abstain from taking a breathing for fear of invoking the wrath of the coach! But push too long and too hard during such exercises and there is a risk of blackout, which is obviously very dangerous indeed.

This has been in the press recently here in Australia following a near-drowning incident with a junior swimmer during a coached squad hypoxic set, begging the question should you avoid all controlled breathing sets?

We would say no… Our philosophy is that conducting controlled breathing sets over short distances for the purpose of technique development can be hugely valuable but we never deliberately target oxygen deprivation (or CO2 build-up) for training purposes. Compared to classical hypoxic training our sets give a much lower stress on the body.

One contributing problem here is that coaches commonly refer to reduced breathing sets as ‘breath holding’ – which is very misleading (and possibly dangerous in its own right). As we shall highlight below, you should never hold your breath when you swim – you should always blow out into the water!

Controlled Breathing & Stroke Technique

Even at the elite swimming level, if a stroke flaw is going to occur it is most likely to occur when going to take a breath. Cross-overs, over-rotation, scissor kicks, pushing down on the water during the catch and loss of stroke rhythm are all issues triggered and exacerbated when breathing:

Ron presses down on the water whilst breathing, lifting him up at the front and sinking his legs at the rear. (courtesy of Paul Newsome, SwimSmooth Head Coach)

Ron presses down on the water whilst breathing, lifting him
up at the front and sinking his legs at the rear. (courtesy of Paul Newsome, SwimSmooth Head Coach)

Whilst an elite swimmer suffers a lot less from these issues, if any swimmer were able to swim down the pool without breathing in at all, they’d automatically side-step these potential flaws and so swim significantly faster and more efficiently. Going many strokes between breaths is fine if you’re a 50m sprinter racing for less than 30 seconds but if you’re swimming anything longer then breathing regularly is essential to take on sufficient oxygen.

So how do we work to overcome stroke flaws whilst breathing? One key way is to swim short distances at moderate pace breathing less frequently, perhaps every 5 or 7 strokes. These are short enough to be perfectly safe but give you plenty of opportunity to learn good motor patterns without the distraction of breathing so that when you do go to breathe they are much more likely to stick.

Note the key here isn’t oxygen deprivation but stroke technique development over short distances. The use of fins (kicking gently) and pull-buoys may also reduce your oxygen consumption and make these sets easier to achieve.

The Wrong Terminology?

When you read information about reduced breathing sets, coaches often make the mistake of referring to them as being challenging because of their “breath holding” element. Ironically that is the exact opposite of what they should be – you should never hold your breath when you swim!

Whenever your face is in the water you should exhale in a long continuous stream of bubbles, getting rid of the CO2 you produce. By holding your breath underwater the levels of carbon dioxide in the lungs and blood stream start to increase which triggers the urge to breathe in, a condition called hypercania. This can be very stressful indeed and quickly worsens with reducing frequency of inhalation. By exhaling into the water your CO2 levels immediately drop.

In addition CO2 is in itself is poisonous to the body with symptoms ranging from headaches to nausea to eventual black-out. Do you get a headache from swimming? If you don’t exhale well into the water then it’s quite possibility a CO2 headache.

The problem with the term Hypoxic Training is that it has become synonymous with holding your breath underwater. We propose a change in terminology to call these sets Exhalation Control which accurately describes what they should be about. If you are breathing every 5 strokes you should exhale the same amount as you would over 3 strokes but exhale slightly slower to cover the longer duration.

Whilst we’re here, it’s also worth mentioning that holding your breath underwater is bad for your swimming in another way. It increases the buoyancy in your chest which lifts you up at the front and sinks the legs. If you have a poor body position then the very first thing you should work on in your stroke is your exhalation technique.

The Benefits of Exhalation Control

Performed over short distances, exhalation control exercises are a very effective way to develop your stroke:

– Allowing you to develop good exhalation technique and appreciate how much air you have in the lungs to exhale. As we posted two weeks ago on the blog, breathing every two strokes is simply not enough time to exhale properly.

– Allowing you to focus on aspects of the stroke such as alignment and the catch phase without being ‘interrupted’ with the process of inhalation.

– Giving you time to recognise what a smooth, fluid stroke feels like and equally how inhalation interrupts that rhythm.

– Bringing you confidence that if you do miss a breath during a rough open water swim, that you can simply complete another stroke and rotate to breathe to the other side without panicking.

– Regaining your rhythm and focus in your longer, continuous swims when you feel you may be starting to daydream.

Using Exhalation Control

Here’s our tips on using exhalation control sets:

– Just like in your normal stroke, never ever hold your breath – just reduce the rate of exhalation the longer you go between breaths in, maintaining a smooth steady sigh into the water.

– Never be afraid to take a couple of extra breaths here and there – remember this is not an exercise in how big your lungs are but an opportunity to focus on elements of your stroke which would otherwise be lost to the interruption of breathing in.

– Don’t push yourself, literally go with the flow and recognise that by placing the emphasis on your exhalation you will feel much more relaxed.

– Initially limit your exhalation control swims to 25m or 50m, resting between each for 15 to 20 seconds.

– A classic exhalation control exercise to try is to rotate through breathing every 3, 5 and 7 strokes within a length or every 2, 4 and 6 strokes to your least favourite side. After the longer count you’ll really appreciate the brief drop back down to your normal pattern.

– An exhalation control exercise only needs to be one more stroke than normal between breathing – you don’t need to go crazy here. Even going from breathing ever 2 to every 3 strokes counts.

– Use a Finis Tempo Trainer Pro set to your normal stroke rhythm and breathing every 5 or 7 strokes notice how you lose timing when breathing – either getting ahead or behind the beeper. This is much easier to discern that when you are breathing every 2 or 3 strokes.

– Try using a pull buoy between your legs and see how that immediately makes the process much easier due to a reduced reliance on the large muscle groups of the legs to provide lift and push you forwards.

– Using paddles (particularly technique paddles such as the Finis Agilities) will give you greater feedback on your stroke technique when breathing every 5 or 7 strokes. Use paddles together with a pull-buoy for best effect.


Remember, when Swim Smooth recommends an exhalation control set we perform it over a short distance to work on your stroke technique, not to challenge your lung capacity or aerobic system. You shouldn’t experience significant oxygen deprivation performing these short technique swims at moderate pace. If you have any medical conditions, always seek professional advice from your doctor before commencing. Stay safe and swim smart!

 About Swim Smooth

Swim Smooth is an innovative swimming coaching company devoted to all levels of swimmers and triathletes. Whether you’re a beginner who’d like to learn freestyle, an intermediate triathlete who wants to develop their stroke technique or an advanced swimmer looking to excel further, Swim Smooth is for you.

About VASA and Rob Sleamaker’s Mission to Further Shallow Water Blackout Awareness 

VASA's Rob Sleamaker

VASA’s Rob Sleamaker

As Vasa’s Rob Sleamaker indicated in a recent interview on shallow water blackout featured on SwimSwam, “It’s clear that with proper education, and by making informed, positive shifts in current training methods, the tragedies associated with shallow water blackout can be reduced dramatically, if not eliminated completely. If these efforts manage to save lives, then we have achieved something of value that no words could ever describe.”
We encourage anyone to share our shallow water blackout series with as many people as possible, through as many channels of communication as possible. And if you haven’t already done so, please complete our survey below. Help us save lives and eliminate shallow water blackout! 

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6 years ago

Great article! Thought provoking. Thanks for posting.

6 years ago

Interesting. I had the wonderful opportunity to work with with Richard Quick before he died. I have never met a better stroke technician. He was firmly of the opinion that elite swimmers should maintain the air in their lungs as long as possible and exhale forcefully right before taking their next breath. The reason for this was that by exhaling slowly over the course of several strokes the body’s bouyancy would vary. We want to swim as high on the water as possible, and the best way to learn optimal body position and technique is if a swimmer learns to swim with as close to perfect position (ie as high on the water) as possible the greatest amount of time… Read more »

Reply to  CraigH
6 years ago

Interesting. That certainly makes some sense (I’ve heard similar statements around backstroke breakouts; don’t exhale underwater so you surface with more force/speed). However, at some point Coach Quick’s thoughts on this must have changed. I am not sure when you worked with him, but during his last season with Stanford (2005?), I got to observe a practice or two of his. One thing he said to the women’s team that has stuck with me was, “If you want to go harder, exhale longer.”

Did he change from exhaling to holding or from holding to exhaling? (i.e. when did you hear him talking about maintaining air for as long as possible?)

tall n wet
6 years ago

Hypoxic is both good and bad. For a swimmer that is actively training and is under good coaching supervision, it helps. For the casual lap swimmer that frequents the local gym 3 days a week, they should avoid it like ebola

6 years ago

The best way to work on technique without turning your head to breathe is to use a snorkel.

Hypoxia occurs when venous blood oxygen saturation drops below 90%. Normal levels in a healthy individual at rest are above 96%. A well trained athlete working near their maximal oxygen consumption has a blood saturation of about 93%. For hypoxia to cause blackout (and very likely death or organ failure), levels would have to drop below 85%, which would be very unlikely to occur, as most people would pass out well before that as a response to a very high concentration of carbon dioxide.

Our medulla (brainstem) is the area of our brain responsible for the breathing reflex, and the urge… Read more »

6 years ago

I agree with 90% of this. However, holding air in the lungs while underwater kicking off walls is extremely important to increasing buoyancy and allowing the swimmer to “break out” high on the surface of the water. Once atop the water, swimmers should breathe as much as possible (without disrupting stroke rhythm) unless it is a 50.

6 years ago

I have to correct a statement I made…it has been a while since I polished up my understanding of some of this stuff, and it was nagging at me after my long-winded answer…my bad folks…the diaphragm causes exhalation the relaxed position. Not sure why I had my wires crossed on that, but for some reason I had it in my mind that it was the opposite. Probably the same reason I always want to spell “field” as “feild…”

6 years ago

Mr. Newsome and Cynic both make valid points. I guess the jury is still our on the training benefits of breathing control and how to best do it.

As far as competition: maybe a follow up article can be done on breathing while racing. On the one hand, you have the desire for efficiency and taking less breaths, but on the other hand you want to maximize oxygen intake. It seems to more are going in the direction of the latter, which I think is a good thing. For example, breathing every stroke on fly or distance freestyle. Back in the day a 400 free was more likely to be swum doing bilateral breathing every three strokes. Also, more… Read more »

6 years ago

*last sentence: you are less efficient doing an open turn but benefiting from more oxygen