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by Terry Heggy

February 3, 2015

Why breathing out is just as important as breathing in

Even before the development of scientific studies and advanced laboratories for metabolic analysis, swimmers became aware of the following basic facts:

  • Breathing in while your face is underwater is NOT the best respiratory strategy, and
  • Air is absolutely necessary if you’re planning to swim more than about 50 yards.

These two obvious truths made it necessary to create swimming strokes that allow the mouth and nose to exit the water to access the air. Nearly everyone understands that part, and no one has trouble inhaling while their heads are turned.

But when you're swimming freestyle, butterfly, or breaststroke, it’s underwater where the magic really happens. (These same principles apply to backstroke, even though your face isn't submerged.)

The CO2 Reflex

Most people think that they feel out-of-breath when they aren’t getting enough oxygen. The reality is a bit more complicated.

As your body uses oxygen, it creates carbon dioxide (CO2) as a waste product. As CO2 builds up within you, your body senses it and tells your brain that you need to breathe. Your breathing urges are driven by excessive CO2, not by a lack of oxygen. Getting rid of the CO2 helps relieve the out-of-breath distress.

Swimmers who don’t exhale properly will quickly feel winded because of this reflex, even though they probably aren’t really suffering oxygen debt. This is why many extremely fit triathletes may feel that they can only swim a few lengths of the pool before needing a long rest break—they’re holding their breath.

A word of caution: Hyperventilating (taking a series of deep, fast breaths before you swim) purges your CO2 reserves, which eliminates the safety mechanism of the breathing reflex. This can cause shallow water blackout, a condition in which your body runs out of oxygen and you pass out and drown without ever recognizing that you’re in danger. You should never hyperventilate before swimming and you should not attempt to swim long distances underwater.

Tips for Land Animals

Distance runners and cyclists would never dream of holding their breath during a competition, yet our instincts are to clamp up and stop breathing when our faces are in the water. To become an effective swimmer, we must fight this instinct.

  • Go for a hard run or bike ride, and pay attention to your breathing. You’ll most likely find that air is always moving either in or out, and that you inhale and exhale for very close to the same duration.
  • Apply that same breathing pattern in the pool. This means that you’ll start blowing out as soon as you finish inhaling, and that you’ll more effectively get the CO2 out of your lungs before turning for the next breath.

Some people find it helpful to count “1, 2,” or to silently think the words in and out to create the habit of rhythm. Experiment to find what works for you.

It's also important to blow at least some of the air out your nose to maximize the airflow and avoid getting water in your sinuses. This is especially critical when exhaling while you're upside down during a flip turn or on a backstroke start. Getting water up your nose is a memorably unpleasant experience.

Many experienced and elite swimmers are able to achieve full exhalation primarily through their noses. For less experienced swimmers, this takes practice—the important thing is to exhale completely so that you're ready to inhale during the breathing phase of the stroke.

Alternate Breathing

Many coaches urge swimmers to breathe on every third arm instead of constantly breathing on the same side. This has two primary benefits:

  • It makes your stroke more symmetrical and helps you recognize stroke anomalies.
  • It makes it easier to switch breathing sides in a race, so you can see your competitors or avoid chaos in open water.

For an alternate-side breathing pattern, you’ll have to slightly change your inhale/exhale timing ratio to an “out-out-in” count—but you should still keep air moving at all times.

Breathing with Economy

It seems logical to assume that it’s better to take as many strokes as possible between breaths to avoid any drag created by the breathing motion. Well, this might work for some sprinters, but after about 30 seconds of effort, your body switches to metabolic processes that require oxygen. If you want to maintain power past that point, you must breathe.

Although it’s a wonderful stroke aid to swim with a snorkel to perfect your alignment and posture, you really do need all the air you can get when it’s race time. If you’re swimming any sort of distance at all, you should not ever hold your breath. Instead, work with your coach to develop a smooth and drag-free breathing motion and good inhale/exhale rhythm.

Blow Away Panic and Keep Your Speed

There are times when you’ll feel especially out of breath, such as during the madness of a triathlon start, or coming off the wall from a flip turn. In those cases, rather than slowing down to rest, try blowing out a little harder to curtail the CO2 reflex. You’ll often find that you have more energy than you thought after you get rid of the “bad air.”

Are you ready to take the next step in your swimming journey? Try a free workout with a Masters club this July as part of our Try Masters Swimming campaign.

All you need to do is fill out our trial membership form, find a participating club in your area, and pick a workout time to swim with the club. Come experience for yourself the amazing emotional, mental, and physical health benefits tens of thousands of adults just like you across the country are already enjoying.



  • Technique and Training