How Oxygen Affects Our Bodies in a Swim Race

The Art of Breathing Part I – Swim Race

Breathing while swimming seems like a natural thing to do. After all, we do it all the time without even thinking about it and, if we stop doing it, we cannot survive for more than about 7 minutes. Yet, while swimming, breathing is not that simple. The questions ‘How often do we breathe?’ ‘Where do we breathe?’ or even ‘How do we breathe?’ are legitimate ones. The answers are not that obvious, either.

Breathing in swimming freestyle or butterfly can be problematic. It can slow the stroke rate, if one takes too long to get the breath. It can lead to an increase in frontal drag, if the breath causes an alteration in the pulling motion of the arm under water, or if the head lifts too much for the breath. Yet, in any race lasting longer than about 20 seconds, the delivery of oxygen to the muscles, in order to provide an important source of energy, is vital to our ability to sustain speed. In other words, we have to breathe to keep our pace.

The fastest way to swim fly and free is without breathing. Unfortunately, in any race event over a 50 sprint, not breathing enough leads to a catastrophic dependence on anaerobic sources of energy, which leads quickly to a lowering of the body’s pH (H+ ions). Once the body begins to become acidic, the muscles cease to recover or function at the same rate. In swimming vernacular, we ‘die’ in our races.

Perhaps the fastest way to increase the body’s pH, to restore neutrality, is by breathing. The faster the respiratory rate, the more CO2 we blow off in order to increase our body’s pH. Frequent breathing during intense exercise not only helps to maintain a neutral pH, but it also helps prevent the acidosis to begin with by delivering more oxygen to the muscles. Having a pipeline flow of oxygen delivered to the muscles engaged in the activity is essential to high performance swimming. Increasing the stroke volume of the heart, increasing the numbers of red blood cells, improving the transport systems for delivering oxygen to the muscle cells, increasing the numbers of mitochondria in the muscle cells available to convert glucose into ATP (Adenosine triphosphate, the fuel for our muscles), and increasing the number and type of muscle fibers available for contraction are all important parts of the physiological and anatomical improvements we seek from training. Yet, even if we develop those systems, none of them are optimized if we don’t have a nice flow of oxygen arriving at the alveoli of our lungs, ready to be delivered to the muscle.

After the first 20 seconds or so of our race, when we have used up the most readily available and stored sources of high-energy phosphate (Creatine phosphate), the two systems of producing ATP on an ongoing basis are the aerobic (with oxygen) and the anaerobic (without oxygen) systems. The two systems are needed and work simultaneously during intense exercise to produce the kind of power required to swim very fast. While the aerobic system produces more ATP per molecule of glucose than the anaerobic system (approximately 36 moles of ATP vs 2 moles of ATP), the anaerobic system produces ATP faster than the aerobic system. In this respect, they each may have their advantage, yet only the anaerobic system will lower our body’s pH, leading to a dysfunction of muscular contraction. The more we can utilize our aerobic system of producing ATP, the longer we can sustain our power.

If you compare the respiratory rates of swimmers racing with competing athletes from other sports, like running or cycling, where they can breathe at will, the rates of swimmers are usually slower. At maximum effort on land, the respiratory rate of an athlete is typically 50-60 breaths per minute. Rarely is a swimmer breathing that often, either in a race or in practice. One can make the argument that swimmers train hypoxically most of the time, which means that by under delivering oxygen to the lungs, swimmers are developing all of the other body’s mechanisms to deliver oxygen more efficiently to our muscles and to manage lactate production. By training at altitude, where even less oxygen gets delivered to the muscles, one can build all of those mechanisms even better and faster. That is a good thing. But when it comes to racing, other than in the 50 sprints, do we want to race hypoxically? I think not. I can still recall the pain of swimming the 400 IM at the Olympic Games of Mexico City (7,000 feet) in a time about 10 seconds slower than I would have swum at sea level. At altitude, we may not have the choice of getting as much as oxygen as we need, but at sea level, it makes less sense to deprive ourselves of getting that oxygen. That means swimmers should be breathing more, not less.

Next time, we will discuss the how and where of breathing in freestyle and fly.

Yours in swimming,

Gary Sr.

Read How to Inhale and Exhale While Swimming Fast: The Art of Breathing Part II

Read Oxygen! How Often Should I Breathe in Swimming: The Art of Breathing Part III

23 Responses to How Oxygen Affects Our Bodies in a Swim Race

  1. Carol-Ann Infante

    Hi, great aqua note. Many thanks for the advice. Lately I have been training for a 400m breastroke, my stroke rate is quite slow, only 6-7 breaths per length, I find after the first 100m I have difficulty sustaining the underwater pullout, as my lungs feel like they are going to burst and my body just has this weird feeling all over and my muscular output is seriously diminished. I deliberately chose a slower stroke rate to be able to last the 400m, but I am wondering after your Aqua note if I am breathing so little that the weird feeling is acidosis, and so it might be better to take 8-9 strokes per length and breathe more? I would be grateful for any opinion you have on this.
    Many thanks for the great vids and advice

    • Gary Hall Sr.

      Although in freestyle we can choose between different breathing patterns, in backstroke, breast and fly, our respiratory rate is tied directly to our stroke rate. Even though our oxygen demand will go up with stroke rate, it is better to try to get closer to the physiological ideal of 45-55 breaths per minute, if we can. Of course, to race that way, we need to train that way. In your case, I would try to get to the higher stroke rate with more breaths, if you can. But practice that way!

  2. Marcia Hill

    I never know how many breaths to take. In the 200 free I breathe 2 and 2, but in the 100 and 50 I’m always experimenting never sure what will work best. Please hurry, I have big meets coming up lol.

    • Gary Hall Sr.

      Hi Marcia! In any event over the 50 meter sprint, you are really depending on a fully developed aerobic system and want to maximize its use. Although I am fan of breathing every cycle (so long as the breath is done correctly), for those that insist on breathing to both sides, try breathing 3 in a row to one side, hold one cycle, then breath 3 in a row to the opposite side. That comes close to the respiratory rate of every cycle, yet gives you a look to both sides of the pool. In your 50 breath as little as possible, within your capability.

  3. Jana Fitzpatrick

    Yes – and adding on to Marcia..what side would be best for freestyle? Alternating? Favorite? Sighting the competition? and in a pattern of some kind or what?

    • Gary Hall Sr.

      See above comment..but I like breathing in a pattern. Otherwise, we tend to hold our breath too long at the beginning of the race. Once we lower our pH a certain amount all systems begin to fail.
      Sometimes, the mechanics of the breath and underwater pull are better when an athlete breaths to one side versus the other. I usually pick that side for the breath…and it may not be the side you are most comfortable breathing on.

  4. Sofia de Lucas

    Hey! In freestyle events I swim the 400, 800 and some marathons.. So, Even in 50/100 meters sprints I have a lot of difficultly breathing each 3 strokes.

    How can I train my body, in a way I don’t breath so much in 50/100 meters events?

    • Gary Hall Sr.

      Train hypoxically (less oxygen than ideal). Race aerobically (breathing as often as practical). I also recommend all of you wear a training mask for 45 minutes each day after practice (you can order them on our site…most people wear medium). It will train you to breathe better and strengthen your core. It is a great tool for breathing.

  5. Sam Penny

    A great article Gary Snr. I’m looking forward to your next article on how and where of breathing as there aren’t any great articles out there. Would be great if there was a video for this as well.



  7. John

    For me this is fascinating topic and experience as a swimmer and lung doctor.

    Oxygen delivery to the muscles which facilitates aerobic metabolism is rate limited by cardiac output (how much and how fast the heart delivers oxygenated blood). A healthy adult is limited up to maximum exertion by cardiovascular function (in essences, we have excess lung function in reserve). As you indicate, a runner can breathe 50-60/sec but a swimmer perhaps much less so. Gary, I am wondering if:

    a) are swimmers noted to have low oxygen saturation when swimming due to an inability to breath as much as the body would like
    b) Where do elite swimmers end up on V02 max recordings. Presumably high, but perhaps not as high as cyclists and cross country skier.
    c) Is it possible the MOST important thing is to reduce frontal drag?
    d) The sensation of shortness of breath for me on the breakout is so extreme that I can’t help but pop up for air like a cork which destroys my streamline. Am I hypoxic, hypercarbic or maybe I have a low pain threshold for suffocation?!

    Thanks for a great website!

  8. Gary Hall Sr.


    These are all great questions. As adults growing older, our maximum heart rate diminishes and likely our stroke volume, although both are likely to improve with aerobic training at any age. Here are my best guesses to your questions:

    a) Swimming with a lower than ideal respiratory rate contributes to lower oxygen saturation and earlier lowering of body pH
    b) VO2 max rates are variable among elite swimmers and higher in endurance swimmers. How those stack up against elite cyclists or runners, I am not sure. It would be interesting to look at. I know Mark Spitz had a higher VO2 max than I did, even though I trained more than he did.
    c) Frontal drag is the number one enemy of the swimmer. With the relationship to velocity squared, frontal drag (ie technique) becomes even more important at the elite level.
    d) Could be all three, plus underdeveloped aerobic systems. I love spearfishing here in the Keys with my sons and daughters, but at around 30 years younger, they can stay down a minute or so longer than I can. There is a tremendous mental component to free diving, but while swimming, when you are already in oxygen debt, training hypoxically will help you get through the turn with a good streamline and your head down. Just don’t take two many dolphin kicks!

    • Gary Hall Sr.

      I mean ‘too many’…but was thinking two is max..if any at all. sometimes better for masters swimmers to flutter kick off the wall.

  9. Marcia Hill

    This whole discussion is extremely helpful. I like to breathe to both side because I feel it balances my stroke, otherwise I lose the rhythm somehow. I will try breathing 3 and 3 for the mee this week. Then we’ll see.

  10. Marcia Hill

    How did you breathe in the mid to longer distances when you were racing? Just curious.

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  15. Tom Shroyer

    Compare and contrast the flutter kicks off the wall vs dolphin kicks off the wall/two max as per the comment above for older (60) Masters.

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