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Breathing: The Limiting Factor

March 3, 2013

I was recently challenged by an old friend (Sue Chen @1650sue) to consider the question of breathing into and out of flip turns.  My personal thoughts on the subject have always been simple: if you can get away with it, do it.  However, this was an opportunity to question my beliefs on the subject.   What resulted was aa veritable rabbit’s hole of inquiry.  Thus, this will form a series of blogs where I try to lay out the basic state of scientific knowledge of the factors governing breathing rate in swimming.

“You want to know the secret of life,” he asked. “It is to breathe in and out.” — Sixto Rodriguez


  • Swimming performance is limited by oxygen consumption especially longer distance races (200-500 free and above).
  • Oxygen consumption is a function of respiration rate (breaths per minute) and tidal volume (size of breaths).
  • Tidal volume can be adjusted somewhat to accommodate conditions, but within certain individual limits.
  • In swimming, respiration rate is limited by stroke rate (strokes per minute) and breathing pattern (strokes per breath).
  • Increases in respiration rate are also limited, and at some point become counter-productive due to “hyper-ventilation”.

Looking at these assumptions, it becomes clear that the regulation of our oxygen supply in the form of breathing pattern, and the actual mechanisms that govern the absorption of oxygen into the blood stream are of critical importance.  Two related questions come to mind:

  1. Is there a limit to our ability to adjust tidal volume?
  2. In other words, is there a point at which we need to take more frequent breaths instead of simply larger breaths?

A Decent Proposal
If the answer to these questions is in the affirmative, I will make one proposition:

It is in our best interest to take as many breaths per length as possible without hyperventilating.

So, in order to come up with real recommendations about breathing into and out of turns, we need to figure out if their is a real physiological need for extra breaths, and the bio-mechanical/hydrodynamic costs of taking those breaths.  If the physiological need is there, it leads us to one more final proposition:

There are better and worse ways to execute a breath in the strokes leading into and coming out of a turn.

To be continued…

  1. Grant permalink

    More points to consider. The need to breath in the human body is triggered by the concentration of CO2, not the amount of O2 present. We almost always have the requisite amount of O2 available. See CPR. So, the ability to exhale fully and not panic breath or pile additional air on top of air is key.

    Point #2 or as I like to call it Grant being a pain in the ass (or Devil’s Advocate)
    Cyclist attempting to break any record on the track travel to altitude to make their attempts. The proven reality is that that increased efficiency of the thinner air is worth the offset of decreased available O2. So when looking at breaths in Distance swimming, the increased intake of O2 (ie breathing in and out of walls, or increasing stroke rate) has to be match by a small decrease in efficiency. Or the other way, does the increased efficiency of not breathing supersede the increased 02.

    • robertwb permalink

      Hey Grant – Sue made the same clarification, i.e., that we are quite possibly as interested in the voiding of CO2 as opposed to intake of O2. Though, given your points, do you think that we need to place some metric on the quality of the breath? Other than my generalistic “avoid hyperventilation” criteria?

      To your other notion, not sure if I understand what you are getting at – or are you just talking about if the extra air is worth the hydrodynamic cost of turning the head to the side and grabbing a breath ( what I called “a real physiological need for extra breaths [vs.] the bio-mechanical/hydrodynamic costs of taking those breaths”)?? Going into that part next blog, but if you have some thoughts I wanna hear’em. One of the things I want to question, of course, is whether the gain in respiration “has to be matched” by a loss in hydrodynamic efficiency. If I am missing your point, then please explain :).

    • robertwb permalink

      Oh hey – while you’re at it — in terms of the CO2/O2 issue – what are the mechanisms involved that make the CO2 the limiting factor here? Thanks!

  2. grant permalink

    Chemo receptors in the aorta and other arteries measure CO2 amounts in arterial blood and send info to the Medulla which triggers breathing.

    My point on the efficiency is difficult to measure that breath in and out of the turn changes our form and turn form, especially when fatigued. My question is what effect does that loss of momentum have on overall speed. And is the extra air worth the loss in momentum in addition to the usage of energy to get the breath. I would argue that in the vast majority of athletes, the former is a bigger loss than the later

    • robertwb permalink

      Thanks for the Medulla info. My question about that pertains to actual need versus perceived need. I am wondering if you are arguing that we don’t actually need to breathe due to lack of oxygen absorption, but rather need to breathe because we “hurt” due to CO2 build-up. Curious?

      Well, you were talking about what I thought. We will look into this later, though I think it slightly misleading to use the analogy of time trialling a bike at higher altitude, since the difference in resistance is observed on every single pedal stroke of the effort, whereas the difference in hydrodynamic resistance of adding an extra breath in is only witnessed on the actual stroke in question – IF it exists at all. Not to get ahead of myself, but I would argue that if the concern of loss of proficiency at higher levels of fatigue is justofoed (and i think that it is) it just makes it all the more important to practice.

  3. grant permalink

    Could not agree more at the practice comment. There is no doubt that there is a perception of need that we can overcome, but some of it is very real. Hence the quality of exhalation measurement. If that is even possible.

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