I recently asked about underwater swimming and the topic of hyperventilating came up. If I do a 5 minute session of hyperventilating twice a week prior to swimming is this likely to have any significant effect for good or bad on my fitness?

  • I should mention that when I suggested some hyperventilating before an underwater swim, I meant a few seconds just before you submerge, and not a several minute session of it. Anecdotally, those few seconds have benefitted my ability to swim lengths underwater.
    – Alec
    Commented Nov 22, 2017 at 13:10
  • @Alec I'm impressed that you can swim a length with just a few seconds of hyperventtilating. I certaily need lots of minutes to do it, but you may well be younger and or fitter than me...
    – Slarty
    Commented Nov 22, 2017 at 16:19
  • Well, I can swim almost the full length (25m) without hyperventilating. But I see the local swimming club pull that off without even trying. There is definitely something to be said for their technique though. They get more mileage per stroke, and spend less energy/oxygen on it.
    – Alec
    Commented Nov 22, 2017 at 17:18
  • Clarifying question: do you just want to be able to swim the whole length underwater for the sake of doing it? Or do you want to do it because you think that it's especially valuable in terms of staying fit? If it's the latter, we could are tons of breath control exercises that are more valuable for overall fitness.
    – zigzag
    Commented Nov 28, 2017 at 15:18
  • @zigzag I'm just doing it for the sake of it realy. Managed another under water length today. I think I have the measure of it now - it just needs (for me) several minutes of deep breathing. I was mildly concerned that I might do my self some harm...
    – Slarty
    Commented Nov 28, 2017 at 16:51

1 Answer 1


Hyperventilation is a legitimate method for increasing the proportion of oxygen in the blood for the purpose of things like holding one's breath. However, there is a caveat to it, namely that the body tracks both carbon dioxide levels and oxygen levels, and with what's essentially two different mechanisms. Hyperventilation decreases CO2 faster than it increases oxygen, which means extensive hyperventilation can lead to a situation where, while holding your breath, your oxygen levels drop too low, leading to a black-out, but the CO2 levels are not elevated enough to trigger the breathing reflex. This has a practical benefit in that, if it happens when you are swimming, you don't immediately start inhaling water. However, due to the different parts of the brain and when they shut down, people will often continue swimming while unconscious, and risk injury from running into walls and the like. Additionally, the period of time between when your body is starved for oxygen and when you start breathing again can lead to a situation of hypoxia, a lack of oxygen in the tissues. This generally does not cause brain damage, because the body begins to horde the remaining oxygen to preserve your brain, but the resultant lack of oxygenation in the extremities can lead to painful cramping.

More anecdotally, I've heard that repeated hyperventilation can change the point at which your body believes it needs more oxygen, which can eventually lead to not getting sufficient oxygenation because you've effectively trained your brain into believing that famine is the new norm. However, I can't find any actual scientific proof of that online, so that could be a wives tale.

As for whether it works as an exercise, I can't really say. The general use of it is instead to facilitate being able to hold one's breath, or to artificially boost performance by putting the body into a state of hyperoxygenation, done as a preparation for an exercise rather than an exercise itself.

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