Why is hyperventilation not good for you? That's my secret weapon in competitive breath-holding situations with children.
hyperventilating before a breath-hold is bad. From the AIDA Freedive manual:
Simply defined, hyperventilation is in- and exhaling more air than you need to maintain a neutral level of CO2 in your blood.
Of course this definition depends greatly on your current state of activity. In a relaxation exercise while lying on your bed you are barely producing CO2, whereas in a 400m sprint you produce such big amounts that your breathing cannot catch up with exhaling enough of it. In the first case any audible breath would already considered to be hyperventilation, while it is not possible to hyperventilate during the 400m run.
No additional O2 storage
With an Oximeter the Oxygen saturation of your blood can be measured by attaching it to your finger. at at any given time your blood is saturated with Oxygen levels at around 96-99%. If you are significantly below that reading you are either exerted and need to rest or you are sick and should consult a doctor.
You can prove to not be able to increase the readings by hyperventilating with the Oximeter still on your finger. the reading remains more or less steady. You cannot put more tea in a cup that is already full. Sometimes the blood saturation with Oxygen might increase by one percent, but at a great cost: You have to literally over-exert yourself with breathing!
after all, hyperventilation does not store more Oxygen in your blood!
Negative effects of hyperventilation
In the breath hold exercise mentioned earlier it was not possible to do extend the
Feeling the water carrying you helps to relax
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AIDA2 MANUAL CHAPTER 04
breath hold indefinitely because of the rising level of CO2. But by hyperventilating before the experiment it is possible that you pass out from low Oxygen levels without even feeling the first signal of rising CO2. hyperventilation can postpone the signals of rising CO2 to such an extent! hyperventilation does not store more Oxygen, it actually lowers the level of CO2.
If you pass out while your face is submerged, you will not unconsciously inhale water, but simply die after a few minutes. Only a buddy watching over you at all times and performing a timely rescue if needed will save you from this ill fate. this is the main reason why hyperventilating before freediving is so dangerous.
apart from the potentially fatal danger, hyperventilation has other disadvantages for breath holding. hyperventilation raises the heart rate, which goes against the goal of starting a breath hold in the most relaxed state as possible. hyperventilation also reduces the blood flow to the brain while increasing it towards the extremities. Once you have started your breath hold, your body will need to reverse this process to conserve Oxygen (see the chapter about the “Mammalian Dive response” in aIDa4). In short, in a breath hold after hyperventilation, your body will not conserve Oxygen as much as it potentially could and is thus using up its Oxygen reserves faster. You can black out earlier than you would have in a completely relaxed state.