And what about people like David Blaine or Tom Sietas? Sietas held his breath underwater for over 22 minutes (world record). I know they train for it like months and even years, but doesn’t holding your breath = no oxygen to brain?
Permanent brain damage apparently occurs just after 4 minutes of lack of oxygen to the brain, so why are freedivers left generally unscathed after 8 or 10 minutes without air?
In: Biology
The athletes inhale before holding their breath, and trap a large amount of air in their lungs. Heart continues to pump blood through the lungs (loading up oxygen) and to the brain (oxygenating the brain) and back to the lungs (unloading carbon dioxide and loading oxygen again). This slowly replaces the oxygen in the air in the lungs with carbon dioxide in the air in the lungs, so they will run out of oxygen eventually, but as you can see it can take some time.
When you breathe normally, only [a small percentage](https://www.sharecare.com/health/air-quality/oxygen-person-consume-a-day) of the oxygen in the air you inhale actually gets into the blood. You could take several breaths of the same air, and it would still have sufficient oxygen for you.
Athletes train to improve their circulation (blood flow, blood effectiveness at transporting oxygen) and lung capacity (how much air is held per breath) to maximize the process of “breathing” and getting oxygen to their brain.
You should know that the other cells in your body require oxygen too. Muscles, for example, will consume a lot of it if you exercise them. So part of the training is also to minimize muscle effort during the dive, in order to reserve as much of the oxygen as possible for the brain.
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