If the brain can only survive 4-6 minutes without oxygen, how can freedivers hold their breath for 8+ minutes?

Question

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

Answer 1

Aside from all the things already mentioned there are specific techniques free divers can use to gather large quantities of oxygen in their lungs and bloodystem prior to diving, like breathing techniques and such.