breath hold

Hello, When using an oximeter or a similar device to monitor oxygen levels during freediving, what is the percent/number that you should start to ascend for (ex. do I start ascending at 90% ,80% , etc.?) I know the precents can vary between beginners and advanced free divers so I want to know...

I made a brief video about the neurobiology of holding your breath. In brief, two regions in the brain stem, the pre-Bötzinger complex and the retinotrapezoid nucleus are mainly responsible for automatic breathing. The motor cortex and the cerebellum are the regions responsible for willfully...