Hyperventilation

Hyperventilation means breathing more forcefully, rapidly or shallowly than normal.

It is common in practices like holotropic breathwork, Wim Hof, and some types of meditation.

It has various benefits in these practices, like releasing difficult emotions and staying warm in the cold. But it is dangerous in a freediving context and should never be combined with freediving.

Hyperventilation deprives cells of oxygen

By reducing CO2 below normal levels, hyperventilation changes the pH of your blood in such a way as to cause haemoglobin to bind more tightly to oxygen.

This means the haemoglobin does not release oxygen to the cells that need it.

If you are training your cells to be more tolerant of low-oxygen environments, like high altitudes, this can be a useful exercise, but it is dangerous to be in this state while holding your breath underwater.

Raises the heart rate

Hyperventilation significantly raises your heart rate, which more quickly burns up your oxygen supply.

Deprives the brain of blood

Hyperventilation pushes blood away from your brain and towards your extremities, like your hands and feet, which can be useful for staying warm in an icebath, but makes you more prone to blackout when your brain's oxygen is already low.