What it's for

Trains you to stay calm as carbon dioxide builds up. The hold stays the same each round while the rests between holds get shorter, so each hold starts with more CO2 in your body than the last.

It's the urge to breathe you're training, not your oxygen. Over time the urge tends to arrive later and feel less pressing, which is why the first contraction is the number to watch.

How to do it

Hold on a relaxed full breath in, not packed. Breathe calmly and normally beforehand: never hyperventilate.

Sit or lie down and stay relaxed. Tap Contraction at your first diaphragm contraction, and Breathe if a hold stops feeling controlled.

Contractions

A contraction is an involuntary jerk or pulse of your diaphragm, felt in your belly or chest. It can feel like a hiccup or an urge to swallow. It's a normal sign of rising CO2, not an emergency, and many people keep holding calmly through the first few.

Tap Contraction the first time you feel one: it records how far into the hold it came, and a later first contraction over time shows your tolerance improving. It's optional, and skipping it never affects your progression.

What it's for

Trains you to cope with lower oxygen. The rests stay the same while the holds get longer, rising from 40% of your max to the level's final hold, never more than 80% of your max.

It's the more demanding table, so it's used less often, with at least two clear days between O2 tables and max tests.

How to do it

Hold on a relaxed full breath in, not packed. Breathe calmly and normally beforehand: never hyperventilate.

Sit or lie down and stay relaxed. Tap Breathe if a hold stops feeling controlled.

Contractions

A contraction is an involuntary jerk or pulse of your diaphragm, felt in your belly or chest. It can feel like a hiccup or an urge to swallow. It's a normal sign of rising CO2, not an emergency, and many people keep holding calmly through the first few.

Tap Contraction the first time you feel one: it records how far into the hold it came, and a later first contraction over time shows your tolerance improving. It's optional, and skipping it never affects your progression.

What it's for

Adds gentle movement, which builds CO2 faster, so you practise staying relaxed while your body is working. The holds are short and stop at moderate air hunger, so they train tolerance without strain.

How to do it

Walk at an easy pace on flat ground. After a normal breath out (not forced), pinch your nose and keep walking.

Tap Breathe at moderate air hunger, then breathe through your nose and keep walking for at least 1:00, until your breathing feels normal.

What it's for

Breathing a little less than you'd like, for a few minutes at a time, raises CO2 gently and steadily. It trains you to sit comfortably with mild air hunger, with no breath holds at all.

How to do it

Seated, or during very easy walking or cycling. Breathe through your nose, slower and softer than you'd like, keeping a light but steady air hunger.

If it becomes stressful or your breathing turns ragged, breathe normally.

What it's for

Measures your longest relaxed breath hold. Every table is built as a percentage of it, so retesting every few weeks keeps your tables matched to you.

How to do it

2:00 of calm breathing, two easy warm-up holds with rests between, then the max attempt.

Hold on a relaxed full breath in, not packed. Breathe calmly and normally beforehand: never hyperventilate.

Stop when staying relaxed becomes a struggle: it's a test, not a fight.

Contractions

A contraction is an involuntary jerk or pulse of your diaphragm, felt in your belly or chest. It can feel like a hiccup or an urge to swallow. It's a normal sign of rising CO2, not an emergency, and many people keep holding calmly through the first few.

Tap Contraction the first time you feel one: it records how far into the hold it came, and a later first contraction over time shows your tolerance improving. It's optional, and skipping it never affects your progression.