Measuring your static personal best safely

Updated October 18, 2026

CO2 and O2 tables are both built from your personal best (PB): the longest breath hold you can do relaxed, lying down, on dry land. Get it too high and every table is a struggle; too low and the sessions don’t do much. The goal is a calm, repeatable number — not a test of willpower.

Before you measure

Lie down on a bed or mat where you can’t fall.
Have someone nearby who knows what you are doing. Blackouts can happen without warning, even on dry land.
Be rested. Not straight after a meal, exercise or a table.
Remove distractions so you can relax completely.

How to measure

Breathe up for about two minutes with relaxed breathing: normal volume, exhaling longer than you inhale. No hyperventilating.
Breathe out fully, then take a full but comfortable final breath, belly first, then chest.
Hold and relax everything. Work through your body from feet to head — legs, hips, hands, shoulders, jaw — letting each part go loose. Relaxation is the single biggest factor in how long you can hold.
Stop when holding on would mean fighting — strong, rhythmic contractions, or any dizziness, tingling or change in your vision.
Take three recovery breaths straight away.

That time is your PB for tables. It is deliberately not your absolute limit.

Measuring in breathtable

Choose “Measure PB”. You get a breathe-up of the length you set, then an open-ended hold with a clock counting up. Tap “Breathe now” when you are done; the trainer runs your recovery breaths and offers to save the time as your PB. Both tables are rebuilt from it automatically, unless you edited a table yourself — then use “Rebuild from PB”.

Why not go to the absolute limit

Pushing to your maximum on dry land teaches you to fight the hold rather than relax into it, and it brings you closer to a blackout. Since tables use a percentage of your PB, a number you can reach calmly on any normal day gives better tables than a one-off maximum.

How often to re-measure

Every few weeks, or whenever your tables start to feel easy. Measure on a different day from a table session, and rebuild your tables from the new number. If your PB drops — after illness, poor sleep or a long break — that’s normal; build from the lower number until it comes back.

Open the trainer