O2 tables: longer holds with a fixed rest
Updated October 18, 2026
An O2 table flips the CO2 table around: the rest stays the same and every hold gets a little longer. Where a CO2 table works on the urge to breathe, an O2 table works on holding as oxygen runs lower. That makes it the more advanced exercise of the two — SSI suggests practising tables only after a freediving course, and only with a qualified buddy.
How it differs from a CO2 table
| CO2 table | O2 table | |
|---|---|---|
| Hold | Same every round | Longer every round |
| Rest | Shorter every round | 2:00 every round |
| Mainly trains | The urge to breathe | Holding with less oxygen |
How an O2 table is built
- Rest: 2:00, every round. The first rest doubles as your breathe-up.
- Hold: starts around 50% of your personal best and climbs in steps — often 15 seconds — to about 80% of it. Some programmes go higher; stopping at 80% keeps a margin below your maximum.
- Rounds: 8.
breathtable spreads the steps evenly between 50% and 80% of your PB and rounds them to 5 seconds. For a PB of 2:00:
| Round | Rest | Hold |
|---|---|---|
| 1 | 2:00 | 1:00 |
| 2 | 2:00 | 1:05 |
| 3 | 2:00 | 1:10 |
| 4 | 2:00 | 1:15 |
| 5 | 2:00 | 1:20 |
| 6 | 2:00 | 1:25 |
| 7 | 2:00 | 1:30 |
| 8 | 2:00 | 1:35 |
Why it needs more care
The last holds of an O2 table sit close to your limit, and oxygen keeps falling from one round to the next. A blackout can come without any warning — lying on a bed or mat lowers the danger of a fall but does not remove the risk of blacking out. So:
- Always have a buddy right next to you who knows what you are doing and is watching.
- Stay lying down for the whole table. Never practise holds standing or walking: a standing blackout means a hard fall.
- In the final rounds, end the hold when the urge to breathe turns strong. Don’t try to “earn” the round.
- Never do an O2 table in or near water.
Running it in the trainer
The rhythm is the same as a CO2 table: breathe-up, final breath, hold, three recovery breaths. A 2:00 rest leaves plenty of room for relaxed breathing. If you end a hold early with “Breathe now”, the result screen shows where you stopped, which is useful when you rebuild the table later.
Using O2 and CO2 tables together
If you train with both, keep O2 tables the less frequent of the two and don’t put both on the same day. Build each from a recently measured PB, and when your PB changes, rebuild both.
Open the trainer