— Chapter 01

How CO2 Tables Work

The urge to breathe during a breath hold is not caused by lack of oxygen. It is caused by rising carbon dioxide (CO2) levels in the blood, which trigger the diaphragm to contract involuntarily. These contractions — the sensation of needing to breathe — begin well before oxygen reaches dangerous levels.

CO2 tables train your nervous system to tolerate those contractions without aborting the hold. By progressively reducing rest intervals between sets, CO2 accumulates across the session. Each successive hold starts with a higher CO2 baseline than the one before. This repeated exposure desensitizes the response over weeks of training.

— Chapter 02

CO2 Table Protocol

Classic CO2 table structure: constant hold time, decreasing rest intervals. The hold time is set at 60-75% of your personal best static apnea time.

Example: 2:00 PB diver

Set
Hold time
Rest interval
1
1:30
2:00
2
1:30
1:55
3
1:30
1:50
4
1:30
1:45
5
1:30
1:40
6
1:30
1:35
7
1:30
1:30
8
1:30
1:25 (done)

The rest decreases by 5 seconds each round. Total session: approximately 25-30 minutes. The hold time stays constant — what changes is the amount of CO2 recovery between sets.

Adapting the table to your PB

1:30 PB
Hold time: 1:00. Rest starts at 2:00, decreases by 5 seconds per set.
2:00 PB
Hold time: 1:30. Rest starts at 2:00, decreases by 5 seconds per set.
3:00 PB
Hold time: 2:15. Rest starts at 2:30, decreases by 5 seconds per set.
4:00 PB
Hold time: 3:00. Rest starts at 3:00, decreases by 5 seconds per set.
— Chapter 03

How O2 Tables Work

O2 tables train the opposite adaptation. Instead of building CO2 tolerance, they train the body to function at low oxygen levels — to maintain consciousness and motor control during the hypoxic phase of a breath hold.

The structure is the inverse of CO2 tables: hold times increase with each set, rest stays constant. As holds get longer, each successive hold pushes oxygen lower. The fixed rest allows partial but not full recovery. Over a 6-8 week training block, the physiological adaptations include improved oxygen extraction efficiency and a lower threshold at which muscles switch from aerobic to anaerobic metabolism.

— Chapter 04

O2 Table Protocol

Classic O2 table structure: increasing hold times, constant rest. The final hold must not exceed 80% of your current static personal best.

Example: 4:00 PB diver

Set
Hold time
Rest interval
1
1:30
2:00
2
1:45
2:00
3
2:00
2:00
4
2:15
2:00
5
2:30
2:00
6
2:45
2:00
7
3:00
2:00
8
3:15
done

Hold time increases by 15 seconds each set. Rest stays at 2:00. Set 8 hold time (3:15) is 81% of a 4:00 PB — right at the safe ceiling. Do not program final holds above 80% of current PB.

Scaling for lower PB

2:00 PB
Holds: 0:45, 1:00, 1:00, 1:00, 1:00, 1:00, 1:15, 1:30. Rest: 2:00 constant.
3:00 PB
Holds: 1:00, 1:15, 1:30, 1:45, 2:00, 2:00, 2:00, 2:15. Rest: 2:00 constant.
— Chapter 05

Safety Rules

  • Never perform O2 tables alone in water — a trained rescue buddy must be present at all times.
  • CO2 tables done dry on land are safe for solo practice. CO2 tables in water still require a buddy.
  • Never combine CO2 and O2 tables in a single session — rest at least 24 hours between types.
  • Maximum 2-3 sessions per week total. Nervous system adaptation requires rest between exposures.
  • Stop any hold immediately if you feel lightheaded, experience visual disturbance, or feel a sudden loss of urge to breathe after heavy contractions — the latter is a pre-blackout warning.
  • Do not perform O2 tables after any alcohol consumption, medication that affects respiratory drive, or illness.
  • Final O2 table hold must not exceed 80% of your current static personal best.
— Chapter 06

6-Week Beginner Progression

This progression assumes no prior table training and a wet static PB of 1:30-2:00 minutes.

Week
Session type
Protocol
1
CO2 only (dry)
6 sets x 1:00 hold, rest 2:00 decreasing to 1:35
2
CO2 only (dry)
8 sets x 1:10 hold, rest 2:00 decreasing to 1:25
3
CO2 (dry) + CO2 (wet with buddy)
Dry: 8 x 1:15. Wet: 6 x 1:00.
4
CO2 (dry) + O2 first attempt (wet with buddy)
Dry CO2 as normal. O2 wet: 6 sets only, hold max 70% of PB.
5
CO2 (dry) + O2 (wet with buddy)
Full 8-set O2 table at 75% PB ceiling.
6
Assessment
Run best CO2 and O2 tables. Compare contractions onset time vs Week 1.

By week 6, most divers with consistent training report a 15-25% improvement in the time before first contraction on a static hold, and a 10-20% extension in total static PB. These improvements come from the CO2 tolerance and O2 efficiency adaptations respectively.