Hi Greg, interesting and possibly educational question, something a knowledgeable freedive instructor should know.
I think the answer lies in your trainings objective, what is your goal?
My guess (derived from further posts) is: - a longer breath-hold ability.
Then my question is, how would you reach that goal? Answer: practice, or - better - training.
What is training? - A structured number of exercises.
What exercises do you need?
This depends on your current skill and level of tolerances.
The CO2 and O2 tables are designed for training the two different aspects of breath-holding (more) separately.
Now you wish to combine them? Why? Presumably to safe training time, and or explore something new.
I see great benefit in splitting up performances in components, and training those components separately because it allows me to focus and find improvements quicker without sharing much attention to the other parts of the whole, therefore learning faster, which is more measurable and more fun.
CO2:
In the interest of time I've changed my CO2 schedule to something like this:
Normal static relaxation prep, including warming up muscles, gentle stretching, and bringing my metabolism down.
3' hold,
1'rest.
3' hold,
45' rest.
3' hold,
30' rest.
3' hold,
15' rest./ 2 breaths.
3' hold,
15' rest./ 2 breaths.
3' hold,
15' rest./ 2 breaths.
3' hold,
15' rest./ 2 breaths.
3' hold,
15' rest./ 2 breaths.
24min hold - 3:30 rest.
You see I've cut out a lot of in-between rest time, and quickly arrive at just taking 2 breaths. This ensures that I have more time in 'training range', the time when CO2 levels are high and need to learn to deal with them.
During and afterwards this gives me a nice CO2 buzz, which to me make breath-holding enjoyable.
O2.
For O2 training I like to the very challenging Herbert Nitch 'Crazy Table'.
Same prep as the CO2.
Exhale fully, dive.
Hold as long as you can, but stay away from samba's off cause! - so I estimate to 85% effort. Then briefly surface and inhale 1 mouth-full of air dive again to 85%.
Repeat until you lungs are full.
With practice you're total dive time should be around to your maximum full breath-hold time.
The beauty of this exercise is that you'll experience a steep O2 challenge in short blocks of time, making it feel like the last 1 minute of a normal maximum hold repeatedly. With this repetition you have more time to get used to and find your way around that most challenging part of the maximum breath-hold. So that your 6-7 minute exercise may create 6-7 times that 'last minute' experience.
Levels of training.
These steep tables are not suited for beginners: men below the 5' maximum breath-hold level, and women below the 4'. This is because beginners can learn more from having a easier and more gradual increase in difficulty, allowing them more recovery and time at the medium high CO2 and O2 levels.
But if you have an able dedicated dive buddy and coach you can try them for sure, maybe with some base time adaptations, like taking 2' instead of 3' for the CO2 schedule. Another warning, the 'Crazy Table' starts and feels like an empty lung dive. Those put extra tension on the breathing system when contractions appear. Also diving empty lungs yield less response time between doing fine and needing to get O2. Because of this I have my hands on the edge of the pool, and my head floating on the surface, so I can nearly
instantly take that mouth of air when I feel I need it.
To novices I really want to stress that Freeving in water should be done with a dedicated and educated in freediving safety buddy.
Empty lung + hyperventilation is a very easy way to loose consciousness and control of your mind and body. With nobody next to you checking and observing you'll sink and be dead in minutes. With a pool staff unaware, shocked, angry, fired, sued; underwater swimming is very probable to be forbidding after you drown! And besides the immense grief to your parents and loved ones this little understood sport will suffer much from a very bad image. So please think things through and be able to respond (responsible) to questions about safety.
