[trux]

Personally, I do not do any breath up or deep breathing at all, when training. I just breath as usually, and rather work on relaxation. Finally, the purpose of the training is not to do longer tables than others, but to accustom the body and soul to harder conditions. So for example it makes no sense to breath deeply when you do static or dynamic hypercapnic exercises, because you would kill their purpose which is in building up high level of CO2. It is much more efficient doing a CO2 exercise without hyperventilation, deep breathing, and/or purges, than doing a longer table with it. Unfortunately, I often see that people mostly prefer doing longer tables with a lot of breathing, just to be in the "upper class" of freedivers who do the longest tables.

There is a nice hypercapnic exercise that avoids such hyperventilation - do a series of apneas during 5, 8 or 10 minutes (or more; depending on your level), taking always only a single and slow breath in between. The length of the individual breath hold is not important, but you should not reduce the time in the series, but rather try increasing it. Hence, you better start with about 25% of your max. This exercise will assure a nice CO2 build-up and avoid excess hyperventilation.

And hyperventilating is unwanted at hypoxic exercises as well, since by hyperventilating or deep breaths you risk samba or blackout. So I'd recommend little bit deeper breathing only occasionally, with good surveillance, just to see the difference and for knowing how far you can go safely when doing max.