[trux]

Excellent post, GetawayFK! Although you did not really address the question directly, the answer was quite informative anyway. Since you seem to be an expert in the area, I use the thread to ask you little bit more (moderators please feel free to move it to the general freediving forum. BTW, I think DB deserves to have a separate sub-forum specifically for freediving physiology, medical, and scientific topics - such threads are not unusual here and it wouldn't be bad having all those interesting posts nicely together in one place).

So, GetawayFK, while most people here know that hyperventilation is dangerous and even counterproductive for freediving, there was so far only little information about the impact of altitude adoption (or the use of hypoxic tents) on breath-holding. I wonder if there was any deeper study made.

From what I understood, the 2,3-DPG's ability to stabilize Hb in the T-state, although it is working well for moderate hypoxic states, especially if the ventilation of air in lungs is assured (even if with lower O2 content), it may be quite counterproductive for breath holding: when the level of O2 in lungs drops below certain level, due to Hb stabilized by 2,3-DPG in the deoxygenated state, blood won't be able to get the remaining O2 the freediver holds in his lungs. At least it won't be able to pull from the lungs as much remaining O2 as it could without 2,3-DPG. Am I right here?

Also, what's the longterm health effect of having higher Hb levels (or higher 2,3-DPG). I've been already searching some information about possible negative health effects of Hb, but so far I did not find a lot of interesting documents. Just some information about higher blood viscosity and hence possibly faster wearing out of the organism, but I think there may be more behind it. It is clear that there are considerable positive effects of altitude trainings or hypoxic tent therapies for top sportsmen, but since such positive effects are rarely without some trade-off, I wonder what the real disadvantages and dangers of the hypoxic adoption are. Faster aging perhaps? Do you have any more info here?