I'd like to address some of the common misconceptions that appeared in this thread:
1) As Ulf wrote, most of so-called "breath-up" methods are nothing else than plain and simple hyperventilation. Perhaps little bit slower hyperventilation than the commonly known and feared "fire breathing", but nevertheless it is still hyperventilation with the same effects.
2) You do
not want to reduce your heart-rate
before the dive. That would be counterproductive, since it would reduce the blood flow, hence the oxygenation of organs and muscles, and cause desaturation of the venous blood. What you want is dropping the heart rate as soon as possible
after starting the apnea, not before! Before the apnea you want though reducing your oxygen consumption to the necessary minimum. So the maximal possible relaxation is necessary, but if you manage to keep your heart rate high despite the relaxation, it is only good! It will lead to bigger stocks of oxygen in tissues and especially in the venous blood (arterial blood is practically saturated at normal breathing anyway)
3) If you are able to make 3 times longer dives during few days (like 96ekhatch wrote in the last post) just thanks to the "breath-up", then you want to know that it is very likely not because you got so quickly so good, but more likely because you found that the more you hyperventilate (or breathe-up, breathe deep, purge, ...) the easier you can hold your breath. What you miss though is that the body gets hypoxic with the same speed (and often even quicker), you just do not get the signals about it, and feel no urge to breath. If connected with an ascent, you may be quite likely quite close to your physiological limits at every dive. It is only a question of time when you overdo the hyperventilation, the depth, the time, or encounter unusual situation and you pass away without even getting any warning.
More about hyperventilation here:
http://forums.deeperblue.net/safety/77624-hyperventilation.html?highlight=hyperventialtion
