Freediving training info exercises etc...

[lliw]

Hi, I have been spearfishing on and off for a few years, I am just after some info on different methods of extending bottom time, info on SWB etc.

I am thinking of buying Manual of Freediving: Underwater on a Single Breath. Is this a good book?

I also read the sticky thread in this forum and I am doing the exercises at the moment.

[Gwaihir]

it is a really good book..
Good luck..

[sanso]

That thread will keep You busy for a while, and with that book You should be well-covered. Have fun and let us know about Your successes (and not so successes, if they're funny )

[lliw]

Thanks, are there any web resources about freediving similar to the book?

Also, I just usually come up from the bottom when i start getting contractions, is this a safe practice? I usually only dive in less than 10m of water.

[sanso]

Originally Posted by lliw

Thanks, are there any web resources about freediving similar to the book?

I think there's a site called DeeperBlue - I can look up the url for You.

Also, I just usually come up from the bottom when i start getting contractions, is this a safe practice? I usually only dive in less than 10m of water.

With a buddy, that is a safe practice, If Your buddy knows his/her safety procedures (blue lips, samba) and You trust him/her, You can slowly increase bottom time past contractions and see how that goes. But this is fairly advanced, I recommend taking a course, which will answer many of those questions and work wonders for Your diving.

Oh, and without a buddy, this is _not_ a safe practice. You absolutely need a buddy to be safe. Absolutely.

[lliw]

Thanks, so SWB is more related to deeper dives?

[trux]

Originally Posted by lliw

Thanks, so SWB is more related to deeper dives?

The definition SWB differs - some sources (i.e. Wikipedia) define SWB differently than others, but among freedivers SWB is indeed related to the effect of depressurizing during the ascent which then accelerates the hypoxia. It does not mean though that you cannot blackout when diving shallow. It only means that at deeper dives there is another risk factor (the depressurizing of lungs, and the resulting negative PaO2 gradient, reversing the flow of oxygen in your blood)

[salibandy]

trux, how do others define SWB differently to Wikipedia? I would like to know. Thanks.

[trux]

Just as I wrote: SWB = the depressurizing blackout, while for Wiki depressurizing blackout = deepwater blackout, and plain hypoxic blackout (as in statics or dynamics) is SWB for the guy who created the Wiki entry. Commonly SWB is more often understood as depressurizing blackout, static or dynamic is plain (hypoxic) blackout, and the rare deep water blackout usually describes other causes (oxygen toxicity, extreme hypercapnia, depth narcose, ...). For these reasons, to avoid confusion or misunderstanding, I personally prefer using the term depressurizing or ascent blackout than SWB, although for historical reasons the term SWB for the depressurizing blackout is more correct than the definition in Wikipedia.

[lliw]

Thanks guys.

How deep does it have to be to be conciderd a deep dive and be at risk of SWB?

Whats the chances of SWB and just normal blackout if you come up just as you get contractions?

[trux]

Ascending from any depth adds to the depressurizing effect, so depending on the previous conditions you may blackout due to the depressurizing effect even when ascending from 5 meters or less. The depressurizing effect (pressure gradient) is the stronger the closer to the surface you come. For this reasons it usually hits divers when they are already in a quite shallow water (just few meters deep, or even on the surface).

Contractions have little to do with it. Contractions are quite individual, and dependent on diverse factors, including psychology, stress, focus, effort, but especially on the CO2 level. Contractions won't tell you anything about the level of hypoxemia in your blood. Some people may not get any contractions at all, and get hit by SWB anyway.