Quote:
Originally Posted by hteas
Sean,
You state that contractions are nearly impossible with negatives. Is that an assumption or do you have any information you could share?
By the end of a 120 second negative (my best) I have been assuming that the concentration of CO2 in my blood is pretty high, but may be wrong. if you are right then the training is all based on hypoxia. I've been assuming that it was a hybrid with some aspects of both hypercapnia and hypoxia, since I limit breathing to 60 seconds between holds.
Howard
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actually, no. i said that contractions due to carbon dioxide are nearly impossible with negatives.
to my knowledge, contractions can be caused by either high carbon dioxide levels or very low oxygen levels. in the case of low oxygen, contractions often feel more intense/urgent or are accompanied by a feeling of panic. these factors make them much more excruciating to endure as colin so aptly described.
the length of time you can hold a negative will greatly depend upon how much air you exhale before starting. the amount of air you can exhale will increase with practice as well. many people even do a series of reverse packs to further empty their lungs prior to doing a negative breath hold. look for some excellent descriptions of this and associated yoga techniques from will here on db (william trubridge). prior to a negative i do anywhere from 5 to 9 forceful exhales, the last half of which are only mouthfuls of air (reverse packs). leaning over and gently pressing on your diaphragm as you exhale can help decrease the volume of air left in your lungs.
as far as training hypercapnia, in my opinion negatives (forceful exhales) will not lead to particularly high levels of co2. although, i guess combined with short recoveries, this might allow co2 to build up over repeated holds.
one way of training both hypoxia and hypercapnia is to combine oxygen and co2 tables into one table. the table would have both a hold of increasing duration AND less ventilation time between successive holds.
howard, as a middle ground you could try using a passive exhale (instead of forceful exhales) to complete this kind of combined o2 and co2 table. this would allow you to reach hypoxic levels faster than with full lungs but also allow more opportunity for co2 to build up than with completely empty lungs.
as always, more experienced divers (or anyone for that matter
) please feel free to step in here.
cheers,
sean
vancouver, canada
