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A Few Things Learnt

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Deeper Blue Hypoxyphiliac
Oct 24, 2002
I was reading a post Wal made on an Aussie site the other day (http://www.spearfishing.com.au/cgi/...oard=freecorner;action=display;num=1090937078), which basically has two graphs from him - one of a 7 minute static, and another a 2:30 exhale (on a pulse-oximeter). It got me thinking of a course I did a couple of months ago, and a few things I learnt.

The course was an aviation one, and related primarly to the effect of high performance aircraft on the body. There were four main points I got from it with relation to freediving (passed the test so dumped the rest :)), maybe someone can do something with them?

The first is to do with hypoxic training - there's always a big emphasis on how climbing to a higher altitude means less dense air, hence less O2, hence increased production of Hb, etc. One of the primary factors affecting air density though is temperature - basically, for each degree (celcius) increase in temperature, its equivalent to climbing an additional 120'.
An example - take the difference between Canberra and Cairns. Canberra has an average temperature of about 15 degrees, whereas Cairns is about 30 degrees. Canberra has an elevation of about 1800'; Cairns is pretty much sea level. I was always of the impression that when I went home from Canberra to Cairns, I was moving into more dense air, but if you crunch the numbers, it works out the same: Cairns is an extra 15 degrees (ie 30 - 15), multiply by 120' = 1800'. Using this logic, maybe it would be more beneficial to not necessarily train higher (though that definitely helps) but also hotter, then when its time to set a record, head for colder water?

The second point is to do with hypoxic symptoms. Basically, each individual will react to hypoxia differently, however the individual symptoms will not change over time. The air force here pushes this point by exposing all pilots (in a controlled environment of course) to low blood oxygen saturations, on a regular basis. Every three years we're all required to jump into a barometric chamber to "remember" what it feels like to be hypoxic. I'm not advocationg that everyone goes out and blacks out just to see what its like, but I've seen many arguements that each time is different - that's not what we've been shown.

The third point is probably the least practical of all of them, but I thought I'd throw it in for good measure :) Under and induced G force (ie in a centrifuge, steep turn, whatever), the oxygen saturation in the blood is decreased. To put a number on this, at 5G, saturation is around 85%. Not sure how to use this information in training, but hey, if you've got a spare centrifuge and no hypoxic chamber... :)

Finally, one that *may* be a little more practical (not sure, haven't tested it) - under negative G (ie standing on your head), heart rate decreases dramatically. On our course of 20 studs, the smallest drop I saw was 15bpm after 15s inverted, and the largest was 30bpm after 15s. Additionally, all the blood drains out of the extremeties (ie arms and legs) - maybe doing a hand stand is the way to go with static? I'm not sure how well the heart would cope with pumping the blood from the head back up, but it would seem to keep the constant supply going from the heart to the brain?

I'm not sure if any of that's any use to anyone, I've been meaning to write it up for a while. If anyones keen on anything there and wants more info, throw me a message and I'll see if I can help you out :)

Safe diving,

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Hi Brad,

On another aviator related topic, i've a question. Please correct me where I go wrong (after all, i'm an accountant, not an aviator :cool: ).

Jet fighter pilots wear suits to combat high g forces, these apply pressure around the legs and other bits to keep the blood pressure up enough to avoid blacking out. Could this philosophy be applied to apnea (or maybe already is) whereby a similar pressure suit could help direct the blood away from extremeties and concentrate around the chest/head area.
I'm not sure if this would extend a static breath hold or if it would rather extend the comfortable phase. Anyone got any ideas?
Seeing as most wetsuits are fairly tight already this could already be in practice.

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Mate to be honest I have no idea! I'll take my suit home with me this weekend and give it a whirl dry, but I don't think it'll make that much difference... I'll let you know when I give it a go :)
Jet fighter pilots wear suits to combat high g forces, these apply pressure around the legs and other bits to keep the blood pressure up enough to avoid blacking out. Could this philosophy be applied to apnea (or maybe already is) whereby a similar pressure suit could help direct the blood away from extremeties and concentrate around the chest/head area.

Makes sense, save one difference (from my perspective as a private pilot...not a jet fighter pilot!):

Pilots don't need to use their legs as much as freedivers. Thus, it would seem acceptable to significantly reduce blood flow to a pilot's legs in exchange for ensuring he/she doesn't experience BO. However, I would think it prety important that freedivers have sufficient O2 available to the legs so that enough kicking can occur to return to the surfave, withouth a severe cramp occuring. A severe cramp could be almost as bad as a BO.

Re wetsuit compression, having worn many varieties, I seriously doubt any of them provide as much compression to a diver's extremities as a jet-pilot's flight suit does....by design. That's a good thing.

On the other hand, in divers who keep their arms extended over their heads (hands clasped) while ascending, this pose may cause a reduction in blood flow to the arms due to gravity, with an equivalent transfer of same to the body core. So, that would seem to make a good argument for ascending in this manner, rather than with arms trailing at the diver's sides (as I typically do). Any experience with comparing these two poses for ascent?
Originally posted by jimbodiver
[BPilots don't need to use their legs as much as freedivers.[/B]

Sorry - I thought Benny was talking about static? I know I get lazy on the rudder pedals, but geez... :D

If you're talking about cutting blood flow off in a depth dive though and you're worried about compression effects, then why not use something like a torniquet? I'm not too convinced on how well that would work though - wouldn't the lactic build up be incredible without any blood flow?

I like the idea of hands up ascent though - when you're in the water though, I think you might have to take into account the relative densities of blood/water and bouyancy. I'd imagine that it would work, but might take a bit longer than on land?
G'Day Ben - tried the G suit out for statics this morning. It's got a one way valve on the hose, so that you can blow as much air in as you want, then lock it off. I only went to contractions on both, but basically after warmup managed 3:21 on the first (no suit), and 3:08 on the second (with suit). I don't know if the suit had any effect on blood flow or not, but it was pretty uncomfortable, and I think a lack of relaxation might have caused that loss of 13s.
Hi Loops,

I guess the benefit (if any) would most likely be outweighed by the discomfort in wearing it (plus the air force would stop giving you suits if they found out you keep wearing them in the pool :naughty ).


ps. Your contractions started at 3:21? Jeez I envy you lot. I did a 5:00 wet static the other night (new pb :D), and the contractions started at about 2:10. And that's only cause I did a few more purge breaths than normal, the contractions normally kick in at 1:45!! Tell you what, I felt like i'd done a couple of rounds with Tyson afterwards!
Nah its this diet mate - wouldn't have gone much past that. Normal for me used to be 2:45-3:00 and thats with three to four deep breaths beforehand... don't sell yourself short, if you guys make it to the JB comp and I'm there, I'm gunna be struggling... :D
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