I am a diver and we would regularly train en apnée, its very very dangerous and should only be done in buddy pairs, I should be able to relate the physics to you but am rusty, basically as you come to the surface after a long and strenous apnée, for me 2+ lengths there is a high risk of a syncope in the last 50cm before the surface, its like a faint, the brain stops but the vital systems like breathing continue, not what you want when sinking to the bottom.
the Buddy has to be right with you when you surface and be ready to get you to the surface, out of the pool and to render first aid, I have had to do it once, it was OK because I Grabbed my Buddy Partner before they had sunk Under the water, they came back to consciousness very quickly.
That said whenever I go to the pool I swim en apnée as I cannot breathe when doing the crawl and find it easier to do the breast stroke just breathing once or twice a length.
My apologies for all the misplaced capital letters, this f***ing bug in Windows puts replaces what i type with a capital letter for Windows, Buddy, Partner, Grabbed Under, and lord only knows what else, drives me up the *** wall
Do some Googling, dont know the terms in English but its syncope nage apnée in French.
We also do,(or did as I no longer have the time to keep up the sport) free diving in the fosse at Amiens, its 15m (45 feet) deep and we are very Lucky to have it, there are none in the UK except the Navy ones, anyway whilst we always have an instructor/lifeguard watching I dont think the danger is the same one, I'm pretty sure the syncope occurs when you are breath-holding at shallow depths where the pressure change is greatest, its all about partial pressures and CO2 concentration, sorry that I cant recall the science.
3 lengths of a 10m pool is less effort than 2 lengths of a 25 m pool as you get 3 kick offs.
As an aside I just looked at the website for our local pool, just look at the comments about the accueil and the staff, this is absolutely par for the course for all businesses around here especially those dealing with tourists who really should know better.
By the way, free diving to 15m and spending quite a bit of bottom time is very easy once you have trained a bit and overcome what your brain and chest is telling you, once you get to a certain depth water pressure compresses the body to negative bouyancy and you fall like a stone with no effort, a good impulsion from the bottom and some vigourous kicks and strokes will bring you to the same point whereby you can rise to the surface with no effort all you have to do is concentrate on remaining calm, easire said than done of course.
I actually am one of the few people to have experienced it as an obese person, very hard to descend but easy to come back up, and an athletic lean build which is the opposite, it took a lot of retraining, recalibrating of my instincts, one of the exercises we do is to go down a marker line and clip on a clothes peg at the depth we start to fall (negative bouyancy) there is a huge difference between the different body types, women have some built in airbags my peg used to be a long way down, now its right near the top, treading water now takes frenetic effort yet all my life before I could float by just the occasional flutter of the hands.
Chancer wrote:this f***ing bug in Windows puts replaces what i type with a capital letter for Windows, Buddy, Partner, Grabbed Under
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