Why does a swimmer hyperventilate before diving in and then is under for 5 min and dies?
446201
Hypervenilating removes extra carbon dioxide from the blood.  Our urge to breathe is not driven by lack of oxygen, but by extra CO2 building up; this also affects blood pH, as it forms carbonic acid, so low pH stimulates breathing, too.\n\nThus, the person can hold their breath longer, after hyperventilating.  he / she will not be forced to surface to breathe, to relieve the urge to remove more CO2.\n\nHowever, they will have disturbed their blood pH, which can cause the brain to malfunction, leading to loss of muscular control, and to drowning.\n\nThey might get low on oxygen, too.  Normally, we carry plenty of oxygen in our bodies; even the air we breathe out has plenty of oxygen in it, and can be forced into the lungs of an unconscious person, in "mouth to mouth resuscitation".  IRC the proper name for this is "expired air resuscitation" but I am not sure.
967696
because the blood supply that would normally be used to help digest the food is diverted to your muscles for swimming. So the food doesn't digest properly and you get indigestion.
590617
It requires practice.  Hyperventilate for a few breaths, then stay under as long as you can.  Over time, the period you can stay under increases.  The hyperventilation is the key.
395427
Your heartrate will slow down as you keep holding your breath. Once you start breathing again, it will increase to above normal for a while and then settle back to normal.\n\n(Assuming you are not exerting additional force, such as swimming underwater)
48352
It's a sealed room with high barometric pressure.  Sometimes if divers come up too soon, they get a condition called "the bends" in which nitrogen dissolved in the bloodstream starts to come out as bubbles of gas.  (Think of how bubbles come out of soda when you lower the pressure by opening the top.)  So the divers can be put in a hyperbaric chamber, where more of the gas will stay dissolved and the pressure can be lowered gradually.
478875
Good info Klaus, but you mostly are discussing decompression, in which dissolved gases (usually nitrogen) bubbles out of the blood when going from high to low pressure-Not the reason oxygen is toxic.  The blood requires a certain pressure of oxygen, in other words, and certain number of molecules.  The normal concentration of oxygen in the atmosphere is about 21%, which of course is about perfect.  If you are in an environment that has twice the pressure, you require oxygen at half the concentration, or about 10%.  Its still the same number of molecules total, just a lower concentration.  Clearly, if you are in an environment of 10X the pressure compared to sealevel, you only need a concentration of oxygen of about 2%...again, its still the same number of molecules of oxygen, but because of the greater pressure, there is a lot more total gas molecules present.  Oxygen is a highly reactive molecule, and causes (obviously) oxidation...such as rust on iron.  In the body, this is a toxic effect-More to the point, though, is that the body requires a certain amount of carbon dioxide to maintain the proper acid-base balance.  If far too much oxygen is given, it swamps the ability of hemoglobin to bind CO2, thus causing acidosis-the acidification of the blood.  So, the deeper you dive, the lower *percentage8 of oxygen you require (though again, its the same *amount* of oxygen)- the oxygen is replaced by the most inert gas that can be obtained-helium usually.
507205
Wait...doesn't everyone in the world already breathe at the same time?  \n\nAre you trying to say that if some people weren't swimming under water or having a breath holding contest, we'd run out of air?  Wow-I thought I came up with some crazy stuff.\n\nI'm going with no on this one.
257388
Hyperventilation is rapid and shallow breathing. Many conditions can cause it (you'll find them easily if you do a search, besides stress and anxiety there's metabolic causes). The short answer: When you hyperventilate your levels of carbon dioxide in your blood rise and throws off your acid-base equilibrium. You can pass out, your muscles cramp (happened to me, not fun, i had the stomach flu), etc. Besides trying to control your breathing, you can breathe into a paper bag so that you are breathing carbon dioxide back in and the levels normalize.
965765
It differs a bit as those who live at high altitudes have built up a tolerance.  It also depends on how long you will be above a certain altitude.  However, prolongned exposure above 17,000 feet can result in hypoxia which causes fluid build up so that the person actually drowns from the fluid accumulation in their lungs.
861130
A person flushed into space would remain conscious for about ten seconds and die in about ninety seconds.  It's best if I quote from the "Bioastronautics Data Book" from NASA:\n\n"Some degree of consciousness will probably be retained for 9 to 11 seconds (see chapter 2 under Hypoxia). In rapid sequence thereafter, paralysis will be followed by generalized convulsions and paralysis once again. During this time, water vapor will form rapidly in the soft tissues and somewhat less rapidly in the venous blood. This evolution of water vapor will cause marked swelling of the body to perhaps twice its normal volume unless it is restrained by a pressure suit. (It has been demonstrated that a properly fitted elastic garment can entirely prevent ebullism at pressures as low as 15 mm Hg absolute [Webb, 1969, 1970].) Heart rate may rise initially, but will fall rapidly thereafter. Arterial blood pressure will also fall over a period of 30 to 60 seconds, while venous pressure rises due to distention of the venous system by gas and vapor. Venous pressure will meet or exceed arterial pressure within one minute. There will be virtually no effective circulation of blood. After an initial rush of gas from the lungs during decompression, gas and water vapor will continue to flow outward through the airways. This continual evaporation of water will cool the mouth and nose to near-freezing temperatures; the remainder of the body will also become cooled, but more slowly. \n\n"Cook and Bancroft (1966) reported occasional deaths of animals due to fibrillation of the heart during the first minute of exposure to near vacuum conditions. Ordinarily, however, survival was the rule if recompression occurred within about 90 seconds. ... Once heart action ceased, death was inevitable, despite attempts at resuscitation...."\n\nNOT FUN would be my summation.  It bears mention that there are examples of people who have been exposed to vacuum and recovered with virtuall no ill effects and people who have died because they were exposed to vacuum.  They tend to fall very well within the guidelines laid down above.  For more information and accounts, follow the link.\n\nOf course, if you're just asking how long it's possible to live in a space station, then the answer is indefinitely.  The current record-holder for a space stay is Valeri Polyakov who stayed in orbit for 14 months.  It was only staying on Earth afterward that was the hard part.
1150640
Yes.  Technically, you only need to suck water into your lungs to drown.  Since doing so usually causes death almost instantly, very few people survive the ordeal.  \n\nThat said, though, if someone is able to force the water out of your lungs and revive you, then you drowned and lived to talk about it.
916868
For swimming underwater, you need to condition yourself small steps at a time. First just dunk your head underwater with a stopwatch, see how long you last, then try going longer, at least like 2 seconds, each try, after a while your lungs will get used to it. I did that and after a while I could hold my breath for 2 minutes and 10 seconds underwater, it's not much but it's a lot better than the 45 seconds I could before. For singing, it works differently, although you could reinforce your breath holding by using the technique above. What works for me though, is taking small breaths, like 1/2 seconds breath every once in a while. I learned to do so by watching rappers, they do it from time to time to be able to keep on going. Good luck with that.
686980
to allow time for digestion\nif u dont wait, u may cramp up and u wont be able to swim if the tide takes u out too far.\n\n\n\nActually, the recommendation \nto wait an hour after swimming probably should be applied to most forms of \nphysical exercise/exertion.  When you eat and the food gets into the \nstomach and then into the small intestine (where most of the work of \ndigestion and absorption takes place), the body 'pulls' extra blood into \nthe body's middle (around the internal organs), so that the nutrients can \nthen be transferred into the blood and sent to the rest of the body.  \nSince you have a fixed amount of blood in your body, the amount of the \nblood that is left in the outer muscles must then be less.  So, you have \nless blood in the large muscles that you need for exercise...and that \nincreases the chances for muscle cramping (due to the production of by-\nproducts, such as lactic acid, which are toxic to the muscles).\n\n     Dr. Titchenal also mentioned that maybe where the 'old wive's tale' \nabout waiting for swimming, in particular, originated because when you are \nswimming you are usually face-down.  This might make you more prone to \ngetting sick to your stomach and throwing up, because of the stomach being \nfull and your face is in the water.  I wonder if anyone ever tested this \nafter eating by swimming face down and then swimming on his/her back?\n \n     So, bottom line:  it may be a good idea not to exercise for about an \nhour after eating (particularly a big meal), regardless of the exercise.
1047861
I have been on the swim team for a long time and im 3rd in the state at breast stroke, but i still know about freestyle. i usually dont think about how many strokes i take before a breathe. i think if u just do whatever feels comfortable you will have 1 less thing to think about so you go faster. When i first hit the water I'll usually take 4 or 5 strokes before i take a breathe cuz im so pumped up.
299063
Please.  Your lungs can not be down as much as 3 feet I believe, or the air would be forced out of your lungs.  Now if you snorkel at normal depth, you can hold your breath and go down as far as you can make it.  But you can't breath continuously unless the air is being pumped.  Your head will not collapse, it's filled with liquid which doesn't compress.
73393
It depends on what level you are talking about learning to breath.\nFor a first-time swimmer, doing bobs (submerging the face and blowing bubbles, then coming up for air, repeatedly) helps. This reinforces the practice of blowing out your breath underwater and not holding your breath.\nFor beginners, being comfortable in the water. Might sound simplistic but a fear of the water (even a slight apprehension) makes breathing difficult.\nIf you are talking about the front crawl (freestyle), the one hand stroke drill helps to emphasize correct body positioning while breathing and practices breathing on both sides.
528197
is this for holding your breath?? \n\nThe technique used by the record deep divers is to bring their heart rate down to 10 beats per min, by meditating and relaxing all their muscles\n\nHow you do it? it takes a looot of practice.. I have done relaxation exercises and have gotten my heart rate to under 30.. but those guys are crazy