rsq_a said:
It seems established that some people can hold their breath for longer than 15 minutes with various tricks and whatever. There is a Guinness record http://www.guinnessworldrecords.com/news/2008/02/080229.aspx.
You're saying that it's all fake?
(Smiling)... Keep in mind this is a science forum and the Guiness Book of Records and Time magazine are not scientific journals. Also, note that the Guiness record for Blaine has an asterisk. As entertainment and semi-news publications, they are NOT reliable sources for scientific observations or conclusions.
examine the evidence and assumptions made in connection with David Blaine. Illusionists fool people with assumptions and misdirection. The assumptions are David held his breath, under water, for an extended length of time which far exceeded normal people's ability. Other assumptions are David told the truth about why he did the things he did and used the things he used.
We'll start with the tank. David made a big deal about the specially made sphere and the expense. I have to ask, why a sphere? David had a cubical tank that he had used in other performances. So why not use that? What is the difference between a sphere and a cube? Don't say shape!
Then, in a pre-performance ad, Oprah made a big deal about David providing his own water. Why would he do that? Like Oprah doesn't have water. Don't be distracted by the salinity story. Remember that in illusions, things aren't always what they appear to be. Is there something that looks like water, moves like water, but isn't water? Short answer... yes.
Another misdirection was the explanation that the water was cold because cold decreases the oxygen requirements for the body/brain, as in cold water drownings. So, why the wetsuit, which would completely counteract the effect of the cold water on the physiology of the body, thus negating the "benefits" of cold water on oxygen demands. The wetsuit could be used for camophlague of chest movements and to counter the cold, because it was cold, as is the nature of the "water."
Back to the breath holding... knowing it is impossible for you or anyone you know to hold one's breath for so long, what other possibilities are there. Oh, yeah... breathing! ;) But, if he was breathing air, there would be bubbles. No bubbles, so it wasn't air. Can something other than air be breathed? Yes, just ask the mouse in the beaker. (Reference previous post.)
Why didn't Blaine's heart rate decrease to a reasonable rate, to at least something that might indicate he had trained to relax himself and preserve oxygen. His heart rate remained high throughout the performance. Why? Why would a person's heart rate remain high? Could it be he was exerting himself? Short answer... yes. But, don't be distracted by the reason he would like you to believe, that the exertion was from holding his breath. If the exertion wasn't from holding his breath, what was it from? Could it be breathing? Short answer... yes. (Reference the stiff upper body wetsuit and the mouse in the beaker. I reiterate he wasn't breathing air.)
If he really wanted to prove he was breath holding, why not use a monitor to register chest movements (inhalation/exhalation)? Instead, he used a monitor for his heart rate, which proved he was working hard during his performance, when he should have been relaxing to preserve oxygen.
Where was the "trick" part of the performance art? The trick was in the preparation and when he entered and exited the tank. The misdirection was the "patter," including the misdirection that the tank contained water. The illusion was that he wasn't breathing. That's as much as I can tell you without telling you the solution (pun). This was a great trick and difficult to pull off, because he had to overcome basic human instincts and fears. It was hazardous, but not for the reasons people were misdirected to believe. Find the mouse and you'll find your answers.