When humans enter water they can automatically hold their breath longer than they can on land.
That's because the body immediately goes into "oxygen saving mode" by slowing the heart rate and shunting blood to the body's core.
Known as the mammalian diving reflex, this trick of human physiology (and of whales, dolphins and seals) will benefit magician David Blaine, who is living underwater in an 8-foot acrylic sphere in front of New York's Lincoln Center all this week.
During the last few minutes of his stay, Blaine will remove his breathing tube and attempt to break the current record for breathing underwater, which is 8 minutes, 58 seconds.
To get ready for this feat, he has been working with the staff of Performance Freediving. The staff has helped him improve his physical and mental conditioning, said lead trainer Kirk Krack, who will remain near Blaine all week.
Blaine has been working on maneuvers to increase his body's ability to withstand carbon dioxide while also doing yoga-style moves to expand his rib cage and the connecting muscles to get more oxygen into his lungs during his final breath.
"We want him to be able to tolerate a higher level of carbon dioxide and also to function on lower oxygen levels than the average person," said Krack, whose personal best is 6 minutes, 45 seconds.
In recent years, more people have become interested in the science of free diving and breath-hold diving, resulting in a better understanding of the abilities and limits of the human body underwater.
"Five to six years ago, the record was seven-and-a-half minutes. In 2001, one of my team members put it to eight minutes. It seems to be, with the current limit, we'll probably see it broken very quickly as well," Krack said. "The more we train, the more we discover."
Blaine's ordeal will be aired during a two-hour primetime special, "David Blaine: Drowned Alive," next Monday from 8 to 10 p.m., ET, on the ABC Television Network.
For added drama, Blaine will handcuff himself to about 150 pounds of chains and try to break free while attempting to hold his breath.
"For the first few minutes of his submersion, he's not going to do anything to attempt to escape," Krack said. "At the four-minute mark, he's then going to start making his escape. It might take three minutes. If he runs into difficulty it might take four minutes or longer. He'll either get himself out of the chains, or we'll see he's in trouble, blacking out and losing motor control."
If that happens, the team will enter the sphere, resuscitate Blaine and provide emergency medical care.