This Time, He'll Be Left Breathless looks at “endurance artist” David Blaine and modern free divers:
A century ago, Houdini was celebrated for being able to hold his breath for three and a half minutes. Today even a novice can quickly learn to last longer than that, as I discovered under the tutelage of Kirk Krack, the free-diving coach who has been training Mr. Blaine for his world-record attempt.
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Researchers in the 1960s calculated, based on lung capacity and the effect of water pressure, that humans couldn’t dive deeper than 165 feet. Today free divers are going down more than 600 feet and returning in apparently fine shape. Most of the time.The day before his attempt in the pool, Mr. Blaine was practicing in the ocean and told me he was headed down for a dive of 100 feet, so routine that he didn’t bother doing the usual preparatory ritual: a slow, steady “breathe-up,” followed by exhalations to purge carbon dioxide and then a final series of quick gulps of air called lung-packing.
I watched him disappear into the depths and then reappear about two minutes later, swimming smoothly upward next to a guide rope. But about 20 feet from the surface, he suddenly veered away from the rope and appeared to struggle upward with his arms flailing. His coach, Mr. Krack, recognized the symptoms of a blackout instantly and rushed to grab Mr. Blaine, supporting his head above the surface until he regained consciousness.
He’d succumbed, Dr. Potkin said, to one of the most common and sometimes fatal dangers of free diving — and one of the reasons you shouldn’t try any prolonged breath-holding unless someone like Mr. Krack is supervising.
“Divers rarely get into trouble at depth,” Dr. Potkin said. “But as the diver approaches the surface, the decreasing water pressure causes a drop in pressure of the oxygen in the brain. If the level in the brain gets too low, it’s like a switch: lights out.”
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The natural impulse to stop holding your breath (typically within 30 seconds or a minute) is not because of an oxygen shortage but because of the painful buildup of carbon dioxide. Mr. Blaine said he began trying to overcome that urge when he was a child in Brooklyn and at age 11 managed to hold his breath for three and a half minutes.In his current training, he said, he does exercises every morning in which he breathes for no more than 12 minutes over the course of an hour, and he sleeps in a hypoxic tent in his Manhattan apartment that simulates the thin air at 15,000 feet above sea level.
He has been concentrating on lowering his oxygen consumption by slowing his metabolism, partly through diet (he fasted for 18 hours before the breath-hold in the pool) and partly through relaxation. In a test by Dr. Potkin, Mr. Blaine on command quickly lowered his heart rate by 25 percent.
“David seems to have a phenomenal ability, like Buddhist monks, to control his body,” Dr. Potkin said.
When Mr. Blaine began his breath-hold in the pool, his heart rate during the first minute fell to 46 from 81, a drop that was not entirely his own doing. Immersing the face in water produces a protective action in humans similar to that in dolphins, seals, otters and whales. Called the mammalian diving reflex, it quickly lowers the heart rate and then constricts blood vessels in the limbs so that blood is reserved for the heart and the brain.
By exploiting that reflex, free divers can remain active underwater for more than four minutes, and much longer if they remain still. The world-record holders have exceeded nine minutes after filling their lungs with ordinary air, and more than 16 minutes after inhaling pure oxygen.