Underwater, He's an Extreme Success

Tom Sietas, world champion breath-holder, holds three records in "free diving," in which competitors see how long they can stay underwater. (Courtesy Of Tom Sietas)

His scuba instructors noticed that he had a talent for holding his breath. They provided a little coaching. By the end of his vacation, Sietas was going without air for more than four minutes.

"I was like, 'Whoa, if you put some effort into it, Tom, you could be really good,' " he recalled.

Back home in Hamburg, he began training with other free-diving aficionados. It wasn't long before he was attracting attention. In 2004, he smashed the world record for underwater breath-holding (without extra oxygen) with a mark of 7 minutes 48 seconds.

Sietas attributes his success to a strict training regimen that he has developed himself. It is a combination of strength exercises, endurance workouts and concentration tactics. When he is submerged, he goes completely limp and blanks his mind to lower his heart rate and conserve energy.

"I have a strong will and a strong discipline," he said.

Elite free divers also rely on an advanced technique called "lung packing," by which they force extra air into their lungs by inhaling through the mouth and swallowing at the same time.

Sietas said he has developed other breathing patterns as well but is reluctant to divulge his secrets for competitive reasons. "I don't want to share all my knowledge," he said.

Sietas is also blessed with an above-average pair of lungs. But doctors who have examined him said they aren't as large as you might expect: about 15 percent bigger than an average person of his height.

Kay Tetzlaff, a physician from Freiburg, Germany, who has examined Sietas and other free divers as part of an ongoing study, said they are able to expand their normal lung capacity by almost 50 percent through lung packing.

"That, of course, is enormous," Tetzlaff said. "These guys have some features that make them come closer to diving birds and mammals."

Some, like Sietas, also benefit from high levels of hemoglobin in their blood, which enables them to absorb oxygen more efficiently.

Although free diving can be a risky sport, especially for those who practice in the depths of the ocean, Tetzlaff said it is difficult to hurt yourself by holding your breath. Rising levels of carbon dioxide in the blood send signals to the brain that make it almost impossible to withstand the urge to breathe.