Free divers prepare to take the plunge

Don't try this at home! In June of 2000, Loic Leferme made a record breaking deep dive of 450 feet -- on a single lungful of air. Breath-holding, or "apnea," diving is an increasingly popular sport in Europe and the U.S. As more and more people push their lungs to the limit, amazing new records are set each year.

In "No Limit," Alan Alda joins Loic and the French national team as they train at the University of Nice. Team doctor Phillipe Afriat shows what happens during the "dive response" -- a primitive reflex, triggered when our faces are plunged into water, which reduces the body's demand for oxygen.

Relaxation techniques nearly doubled Alan's breath holding skills

Deep divers try to exaggerate their dive response using relaxation techniques. Then on top of that, Loic and the French team learn a special pumping technique which forces extra air into the lungs, blowing them up like a balloon. After a few hours' training, Alan nearly doubles the length of time he can remain submerged.

For more on this topic, see the web features:
The Deepest Divers and Weight of Water