David Blaine masks his endurance abilities as magic, something I've remembered ever since I watched him frozen in ice in NYC a few years back. His latest big trick, regurgitating frogs and other live animals, seems like a trick and it certainly makes you wonder how it's done, but the answer is pretty plain: He actually swallows frogs and regurgitates it back up.
Most people cannot do this, but the human body, as Blaine can testify, is capable of being trained to do incredible things. That's the real magic here -- that Blaine has the patience to train himself to do these stunts. As for those frogs...who knows what they feel in his esophagus.