What does a 'polar bear plunge' do your body? Jumping into icy waters isn't for the faint of heart

Do you like to ring in the New Year with an icy dip in the Atlantic?

Taking a 'polar bear plunge' is more than just a cold shock to the skin – it's a shock to your entire system.

Brave souls who race to Coney Island each year to jump into frigid waters boast the plunge's invigorating qualities – After all, the Scandinavians have been diving into cold water and then warming up in the saunas since the time of the Vikings.

But does it really give your health a boost?

"I don't know of any definitive medical studies that have been done to measure the health benefits of cold-water swimming," Dr. Alan Steinman, one of the country's foremost experts on hypothermia and cold-water survival told Msnbc.com.

He's worried that these chilly revelers may be taking health risks.

He recommends a gentle dip, slowly into shallow water, rather than a total, sudden plunge. Yes, this sort of defeats the purpose for these daredevil human polar bears.

When the body is suddenly immersed in icy water, there's a sudden gasp, an inhalation, rapid breathing and the inability to hold your breath, "which can be a problem if your head's underwater," he says.

For that reason, it's better to "plunge" gradually, from shallow water, and not off a dock or a boardwalk. It's possible to go into cardiac arrest due to shock -- The small blood vessels constrict on the surface of your body as a defense mechanism, so you don't lose heat. That means that a whole lot more blood is being squeezed into the same amount of blood vessels, which "serves to increase the effect on blood pressure," said Steinman.

Still, organizers of the Maryland State Police Polar Bear Plungefest, which raises money for charity, has been incident-free.

Around 12,000 people are expected to run wild in the Chesapeake.

nydailynews.com