When people first immerse themselves in such frigid water, their bodies go into "cold shock, " and they start gasping for air, which puts a strain on the heart.

CNN: Are polar bear plunges good for you?

In one unusual but revealing study, his researchers repeatedly immersed one side of people's bodies until it showed evidence of habituation, while keeping the other side warm -- and then turned them over and immersed the side that had never been in the cold water and found that there was still a significant reduction in their cold shock response.

CNN: Are polar bear plunges good for you?

Tipton, who conducts research on the human body's physiological and psychological response to adverse environments, found that it takes as few as five immersions in icy water for the body to develop a tolerance that can reduce the risk of cold-shock response by half.

CNN: Are polar bear plunges good for you?

Suzie stepped in, tottered at the shock of cold, forged on up to her knees, then with a shriek plunged and swam the crawl with strong strokes into the glittering path.

NEWYORKER: The Swan

That's caused by the adrenaline and stress hormones that the body releases in response to the shock of the cold temperature, but experts say that these rushes are not as healthy as people think.

CNN: Are polar bear plunges good for you?

She added that when she knelt down to touch her mother's neck, to see if there was a pulse, she got a shock because she was "as cold as marble".

BBC: Kathleen Milward

Here are a few tips to shop your closet, make old things new again, and renew your excitement for getting dressed in the morning, once you have gotten past the fact that getting out of bed requires getting over the shock to the system when your feet hit the cold floor.

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