Hypothermia: What Happens to Your Body

As most of the country wakes up to bone-chilling temperatures, "Good Morning America's" Sam Champion exposed himself to the elements to see what happens to the human body in the extreme cold.

Champion went out in 18-degree weather with a wind chill at about zero. He wore a coat, a hat, gloves and a scarf, and his heart rate was initially 81.

Dr. Wallace Carter of New York Presbyterian Hospital tested Champion's motor skills and monitored his body's ability to withstand the temperatures.

About 3½ minutes into the experiment, Champion started to shiver.

"The longer you wait out in the cold, the more accelerated the heart rate will become -- the respiratory pattern," Carter said. "You may even notice in a few minutes it may even be difficult to talk. Your jaw may seem kind of stiff."

After five minutes, Champion was visibly shaking.

"So we … went up to 91, now we are at 99 and you are now visibly shivering," Carter told Champion. "Your hands are moving. Your legs are moving. You look like you are in pain. … What you are going through right now is mild hypothermia, where you still have the ability to compensate. Your body is doing all the right things."

At nine minutes, the effects on Champion's system were more evident.

"Your heart rate is now about 101," Carter said. "You have gone up about 14 beats."

Carter tested Champion's motor skills again, and they were visibly impaired.

Each year hypothermia kills 25,000 people in the United States. Without the right protection in these dangerously cold temperatures, hypothermia can set in in just minutes.