The Science of Survival: Hypothermia

Explaining four of the most common threats in the outdoors

Dress warm to survive.     Photo: Sergii Titov/Shutterstock

Watch out for the umbles.

Hypothermia has a twisted history. For one, the literature comes with baggage: unthinkably inhumane tests on prisoners during the Holocaust ground a fair bit of what doctors and scientists know. Additionally, the fear of freezing to death is so linked to mountaineering and Arctic exploration that people often don’t take the risks seriously.

So how big a risk is hypothermia for an outdoor athlete? Not a major one, provided that you don't run certain risk factors. According to Dr. Thomas Cappaert, an expert in cold weather safety at Central Michigan University, only one to three incidents of hypothermia result from every 1,000 exposures to cold weather. If you're exercising on land with a fair bit of clothing on, you're probably OK: you'll feel cold and turn back before you get into serious trouble.

Unless you don't. Outdoor athletes have a tendency to ignore their perception of cold, says Cappaert. “If you want to go hiking, you accept that it’s cold and ignore the psychic impulse,” he says. “When you do that repeatedly, the impulse becomes weaker. And you ignore the symptoms until you cannot react.”

WHAT HAPPENS: Your body is cooling faster than it can produce heat. Soon you’re dropping below the temperature from which the body can recover. Shivering and your other defenses cannot handle the change. As the body continues to cool, organs shut down.

SIGNS AND SYMPTOMS: Watch out for the umbles: “You start to stumble, mumble, bumble, and grumble,” says Cappaert.

PREVENTION: Be prepared for the weather to change, carry extra layers and food, and listen to your body.

TREATMENT: "Keep moving and seek out some sort of shelter,” Cappaert says. If you’re with a buddy, try to share body heat by huddling together. And if you have food, eat it: metabolizing fuel generates heat and “fills your carbohydrate stores so you have the energy to keep shivering.” Once inside, use passive rewarming and focus on the trunk if you have a hot bottle. If you have frostbite, wait to get out of the cold before slowly warming the tissue under hot water: refreezing thawed-out fingers and toes can cause extra damage.

THE MYTH: Booze can help warm up a hypothermic person.

THE REALITY: Alcohol causes blood vessels to dilate, increasing heat loss.

THE BOTTOM LINE: Hypothermia isn't a joke. Dress warm and listen to your body.

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