When the body is chilled, things donít work right. To oversimplify, we humans are electrified bags of goo, the circuitry of which is very sensitive to cold, which explains why early symptoms of hypothermia are lethargy and confusion. The colder the body, the less brain activity there is, and the more confused and sluggish a person can become. This confusion can lead to a lack of awareness of what is happening: being hypothermic impairs your ability to understand that you are hypothermic.
So what does your body do in the cold? First up is vasomotion, which sounds like a terrible DJ name but actually refers to the bodyís protective constriction of peripheral blood vessels. Itís a bid to staunch heat loss from the extremities, concentrating warm blood in the center of the body and reducing heat loss from the surface of the skin. Vasomotion is accompanied by shiveringórapid muscle contractions that overtake oneís somatic stillness to help generate extra heat. Athletes exercising in the cold will also get a heat boost from their workout, the furnace of their activity at odds with icy temps. This internal warming in the face of bitter cold is good for maintaining core body temperature and keeping fussy organs toasty, but the vasoconstriction keeping blood from the edges of the body can mean that warm blood from deep within the body doesnít make it out to fingers and noses, putting our intrepid cold weather athlete at risk of frostbite. (Frostbite occurs when the water in your cells starts to freeze. It is distinct from hypothermia, though obviously they two can occur under similar circumstances.)
In addition to confusion and shivering, mild hypothermia can also make a person feel hungry or nauseous, but the feeling will fade to apathy as the bodyís temperature continues to drop. Once youíre around 90 degrees fahrenheit, shivering stops and confusion worsens. This stage is known as moderate hypothermia, but donít let the name fool you: the next stage, severe hypothermia, means you are probably in a coma and are about to have a heart attack. In the precursor to such an end, the heart, struggling to maintain its electrical regularity in the absence of warmth, will slow down. It may become irregular in its rhythms, flirting with cardiac arrest. Itís at this stage of hypothermia that a person may feel compelled to strip off all their clothing, a phenomenon called paradoxical undressing. Despite all the research done on hypothermia, weíre still not really sure exactly why this happens. Something about the bodyís thermoregulators malfunctioning. Suddenly, the victim of hypothermia feels like their skin is much too hot. Itís why bodies are sometimes found frozen and naked in the snow..