Hypothermia occurs when the body’s core temperature drops so low that the body loses its ability to manage its temperature. It usually occurs as a result of external circumstances, such as a drop in outside temperature combined with insufficient clothing or layers, and then can become compounded if you are not taking in enough fluids or nutrition to help combat it.
As temperatures drop, you require more calories to stay warm. So you must fuel beyond what you need simply to get through the miles; you also must fuel to meet the demands of your environment. To make it worse, if your pace falls off, or you pause at an aid station, you stop generating heat through running, just when you need it most.
While it takes time to reach a hypothermic state, the symptoms can come on quickly. They include uncontrollable shaking, numb extremities, a feeling of cold that goes all the way to your core, blue lips, and chattering teeth.
Know where you are going to be running and the potential extremes. If you know you will be on high peaks, at altitude, in exposed, windy areas and in certain types of weather, be prepared with clothing, either in your pack, left in an appropriate drop bag, or held by your crew. I have seen the weather change in an instant at races. At Leadville, which takes place in August, you may find yourself sifting through snow at the top of Hope Pass; for a runner who is unprepared, this could dampen even the heartiest ambitions.
One of my first 100-milers was the Iditasport in Alaska. This race is run along the famed Iditarod Trail as well as frozen lakes and streams. You must navigate snow machines and teams of mushing dogsleds, as well as snow and freezing temps in the mid-February darkness. I had been leading most of the race with another competitor when things took a turn for the worse. I went for a long stretch without water after my hydration pack became clogged with electrolyte drink powder. Although I had taken the necessary precautions to make sure I had insulated tubing, I hastily (and mistakenly) added the mix first instead of my water; this choked my water supply by pushing the mix into the tube.
Because I was afraid of getting lost, I opted to stay close to the runner ahead of me rather than take time to stop and fix my bladder. I’d like to say that was my only error, but, unfortunately, both that runner and I ended up getting lost later on just when I couldn’t afford more time out in the elements. To add insult to injury, we ran on unstable frozen water that had pooled above the ice, drenching our shoes and pants. Recipe for disaster? You bet. Without water, without sufficient calories to compensate for getting lost, and now hypothermic, I went from leading the race to barely finishing the next day, after spending some 5 hours in a warming hut.
The good news is that aid stations usually have warm liquids and often a heat source, such as a fire or heater. If you are not prepared, beware. You can be removed from the race for hypothermia, and rightly so, because it can become a serious health concern if not arrested.