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How Cold Is Too Cold for Exercising Outside?

The only thing worse than being sore and sweaty is being sore and sweaty and cold

You were aching for a change of scenery to ring in the new year, and you found several websites informing you of what an inviting New Year’s Eve celebration destination Alaska could be. Leaving the security of your Southern California home, you ventured far north in pursuit of a location from which one could possibly see Russia from their house. Not wanting to leave your post-Christmas workout routine back in SoCal, you pulled on your Asics trail-running attire, stepped through the doors of the Marriott Downtown Anchorage and were immediately frozen into a state of petrification by the painful blast of frigid air that cut clean through your body.

“How can anyone train outside in weather like this?!” you mutter to yourself. 

You immediately turn and retreat to the hotel gym in search of a treadmill, fully understanding why even 30 years ago, it was being theorized that 1 in 10 Alaskans suffered from depression due to all of that cold and darkness. How is anyone supposed to go outside to contend with such an oppressive environment, let alone exercise in it?

How can you tell if it’s too cold outside to train?

Let’s start by talking about when it can become too dangerous to be outside in general. Doctors advise that you pay very close attention to three key contributors to chilliness before you venture outside and into an unforgivably cold environment. 

The first is the actual temperature of the air, and the foremost physical concern of people exposed to the cold is usually the potential onset of hypothermia, which occurs when the body’s core temperature dips below 95 degrees Fahrenheit. Depending on the state of dress a person is in, or the amount of protection they armor their bodies with, hypothermia can become a serious cause for concern as soon as the air temperature dips below 50 degrees. In fact, the majority of hypothermic incidents occur in air temperatures between 30 degrees and 50 degrees, in cases where potential victims of hypothermia are the least cognizant of their vulnerability to the cold.

Precise measurements of the rates at which body temperature can drop relative to a decrease in temperature are justifiably unavailable, since it’s impossible to ethically run a controlled experiment where you intentionally lower a person’s core body temperature. After all, the damage caused by such an experiment might be permanent, and once a person’s body temperature sinks into the 82-degree range, they’re at risk of cardiac arrest, coma and death. However, evidence indicates that even an adequately dressed person can become hypothermic in less than 10 minutes when they’re situated in air temperatures near or within a sub-zero range.

That’s terrifying. So what are the other two factors?

One of them is wind chill, and this is a complicated subject to broach. Despite the reporting of wind chill as the ultimate danger, or as the truest, rawest measure of iciness, wind chill doesn’t actually make your body colder; it only influences your perception of how cold the air is. Your body constantly pumps heat to the surface of your skin, so you always perceive the air temperature to be warmer than it is unless the wind emerges to deprive you of your comfort. 

Remember, the average body temperature is 98.6 degrees, so it takes quite a warm environment for the external air atmosphere to exceed your body’s temperature. When the wind interacts with your body in a cold environment, it whisks the heat away from the surface of your skin, enabling you to feel the real temperature without the benefit of the heat protection your body naturally provides you on an ongoing basis. Keep in mind, two thermometers left in the same environment will register the same temperature no matter how much you vary the volume of wind that is being blasted onto each of them.

The more important factor for our purposes is moisture, specifically because you may be tempted to run outside in cold temperatures, generate a sweat and then linger outside in your damp clothes. Once your sweat is outside of your body, you’ll physically interact with it as if it were never within your body. Water carries heat away from the body 25 times faster than the air, and if that water freezes, it greatly accelerates your body’s heat loss. Think about how your body would react to being pressed directly against ice for an extended period of time.

Okay, let’s get down to brass tacks: When is it absolutely too cold to train?

Well, you’re obviously going to dress for the conditions, and aside from ensuring that you cover yourself thoroughly — including attiring yourself in gloves and a hat — it’s been suggested by people who know what they’re doing that you should dress for temperatures 20 degrees warmer than the cold air you’re training in. This will prepare your body for how it will feel when you’re 20 minutes into your workout, and the production of energy has warmed it considerably.

Hypothermia aside, the greater risk is frostbite. Even at a temperature of 25 degrees, ice crystals can form in bodily tissues, and temperatures in the range of 5 degrees can rapidly increase the likelihood of frostbite. On top of this, inhaling frigid air can result in asthma-like symptoms — especially in people who have been diagnosed with asthma — but also in some people who don’t typically suffer from asthma. For this reason, it’s recommended that you not train in temperatures below 10 degrees.

So, taking all of the factors into consideration, it’s highly inadvisable for you to train in temperatures below 10 degrees under any circumstances, since you’re exposing yourself to damage from the entire unholy frozen trinity of hypothermia, frostbite and cold-induced asthma. 

No matter how many times you’ve viewed the training sequences from Rocky IV and pumped yourself up to train in an environment resembling a frosty Siberian landscape, the reality is that when Rocky’s trainer Duke Evers motivates him with shouts of, “No pain,” it would have doubled as an accurate medical assessment because the frostbite would have already deadened the pain receptors in Rocky’s skin.