When you’re outdoors in cold climates, it’s important to stay warm. Prolonged exposure to the cold without ample protection can spell hypothermia, something that will most certainly ruin your outdoor adventures. Whether you’re hiking, climbing, or camping, you’ll want to take care to keep warm.
But there are certain areas of the body that require more protection since they are the most prone to heat loss. Knowing which areas these are can help you stop heat loss and stay safe in the wilds.
Which areas of the body are most prone to heat loss? Most people know the head is one place that needs protection or else they wouldn’t dare go outside in winter without a hat on. The armpits, fingers, and toes also lose heat more quickly than other parts of the body. This is because lots of blood is flowing around these areas and the skin in these parts is thinner which means it’s easier for heat to leave the body more rapidly.
Before you take to the great outdoors on your next adventure in cold weather, keep reading to find out why this happens and what you can do to protect yourself from heat loss!
Why your head, armpits, and extremities lose the most heat
Your head, armpits, and other extremities lose the most heat though every part of your body can let heat escape from it if you’re not properly protected in the cold. If you were to throw on your jacket but walk out of your house into the snow to get the morning paper or the mail, your legs would lose more heat than would your torso. But if you decided to bound out the door wearing fleece pants and a t-shirt to do those things, your torso would be the one losing more heat.
The point is that any exposed parts are where heat will leak out. And thus, if you want to retain your heat and keep from suffering from hypothermia, you’ve got to cover yourself the best you can. The larger the surface, the more problematic it can be. So while running outside in the cold to grab that paper or your mail isn’t going to be life-threatening, try doing that for prolonged periods of exposure and you’re going to have very serious results.
Still though, while every part of your exposed skin can lose heat, it does not happen at the same rate. Some parts will lose heat faster than others. To understand this is to understand your blood.
Blood doesn’t just pump oxygen around to your body. It also provides the function of thermoregulation. This is so that we can release heat when our bodies get too hot. In these particular areas, the volume of blood flow is high and it passes close to the skin. The areas it does this in are the head, groin, armpits, fingers, and toes.
Why does this happen? The skin is thinner in these parts allowing for heat to flee the blood more easily.
Why should you know this? Simple. It’s a matter of survival. And if somehow, you get cut off from your trail by an avalanche or something happens where you need to rely on your skills to survive, you will now know which parts of your body you should focus on to keep warm and prevent hypothermia.
Hopefully, you won’t be out in the wilds without proper attire for the cold weather. Even still, to keep your armpits warm, keeping your elbows down and tucked into your sides can make a world of difference.
Underwear should be the kind that keeps you warm. It probably should go without saying that it should be dry, but if you’ve somehow skidded out on your butt in the snow and your pants are damp, you’ll want to find your way to a dry pair pronto.
A hat is one of the quintessential winter wear items you need to have on while outdoors. It makes no difference when walking up and back on your driveway for one minute. It makes ALL the difference when you’re miles away from home out in the cold. Your head won’t lose the majority of the heat though, but it is where that heat can leave more quickly.
Warm socks and good shoes will help keep toes protected while fingers need a solid pair of dry gloves. Anyone that goes running in the winter can probably tell you that they stay nice and cozy wearing a t-shirt, running shorts, thick socks, shoes, a beanie, and gloves because those major heat-escaping areas where the heat leaves the quickest are fully covered and protected.
The myth that most of your body heat is lost through the head
You’ve likely heard that most of your body heat is lost from your head, right? You’d think so since when babies are born, keeping them warm is essential and they always cover a baby’s head with a warm hat.
But this is all false. Scientists have proven it. The origins of this myth go way back to an old US army survival guide that was published in the 1970s. In it, it recommended that the head be covered when it’s cold out because 40% to 45% of the body’s heat could escape from there. So in 2006, scientists set out to see if this had any merit. They had subjects in cold water, both with and without wetsuits. Some of them had their heads above the water at times while others were fully submerged. It turns out that heat loss is proportional to the amount of exposed skin.
In an updated report from 2008 in BMJ, it was found that you lose at most 7% to 10% of your body heat through your head. The belief that this persisted for so long comes from the misinterpretation of a military experiment conducted in the 1950s. Volunteers donned Arctic survival suits and were exposed to frigidly cold conditions. The head was the only part of the body left uncovered and hence where most of their heat was lost.
Your face, head, and chest are much more sensitive to temperature changes than any other part of your body so when you cover them up, you FEEL like it’s helping more to prevent heat loss. But when you cover one part of the body, it’s really the same as covering any other part. So if this experiment had been done with people wearing just swim shorts, they would have lost no more than 10% of that body heat from out of their heads is basically what this all boils down to.
Should you go out for long periods of time in winter without a hat? No, but you shouldn’t leave other parts of you uncovered either as your body hit will escape and put you in danger.
Heat Loss Mechanisms
There are 4 ways we lose heat from our bodies. Those ways are radiation, conduction, convection, and evaporation. When you understand how these heat loss mechanisms come into play, it is much easier to protect yourself during winter excursions outdoors. Even if you don’t plan on hiking in the wilderness, climbing a mountain, or camping in the snow, this information is important for those living in or visiting cold climates. You never know when your car might break down on a remote road. Staying warm is critical to your survival.
Keep reading to explore the 4 heat loss mechanisms!
Radiation is energy that is moved in the form of electromagnetic waves. One example of this is the sun. Another, a bonfire. When you stand under the sun or beside that bonfire, you can feel that heat radiating from the source.
Your body also operates in this fashion and thus, radiation is often the largest source of our heat loss. Even in a normal and calm climate situation, say around 70°F, when you’re clothed and sedentary, you lose about 60% of your body heat via radiation. It’s hard to prevent this type of heat loss. That’s why space blankets are a handy survival tool. This reflective material essentially bounces your radiation back into your body.
The other sources of heat loss are easier to contain though so keep reading to learn about them.
Conduction is the direct transfer of heat away from your body by what it comes into contact with. Air is a poor conductor of heat, but not water. Water conducts heat much more efficiently, up to 25 times more than air does. When you swim, the water is drawing heat from you very quickly.
But you don’t even need to be in the water yourself to have this happen. You could be kayaking along on a cold river or lake and if your body isn’t dressed appropriately, you will feel the rapid chill come through it.
Convection happens when cooler water or air contacts your body gets warmed by your body and then moves away. So that heat that caused the air or water to warm up becomes lost and replaced by cooler air or water which needs to be warmed which further increases heat loss.
To illustrate this point, picture your hot cup of coffee in the morning. You might blow on it so you can take a sip without burning your tongue. When you do, the air above your coffee cup is warmed right above the surface. Blowing on it moves that air away and allows the cooler air to come in and replace it while taking more heat from the cup.
Convective heat loss is the most extreme in a moving body of water like a river. Say you go for a swim in a rapid current. The water is taking the heat away from you more than the air and it is sweeping away any warmed water from around you. Even air sucks heat away in an efficient way. This is where wind chill comes from and why you can feel so much colder than it actually is.
You probably know evaporation more from science class. This is when water in liquid form turns to water vapor. Heat is required for this to happen. Take your breath for example. Every time you breathe out in the cold, you bring the cold air from around you into your lungs. As your body does this, it warms the air and when you exhale, you release the warmed air back out.
When you compare that to the other ways of heat loss, this is the most minor, but you can stop it by covering your face lightly to warm up some of the air you breathe in before you draw it into your lungs.
What your body does to reduce heat loss
As your blood runs through your body with all those nutrients, oxygen, and other things, it brings heat that your muscles create to your skin. From your skin, it is then released. So go out into the cold and your body starts redistributing blood to your trunk to protect your vital organs and keep them safe.
Your body also constricts your blood flow to the skin. By doing so, it means that less heat can escape. When you minimize this, it helps you retain your internal heat for longer. That’s why wearing the right clothes always matters when spending prolonged periods out in the cold.
You can also use your muscles to help stay warm. Cranking up your activity increases your metabolism and generates more heat. Your body does this even when you’re not thinking about it. Perhaps you’re amply bundled but have been walking for blocks along big city streets in Chicago or NYC and your teeth start chattering or you may be shivering. But this is your body’s way of generating more warmth for you until you retreat to the warmth of a coffee shop or the subway station.
The differences in our body sizes and metabolic activity influence how we feel the could too. A smaller person with less body fat will lose more heat to their surroundings than a larger, fatter person. Bigger people may have more muscle mass which produces more heat, or they may have more body fat which acts as insulation to protect from heat loss.
That’s not to say that if you’re a small and fit person, you should just stuff yourself silly to fatten up. But these things do have an impact and often, they’re not so easy to change. Luckily, there are some things you can do that make more sense and won’t require changing your size.
What you can do to help reduce your body heat loss
Get ready for the cold by retaining heat. We’re going to cover the best ways to keep yourself covered in the cold so you can stay warm and stay healthy.
– Wear a jacket that can trap warmth to limit convection and radiation
The 2 most common ways of heat loss are convection and radiation, and as such, you’ll be wise to protect yourself from them. It’s a simple process thankfully. All you need is a jacket that is rated to face the temperatures you’re coming into contact with.
Let’s say for example you’re going to spend a month visiting relatives up north in the dead of winter. If it’s going to be about 30F give or take and you’re not planning on being very active, a jacket that can protect you to temperatures of 20 to 30F is ideal.
Your jacket should be able to trap warm air inside of it while keeping drafts out. That warm air in the jacket is what will keep you warm. So choose something that keeps cold air from replacing that warm air from your body.
For radiation heat, protect areas of your body that are normally exposed. In warm climates, you think nothing of your hands, head, ears, and throat being exposed to the air. But when your body gets cold, it will move your blood to those vital organs and make these exposed areas feel colder, putting you more at risk. In addition to that jacket, take along a warm scarf, a ski cap, gloves, and earmuffs to fully protect yourself.
– Wear gloves to avoid conduction
Here’s why your hands get so cold when you don’t wear gloves in winter. Everything we do involves our hands (and feet too) coming into contact with other surfaces. We open doors, hold things, and even when we walk across a cold sidewalk, those surfaces transfer cold into our bodies.
Choose gloves that can handle the cold temperatures and cover your wrists. Insulated gloves are ideal as are leather, but you may also want to add a liner into them for extreme temperatures.
For your feet, you might not think as much about them but they matter too. Sure, you’d never walk out into the snow in sandals, but perhaps you’d throw on your outdoor hiking boots you use on summer hikes. That’s not the same though. Some boots might be great for insulation in the upper portions but the soles could conduct more cold air to your feet.
Rubber, in particular, is more conducive than other composites. Plus in extreme cold, it can crack. When you use boots, they have mid-layers above the sole that can give you more protection while using wicking material in the insoles to keep sweat away. These are the kind to look for to keep your feet nice and toasty in the extreme cold.
– Get a good sleeping bag
During sleep, your metabolism naturally keeps your core temperature regulated to safe levels. Should you lose heat by any of the 4 means above, you’ll wake up from the cold. Thermal insulation is essential when sleeping outdoors, even in a tent.
Sure, sleeping bags seem really obvious. But the one you rely on for your summer excursions isn’t going to cut it. In fact, sleeping bags designed for cold temperatures cold just save your life. By design, a sleeping bag traps the air around your body. While you’re zipped into it, your body heats that trapped air by way of radiation and conduction. When that air in the sleeping bag gets warm, your body doesn’t have to work so hard to keep the balance. Air isn’t a good conductor of heat so that warmed air helps keep you insulated and safe.
The sleeping bag material is also important to prevent heat loss via conduction. While it’s not its main function, it can certainly help. It all has to do with the shell and the filling. These things should be thick and dense so that the warm air trapped in there with you doesn’t escape. If that fill material compresses under your body and moves around, you’ll lose that air.
Additionally, you should look for other things that will ensure the sleeping bag stays warm. Overlapping layers at the seams, insulated neck areas, draft tubes at the zippers, and drawstrings around the head area will keep warm air from getting out.
An easier way to go about this is to look for specific temperature ratings on the sleeping bags you want to buy. If it’s rated -10 degrees, it will keep you alive in cold temperatures but won’t necessarily keep you comfortable if the temperatures drop that low. Instead, you should choose a sleeping bag rated 20 to 25 degrees colder than you anticipate the air temperatures for your campout.
– … and use a sleeping pad
Many people are surprised to find out that the cold ground is more dangerous than cold temperatures in the air. When the ground is colder than your body, it will keep drawing your body heat away from you to get to a state of equilibrium. This process is never-ending though and the ground will continue to do this until you match it in temperature. Brrrrr!!!!
Keep in mind, that’s not ideal in the summer either. Say it’s 85°F (29°C) where you are during the day then falls to 70°F (21°C) at night. Comfortable, right? Not for you! The soil temperature may linger at 75°F (24°C) so your body will eventually match that temperature. Do the math… that’s over 20 degrees lower than the normal temperature for the human body.
A sleeping bag can only help so much, even if it’s thick. So using a sleeping pad solves this problem at any temperature, warm or cold. They can be inflatable and can get chilly at night too when the air outside cools down. You should read our post about air mattresses to learn more but in essence, using a regular air mattress might make you feel even colder than if you were on a thin sleeping pad. Add layers of foam or felt or even blankets between them to keep from heat loss. Foam is ideal though because it’s a great insulator that stops heat from leaving your body and going into the ground.
You need to look for the R-value when buying them to find the level of insulation. The higher this value, the better it will be at protecting you while you’re in the cold. Be advised though if you’re tall and that pad is shorter than you, you should put your feet on your backpack or a blanket so you don’t lose heat out of them.
– Stay hydrated to reduce body heat loss due to evaporation
In the summer, it’s easy to gulp down plenty of water because it’s so hot. When it’s cold, we often forget that our bodies still need plenty of water. It’s especially important when spending time outdoors though because the loss of water in your body can quickly turn into heat loss. Always keep water with you to stay hydrated. When your body dehydrates, it becomes cold.
Wearing a mask or covering on your nose and mouth can help a lot in extremely cold temperatures so you’re not directly breathing cold air in. It helps keep your throat warm where your oxygen comes through. And hey, when you eat, you boost your heat production. Have a snack before bed on that campout to help your body stay warmer until the sun rises again. This can mitigate that tipping point between heat loss and balance of heat so you sleep comfortably and feel warm.
– Try to stay active
When you keep active, your muscles contract which breaks down more nutrients. This leads to generating more heat. That added heat helps your body temperature stay at a good place and allows you to feel warm. Try running in place for a few minutes or doing some jumping jacks to warm up in the cold weather.
– A campfire can also help keep you warm
Campfires are one of the best parts of camping, but in winter, they’re a wonderful way to warm up if your campsite allows them. The heat you receive from the fire is from thermal radiation. Those electromagnetic waves carry energy that converts to heat when it hits another object, in this case, you! So you absorb that heat and stay warm and cozy while telling scary stories, making s’mores or just enjoying those soothing pops and crackles from the wood on the fire.
Since thermal radiation like that coming off your campfire spreads in all directions, that heat reaches you via infrared waves and visible light. Sitting next to it only warms you on the side you have facing the fire. So if you’re sitting on a log, toasting your marshmallows on a stick in the campfire, the front of your body feels almost as toasty as that marshmallow while the rest of you turned away from it can feel the cold.
Another thing you’ll notice if you’re losing body heat is that you’ll feel like you have to pee a lot. This is called cold diuresis, a side effect of constricted blood vessels. This is the result of an increase in blood pressure. If you notice you keep having to urinate while on your campout or just in the cold in general, it’s most definitely time to employ our heat loss reduction tactics so you can keep your body in a safe state of warmth and health.