What are the higher heat loss areas of the body and how can I reduce heat loss in those areas?
What are areas of the body which lose heat more quickly, and how can I reduce that loss?
6a head - it is good to take a cap a with you when sleeping under the sky, even in summer.– TomasJan 29, 2012 at 22:37
2Related on Keptics Do we lose most of our body heat through our heads?– user2766Nov 26, 2014 at 16:12
While it's not strictly an answer to the question, I would caution you to ensure that any part of your body that you are going to be using in any activity must be kept warm. For example if you are climbing while it is cold it is even more important to keep hands warm than if you were walking in the same temprature– RugnirJan 25, 2017 at 15:39
My original answer to this question sparked a surprisingly intense debate, so I'm rewriting it to clarify a few points and offer a more holistic answer.
Let me start by saying that every square inch of skin on the human body is capable of allowing heat to escape. That is to say, if you wear a jacket with no pants, your legs will lose more heat than your torso -- but if you wear pants with no jacket, your torso will lose more heat than your legs. Both areas are capable of losing heat -- and will do so more quickly when exposed. Therefore, any part of your body that's more exposed to the cold than another part has the potential to lose more heat than other than parts that are less exposed.
This is fairly obvious, but I mention it for completeness' sake. This generally means that you should try to cover yourself as much as possible, especially larger skin surfaces like the torso.
However, the point that I think the OP is trying to get at is that -- all else being equal -- every square inch of exposed human skin does NOT lose heat at the same rate. That is to say, some areas of skin lose heat faster than others. If you were to stand in the cold totally naked, some parts of you would lose heat more quickly than others. This is an indisputable, biological fact. Allow me to explain:
Human blood serves many functions -- one of which is thermoregulation. As an evolutionary adaption, humans have areas on their body that are especially suited for releasing heat, in order to cool us off when we get too hot. In these areas, there is a high volume of blood flow, and that blood passes very close to the skin. These areas are:
- The skull
- The groin
- The armpits
- Some might also say the extremities, like fingers and toes.
In these areas, there is a lot of blood flowing around, and the skin is fairly thin, allowing heat to escape from the blood more quickly than in other areas.
Therefore, if you are in a desperate survival situation where you risk hypothermia, these are the areas of the body you should focus on keeping the warmest.
Armpits are fairly easy to keep warm, just keep your elbows down and they'll be insulated by your torso and upper arm.
It's important to keep warm, dry underwear in order to keep your groin warm as well.
And yes, YOU SHOULD WEAR A HAT. While you might not lose the "majority" of body heat through your head, it is one of the areas of skin that loses heat most quickly and it should be one of the main things you focus on keeping warm.
The extremities are also important to keep warm. I have friends that go out jogging in the winter wearing shorts and a t-shirt. They don a warm beanie and gloves right before they go out, and those are all it takes to keep them warm in freezing temperatures.
In summary: If you have clothes or ways to protect every inch of skin on your body, you should do that. I thought this was basic common sense, but people were squabbling so I'll reiterate.
However, if you only have limited means of protection and you need to focus on warming only a small area of your body, you're best off focusing on the four areas listed above.
5guardian.co.uk/science/2008/dec/17/… -- "The face, head and chest are more sensitive to changes in temperature than the rest of the body, making it feel as if covering them up does more to prevent heat loss. In fact, covering one part of the body has as much effect as covering any other." Jan 31, 2012 at 21:57
4This one indicates that this is not nearly so clear cut as you imply. Heat loss is based on skin temperature, which the body can regulate, but tends to be higher (and thus lose more) in the torso, not the head. ncbi.nlm.nih.gov/pmc/articles/PMC1086117/pdf/pnas01858-0029.pdf Jan 31, 2012 at 22:03
4Not available online but these show that the heat loss through the head is relative to the % of exposed skin, not anything special about the head. The head loses heat consistent with its portion of total exposed skin area (ie, at the same rate as other skin) Vreeman R, Carroll A. Seasonal medical myths that lack convincing evidence. BMJ 2008 ; 337 : a2769 (20-27 December). & Collins KJ, Abdel-Rahman TA, Easton JC, Sacco P, Ison J, Dore C. Effects of facial cooling on elderly and young subjects : interaction with breath-holding and lower body negative pressure. Clin Sci 1996 ; 90 : 485 - 492. Jan 31, 2012 at 22:11
It's probably worth pointing out that a lot of people reading this question may be thinking along the (commonly quoted) line that about 80% of body heat is lost through the head - which is much more of a myth than people realise (See here for details.) From what I remember, it was an experiment done with people fully kitted out apart from the fact that they weren't wearing anything on their heads... and, somewhat unsurprisingly, most of the body heat lost in this scenario was from the head.
Of course, it is important to keep the head wrapped up, but it's equally important to keep other parts warm - especially the torso. Even though extremities may feel colder, this is because your body is reserving the heat for its vitals and cutting it off more to things such as your hands and feet. Warm up the core of your body and it'll start warming your extremities as a result!
In terms of how to reduce heat loss in those areas, it's generally as simple as wrapping up as warm as you feasibly can (and as much as is appropriate for the conditions. Obviously full arctic gear isn't required for a damp autumnal day!)
In short, wrap up as best you can all over, but it's especially important on the torso. In practice though, it shouldn't come down to deciding what to wrap up in particular - if it's cold, wrap up as best you can all over!
1@downvoter - Could you explain the reason? Jan 29, 2012 at 22:53
I didn't vote down but again this doesn't answer the question...(but I think this question is turning into an argument REAL fast)– mjriderJan 30, 2012 at 21:10
+1 Increase your covered area (i.e. pants if wearing shorts, jacket if wearing a t-shirt, hat if bald). Add wind layers if it's windy. Add insulated layers to as much area of your body as possible if neither of the previous bits work.– RyleyJan 30, 2012 at 21:24
2PS: my sources tell me that heat loss through your head is pronounced if you are already shivering.– RyleyJan 30, 2012 at 21:32
Heat loss can occur from anywhere on the body through a number of processes:
- Conduction e.g. when sitting on the ground.
- Convection e.g. due to wind chill.
- Radiation i.e. heat loss direct to the environment from exposed skin.
- Evaporation i.e. heat loss through perspiration.
- Metabolism generates heat; conversely, without enough sustenance the body won't generate heat.
- Respiration the body moistens and warms the air on inhalation, this heat is lost on exhalation which increases the colder and dryer the air is.
- Body size the smaller the body the greater the relative surface area to lose heat through.
Combat heat loss by:
- Minimising exposed skin, which will radiate heat.
- Wear wind-proof clothing to minimise convective heat loss.
- Use a sit mat or sit on your rucksack when taking a break to prevent conductive heat loss.
- Wear moisture-wicking undergarments to minimise heat loss by evaporation.
- Eat high-energy foods to keep your metabolism up.
- Breathe through a scarf in cold dry air.
- Monitor children and be aware that they will feel the effects of cold before you.
As for specific, high heat loss, areas of the body, it depends:
- If you are sitting on a rock or camping without ground insulation the high heat loss areas will be those in contact with the ground through conductive heat loss.
- If your back is sweaty under your rucksack, heat loss through evaporation could make your back the high heat loss area.
- Cold, dry air can make respiration a high heat loss area.
In general, the high heat loss areas will be those not adequately protected from the various mechanisms of heat loss prevalent to the situation you are in:
Scientists debunk the myth that you lose most heat through your head
1This addresses heat loss in general, but doesn't really answer the OP's question directly -- what parts of the body to concentrate on warming. Jan 29, 2012 at 2:40
@HartleyBrody -- All parts lose heat evenly. How else could Graham answer this then? There is no single part which should be focused on because heat is lost through the skin uniformly. There was an interesting experiment done on this where people were submerged in ice cold water. I'll see if I can find it. Jan 29, 2012 at 22:29
1Alright, I kind of feel like giving up at this point since I'm getting so trashed for it, but "heat is lost through the skin uniformly" is not true. The OP's question indicates that they know this, and are asking where it's lost the fastest -- but all of the answers neglect this. Jan 29, 2012 at 23:26
1Yes, heat loss can occur from anywhere, but the question asks where it goes the fastest. Jan 29, 2012 at 23:31
1I say good answer to the wrong question– mjriderJan 30, 2012 at 17:01
Here is a thermogram pictorial answer to try and figure this out! I believe this is a un-clothed male under a thermal camera (SFW)
There's not a simple answer to the question of where your body loses heat, because the body is a sophisticated thermoregulator, and the amount of heat your body loses, and where it loses heat, varies depending on how warm or cold it "thinks" it is.
The primary means of thermoregulation are by controlling blood flow near the surface of the skin, and by evaporative cooling (i.e., sweating). Let's assume you're concerned with heat loss in cold conditions and just talk about that. All parts of your body can lose heat, but it is obviously not equal, because heat loss will be greater where blood flows close to the skin in exposed parts of the body. The thermogram link posted by mjrider shows many of these areas.
When cold, your autonomic nervous system uses vasoconstriction to reduce blood flow to areas. In your extremities, blood flow through capillary beds which accelerates heat loss can be completely shut down, and blood flows directly from arteries to the veins through vascular shunts. Note there is some argument about the presence of precapillary sphincters involved in this process, but there is more recent evidence of the involvement of the vascular shunts. Not sure anyone has explained the role of the AV shunts in Raynaud's syndrome, but Raynaud's clearly illustrates just how effective these vascular shunts are when in effect. Similarly, rosacea and erythromelalgia reveal locations of capillary beds used for dissipating heat when hot.
However, as mentioned in other answers, blood flow to the brain is critical and isn't constricted, so areas like the neck and temple where blood flows next to your skin, when not covered, can represent a major loss of heat.
Also note that these mechanisms can also inadvertently contribute to hypothermia or frostbite, and in some cases it's better to maintain some blood flow. Laplanders and Inuit have an intrinsic ability to withstand cold conditions far better than the rest of us. The rest of us would have to practice ancient yogi techniques for maintaining warmth, recently popularized by Wim Hof (The Iceman).
The short answer is age-old knowledge: in addition to regular clothing, wear warm socks, gloves, a hat and a scarf. While the feet and hands won't lose a lot of heat when blood flow is constricted, you will become dysfunctional if you don't keep them warm enough.
from the perspective of hot climate, where losing heat is of interest, do we still concentrate in these areas? Of course air conditioner will keep individuals comfortable, but for those who can't afford that, will applying of water regularly and letting it evaporate in those areas that are efficient in losing heat help? May 27, 2020 at 7:31
Over most of your body your system can restrict blood flow to the skin, cooling the skin (and making you feel cold)
Locations where bloodvessels run close to skin big sources of heat loss. Parts of your body that have sub-cutaneous fat lose heat more slowly. Wehre there is little fat (sides of the chest, under the arms) heat loss is more rapid.
The head has no auto-regulation for heat, and receives about 25% of your blood supply. If you were standing naked, then initially some fairly large percentage (the head isn't 25% by area, so it will be under 25%) will come off your head.
As your body realizes, "hey, it's cold out here" surface circulation will be reduced. Later even main flows to limbs will be reduced. Muscles get stiff. Fingers get inept at doing up zippers and buttons. (Fumbles) You are now in trouble. Further chilling will result in cooler blood going to the brain. Large muscle coordination gets erratic (Stumbles) Judgement starts to go, and speaking is impaired (mumbles) Note that the 'umbles are also characteristic of low blood sugar. Eat.
But backing up, as you cover up, what heat losses there are come from the parts that are still uncovered. So yes, if you are wearing winter boots, good mitts, pants over fleece and a storm parka, then, yes your head is likely to be some very high percentage of your heat loss.
Prevention: Stay cool to stay dry. Open up when you even start to sweat. If your hands get cold put on your hat. If your still cold, put up your hood.
If you start to shiver, your body metabolism is falling behind. Reduce the heat loss. Get out of the wind, get more clothes on. Change wet or sweat soaked clothes for dry ones. You need to fuel that shivering. Eat. Drink. Hot sweet liquids are best. Dehydration interferes with metabolism.
Prevent dehydration. Eat snow if you must.. If you aren't already cold it won't hurt you. The energy of half a snickers will melt a kilogram of snow into water. (The ice crystals however will scrape your throat raw) One trick I use on winter trips is to bring a thermos of triple strength juice at as close to boiling as I can. Fill the cup 1/3 full and pack snow into it until it doesn't melt. One liter in the back becomes 2-3 liters in the field.
Lots of ways to reduce heat loss: Wear a hat scarf and gloves as these keep the most important parts of your body warm. Wear warm knickers (even if you're a guy). You can get fleecy knickers but not fleecy pants. Also, you can huddle, like penguins as it reduces your surface area and conserves bodyheat.
I like the take on huddling together - good emphasis on the fact that there's ways other than clothing to stay warm. Sep 12, 2012 at 21:31
I don't think heat versus temperature is addressed in any answers.
Assuming all skin is the same temperature then cover all skin with equal insulation is optimal. Starting warm all skin is about the same temperature. Cover nose mouth and eyes is problematic.
What happens is a smaller mass will lose temperature faster. There is just not as much thermal capacity (reserve) behind the skin. If you go outside naked on a cold day your fingers, toes, ears, and nose will get cold first. The body could send more blood to those parts to basically share the cold but it does not (and for good reason). The body actually restricts blood flow to the extremities to preserver heat (temperature) for the vital organs. This also reduces heat loss as a cold hand, arm, foot, and leg loses heat at a lower rate. Those parts also recover better from cold with the exception of frostbite. The body considers the brain a vital organ. So from the perspective of what the body does when it is cold then torso and head are most important but most people don't want to rob from extremities and make cold feet and hands even colder.
While I personally disagree to other answers, I'd like to make a point. According to my understanding an uncovered head will loose a lot of heat. Put a hat on and no top and see what happens. I'm a hunter and when I sit, I find the cold area are the shoulders, kidney and wrist.
I had a Saab 900 with heat vents that would blow on my wrist when I put my hand on the dash. It was amazing to experience how quickly my body was warmed up when heat blew on my wrist. These in my experience are the key areas to keep warm when all else in you clothing is equal.
Not entirely true actually– user2766Nov 26, 2014 at 16:13
1I tend to contradict in 2 points: spots that feel cold first are not necessarily ones that lose the most heat but can also be areas that have low insulation and/or blood vessels close to the skin. Especially the wrists (also the veins at the thigh inside) are known to be well suited to manipulate body temperature sensation by "feeding" heat or cold into the body. This does not work because they are spots of heat loss but because they allow easy thermal coupling from the outside and the blood flow transfers the temperature applied there quickly to the body core. Nov 27, 2014 at 10:00
To answer the question directly, the three areas that lose heat the fastest are actually:
- The Head
- The Groin
- The Armpits
This is why those are the areas that naturally grow the most hair on human bodies. It's an evolutionary adaption to keep us warm. In those areas, there is a lot of blood flowing and it passes very close to the outer layer of skin, allowing it to cool of more rapidly and lower our body's temperature. It's all of the blood rushing around your skull, into your legs, or into your arms, respectively.
Covering your head is a no brainer. As others have mentioned and most people already know, the head it where you lose most of your body heat, so wearing a dry, windproof hat with a lot of loft is always a smart idea if you're cold.
The groin and the armpits are a bit more tricky. If you're dressed according to normal human social standards, you'll probably be fine. But if, for some reason, you're out in the cold with little or no clothing, those are the areas to focus on the most.
Keep your arms tight at your sides and cover your groin with your hands. Not only is that our natural reaction to the whole "being naked" thing, it also happens to be the best way to stay warm with no clothes on!
4This is wrong. The myth of heat loss through the head has been debunked and if hair on the groin and armpits was essential for insulation we would have evolved soft downy hair growing from birth not coarse hair growing from adolescence.– GrahamJan 29, 2012 at 13:59
2My source for this is mostly my father, who is a doctor. Also, the "head" claim is backed up by my friends who go running in the winter in shorts and a t-shirt: they put on a hat and gloves and those are enough to keep their entire body warm. While the head may be generally over emphasized in thermal regulation, it's still a very important source of heat loss. It's dangerous to have someone who just read the wikipedia page on thermoregulation proselytizing about the "wrong" ways to stay warm Jan 29, 2012 at 16:00
2I suspect the reason people who go running in shorts and t-shirt need a hat is there is very little muscle around the top of the head so this part of the body gets cold, whereas the rest of the body is kept warm by the muscles they use when running.– PhilJan 29, 2012 at 16:33
5"The head is one of the areas that loses heat most quickly. I'm not saying anything about whether it's most of your heat"... "As others have mentioned and most people already know, the head it where you lose most of your body heat" That's exactly what you said - or at least strongly implied, whether you meant to or not! I agree that the head should be kept warm - see my comments on chat for more info. The biggest problem in my mind is that you're implying (whether you meant to or not) you should concentrate on keeping the head warm above the torso, which I don't believe is sensible! Jan 30, 2012 at 19:44
5If it's an indisputable biological fact I'm sure you can easily cite a dozen studies showing such. "Indisputable scientific fact" is usually the refuge of someone without actual evidence. guardian.co.uk/science/2008/dec/17/… Jan 31, 2012 at 21:52