I recently read through just about every page on Andrew Skurka's website and that quote really stuck in my head. I started to think of ways that I knew how to stay warm when I was cold:

While Hiking
- When windy, wear your windshell to prevent conductive heat loss
- wear a hat
- remove sweaty clothing which may be chilling body

At Camp
- eat a hot meal or drink some hot tea
- put some hot water in a water bottle and sleep with it between your thighs
- wear your packed clothing in your sleeping bag
- eat something
- do stomach crunches
- remove damp/wet clothing

Incidentally, the only BPL article I could find on the subject was by Ryan on Thermoregulation. Perhaps there are more that I'm not finding?

I don't have any trouble staying warm enough (assuming I have eaten enough) on 3 season trips. So when I think about a challenge to stay warm I am thinking <20F & snow. Things I would add come from my incomplete winter activities page.

• Insulating your neck with a gaiter, scarf, or baklava.
  
• Use something to warm up your breath. At 0F, you 1/2 the average persons base metabolism is used warming air.
  
• Sit or stand on a pad to insulate you from the ground.
  
• Make sure you eat enough fat... don't eat just carbs
  
• any isomorphic exercise will warm you up... and since you aren't making big movements, you keep down convection cooling.
  
• If possible, get into the sun. It's warm :-)
  
• Snow caves are a lot warmer than tents
  
• Use a vapor barrier if the temp is less than 10F
  

Edited by verber on 01/12/2008 22:29:12 MST.

At first glance, the below statement sounds WAAAAAAYYY off. Mind sharing the source?

Mark wrote,
"At 0F, you 1/2 the average persons base metabolism is used warming air."

First... keep in mind that that's base metabolism... not active metabolism. 1/2 resting is less than 1/14 of your active (say snowshoeing) output.

I first saw this in Secret of Warmth, hal weiss, pg 23, but the raw information is cited as coming from "hypothermia, death by exposure" by forgey.

Specifically a 0F the average person loses 18 kcal to convection cooling, 24Kcal to evaporation which is a total of 42 kcal. The average base metabolism is 70Kcal/hour (1680Kcal/day).

The explanation is that air coming in needs to be humidified and warmed so the lungs will function properly. The cold air warmed up is very low humidity, so you body has evaporate a fair amount of water to keep the humidity up high enough to keep the lungs happy.

I have certainly noticed that having something that helps warm / humidify the air (warming mask, face mask with breath warmer, etc) gives me a warmth boast during the day. But this has been most noted at night. There have been several trips where I was pushing the envelope (or the conditions charge way more than expected) and I found myself using my 30F down quilt in 0-10F conditions and I didn't have any warming masks. On the trips where I didn't need to worry about accumulated moisture in the quilt I would pull my head completely under and breath into a pocket of space under the quilt. This was a huge help in being able to keep my warmth and I was able to get back to sleep. On the one trip that hit similar conditions but I was concerned about accumulated moisture I was cold through the night.

--mark

Mark,

I share John’s concern that something may be amiss with your references that support the statement, "At 0F, you 1/2 the average persons base metabolism is used warming air." This value should be in the 10 - 12.5% range rather than 50%.

The sleeping bag system provides resistance to the heat exchange between the human body and environment. Heat is lost from the warm body to the cold environment by dry heat transfer (conduction, convection, radiation) and by evaporation of sweat from the skin surface. Heat is also lost through respiration (convective and evaporative losses). When a person is sedentary and comfortable, approximately 25% of his/her heat is lost via respiration and perspiration at the skin surface. The remaining 75% is from dry heat loss from the body surface (ASHRAE, 1997); this is the heat loss that sleeping bag systems are designed to minimize. In addition to ASHRAE model all other models I am familiar with use an average 10 - 12.5% for respiration.

I just looked up the Artic respiration heat loss value in the, “United States Naval Flight Surgeon's Manual: Third Edition 1991: Chapter 20: Thermal Stresses and Injuries”. It states, “Vaporization of water removes heat from the skin surface and the moist mucous membranes of the respiratory epithelium. When one gram of water is converted into water vapor, 0.58 kilocalories of heat must be supplied from the surroundings for the conversion to occur. Although the actual amount of heat loss depends on the ambient relative humidity, in Antarctica, where humidity is very low, respiration alone may account for ten percent (375 kcal) of an individual's total daily heat loss. Insensible perspiration, as is shown in a later section, accounts for an additional loss of about 400 kcal.” Note the 10% value for Artic respiration.

70 Kcal/hour is effectively the same as the 70.77 Kcal/hour BMR value used in the ISO 8996 (2004) International standard. Most physiology models list the constituent components of heat loss as 12.5% (= 8.8 Kcal/hour) respiration, 12.5% (= 8.8 Kcal/hour) insensible perspiration, and 75% dry heat loss (= 53.1 Kcal/hour). I assume that they made a mistake listing 18 Kcal/hr as convection rather than evaporation and things just got more confused after that.

The relevant text on page 23 says, "In Hypothermia, Death by Exposure, Dr. William Forgey notes that at 0 F, and average man's convective heat loss due to warming of incoming air is approximately 18 calories per hour." The warming of incoming air is not a convection loss, it is an evaporation loss.

Other than this respiration loss point of contention, I believe all of your other staying-warm-suggestions, and those from the other posters, is excellent advice.

Edited by richard295 on 01/15/2008 13:11:32 MST.

Richard... clearly the source we have looked at differ. I don't have the time right now to do a full literature search. I appreciate that you think this number it too high, but I am not prepared to disregard Weiss' assertion.

I would like to suggest something that might resolve this. My memory is the average naked person at rest in 0F conditions loses the ability to take care of themselves in less than 30 minutes. In other words, basic metabolism, in fact base + shiver reflex does not generate sufficient heat to preserve function. So even if respiration is only 10% heat lose, it could be 50% of the heat your body needs, because 0F requires you to be running at 5X your base metabolism. Hmm... this is starting to make even more sense to me when I think about clothing requirements at 0F when I am active -vs- sitting.

A similar way to think about this is that if you are sitting in a nice snug sleeping bag (or in your high loft clothing) you have significantly lowered your radiation and convection cooling. So you have lower the % of energy you are losing via the mechanisms which normally dominate heat lost. That means if you don't address other mechanisms they start to take up a larger percent of the heat lose. This actually squares nicely with my experience. There have been several nights that I could not get warm enough to sleep until I did something to pre-warm the air I was breathing.

Edited by verber on 01/15/2008 13:46:27 MST.

Do9n't know about the figures, but

> On the trips where I didn't need to worry about accumulated moisture in the quilt I would pull my head completely under and breath into a pocket of space under the quilt. This was a huge help in being able to keep my warmth and I was able to get back to sleep.

I do this myself in the snow and it works fine, but whether it is due to pre-warming the air I breath or because it really keeps my head warm is another matter. I think keeping my head warm is VERY important.

Cheers

Edited by rcaffin on 01/15/2008 13:53:24 MST.

Check this out...Thermal Efficiency of a Human Being

http://mb-soft.com/public2/humaneff.html

Edited by jshann on 01/15/2008 15:33:22 MST.

While you guys determine the physiological basis for the numbers, I'll go back to the base topic - keeping warm when it's cold. Here in the southeast when we go winter hiking we haven't encountered the depth of snow that allows snow cave building, but the temps can easily be near 0degF. Keeping warm is basically a matter of generating warmth through movement and being as efficient about keeping that warmth as possible. I find that this is the most difficult for me when coming into camp at the end of the day's hike, especially when I'm with others that want a shorter day. I don't want to jump into my sleeping bag and spend 12-13 hours there, but quite often my base layer is wet from exertion. If I change it out, it will only freeze, rendering it useless because I won't be able to thaw it out again. So I usually keep it on and keep moving to try to dry it out while working at a much lower exertion level. During the day while hiking, I find that what worked heading out in the morning needs to be changed pretty quickly on the first big climb of the day to something a little lighter, but in the act of doing so I lose so much body heat that I end up on the negative side of the exchange and it takes a long time to recoup that body heat. What gets me the most is my hands - they can really hurt when it gets cold, and when I stop moving, they feel it first. I have yet to find anything that keeps my hands warm enough, although the possum down gloves do a far sight better job than anything I've tried in the past.

A couple thoughts in response to Ron's post:

0) Use a Belay(ish) jacket/vest: Having an insulation piece that can go over whatever shell you are wearing while active. This way you can keep warm when you stop without loosing all that nice warmth you generated when moving. It also means that you can stay warm at the beginning of an activity and when you start to generate heat and can transition smoothly to lighter insulation. Related to this, use a highly breathable windshirt or soft shell while active in your layering system.

1) Drying shirt at end of day: I use a similar approach... keep active, but make sure my activity level doesn't go so high as to cause me to sweat. On rare occasions (like when I am really chilled) I will immediately change base layer and get into my sleeping bag (or under my quilt). I leave the damp clothing outside the sleeping bag until I am no longer chilled. Once I am doing OK, I bring the damp item into my sleeping bag. This is typically before it gets to the point of needing to be thawed. On longer trips where I was concerned about moisture accumulation in my bag (was wear VB clothing rather than using a bag liner) I would put the damp items in tall garbage bag and have to mouth of the garbage bag outside my sleeping bag. I don't actually know it this helped, but I figured it didn't hurt.

2) Overheating/changing beginning of the day: Something I learned by example and a recent podcast made me realize was most likely intentional on is to plan campsites so the very first thing is a demanding activity like a hard climb. I will get up and the morning wearing what I expect to wear while hiking, and layer over that an insulation piece. Take care of morning housekeeping, break camp, pack up my over the shell insulation, and start up the hill. At the beginning I the beginning I am still flush with heat from the belay jacket. I start to chill without the insulation but my activity level is heating me up. Normally I find myself chilled for say 10 minutes (I would rather be slightly chilled than overheat) and then I am comfortable. The podcast I listened to suggested that if you minimize what you need to do when breaking camp you can get away with less clothing because you only need cloths to keep you warm when activity, not sitting around (when you can be in your sleeping bag). I don't do this, but it's an interesting ideal for people on thru hikes.

3) Hands: A layered approach has worked well for me. I will hike / climb in whatever is best for my hands when active, typically no more than a lighting lined shell, often it is a light pair of liners made from powerdry or powerstretch. Some people use vapor barrier gloves for this layer. When I stop I layer something over the gloves I am active in. This is typically part of a modular mitten: either the unlined shell from the mittens to block wind, or the whole mitten which uses fleece for the palm and primaloft to insulate the back of the hand. When it's time to get moving again, the mittens come off.

Enough of my experiences... there are plenty of people on this list with more experience that me. What are your secrets. BTW: Allen & Mike's Really Cool Backcountry Ski Book by Allen OBannon (with illustrations by Mike Clelland) is fun and has some good tips.

--mark

Edited by verber on 01/16/2008 10:18:39 MST.

There are lots of things you can do to stay warm, both in terms of gear and techniques.

For me, I think it boils down to one thing: I stay moving all day. I put in long days (14-16 hours during 3-seasons, 11-13 in the winter) and if I'm not hiking I'm sleeping. I suppose this is a luxury I have by being in decent shape and by usually not traveling with anyone -- there's really no need or desire to stop early and set up camp. Since my body is generating lots of heat all day, I can get away with carrying less clothing; and I'm also generating heat well into my nighttime rests.

Another important thing to do is to make sure that you're dry when you go to bed, i.e. not drenched with sweat. Unless it's the peak of summer, and you're in a humid environment, there's no reason to be sweating when you pull into camp -- otherwise you're going to get chilled and lose body heat in the process of evaporating that moisture or keeping it warm. I think the key to not sweating is to dress in the lightest layers (so that you can micro-manage your insulation) and to opt for universal coverage instead of concentrated coverage, i.e. if your hands are cold, put on some liner gloves -- don't put on an extra shirt so that your core generates more heat (and sweat), some of which will get dispersed to your cold hands.

A few random thoughts based on numerous nights in the -10F to -20F range camping in the Adirondacks over the years:

- bring down booties, the kind you can walk in the snow with. If you haven't walked in fresh snow in down booties you are missing a truly transcendant experience.

- try to stay pleasantly cool all day by constantly adjusting your many-layered clothing to minimize dampness.

- keep moving, and snack all day.

- undressing or changing clothes in a cold, tight mummy bag generates a LOT of heat, and really warms you and the bag up. It also is frustrating as hell.

- breath through a sock or mitten through the small opening created by closing the mummy hood.

- try to protect the fabric near your mouth from frost buildup and subsequent loss of down loft

- air out your bag every morning if at all possible.

- running through deep snow can really warm you up while waiting for food to heat.

- don't bring complicated meals that need two pots unless you have two stoves as well.

- the hole you chip in the lake ice in the morning for water won't be there around dinner time.

- the sound of a roaring stove is music to your ears when it is below 0F.

- a candle lantern is great during those long nights in the tent. Be careful to ventilate, though.

- bring down booties.

- use a snow saw to build wind breaks, seats, cooking areas, etc. Construct a covered tent alcove and cook in there, hang the lantern there, etc. Again be careful about ventilation.

- wear mittens and finger-glove liners.

- don't leave your full water bottle in your pack overnight.

- don't kiss your metal fuel bottle, or let your tongue get anywhere near it!

- if you are x-c skiing, and trust some water you come across, try the following: dunk the ski pole in some snow so when you pull it out a cylinder of snow remains above the basket. Carefully lower the basket into the water, let it absorb water, then pull it up and suck on the snow to get a nice gulp of really cold water.

- when melting snow for water, be ABSOLUTELY certain there is always some liquid water in the pot. Snow can absorb a lot of liquid, and can cause the pot to dry out, with subsequent burning of whatever's left at the bottom. Having to drink burned water is a truly transcendent experience you WANT to miss! Trust me on this...

- Did I mention that you should bring down booties?

Edited by ewolin on 01/16/2008 12:49:11 MST.

most of you probably know this already but just in case, a very good hand warming technique is swinging your arms vigorously so your hands go in a semi-circle. Up and down is better than left to right. By doing this, you force blood out to your limbs

I didn't know that, thanks for the great tip!

On another thread a poster mentioned that to keep your hands warm, you can put them in a fist. I could understand how keeping your fingers wrapped in your hand [so to speak] would make them warmer, but wouldn't that also restrict circulation?

I don't think it does significantly unless you apply pressure.

What happens here is you're reducing the surface area of your hand which is good to minimize heat loss. The finger part has a huge surface area.

Edited by inaki on 01/17/2008 10:25:59 MST.

Nevermind guys, I found this video that answers all my questions:

How to Pack for Cold Weather Hiking

Read the comments.

I agree with many of the suggestions. Eating enough is critical - 6000 calories? Along with eating - hydration. In winter, people often get dehydrated because they don't feel hot and drink, but also lose more water from breathing and transpiration ("insensible" sweating). Partly because the ambient air is colder, it is also drier. Multiply the xeric effect by wind speed. Chapped lips in winter, right?

Drugs and alcohol can mess with the body's ability to thermoregulate, as well as lead to poor decisions or lack of action.

Sure, plenty of clothes. I sometimes bring an extra down hood. Don't let yourself get sweaty.

Have a fire, if you can. GF, dogs, something warm.

Isolate yourself from the cold, sit on your pack, sitpad, etc.

Pay close attention to your mental status, and what could be warning signs. Be a little extra alert - don't zone out into your workout and lose awareness of environmental or other factors until you are experienced enough in that area. Or if you do, "come up for air" a little more, take an extra break per half day or something, where you force-hydrate and check the snow conditions in your immediate area, and try to predict what you will see next.

unfinito but gotta go!

Having cold hands can put a damper on things in a hurry, and it always seems that they just don't want to warm up! In addition to the many insightful suggestions above, I will add a couple:

Don't wear anything with tight elastic around the wrist or ankle! Doing so will constrict the blood flow and you're guaranteed to have cold hands (or feet). The US Army attributed most of its cases of frostbite to elastic cuffs according to Paul Petzoldt.

Keep the wrist area warm; this will keep the capillaries of the fingers from constricting and reducing blood flow. I wear alpaca (a short llama?) wool gloves, and they're unusual in that the wrist area is twice as thick as the fingers...kind of counterintuitive. In the same vein, or is it capillary, the people that make the HotHands Hand Warmers also make a miniature version to wear on the wrist for this purpose.

Some people have a syndrome called Raynaud's, which is an extreme sensitivity to the cold, and I'm talking about only 45F. Their fingers turn white in cool weather and blue in cold...very painful. Again, this has to do with blood flow.

Don't touch cold metal - ski bindings and such - with your bare fingers; doing so could start a cascade of physiological events that give you cold hands.