Keeping your fingers and toes warm in cold weather: a guide for endurance skiers with poor circulation

In recent years I have had severe trouble keeping my finger tips and toes warm while outside in winter.
I blame it on too much cold-weather camping and letting my extremities get numb in my younger days, but it may be as much genetic as anything.
In any case, it has made my winter outdoor activities, especially cross-country skiing, difficult and often desperate. As soon as my fingers or toes get a bit cold, they stay that way even if my core temperature is so high that my palms are sweating profusely.

In late 2016, in preparation for skiing the 160 km Canadian Ski Marathon for the third time, I gathered all my best ideas for keeping my distal phalanges warm. Below, I outline what I tried and what worked best.

20161229-coldhands-00004

My old approach

I learned years ago that I could always force warm blood into my fingers by spinning my arms around in giant circles, using centrifugal pressure to reopen all the stubborn arterioles that have clamped shut. I can even do the same thing (but it’s slower) for my toes, by maniacally swinging a leg back and forth.

med_2013-01-01-DSC01616-crop.jpeg.gif

Alas, I have developed chronic rotator cuff tendonosis in both shoulders, and a tear in one labrum, and I can’t think how I could have damaged the labrum except through my aggressive arm swinging.

Reynaud’s disease

People get diagnosed with “Reynaud’s syndrome” when they have fingers and toes which “shut off” and turn white at the first sign of being cold, and don’t rewarm easily. The condition is even sometimes treated with drugs (beta blockers). I learned back in 1995 from Dr Murray Hamlet of the US Army Cold Weather Research Center that you can treat Reynaud’s by retraining your distal arterioles,  by cycling your core temperature while keeping your extremities warm. Translation: strip down when it’s very cold outside and use a hot tub or buckets of hot water to keep your hands and feet warm while letting your body (core) get alternately warm and cold.
Back then, Dr Hamlet said experiments suggested one needed to do 50 of these body temperature cycles in order to train one’s extremities for a season. Fifty cycles is a lot of effort, but I do take the opportunity on the rare occasions I’m at an outdoor hot tub.

I have found that such “training” works both ways. Whenever I let my fingers or thumbs get cold, I feel it for days and they become even more susceptible to “switching off”. I am now careful in the autumn even to avoid taking things out of the freezer without a mitt because my fingers and thumb can turn off nearly on contact.

Physics interlude

You might say there are four ways we lose heat when outside: conduction, radiation, evaporation, and breathing. (You’ll find people listing a slightly different list of three mechanisms that have been repeated for decades, but often the explanations are loose. Moreover, the quantitative details are still being researched; only detailed modeling or experimental testing can  tell you the numbers for different clothing combinations in different situations).

Conduction happens when you’re touching something. If it’s colder than us, we lose heat to it. We sometimes call it convection when that something is air, which moves, and greatly reduces the insulation provided by non-moving air next to our body. Thus we have thick soles on our shoes, wear thick insulation to trap air, and wear shells to prevent wind from refreshing the trapped air. When clothing gets waterlogged, our insulation material effectively changes from air (thermal conductivity ~0.0243 W/m/K) to water (thermal conductivity ~0.6 W/m/K), meaning wet clothing transports heat away from us much faster than dry.

Interestingly, we are likely in winter to be losing as much heat to radiation as to conduciton. You can think of thermal imaging (infra-red) cameras to visualize the heat energy given off more by warmer things. In fact, everything is radiating this heat energy, but the amount depends very strongly on an object’s temperature, and thus the balance of heat we lose to radiation varies very strongly with the difference in temperature between our outer clothing and the sky, the snow surface, and other objects around us. We deal with this radiation loss in a similar way to the conduction loss — by covering up and increasing the thickness of insulation, so as to reduce the surface temperature of our outermost coverings.

A major determinant of staying warm in winter is reducing heat loss through the third mechanism, evaporation. The amount of heat we lose from one molecule of sweat turning to vapour and leaving our body (2257 J/g) is fifteen times as much energy as it would take to heat that molecule up (4.2 J/g/K * 37 K) all the way from freezing to body temperature! This is one reason (of two) why managing perspiration is the prime focus in learning how to dress for outdoor winter activities. When you wear a permeable shell (a windbreaker) or even semi permeable shell (a goretex jacket), much of your perspiration is leaving, and with it, all that energy (heat). While we’re actually sweating, we want that cooling effect, but we’d like it to stop as soon as we stop sweating.

Actually, I would guess that the vast majority of the evaporation is going on in our lungs, not from our skin or clothing. While we can’t do much to manage our breathing, we lose a lot of water and heat to breathing in the winter. This is because the air is cold and cold air starts out very dry. Thus, when we breathe air in, we not only have to heat it from the outside temperature all the way up to our blood temperature (37 C) but also bring it from essentially zero percent humidity up to 100% humidity at the final, warm temperature.
As mentioned above, this takes a huge amount of energy because we have to evaporate all that water (from our blood) into our lungs.
A friend who spends much of his time at South Pole Station uses a breathing tube running up through his clothing, when it’s -60 outside, to partly pre-heat the air before it reaches his lungs. But he still has to saturate that air with water vapour, starting from completely dry, when it reaches his lungs.

In any case, this post is most concerned about keeping the extremities warm, assuming that we are able to keep our core (including lungs) warm enough.

Down mitts thumbdown-iconthumbdown-iconthumbdown-icon

Surely the warmest possible mittens would be made of down? Only if it’s uncompressed and completely dry. Neither is feasible for cross-country skiing, nor most other activities. Look for other materials if you want to spend a lot on mitts.

Liner gloves thumbdown-icon

Long ago I learned to use layers on my hands the way I do on the rest of my body: thin wicking underlayer, the main insulation, and a shell. However, after trying numerous synthetic glove liners and merino glove liners, I believe they are counterproductive for me. They quickly wear holes in the fingertips, they get damp, and they end up making my fingers colder.

glove-liners

Battery-powered mittens thumbdown-iconthumbdown-iconthumbdown-icon

I tried some of these in a shop. Presumably the target market is those who are afflicted with Reynaud-like symptoms and are desperate enough to shell out hundreds of dollars for a hope. Alas, these may be useful for 20 minute walks to the bus, but even on maximum setting, the power output is not enough to help someone like me. There is a lot more heat in chemical heater packets than in mitten batteries.

“Cotton kills” interlude

You’ll hear this in any discussion of winter clothing, but the details are more subtle than most accounts you’ll read (see
Rossi et al., Dry and Wet Heat Transfer Through Clothing Dependent on the Clothing Properties Under Cold Conditions, International Journal of Occupational Safety and Ergonomics (JOSE) 2008, Vol. 14, No. 1, 69–76.)
Cotton absorbs a lot of water; i.e., it can get heavy when wet. When a layer of clothing is full of water, the insulator becomes more like water and less like air. That is, because of the high heat conductivity of water, a wet cotton garment conducts heat away from your body fast.
However, this might not make an enormous difference if there are other layers which are not waterlogged (see research article, above). Also, it might not be noticeable while you are exercising hard and generating enough heat to balance the heat loss. The bigger problem with carrying around a lot of water in your clothes happens when the wind picks up suddenly, or your level of activity changes. When the wind increases, the rate of heat loss through evaporation can increase suddenly and, worse, if there’s a lot of water sitting in your clothing, there is a lot of heat to be lost, either suddenly, or incessantly, until all the water is gone. Similarly, if you simply slow down or decrease your aerobic output and heat production, you will stop sweating but if you are wearing lots of water, you won’t stop losing heat through evaporation.
Since your body sweats in order to cool down through evaporation, the ideal clothing will allow that cooling effect (ie transport the water or vapour away) when you are sweating, but it will not have any water left around when you stop sweating.

This is why as a simple rule, we avoid cotton clothing (“cotton kills”) in the winter.  Wool, silk, and certain synthetics don’t have the same problem.

Overboots thumbup-iconthumbup-iconthumbup-icon

For $90 you can get neoprene overboots for your cross-country ski boots. Neoprene insulates and does not breathe, so works against all the heat-loss mechanisms. I wear mine at nearly all temperatures. I have found unfortunately that the stitching on the lower cuff and cross-piece wears out long before anything else, and is hard to fix.

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(Definitely not meant to be an advertisement for Salomon, a cynical binding oligopolist)

Vapour-barrier liners (VBLs) interlude

A VBL is a waterproof layer worn next to (or close to) the skin, under the insulation layers.
For those used to trying to avoid any buildup of sweat in the winter, VBLs might seem an odd strategy. While accumulating water next to your body increases the conduction of heat away from your body even when you don’t want it, VBLs help keep you warm because they keep your main insulation dry and they completely eliminate evaporative cooling. VBLs are most often worn on feet, but can in principle be worn elsewhere. Yes, foot VBLs smell dogawful, but only when you take them off, while your outer socks stay completely clean and dry.

Vapour-barrier liner socks thumbup-iconthumbup-iconthumbup-icon

For many years I have used non-breathing VBL socks inside my wool socks on multi-day winter trips. These are cheap and need not be much more sophisticated than a robust plastic bag. For a lot more money, you can buy goretex VBL socks:

20161229-coldhands-00010.jpeg
I am now on my second pair of Rocky goretex socks, and I wear them right next to my skin. Using goretex socks limits the rate of evporative heat loss and keeps my warm socks dry. I wear these every time I cross-country ski and think they are a great help. They always wear out in the same place, though: the seam in front of the toes.

Overmitts and cross-country skiing thumbup-iconthumbup-icon

Overmitts can make a huge difference to your warmth, for obvious reasons: they (1) keep your insulation dry if it’s snowing or raining; (2) limit the rate of evaporative heat loss so that it’s not sudden; and (3) act as a wind shell to reduce convective heat loss. They are standard fare for mountaineering and snow-play.

However, for cross-country skiing, they are certainly not common! The old-school way to attach oneself to one’s cross-country ski poles so as to allow poling force-transfer without gripping the poles is as follows:

oldschool-skistrap

(From skixc.com)

It involves sticking your hand through a simple strap (1a), which needs to be snug enough that you can control the pole without grabbing it (3a). Two problems arise for Reynaud’s sufferers: We don’t want to compress our insulation or circulation with the strap, and we want large enough mitts that the strap, which is adjustable but designed for sleek gloves, may not even adjust to be wide enough.

The more modern option includes a harness that distributes the pressure over a larger area of your glove or mitten. These are often quick-release, so that the harness stays on your mitten and unclips from your pole.

DSC00521.JPG
I got a pair like this and modified my overmitts so that I could put the harness snugly on my insulating gloves/mittens but have the overmitts on over the harness. This means the quick-release tab goes through a hole I made in in my overmitts.

DSC00523

DSC00529

The first year that I tried this for the Canadian Ski Marathon, I found that it was sometimes a little fiddly to get the quick-release tab to insert into the pole without my overmitts getting in the way — too fiddly to do while moving.
In many situations this would not be a big deal, but usually by the time I was leaving an aid station, my core temperature had dropped and every few seconds not moving meant colder hands and feet.

Chemical heaters: hands thumbup-iconthumbup-icon

I bought a box of disposable hand-warmers. These react with air and produce heat for as much as 6 hours. Incidentally, these are chemically inocuous; they are essentially iron rapidly undergoing the rusting process. In my desperation (before I discovered a better technique) I have used these heaters extensively with as many as three at once distributed in each mitten during most cross-country ski days.

20161229-coldhands-00008.jpeg

However, they are are not ideal. It is my finger tips and thumb which go numb, and it’s not possible to keep a heater against each finger. I stuff one half-way up my thumb and have one on the palm of my hand, and fold my fingers down onto/near the heater, as needed, to keep them warm. I’ve also tried putting another one at the end of my thumb, but because the heaters are air-breathing, they do not do much when they are compressed/stuffed in a tight spot. Moreover, if parts of my hands are sweating, they can get damp, and thus end up holding moisture next to my skin.

Switching “off” and reusing disposable heaters

The best trick I have learned with them is that, while disposable, they are not single-use. Because they are air breathing, you can simply turn them off and restart them later. when I return from a short ski, I simply put them in a plastic bag and suck out what air I can from the bag as I tie a knot in the bag. You will notice it stop producing heat quite quickly. Like this, you can store them for as long as you like. I have reused one a year later and it quickly gets as hot as it was when first put in the bag.

DSC00545.JPG

 

I also experimented with devising special wrist bands with a pocket for a heat packet, thinking that I could warm up the blood entering my hand through my wrist enough to keep all my arterioles open. This has not been very effective.

Chemical heaters: feet thumbup-iconthumbup-icon

You can also buy the same kind of heaters for your feet. These are designed for the less-aerobic environment of boots, and they are adhesive, made to stick under your foot. It would be hard to replace them in the middle of a 9-hour Canadian Ski Marathon day, but because staying warm at the start in the mornings can be desperate, I start out with them.

Super-fat enormous expensive mittens thumbup-iconthumbup-icon

The nature of this blog is that I decided to try everything I could think of to find a way to keep my fingers warm, and that included expensive options. So I bought the warmest mitts I could imagine skiing with, even if they were stupidly expensive.

The two pairs I kept were these fat mitts (~$100) :

kombi-mitt.pngand these polar, double-mitten jobs (~$250) that are so fat the thumbs are really not prehensile:

black-diamond-absolute-mittens.png

Here is how they look next to a xc-ski glove from my younger and warmer days:

gloves-and-mitts.jpeg

But how could I maintain a sporty connection to my poles wearing such fatties? The harnesses on my quick-release poles were much too small to fit on either of those pairs of mitts. After asking in vain at several stores for another pair of the harnesses, I contacted Komperdell (who makes them) directly and they kindly sent me a set for free! These I modified by restitching the adjustable strap that goes between thumb and forefinger and connects to the quick-release tab, so that their new range would fit both my large and my enormous mittens.

DSC00541.JPG

This has worked perfectly. I skied the CSM TdB Gold wearing the enormous mittens. Because those mittens have a warm inner “lobster” mitten, I even had the option of leaving the outers clipped to my poles at aid stations and pulling out the inner mittens.

However, none of this would be so useful without my final trick…

Surgical gloves thumbup-iconthumbup-iconthumbup-icon

Even while my thumb and fingers are freezing, the rest of my hands can be sweating madly. This means that on a day-long outing, my gloves and mittens get damp and therefore become less effective insulators.
Having had success with VBL socks, I looked into who was making and using VBL gloves. Not finding much, I simply bought a box of nitrile (as opposed to latex) surgical gloves.

nitrile-gloves-box.jpeg

These I adore. The expected benefits were to keep my mittens dry and to stop almost all evaporative heat loss from my hands. However, there is an added benefit. My sweat can actually accumulate enough that the liquid water bathes my fingers and acts to equalize the skin temperature between my finger tips and the rest of my hands. I wear these gloves very frequently in winter, even when running in above-zero temperatures.
These gloves are also extremely robust (I use each many times) and a box ($15) should last you or your family for years. I do replace a glove as soon as it develops even a small hole, which so far has been in the finger tips.
On the down side, I haven’t found long-cuff nitrile gloves [Update — actually, these exist! and can be found e.g. for $18/box of 50 for 8 mm thickness, or 50$ for 200 of 6mm], so they don’t completely cover my wrists, and sometimes they ride up my palms a little, and therefore don’t protect my entire mitten from sweat.

Stephenson’s Warmlite Vapor Barrier Gloves thumbdown-iconthumbdown-icon

Stephenson’s (warmlite.com) is a legendary name in cold weather gear, and they sell the only VBL gloves I’ve found (US$22):

Stephensons-warmlite-VBL-gloves
Compared with my surgical glove solution, they are looser and have cuffs.
On receiving them, I was completely astonished to find that the cuffs appeared to be made of cotton.
I approached the company to find out how that was possible, and here’s what transpired:

Email conversation with Stephenson’s Warmlite

Date: Wed, 17 Feb 2016 10:35:26 -0500
From: Jane-Warmlite
To: Christopher Barrington-Leigh
Subject: Re: Transaction Report

Hi Chris,

No not at all. The cuffs on the gloves will be inside of your over mitten or glove. I’ve been here 36 years and not one person in all of these years has even
mentioned a problem with the cuffs getting wet. If it is cold enough to need a vb glove your hands won’t be sweating enough to contaminate the cuffs.

Jane

On 2/17/2016 9:47 AM, Christopher Barrington-Leigh wrote:
> Hi Jane,
> Doesn’t that imply that we should all be fine wearing cotton underwear in the winter?
>
> Chris
>
> On Tue, 16 Feb 2016, Jane-Warmlite wrote:
>
> > Because it is never worn outside of any clothing and therefore not exposed to any weather – Jane
> >
> >
> >
> > On 2/16/2016 10:16 AM, Christopher Barrington-Leigh wrote:
> > > Hi Jane,
> > > Hm, that’s what it looks like.
> > >
> > > Since that is one of the more counter-intuitive things I’ve ever read (the last thing I would ever imagine YOUR company to do is to make a VBL glove using
> > > cotton), would you care to explain why cotton is a good idea here?
> > >
> > > Thanks,
> > > Chris
> > >
> > > On Tue, 16 Feb 2016, Jane-Warmlite wrote:
> > >
> > > > The cuffs are made from cotton – Jane
> > > >
> > > >
> > > > On 2/12/2016 5:39 PM, Christopher Barrington-Leigh wrote:
> > > > > Hi Jane,
> > > > >
> > > > > May I ask what are the cuffs of the gloves made of?
> > > > > There is no material information attached to the glove, though I saw some description of the FUZZY fabric in the accompanying printout.
> > > > >

 

That’s right, Jane from Warmlite says that if you’re using VBLs, you won’t be sweating. Sorry, but that’s absurd; VBLs would not be desirable nor interesting if not for sweat.
In any case, when using these in cold weather, I find the cuffs become stiff and icy just as you would imagine they would. I haven’t yet replaced the cuffs with something synthetic, but that would be worthwhile (and make them more usable), as it would wick away the excess sweat further from my mittens.

Summary and conclusion

Using nitrile gloves along with my really fat mittens has kept my fingers warm.
I carry chemical heaters to use outside my surgical gloves for security. Above all, I have learned that for me it is important to avoid letting my fingers get cold in the autumn and early winter, even before the coldest times, because every time they go numb, they become even more prone to switching off in the ensuing weeks. Because I have figured out how to re-use the chemical heaters, I get a full 4-8 hours out of each, which means I don’t go through too many of them, and I can take the approach in the early season of trying to keep my fingers warmer than anything else. When I get back indoors I literally pour the accumulated sweat out of my surgical gloves.

I have also learned to put on, or even leave on, a bit more core clothing than I will want when I’m going at full/steady pace, because keeping one’s core warm is of course the first line of defence against cold extremities. The cost of this policy is a bit more sweat in my under layers, but at all temperatures other than summer my clothing includes a light wind shell with full hood, so I can manage damp clothing if the wind picks up.

As for my toes, they are harder, but the rule of never letting them get cold even in mild weather, and the policy of keeping my core warm as I am starting out, are key. I use my sock VBLs liberally, and occasionally still start out with chemical heaters underfoot.

I hope this helps someone else in my situation enjoy their old (or new) pastime. And if you’re still young (or old), never tolerate numbness!

97n13

In my younger days, wearing leather gloves at the South Pole

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One Response to Keeping your fingers and toes warm in cold weather: a guide for endurance skiers with poor circulation

  1. As someone who is always cold, I appreciate your advice on the best gear and techniques for warming your extremities. Normally I jam a pair of those disposable hand-warmers in my gloves when cross-country skiing or snowshoeing, but that’s not always the most practical solution. I’ll be sure to try out some of these mittens and overmitts you’ve suggested. Thanks!

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