Running in the cold by Alfred Hermida.

Running in the cold requires a little more care and forethought than running in warmer conditions. You don't need particularly sophisticated gear as long as you choose it well.

1 Cold and Wet

When talking about running in the cold, we have to look at how being wet changes things. When the temperature is above freezing, we can become wet through the rain, but regardless of the temperature we can always become wet through our own sweat. Getting wet makes the cold worse for a number of reasons:

Being wet increases heat loss through evaporation.
Wet clothing provides vastly less insulation than dry clothing. Different materials can have different residual insulation properties when wet.
Your body regulates its temperature by blood flow to the skin and by sweating. If you're wet, either through rain or sweat soaked clothing, your body can't control its temperature by sweating, only blood flow to the skin.
Cold rain can directly reduce your body temperature by carrying the heat away as it runs over your body.

2 Common Mistakes

A chart showing three possible temperature changes over time when running in the cold.

The chart above shows the ideal temperature changes include, and the two common mistakes in blue and red.

The green line represents the ideal temperature changes. The runner starts off slightly cool, and warms up during the first part of the run. Once the runner has warmed up, they shed clothing, or undo zippers to maintain their temperature of the right level.
The runner represented by the blue line warms up nicely, but does not shed sufficient clothing. As a result they sweat excessively, soaking wet clothing and become chilled.
The red line shows a runner that does not shed closing, and overheats. While it is strange to think of heatstroke while running in the cold, it is possible. A reasonably well trained runner is likely to simply slow up and will perceive the heat stress as tiredness. This is because the subconscious responds to the rising core temperature by reducing muscle recruitment. However, an untrained individual may raise their core temperature to rapidly, and suffer heatstroke.

3 Staying Warm While Running in the cold

It's tricky to maintain the right temperature when running in the cold because your sweat will reduce the insulation value of your clothing. There are several approaches you can take to overcome this.

Stop before you're cold. A common approach is to be slightly overdressed, but to stop running before your sweat soaks your clothes to the point you get cold. This works well for shorter runs, but you can't run long distances this way.
Change clothes. This requires some logistics, but it's possible to change clothes as each set becomes soaked.
Stay dry. Staying dry while running in the cold is harder than it sounds. You either have to avoid sweating or make sure that all the sweat evaporates before it builds up and soaks your clothing. This can work in mild conditions where you are wearing thin thermal layers that allow for good sweat evaporation, but as you put on more clothing, the harder it is for the sweat to evaporate. For some runners, especially smaller and slower runners, it's possible to run and not sweat much, but for most of us, running results in high sweat rates. If it's raining, it's hard to stay dry as any waterproof layer you wear will prevent your sweat from evaporating. (Breathable waterproof material rarely keeps up with the high sweat rates of runners, and ironically the breathability drops dramatically when the outside of the material is wet.)
Wetsuit. The wet suit approach is to wear sufficient layers to be warm even when soaking wet. This can work reasonably well, and it's often the only viable approach in cold rain. This approach causes your clothing to become heavy with water, but there is a wide variation in how different clothing behaves when soaking wet. Having your skin immersed in cold water can cause problems with maceration (the prune effect), including chaffing, blistering, immersion injuries and chilblains. In cold rain it can be important to have a waterproof layer; this is not to keep you dry, but to prevent the cold rain from washing over your skin and chilling you.
Double waterproofs. While it's not possible to keep you dry, it is possible to keep your clothing dry. This approach uses four layers of clothing. The first is a base layer that keeps your soaking skin somewhat comfortable. Next there is the first waterproof layer that prevents your insulating clothing from getting soaked from the inside by sweat. The third layer is the insulation, which may actually consist of multiple thin layers of insulating clothing. Finally there is a second waterproof layer that keeps the rain from soaking the insulation from the outside. This is a difficult combination to get right, as you do not have the ability to regulate your temperature through sweating. Therefore the risk of heatstroke is quite high, so be careful.

4 General Tips

The 20 degree rule. A good approximation is to dress for temperatures that are 20 degrees Fahrenheit warmer than the actual temperature. So if it's 20 degrees out, dress for walking in 40 degrees.
- The faster your run, the more heat you generate, so the less insulation you need. The same temperature will feel different to different runners based on their height, weight and pace.
- This is a simplified rule, and the details depend on pace, height and weight; Perceived Temperature For Runners will give you a more accurate estimate.
Don't sweat through. If you wear too many clothes and sweat too much, you will sweat through your clothes. Once your clothes are soaked, you will become suddenly chilled.
Stay Cool. To avoid excessive sweating, you should aim to feel slightly cool, rather than comfortably warm. Don't get so cold that you shiver, but it's okay to feel chilly.
Hydrate. Even in cold weather hydration is important. Use your thirst as a guide and for more on hydration see Practical Hydration and Hydration 101.
Numbness is bad. Your extremities may go numb early in your run, but they should warm up. Anything that stays numb needs to be checked as this can result in frostbite or other cold injuries. Beware anything that restricts circulation, such as elastic cuffs, as the reduced blood flow can contribute to frostbite.
Watch for ice. Slipping on ice can pull muscles or cause falls. You can get traction aids to attach to your shoes if ice is a significant problem. See Traction Aids for more details.
Emergency trash bag. If things go badly, a trash bag can help keep you warmer, especially if you have to stop running. You can fold a trash bag up quite small and tuck it in your waistband.

4.1 Clothing

Adjust Your Clothing. It is of most importance that you adjust the amount of insulation you get from your clothing as the conditions change. Trying to make sure that your clothing is as flexible as possible.
Zippers are your friend. And one of the best ways of adjusting the insulation you get from your clothing is to have zippers. Zippers on jackets and clothing allow you to quickly and adjust the amount of insulation to the conditions, and they can provide a fine grained adjustments.
Dress in layers. Layers will keep you warmer than a single layer, and allow for flexibility of removing some of your insulation.
Tuck in or hang out. Tracking your upper body layers into the waistband of your tights can make a surprising difference to the effectiveness of the insulation. When they are tucked in, air circulation is reduced and insulation is improved. Conversely, you can pull the tops loose and the air circulation will reduce the insulation, and improve sweat evaporation. You can even have your top tucked in at the front and out at the back, which keeps the Windward side of you warmer and your sheltered back a little cooler.
Strip off after warm-up. If practical, you can overdress for the first mile or so, until you warm up. This requires you having somewhere to discard the extra clothes, or a way of carrying them. An alternative is to have clothing with zippers so you can reduce your insulation.
Windproof layers are a mixed blessing. A windproof layer will boost the insulation value of the underlying layers, which can really help keep you warm. Unfortunately a windproof layer also stops sweat evaporating, which regulates your temperature. This makes it much more likely that you will sweat though and become cold. I use a windproof layer, but open it up as soon as I warm up, then try to stay slightly cool. A windproof layer is very useful as an extra layer, as it can be wrapped around your waist easily. I will wear it until I warm up, then carry it in case I need some extra warmth later in the run.
Base layer. I recommend a close fitting, very thin base layer. The goal of this base layer is not to provide insulation, but to spread out the sweat, and prevent chafing. I typically run in an UnderArmour HeatGear Top.
Hat and gloves. These are important to keep you warm, but they can also be taken off and tucked in a waist band easily. This allows you to adjust your insulation for the conditions.
Windproof underwear. For men, wearing underwear with a windproof front can provide vital protection.
Protect the front. Wearing tights and top that are thicker and/or windproof on the front provide warmth while preventing overheating. The Go Lite Black Mountain jacket is excellent.
No cotton. This is true for any conditions, but worth restating here. Wear clothes made from synthetic, wicking fibers, such as CoolMax.
Wet insulation. Different materials can have very different characteristics when they are wet.
- Insulation when soaked. Some materials are much warmer when they are completely soaked. Wool has a reputation of being one of the better materials for retaining warmth when wet. However any soaking wet material will cause you to lose heat through evaporation unless there is a windproof layer over the top.
- Weight when soaked. I've found that some synthetic tops become surprisingly heavy when soaking wet. I don't know of any way of predicting this behavior other than trying it out.
- Breathability. Some thermal layers will breathe well and allow sweat to evaporate before the government is soaked. This is good, as it allows your body to control its temperature through sweat affectively. Other materials do not breed so well and so the sweat will not evaporate until the government is completely soaked, at which point your temperature is likely to drop rapidly.
Neck Warmer. A fleece neck warmer can protect your face and neck from the cold. I use a Turtle Fur neck warmer (http://www.rei.com/product/663041).
Sunglasses. Keeping your eyes protected can help you keep a little warmer, and reduce how runny your nose gets. I use Oakley Half Jacket sunglasses with interchangeable lenses, so I can use clear glass when it's dark, or the cheaper and more convenient Tifosi Tyrant sunglasses that have photochromic lenses that go nearly clear in dark conditions.

4.2 Cold hands or feet

If your hands are cold, wear a hat. This is an old boy scout saying, but it works. If you core temperature starts to drop, your body will protect your vital functions by sacrificing your extremities, such as hands and feet. However, this is a delicate balancing act, as you need to stay cool enough that you are not sweating excessively.
If your hands are cold, wear arm warmers. If you suffer from cold hands, then Arm Warmers may be the key. If your arms are cold, the blood flow to your hands is both chilled and restricted.
Chemical Warmers. Using chemical warmers can help keep your hands from getting too cold. I find these seem to not only keep my hands warm, but also provide some extra warmth to the rest of my body and a little physiological boost. You can warm the packs with a hairdryer to get them extra warm (Thanks to Megan H). You can also save the hand warmers for another run by putting them in a sealed bag with the air squeezed out. (Thanks Charles/Kristine).
Vaseline. If you are still having problems with your hands and feet, spreading Vaseline over them before putting on your socks or gloves will dramatically improve the insulation. It's a bit strange the first time you do it, but it works very well.
Convertible Mittens. I've found that the gloves that include a cover to convert them into mittens work remarkably well. My favorites are the Saucony Ulti-Mitt.
Latex Gloves. One runner has suggested using the thin latex gloves under their usual gloves. The latex gloves act as a vapor barrier, creating a "dry suit" (see above) for your hands .

4.3 Extreme Cold

Your lungs are fine. Your lungs will not freeze, not even at -40f/-40c. Your lungs may get irritated by the low humidity, but they will get used to that. (It is possible to get exercised induced asthma, which is a narrowing of the airways when exercising. If you suspect you have this condition, seek medical advice.)
Suck then blow. If you have a problem with the tube on your hydration bladder freezing up, blow air back down the tube each time you have finished drinking. The drink is unlikely to freeze in the bladder itself, but the tube is very hard to keep warm. Insulation around the tube helps a bit, but not enough. (Thanks to Ron Bowman for this tip)
Ski Goggles. Below -10f/-23c wear ski goggles or other eye protection to stop your eyelashes freezing together. Even in moderately cold conditions, eye protection can help keep you warmer and reduce the amount your nose runs.
Cover gaps. Below 0f/-18c, it is critical to ensure there are no gaps or exposed skin. The phrase 'exposed skin freezes in minutes' should be taken seriously.
Warm Up Inside. Often the first mile or so is the worst, as your body has not started to produce sufficient heat to offset the cold. Warming up for 10 minutes inside, by running up and down stairs, doing a jump rope, or using a Treadmill. (Thanks to Melanie M for this tip.)
Start into the wind. If it's windy, start your run into the wind so that on the way back, you won't freeze due to sweating. (Thanks to Bobby A for this tip.)

5 Cold Injuries

There are four main cold injuries you need to consider as a runner.

5.1 Hypothermia

Main article: Hypothermia

Hypothermia is the obvious and most serious problem, which is when your core body temperature drops. Hypothermia can kill and can occur in relatively mild conditions. There are several ways runners are likely to get hypothermia:

Probably the most common is when a runner does not adjust their clothing and sweats through. Once their clothing is saturated, they rapidly become chilled. This can occur relatively quickly, especially when the sweat reaches the surface.
A sudden downpour can rapidly chill a runner. The rain can saturate clothing which reduces its insulation, and heavy rain can wash over the skin taking heat with it.
A runner may be appropriately dressed while running, but should they be forced to stop, they can become rapidly hypothermic.
A sudden change in weather conditions can occur. Typically this is an increase in wind speed, or the drop in temperature that occurs at sunset.

Shivering is the first warning sign of hypothermia. If you are shivering, you should do something to remedy the situation:

If you've stopped running, and are able to start again, then do so.
If you can put on more clothes, or zip up/tuck in the clothes you have, then do so.
If neither of these options is available to you, then try to seek shelter as quickly as possible.

Another symptom of hypothermia is the "umbles" – stumbles, grumbles, mumbles. This is because mental functioning declines with hypothermia, which also results in a decline in the ability to make good decisions. Watch out for those around you the symptoms of hypothermia.

5.2 Frostbite

Frostbite is when your flesh becomes frozen and can lead to permanent damage. The signs of frostbite are numbness, waxy or unusually firm skin, but often the victim of frostbite is not aware of the problem until too late.

Maintain circulation.
- Reduced circulation is a key risk factor for frostbite, so avoid any constricting shoes, clothing or jewelry.
- Stay warm as your body will reduce circulation to your extremities to preserve your core temperature.
- Avoid dehydration, as this may reduce circulation.
- Be especially careful if you are on medication or you have a medical condition that reduces circulation.
Protection from the cold.
- It is important to protect your extremities, especially under severely cold conditions. Even without wind, exposed skin can become frostbitten in 30 min. when the temperature is -15c/5f. (See the chart below for more details.)
Treatment.
- If you suspect frostbite, you should seek professional medical help.
- Do not attempt to re-warm a frostbitten extremity unless definitive medical care is more than two hours away.

NOAA frostbite risk chart.

For more details, read Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Frostbite.

5.3 Immersion injury

Immersion injury occurs when your skin has been soaked in cold water for long periods of time (hours). Immersion injury occurs in water temperatures between 59f/15c and 32f/0c. This is different to frostbite because the skin is not actually frozen, but there is still cold damage to the cells. (Immersion injury is sometimes called trench foot.)

5.4 Chilblains

Chilblains are damage to the skin from rapid warming. Typically the conditions that cause chilblains are similar to immersion injury, but the damage of chilblains can be reduced by slow warming. (There is some degree of genetic predisposition to chilblains.) After a long run in cold conditions, it is best to allow your skin to come back to normal temperatures slowly, rather than jumping into a hot shower. If you do reform your skin too rapidly, you may get a burning itching sensation over the affected skin, or in extreme cases blistering. I've found that turning the shower as cold as it will go can help reduce the burning and itching, but that's thoroughly unpleasant when you're feeling chilled after a long cold run.

Running in the Cold

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