Layering for Ultrarunning Training in Cold Weather

By Darcie Murphy,
CTS Ultrarunning Senior Coach

Weather alert! Temperatures are dropping (or will soon) in many regions of the Northern Hemisphere. Maybe you’re excited or perhaps you’re dreading the cold, but regardless, knowing how to dress appropriately will make winter running more comfortable. These days I love winter, but it took many years for me to be able to say that. One reason for my change of heart is that I’ve refined my understanding of fabrics and how to layer optimally so I’m neither freezing nor stuffing a lot of unnecessary layers in my running pack. Are you a fair-weather runner and think this may not apply to you? Just consider this: learning to layer and stay comfortable in cold weather opens up the opportunity to get outside and run more!

Runner, Know Thyself
First and foremost, it’s important to know yourself. Some runners tend to sweat more than others, some are apt to become cold easily, and others overheat long before their peers. So, as with most aspects of running, there are individual factors to consider when applying the recommendations below. Personalize your layering habits based on your physiology and preferences, as well as your climate. The general idea is to be able to adjust to changing weather conditions and maintain a safe and comfortable core body temperature.

Choose the right fabrics
When choosing garments, it’s advantageous to have a basic understanding of fabric characteristics and construction. There are two general classifications: synthetic (usually manufactured from a petroleum-based plastic) or natural fibers. Included under the synthetic umbrella are fabrics like nylon, polyester, and elastane (spandex). These fabrics are often featured in athletic clothing because they are lightweight, pliable, and quick to dry. They also wick sweat away from the body quite well. On the downside, these fabrics tend to absorb pungent odors and typically are less breathable than natural fibers.

The most common natural fibers utilized for athletic clothing include wool and cotton. Advantages of natural fibers include their breathability and softness on the skin. Wool has a terrific ability to keep you warm even when wet, and cotton is easy to care for and is relatively inexpensive. Wool’s disadvantages are its fragility and weight; it becomes especially heavy when wet.

Cotton is not used as much in athletic apparel, particularly in base or insulating layers, because it does not dry quickly. Once wet, from sweat or rain or snow, a cotton base layer will reduce skin temperature and bring your core temperature down. (Note: in hot weather, this can be an advantage, as when we place cold, wet towels on athletes to cool their skin.) This can spiral quickly into a dangerous situation, such as hypothermia, so it’s never a good idea to use a cotton piece as your base layer. As a rule of thumb, you’re probably best served to leave an item that is mostly cotton home altogether in cold and/or wet conditions.

Fortunately, most well-designed athletic clothing will be a blend of synthetic and natural fibers that offers athletes the best of all options. It’s still a good idea to check the construction of a piece of clothing. This increased awareness can help you compare various materials so you will be able to decipher how each piece performs for you in various conditions.

Combining Layers on Top

Now that you have some basic knowledge of fabrics, how should you combine those pieces? In broad terms, more light layers are better than fewer robust layers. If you have a ski parka over a tank top, you’re likely to end up too cold or too hot. That’s an extreme example of course, but you get the idea. Having several layers that you can add or remove to modulate your core temperature is ideal. While there are some natural fiber base layers, most are made with mostly synthetic fibers (70-90%) to make them form fitting and good for moisture wicking. This creates a type of microclimate where body heat that you produce will be reasonably contained.

Next, add arm sleeves or a light half-zip long sleeve layer that is mostly synthetic fabric. The advantages of arm sleeves are the ability to slide them up or down easily. However, these can be harder to adjust when buried beneath several layers. Experiment with sleeves. They aren’t for every runner, but I find them to be a very modular alternative to a complete top.

Your next layer (we’re getting into ‘cold’ temperatures now, typically sub-40 degrees F) should be a jacket. Again, characteristics matter a lot. If there is little to no chance of precipitation you may only need a windproof/wind-resistant jacket. Windy conditions can whisk away a lot of your body heat, so you’ll be glad to have a windproof jacket at the top of a blustery ridge or peak. If you anticipate the chance of precipitation, or if humidity levels are high, opt for a waterproof jacket. Keep in mind, waterproof jackets tend to be less breathable, so be prepared to vent by adjusting the zipper in order to avoid building up too much body heat and sweating excessively. The ideal goal is to stay warm but minimize the buildup of sweat as you run or hike uphill, because that sweat will make you cold once you start going downhill or the wind picks up.

Choices for Shorts, Tights, and Pants

What about bottoms? Should you stick with shorts year-round or opt for full length tights when it gets cold? Again, know yourself and experiment. In dry temperatures above 45 degrees F most runners prefer to wear shorts which, as long as you are running, should keep you comfortable. Wet conditions between 30-45 degrees call for light tights, capris, or light pants (unless your outing is fast, short, about one hour or less, and weather conditions don’t worsen, in which case you can probably wear shorts and be comfortable and safe). If temperatures are at or below freezing and will remain below freezing for the entirety of the workout, most runners should wear full length tights or pants.

Ultrarunners also benefit from having a variety of hats, buffs, and gloves available at home. These are easy to take on and off and store in a pack as needed. If the weather is going to get colder as your run progresses, or you are climbing first and descending to get back to the trailhead, consider packing a second set of gloves and hat so you can  swap the sweaty ones for dry ones.

When it’s really cold

The above recommendations should take care of you for most cool to cold weather conditions. When the mercury drops into single digits, whether that’s for the duration of your run, at the high point of your route, or if the weather forecast predicts a deterioration of conditions, (you are checking the most recent forecast before you head out the door, right?) add another layer or two to your pack. It’s always a good idea to carry an emergency blanket similar to this in your running pack, but as it suggests, this is for an unexpected situation such as a rolled ankle or other serious problems. For conditions in which the actual or ‘feels like’ temperatures drop below ~10 degrees F, add another layer such as an insulated jacket (down or synthetic both work great and pack down to a very manageable size) and possibly some rain pants. In cool or cold weather you should feel a little chilly as you start your run, knowing that you will warm up with exertion. You may want to stow your insulating layer in your running pack to begin with, but don’t leave home without them if there is a moderate to likely chance you’ll need those extra layers.

It’s no fun being too hot, and it can be dangerous to get cold miles into a trail run if colder weather moves in. I’ve found it incredibly empowering to be confident in a wide ranges of weather conditions and admittedly, have made a few good friends by having that extra layer to share. As advised above, investigate different layering strategies to fine tune your system using the suggestions above as a starting point. Now get out there and test your skills in the conditions Mother Nature delivers.