November 15, 2023, by the Silverskin team
The base layer, better known as a thermal top or simply technical underwear, is an essential garment for anyone who trains and practices sports outdoors. In this article, we will explain what a base layer is and how it works.
We will also provide a practical guide on how to choose the base layer best suited to your needs, based on the sport you practice and the temperatures you will face on your next bike ride, ski trip, or mountain hike.
What Is a Base Layer?
Base layer: the literal translation of base layer makes it immediately clear what it is. The base layer is the first layer in contact with the skin, the foundation on which to build the rest of your sports equipment, regardless of the activity or season.
This important layer, in fact, is used in both winter and summer with two main objectives: to keep the skin dry and regulate body temperature, i.e., to stabilize body temperature. The result? Enjoying your favorite sport in perfect comfort.
Comfort during sports, whether cycling, running, skiing, or mountaineering, means three things:
- not feeling wet with sweat;
- not feeling too hot or too cold;
- not feeling restricted in your movements.
How does a thermal top create an environment of optimal comfort, allowing you to stay focused solely on performance? The answer lies in breathable materials, which promote the evaporation of sweat, innovative yarns that provide protection and keep body temperature constant, and cutting-edge construction techniques that allow for snug thermal underwear that does not restrict athletic movement.
When people talk about a base layer, they mean all those technical garments designed to be worn as the first layer against the skin: this does not only refer to base layer tops, but also other layers, such as base layer leggings or accessories such as liner gloves.
The Role of the Base Layer in Different Sports
The base layer is the layer that can make a difference when practicing outdoor sports: not only does it keep you comfortable, keeping your skin dry and providing perfect temperature regulation, but it also reduces the risk of muscle injuries or falling ill due to temperature fluctuations.
There is no outdoor sport in which the use of thermal underwear is not recommended: let's see what role the first layer plays in the most popular sports.
Base Layer for Cycling
A cyclist who spends many hours in the saddle knows two things for sure: they will sweat a lot and face different temperatures. From the plains to the climbs, and through long mixed terrain, a highly breathable base layer capable of keeping body temperature constant is the key to cycling in complete comfort. A sleeveless base layer such as PRIMO Thermo Dry Pro, designed for high-intensity activities such as a climb with challenging gradients, or a long-sleeved thermal top from the Stay Warm collection, ideal when you don't want to miss out on cycling even in winter, are the perfect technical underwear for road cycling, mountain biking, or gravel biking. By wicking sweat away from the skin and keeping it dry, you can climb without overheating and launch yourself down descents without having to wear a windproof jacket to protect yourself.
Base Layer for Trekking
What do hikers fear most? When a chill sets in or that unpleasant wet feeling hits when they stop their activity. If this happens, it means the first layer in contact with the skin is not suitable. The trekking base layer is an undergarment capable of managing the moisture produced by sweat and drying quickly, providing an insulating layer when needed to protect against temperatures that become harsher as you gain altitude. The choice of the most suitable thermal top for trekking depends on the intensity and weather conditions. For example, if you are speed hiking in winter, the half-sleeved Stay Fresh base layer is the ideal solution, but if the intensity is low or you need to bivouac, with outdoor temperatures plummeting below freezing, it is better to keep your body temperature constant and add an extra layer of warmth with the long-sleeved, high-neck thermal tops from the Stay X-Warm collection.
Base Layer for Running
Running is a sport where intensity is always high or moderate to high, which means that runners sweat a lot, regardless of the season. The perfect technical underwear for those who love running or trail running must therefore have excellent breathability, promote the rapid evaporation of sweat, and regulate temperature. Given the intensity of the run, it is therefore advisable never to overdress and, in general, to choose a base layer based on the length of the route. If you go out for a short training run in the cold season, a long-sleeved top such as PRIMO Thermo Dry Pro offers maximum sweat-wicking capacity and perfect temperature regulation; if, on the other hand, you are tackling a longer run with elevation changes, the ideal combination is a half-sleeved thermal top such as the Stay Fresh base layer and arm sleeves. This way, you can adjust the base layer according to your physical sensations without risking a decrease in performance.
Base Layer for Skiing
In cold environments such as the mountains, where temperatures often drop below freezing and weather conditions can change suddenly, choosing the thermal underwear on which to build the rest of your equipment is particularly important. This layer must keep you dry and protect against harsh temperatures while maintaining a constant body temperature. Depending on the activity, intensity, and preferred layering system, you need to carefully choose the next-to-skin layer. For downhill skiing enthusiasts, the total look of the Stay Warm collection, consisting of a long-sleeved base layer, knee-length leggings, liner gloves, and socks, represents the ideal solution for tackling long days on skis. Ski touring enthusiasts, on the other hand, need technical underwear such as PRIMO Thermo Dry Pro, which maximizes sweat wicking, making the ascent with skins truly comfortable. For more extreme adventures on snow and ice, there is the Stay X-Warm collection, which protects against cold down to -40° with thermal tops that disperse body heat more slowly and practical accessories such as a balaclava.
Base Layer Based on Temperature
Knowing the outdoor temperature at which you will practice your favorite sport is an important variable in choosing which base layer to wear; it is no coincidence that our collections specify the temperature range for which they are best suited. Below you will find a brief summary of the main features of the Stay Fresh, Stay Warm, Stay X-Warm, and PRIMO Thermo Dry Pro collections, the temperatures at which they can be best used, and the main sports for which they were developed.
STAY FRESH
FROM 10° TO 40° - The Stay Fresh collection was designed with particular attention to ensuring comfort and freshness. The base layers in this line prevent the unpleasant wet feeling when practicing moderate to low-intensity sports in high temperatures. Ideal for: cycling, running, trail running, trekking, summer climbing.
STAY WARM
FROM -20° TO 20° - The base layers from the Stay Warm collection are among our most versatile garments, as they can cover a wide range of temperatures and activities, both low and high intensity. They help quickly dissipate sweat while maintaining a pleasant warmth to tackle even sub-zero temperatures. Ideal for: skiing, cycling, running, trail running, mountaineering, trekking.
STAY X-WARM
FROM -10° TO -40° - The thermal tops from the Stay X-Warm collection create a constant-temperature microclimate between the fabric and the skin, ideal for facing the harshest thermal conditions down to -40°C. The heat produced by the body is dispersed more slowly than with base layers from the other lines, helping you stay at the ideal temperature for longer. Ideal for: high-altitude trekking, ice climbing, winter hiking.
PRIMO THERMO DRY PRO
FROM 0° TO 20° - Specifically designed for high intensity, the PRIMO Thermo Dry Pro base layers combine maximum sweat-wicking capacity with perfect temperature regulation, keeping the skin dry during all activities with a strong aerobic component or anaerobic efforts. Although covering a temperature range from 0° to 20°, the choice to use this technical underwear depends on the intensity of the workout rather than the outdoor temperature. Ideal for: cycling, running, trail running, speed hiking, ski touring, cross-country skiing.
Base Layer Based on Fabric
Wool, polyester, silk, hybrid solutions: anyone looking for thermal underwear today has a wide range of materials to choose from. To navigate these options, you must also consider characteristics beyond breathability and temperature regulation – the two main functions that define the base layer itself – such as fit, the ability to counter odors, and durability over time. While merino wool seems to be the most widely used solution thanks to its optimal characteristics, the evolution of technical materials and synthetic fibers has allowed us to overcome some of the limitations of natural fibers, such as faster drying and maximum freedom of movement.
Merino Wool
Among all, merino wool is a natural fiber particularly appreciated for its ability to absorb body moisture and provide an insulating layer capable of protecting against both cold and heat. Soft and comfortable to wear, modern merino wool thermal tops do not itch and retain odors within the fiber, releasing them only when washed. The only downsides of this material concern its shorter life cycle and its care: it tends to develop small holes over time that compromise performance, is the favorite prey of moths, and requires particular attention when washing and drying.
Fabric with Silver Fibers
The technical sports apparel sector has long utilized the benefits offered by silver. There are treated fabrics, such as those with silver ions, and fabrics in which pure silver fibers are an integral part of the yarn, such as those in our base layers. The particular Silverskin yarn technology ensures that the antibacterial, hypoallergenic, and anti-odor properties of silver are preserved over time and are not dispersed during washing. This feature, combined with the hollow-fiber structure and a special yarn processing technique, has allowed our base layers to set new standards not only in terms of breathability and temperature regulation, but also elasticity and comfort of use. Our technical underwear garments are so soft, stretchy, and high-performing that you simply forget you are wearing them.
Guide to Choosing the Right Base Layer
So far, we have explained why the base layer is a must for anyone who practices sports in both summer and winter, how to choose the right one based on the temperatures you will face, and which fabrics are the most high-performing. There is one last thing that can help in deciding which thermal top to buy: the intensity of the sports activity. To make it simple, consider the following infographic:
Conclusions
Choosing the thermal top best suited to your needs requires the same level of consideration of technical features and details as you would use when choosing equipment, such as a new bike, skis, or running shoes. This is because, as we have seen, the base layer is the layer that makes a difference, especially if the sport you practice puts you in particular weather situations. Being well-informed about the available solutions and not compromising on the quality of materials, comfort, and the protection that this second skin must provide is the first step to not making a mistake.
Explore our base layer collections, designed to let you live your sports passion in complete harmony, in any condition.
FIND THE BASE LAYER THAT IS RIGHT FOR YOU
© photo: Camilla Pizzini, Francesco Zigliotto