Regardless of age, gender or the nature of your daily work, a regular yoga practice is great for your body and mind. This type of activity opens up space to fully focus on your breath, get to know your body,
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Published: 1/28/2026💡 Tips|🏂 Winter sports|✨ Lifestyle
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What kind of thermal underwear will be best and what to wear over it?
Thermal underwear is an indispensable part of sports outfit for an outdoor workout. When properly selected, it will protect you from the cold and provide ultimate comfort in any weather. This guide provides advice on how to wear it and what to wear over thermal underwear.
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🧪 How does thermal underwear work? It wicks moisture away from the skin, regulates body temperature and prevents chilling or overheating. It works like a “second skin” during physical activity.
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👕 Which thermal underwear is best? The choice depends on weather conditions and intensity: thin models for training and summer, thicker ones for winter, and merino wool for year-round comfort.
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The best thermal underwear combines lightness, flexibility, quick-drying properties and antibacterial features, ensuring comfort during running, trekking, skiing and snowboarding.
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How to wear thermal underwear? Always as the first layer, fitted close to the body. Flat seams and seamless designs minimise the risk of chafing.
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🧣 What to wear over thermal underwear? Choose functional layers such as fleece, merino wool, softshell or a membrane jacket. Avoid cotton, which traps moisture and cools the body.
In short:
Thermal underwear - what is it and how does it work?
Let’s kick it off with some theory. What exactly is thermal underwear? This is specialised sportswear whose main task is to maintain optimal temperature of the body during exercise and effectively wick moisture away from the skin. Its unique properties ensure that sweat is quickly wicked away from the fabric, keeping the body surface dry. This helps avoid the sensation of cold or overheating.
The following are the advantages of thermal underwear:
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low weight,
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flexibility,
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very often antibacterial properties, which increases wearing comfort and hygiene.
If there's no weather bad enough to prevent you from heading outside to work out, you need sportswear that works in any weather. Thermal underwear is the hero of any outdoor outfit and is a must-have when running, trekking, skiing or snowboarding. It will foster more effective body temperature regulation, not only keeping you comfortable, but also improving your physical performance. Thermal underwear is often referred to as a "second skin" due to its perfect fit and functionality.
Thermal underwear - which one to choose for particular activities
There is a wide range of different types of thermal underwear. When choosing underwear for a given activity, choose the right thickness and material to ensure optimal thermal comfort and effective moisture wicking:
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Thin thermal underwear – a perfect choice for intense physical activities in warmer weather. It primarily aims to wick sweat away quickly and allow the skin to stay dry. In addition, it prevents the body from overheating. Thanks to its lightness and flexibility, it will work well for running or cycling.
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Thicker underwear with a heavier weight – designed for winter training and cold conditions. It provides even better thermal insulation, keeping the body warm while retaining the ability to wick away moisture. Such underwear allows you to successfully complete your workout in the snow or in cold climates.
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Merino wool underwear – this solution is perfect for both colder and warmer days. Merino wool regulates body temperature due to its natural insulating and temperature regulation properties. It is also antibacterial, which prevents odours. In addition, merino wool underwear is pleasant to the touch, non-itchy and breathable, allowing you to maintain optimal comfort throughout the day. It is a great material that cools you down in summer and warms you up in winter.
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€34.90
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€19.90
The lowest price in the last 30 days before the reduction
€25.90
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€14.90
The lowest price in the last 30 days before the reduction
€17.90
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€19.90
The lowest price in the last 30 days before the reduction
€29.99
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€39.90
The lowest price in the last 30 days before the reduction
€49.90
Thermal underwear – how to wear it? Basic tips
Whether you are running outdoors, hiking in the mountains or going wild on the slopes, thermal underwear should be the first layer of your sports outfit. Its properties will keep moisture away from the skin and ensure thermal comfort if it is well-fitted and worn close to the body. In addition, 4F's thermal tops and leggings are made from soft and pleasant-to-touch fabrics, and flat-felled seams reduce the risk of chafing almost completely. This makes the underwear perfect for wearing as the base layer that remains closest to the skin.
The best thermal underwear from 4F's range combines modern technology with high comfort and functionality, making it an ideal choice for a variety of sports activities. Which pieces to choose? Check out a bunch of selected items:
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Men's thermal T-shirt by 4F constitutes a perfect first layer of clothing that acts like a second skin. Thanks to the 4FSkin technology, it fits the body perfectly, providing unrestricted movement and remarkable comfort. The seamless design eliminates the risk of chafing and irritation even during an intense workout. Special ventilation zones provide excellent air circulation, while the quick-dry finish keeps your skin dry all day long. The slim cut is form-fitting without restricting movement, making it suitable for trekking and winter expeditions.
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Women's thermal underwear by 4F acts as your second skin for winter challenges. The material adapts perfectly to the figure, guaranteeing unrestricted movement and comfort even during an intense workout. The seamless design eliminates the risk of irritation and chafing, and the quick-dry finish keeps the skin dry. The slim fit highlights the silhouette while ensuring full comfort on the slopes and during everyday use.
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Women's black seamless thermal underwear with merino wool (bottom) works as your layer for warmth and comfort on the slopes. Thanks to the 4FSkin technology, it fits the body like a second skin, ensuring full freedom of movement. Merino wool supports natural body temperature regulation, so you’ll feel comfortable even on cold days. The seamless design minimises the risk of chafing, and ventilation zones effectively wick away moisture. The quick-dry finish keeps your skin dry during intense exercise. High rise and full leg length provide a great fit and extra thermal protection under ski or winter trousers.
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Natural wool – especially merino wool, is a great choice for those who appreciate natural materials. A wool sweater or sweatshirt perfectly complements thermal underwear in harsher weather conditions.
What to wear over thermal underwear? Here are some sportswear items that will work best
You already have your perfect set of thermal underwear – what’s next? Above all, wear a second layer on top of your thermal underwear that is adapted to outdoor conditions and the type of activity. It should provide thermal insulation and protection from wind and moisture without interfering with the properties of the underwear itself. Choose functional textiles. Avoid cotton, which absorbs moisture quickly and cools the body during physical activity.
Athletic apparel made of synthetic fabrics such as polyester, polyamide or elastane will perform much better. An exception is natural merino wool, which is often used in thermal tops and leggings. This type of knitwear is known for excellent temperature regulation, quick drying, moisture wicking and antibacterial properties.
Not sure what to wear over your thermal underwear? The following can act as a second layer of clothing:
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A fleece jacket – provides good thermal insulation, does not absorb water and protects against cold. Suitable for both mountain trips and everyday use.
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A wool sweater – keeps you warm even in sub-zero temperatures. Wool is breathable, antibacterial and prevents odours, making it ideal for winter activities.
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A softshell jacket or a membrane jacket – protects against wind and rain while remaining breathable. Membrane jackets additionally shield against snow and water during winter training or trekking.
The second layer of sportswear is primarily intended to provide thermal comfort and additional protection against weather conditions. Depending on temperature, humidity or precipitation, you can complete your outfit with a third layer. Usually it is a waterproof membrane jacket, which protects you from getting wet and losing heat during outdoor activities.
€25.90
The lowest price in the last 30 days before the reduction
€34.99
€30.90
The lowest price in the last 30 days before the reduction
€39.99
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€25.90
The lowest price in the last 30 days before the reduction
€29.99
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€30.90
The lowest price in the last 30 days before the reduction
€34.99
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FAQ – frequently asked questions about thermal underwear
1. How does thermal underwear work?
2. Which thermal underwear is the best?
3. What is the difference between thin and thick thermal underwear?
4. Is thermal underwear suitable for winter?
5. What should you wear over thermal underwear?
4F Editorial Team
The 4F editorial team is a group of experts who live and breathe sports and value an active lifestyle. Drawing on the experience of the 4F brand, we show that exercise is a source of energy, balance, and well-being. We provide reliable training advice, follow trends in sports fashion, and support our readers in discovering their motivation to take action.
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