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Thermal underwear

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Thermal underwear has three tasks

Thermal underwear, also known as sports underwear, is the bottom layer of your layering system. It lies directly on the skin and is the first layer to absorb body moisture. This is where it can show what it's made of:

  1. Breathability
  2. Temperature-regulating
  3. Insulation

Thermal underwear therefore has a function - unlike normal underwear. More specifically, it has three functions.


Thermal underwear is breathable if it absorbs body moisture and wicks it away to the outside. Otherwise, you would quickly be standing in your own juices during sweaty activities. The damp underwear would stick to your body and cool you down. Did you know that an untrained person produces around 0.8 litres of sweat in one hour of sport, while a trained person produces 3 litres? Sweating is healthy. That's why your clothing should be designed with this in mind, from the bottom layer onwards - called a baselayer.


Your body always wants to keep its temperature at 37 degrees, no matter what you do. When you exert yourself during your outdoor activities, you sweat so that the evaporative cooling cools your skin. Good thermal underwear helps your body to always stay in the comfort zone of 37 degrees.


Winter sports pose completely different challenges for thermal underwear. Insulation against the cold is particularly important here. Ski underwear or thermal underwear is not only warming, but also breathable - so you stay dry. After all, nothing leads to a cold faster than wet underwear that sticks to your skin and leaves you standing motionless on the lift or freezing in a cold chairlift.

Synthetic fibres or merino wool?

Does natural merino wool or versatile synthetic fibres win the race? This question is not so light to answer. As is so often the case, the only answer is: it depends!

Merino wool has the great advantage that it keeps you warm even when wet. It can absorb up to 30 per cent of its own weight in moisture without feeling wet. Merino underwear is therefore ideal for stop-and-go sports. When you're skiing up the mountain, you're always stopping to catch your breath and enjoy the view. Merino underwear is recommended here as a base layer. It is also odour-neutral and smells fresh again the next day if you hang it up to air overnight.

Synthetic fibres can be produced specifically for a wide variety of requirements using the spinning process. Hollow fibres, bulky yarns, smooth or rough structures - all are possible. The combination of polyester, polyamide and elastic yarns can also ensure a huge range of functions in the yarn itself. Specialised machines use these yarns to produce seam-free, highly elasticated and fast-drying thermal underwear. So why look for an alternative? Synthetic fiber quickly smells unpleasant and should be washed after every strenuous effort. If this is not possible, then merino wool is your first choice.

It's all in the mix!

How good that the advantages of both fibres can also be combined. At Transa, you'll find a quantity of styles made from a pleasant mix of different natural and synthetic fibres. This means you can enjoy the natural warmth of nature while being supported by the functions of synthetic fibres. Thermal underwear doesn't get any better than this.

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