BASE LAYERS GUIDE: FROM SYNTHETICS TO MERINO WOOL. Our WINTER CLOTHING section bring us today bring us today a base layer guide by our specialist, Mayayo. Every base layer’s job is to keep us cozy, by combining natural warmth plus moving perspiration away from your skin, that is “wicking.”

In cool or cold conditions, wicking long-underwear-style base layers are needed to keep our skin dry. That’s essential because liquid cools much faster, therefore damp clothes are a highway to becoming chilled or worse—hypothermic.

Base Layer mountain clothing. Gornergratt (3.300m), Switzerland. Photo: Memphismadrid.






What are the benefits of a base layer?

Base layers offer maximum comfort and regulate your body temperature. They can be adapted to different environments, duration and intensity levels of your activity. The fitted performance fabric wicks moisture away from your skin and warms, which means you’ll stay dry, comfortable and avoid any unpleasant itching, rubbing or chafing while working up a sweat.

The right base layer will fit like a second skin and act like natural climate control; the moisture wicking and fast dry time will keep you from freezing in winter and the breathability of the fibres will cool you down in summer.

Should I wear anything under my base layer?

“Base layers” are sometimes synonymous with “thermal underwear.” However, if you prefer for hygiene reasons, you can wear boxer shorts or panties underneath. For women, we also recommend a sports bra for optimum support.

What does “seamless” mean?

It sounds obvious to say that “seamless” refers to garments without any seams. But what does that actually do for you? Well, it means maximum comfort, no matter the activity or intensity level.

This construction method  refers specifically to how a product is knit and then assembled. Often, everyday athletes explain the benefits of a seamless layer in terms of both comfort and performance. And because of the fit (next-to-skin), it is the optimal, most comfortable, highest performing base layer across almost all conditions and intensity levels.

With seamless, we also eliminate bulk, which makes it a great choice for apparel like boxers and panties because of its streamlined fit.

Vasaloppet:: 90km skiing at -5ºC for 10h. Photo: Mayayo

Merino wool or sythetics?


Base layers made from synthetic fibres are the best choice for high-sweat activities. Synthetic materials like polypropylene, polyamide and polyester are exceptionally lightweight, more efficient at wicking moisture away from the skin and dry faster than natural fibres. They are also fabulously stretchy and durable.
Materials matter

Natural and synthetic fabrics each have their own special advantages, but blends offer the best of both worlds. They make for apparel with maximum performance and outstanding comfort – for all activities, intensity levels and seasons of the year.

Thanks to their moisture-wicking and fast drying properties, synthetic fibres are perfect for demanding activities – like cross-country skiing or running – that really get your heart rate up, while natural fibres like merino feel super warm and cosy.

That means the blend of synthetic and natural fibres is great for endurance sports where you still need to keep warm. And, thanks to their natural odor control, you can wear your garments again if you aren’t ready to tackle your laundry just yet.
Merino – natural performance.

Underwear Weight

It is a most personal choice, always. Base layers thickness, when dealing with top quality fabrics, will always relate to the warmth they may retain from your body. Therefore, thicker means warmer….yet also a harder challenge for wicking away all moisture.

Therefore, yo ought always to consider both your metabolism and activity level. If you’re always “the cold one” in your group, then go with a heavier weight. If you’re training for the Olympic Nordic ski team, then go with a lighter weight.

Here are your three basic weight options for long underwear:

  • Lightweight: Moderate to cool temps.
  • Midweight: Cold temps.
  • Heavyweight: Below-freezing temps.

You might also see “ultralightweight” or “featherweight” or other similarly gossamer descriptors. Those happen when brands try to push the envelope on the light end of the fabric spectrum. On the heavier side of things, you might see alternative terms like “expedition weight.”

Once again: Remember your base layer’s main job is moisture management. Heavier base layers do add some warmth, but it’s your insulating middle layer that’s the primary keeper of your body heat, not your base layer.

It is easier to regulate yourself by wearing the down vest or taking it off, rather than wearing an extra 100gr. thickness long sleeves tee all the time.

MERINO WOOL: Best of nature.

A personal favorite, by Mayayo


This is not your grandparents’ itchy woollies. Merino wool has almost completely replaced traditional wool thanks to its soft, ultrafine fibers. Wool can also be blended with other fabrics, like spandex to enhance fit and flexibility.

Today´s base layer Merino wool is a natural fibre that’s comfortable, breathable, durable, soft to the touch and naturally antibacterial. What’s more, its grammage can be adapted to the changing seasons.

During the summer, you should generally opt for 115 to 150 GSM. For winter, we recommend at least 200 GSM. And merino apparel with at least 260 GSM is ideal for icy cold days on the slopes or for wind-blown winter hikes.
All of our merino wool is mulesing-free.

Merino wool top4 advantages

  • Wicks well: Some moisture in wool is retained in its core, which won’t chill you, but wool will not feel quite as dry as a synthetic fabric. It will also take longer to dry when it gets wet.
  • Cools, too: That moisture in the core of its fibers releases when temps heat up, which can offer a little bit of cooling in warm weather.
  • Moderately durable: Wear it under other layers and enjoy a long and happy life together; as a standalone top under heavy pack straps, it won’t last as long because the constant rubbing can wear through the fabric. You can also opt for a base layer that blends synthetic and wool for increased durability.
  • Odor free: Even if you don’t believe wool fanatics who report endless days of sweaty wear without a discouraging whiff, it’s absolutely true that wool is highly resistant (and naturally resistant) to odor-causing bacteria.

Merino Wool latest news: Performance Wool by Nuyarn

Latest performance base layers collections by top outdoor brands have been developed so you can enjoy outdoor adventures in winter with maximum comfort and performance; specific pieces made with Nuyarn merino fabric are ideally suited to high-intensity activities.

Nuyarn is a twist-free spinning technology that conserves merino’s natural performance properties instead of twisting them out of the wool like traditional spinning methods do. Nuyarn® products dry 5 times faster, are 50 per cent stronger and offer 35 per cent better natural thermoregulation.

The result is a lighter, stronger, better performing wool layer geared towards high heart rate activities and everyday comfort. For those that gravitate towards natural. Unity is strength.

Base layer mountain clothing by ODLO performance wool


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