Simple cut, descent, playful details yet highly functional underwear: the Siren line from Icebreaker has proved invaluable for trekking and backpacking as well as for everyday wear. | Photo: Icebreaker

A common trend among base layers or functional underwear of recent years is a shift toward more fashionable designs suitable for the work-a-day world. Brands like Icebreaker, Arc’teryx and Kari Traa, while known for their uncompromising functionality, have been leading the way in transitioning from dreary black-or-white designs towards lively colours and a more modern fit. Outdoor enthusiasts have of course long known how beneficial base layers and athletic underwear can be in the mountains, where functionality ranks far above looks on the list of priorities. Now that they are becoming more fashionable however, many people are starting to realize that their benefits can be equally felt under a pair of jeans or a skirt. The high level of comfort base layers and functional underwear provide is rooted in the most important requirement for performance sportswear: It has to allow for a free range of movement without itching or chaffing. This goal is achieved through seamless designs, flat seams, and wide, form-fitting cuffs which ensure that the base layer fits and feels like a second skin.

 Synthetic or Merino? The fibre duel

Base layers are usually worn directly next to the skin, as their name suggests. They provide the foundation of proper layering since even the best hardshell won’t do much good if the layers underneath retain excessive moisture or don’t breathe. These criteria exclude pure cotton as a base layer material since it can absorb quite a bit of moisture but then tends to become (and stay) soggy. Modern base layers for outdoor use are commonly made of one of two materials: Synthetic fibre or Merino wool. Sometimes the two are also combined in an attempt to capture the benefits of both. The primary advantage of Merino wool is the fibre’s all-natural functionality and its soft feel. Wool can absorb roughly 30 per cent of its own weight in water without feeling damp and transfers this moisture away from the skin to the other layers for a quick-drying effect. Wool also provides excellent insulation when wet, making it especially ideal for strenuous winter hiking and ski touring. 85 per cent of the fibre consists of air, accounting for its excellent insulating capabilities that keep you toasty in the winter and can help cool you down in the summer. As if that weren’t enough, merino wool is also dirt- and bacteria-repellant, und hems odours – natural qualities that are especially sought-after in base layers, since they tend to get grungy and smelly fairly quickly.

Pure Merino or in a synthetic blend?

Here at Bergzeit, we carry base layers made of 100 per cent Merino wool, by brands such as Devold, Bergans, Mons Royale, Pally’Hi and Ortovox. Numerous other manufacturers have opted for a blend of wool and synthetic fibres in an attempt to get the best of both worlds. Merino-specialist Icebreaker, for example, uses a small amount of Elasthane to improve the stretchiness of their clothing and help it dry even more quickly.

• More on Icebreaker: Rob Fyfe, CEO in an interview

Soft, soft, even softer: A Modal component on the inner side of Ortovox’s Super Soft provides an extra soft feeling for functional underwear. Outdoor merino wool regulates body temperature. | Photo: Ortovox

Ortovox has incorporated Modal, a cellulose fibre made of beech wood, to line the interior of their Supersoft Merino base layer line. As the name suggests it is extremely soft to the touch and effectively wicks away moisture from the skin to the outer Merino layer. The Supersoft liner is perfect for anyone with sensitive skin who values the benefits of Merino wool but finds the material to be a bit rough despite its fine weave. Odlo, on the other hand, chose to combine Merino wool with 55 per cent heavyweight Polyester for their Revolution line. This blend makes for an extremely breathable and quick-drying garment thanks to the polyester while taking advantage of Merino’s natural feel and odour-fighting qualities.

Diverse and straightforward: Synthetic base layers

Synthetic fibres can be manufactured to highly exact standards regarding their size and properties, enabling manufacturers to tailor them to specifically suit their intended use. Being a natural fibre, Merino wool is limited in its malleability; a synthetic fibre, on the other hand, can be optimized in every step of the manufacturing process, from fabric production to the finished article of clothing. Various spinning techniques can shape an identical petroleum-based raw material into various forms, like microfibers or hollow fibres. Different compounds such as polyester, polyamide and polypropylene are also often combined to get the desired qualities in a synthetic fabric. Specialized weaving machines are even capable of joining different materials into seamless body-mapping constructions. Synthetic fibre base layers do not have the odour-fighting benefits of their natural wool counterparts but are often equipped with silver ions to achieve a similar odour-neutralizing effect. Regardless of the materials used and how they are manufactured, synthetic base layers and functional underwear provide one distinct advantage: They dry extremely quickly, be it a lightweight summer top or a pair of heavyweight winter longjohns. In addition, synthetic fibres tend to wear somewhat less than their woollen counterpart.

Frequently used synthetic fibres for functional underwear and base layers

Polyester is a synthetic fibre which is highly valued for the production of performance clothing, thanks to its low moisture retention, excellent insulating properties and durability. PES is highly tear-resistant and can be spun very fine, making it soft and comfortable. It is often used for the production of fleece, as can be found in base layers made of Polartec Power Dry and Polartec Power Stretch. As an additional bonus polyester is low-maintenance, and can easily be produced using recycled materials. Coolmax is the brand name polyester fibre of Invista, available in various weights. Thanks to its specialized fibre shape Coolmax has a larger surface area than the common round polyester fibres, accounting for its quick moisture transportation, excellent breathability and improved ease of care.

• Polyamide is a very robust synthetic fibre and is also highly elastic. It is often used in synthetic blends to improve a garment’s durability.
• Polypropylene absorbs nearly no moisture, which means that it essentially does not get wet. When combined with polyester it cuts drying time significantly.
• Elasthane is used both with natural and synthetic fibres to create a more elastic fabric. The more elastane a product contains, the more stretchy it will be.
• Modal is produced from cellulose in the same fashion as viscose, but has improved characteristics: The fibre is soft, durable, low-maintenance and has a pleasant silk-like sheen. Modal absorbs moisture and dries quickly, and does not have the synthetic feel of petroleum-based fabrics.
• Tencel or Lyocell is also made of cellulose. The fibre is soft and durable, absorbs moisture well and is cool to the touch. To take full advantage of these characteristics it is most commonly used to produce easy-to-clean summer wear.

Panties, briefs or boxers: How would you like your functional underwear?

Choosing a style of athletic functional underwear is as much a question of the intended use as of personal taste. While bikini panties offer a completely uninhibited range of movement for the legs, briefs or hipsters may dig in a little less by distributing pressure across a larger area of fabric. Differences in fit may be marginal, but in cold weather, a little extra fabric around the legs and hips can’t hurt, especially for those who are sensitive to frigid temperatures. Of course, it is always a good idea to throw on a pair of classic (thermal) long underwear when it gets too cold; ¾-leg bottoms are recommended for skiing and snowboarding since they don’t create uncomfortable bunches in the boots.

Long sleeve base layer tops are the go-to choice for skiing and other winter activities, but the options don’t end there: Ladies especially have a variety of choices when it comes to summer base layer tops, be it spaghetti straps, racerback or a classic tank top. Though it may seem arbitrary, it is worth putting some time into thinking about the intended use before choosing a style. Wider shoulder straps are significantly more comfortable when carrying a heavy pack for example, while a simple T-shirt provides sun protection. Less fabric, on the other hand, means extra ventilation and freedom of movement, a definite plus for activities like running and sport climbing. Oh, and they look good, too.

Environmental concerns

An important factor in the production of outdoor clothing is of course sustainability; it is after all designed for use in pristine nature and should be made in a way that seeks to conserve it. Merino wool is a renewable natural resource, in contrast to petroleum-based synthetic fibres. Unfortunately, it isn’t perfect either, however: In recent times industrial Australian sheep farmers have been facing heavy criticism for Mulesing, a very painful procedure which is supposed to prevent the sheep from becoming infested with maggots in the hot climate. The brand-name producers of Merino wool clothing represented at Bergzeit are currently checking their supply chains to ensure that their products are made using only Mulesing-free wool. Further information can be found on the manufacturer’s websites.

More reading on functional fabrics and underwear

•  How to wash merino wool: gentle cycle or normal?
• Ultra functional underwear from Ortovox: A review
• Merino vs synthetic: What are the pros & cons of these fabrics for wearing as a base layer