Reliable clothing for every layer of your trail run
Sweaty climb, cool break – how should you dress for trail running?
Trail running is varied exercise in which your heart rate rises and falls with the terrain. On climbs and at a fast pace you sweat a lot, but on technical descents, during breaks and after your run your body cools quickly. The wrong layers mean sweating on the climbs and getting cold on the descents. The right ones keep you dry and warm for the whole run, from the first metres to the last.
That is why we have put together a complete set that works on this page: one go-to garment for each layer. With these garments, you cannot get your clothing wrong, whether you run long distances regularly or are just starting out on the trails. You do not need to compare dozens of options or guess whether the garments work together. Here is a set in which every layer is designed to work with the next.
Every layer does its own job
The Zero Layer moves sweat away from your skin, the Base Layer brings warmth, the Mid Layer adds insulation for cool weather and breaks, and the Shell Layer shields you from wind and rain. Merino and Airbase take care of moisture and warmth, so you can focus on your pace and the terrain.
Four layers, one set that works
Layering is the answer to dressing for trail running. For each layer, we chose one go-to garment that works at both extremes of a run: on a sweaty climb and on a cool descent or during a break. Together they form the Svala AIR System™ layering system: four layers, each doing its own job, from the Zero Layer to the Shell Layer. You do not always need all four. For a short, brisk run in warm weather a few layers are enough, and for cool weather and long breaks you wear the whole system.
Zero Layer – Next-to-skin performance
Trail running is aerobic exercise that makes you sweat heavily even in cool weather. An Airbase-mesh shirt and -bottoms worn next to the skin keep your skin dry. Airbase is 100 % polypropylene, which does not absorb any moisture but transfers sweat away from the skin to the next layer. This means you will not feel cold on descents or during breaks with a wet shirt clinging to your back.
The loops in the 3D-mesh knit, weighing 120 g/m², allow air to circulate and trap air, forming a thin layer against the skin: it cools you as you move and provides insulation during breaks. Airbase is thin and stretchy, so it follows the contours of your body without restricting movement. Silver ion treatment keeps the garments fresh, so you can wear them for several runs.
Men's Original Airbase 120 mesh set
Women's Original Airbase 120 mesh set
“Svala's Merino Extreme hoodie is my absolute favourite because it is so versatile. It works on the fells, on cycling trips and at summer festivals. It is light, warm, packs down small and looks good.”
Base Layer – Temperature regulation
When you slow down or stop for a break, your body no longer generates heat in the same way, and you need a layer that keeps you warm. A warming merino layer is worn over Airbase. Merino regulates temperature in both directions, so it does not feel stifling when you are moving or leave you feeling cold during breaks or downhill sections. It keeps you warm even when damp with sweat, which is crucial in trail running, where sweat builds up on your body even on long runs.
Together, Airbase and Merino Extreme are the best layer pairing for trail runners: the mesh layer moves moisture away from the skin, while Merino Extreme provides warmth. Its two-layer construction combines the warmth of merino wool with the moisture-wicking properties of a technical fabric, keeping you warm while remaining breathable even at a fast pace. This means the same shirt works both on sweaty climbs and when you slow down.
Men's Merino Extreme 200 base layer set
Women's Merino Extreme 200 base layer set
Mid Layer – Thermal insulation
When the weather turns cooler or you take a longer break, you need an insulating layer over the first two. A warming layer goes over the merino wool to provide extra warmth when your body no longer generates it itself.
Svala's Polartec Alpha™ hoodie is made for this. It is lightweight, provides warmth even when slightly damp and breathes so well that you can keep it on even at a fast pace. The hoodie manages your warmth for you as you alternate between fast running and easier stretches, so you do not need to keep taking it off and putting it back on. You can leave this layer at home for a brisk run and put it on in cooler weather or during a long break.
Men's Polartec Alpha 90 hoodie
Women's Polartec Alpha 90 hoodie
Shell Layer – Weather protection
The outermost layer completes your layering: a lightweight shell jacket or a windproof running jacket. Its job is to cut the wind and keep rain and moisture out, so that the warm air trapped in the layers beneath cannot escape. Protection alone is not enough, though: the shell must also be highly breathable. Trail running produces a lot of moisture, which soaks your layers from the inside if it cannot evaporate. That is why many runners leave the shell off entirely on a brisk run and put it on only for rain, wind or breaks.
Choose a shell roomy enough to fit over your other layers, because the air between the layers keeps the warmth in. Svala's own Shell Layer, Ventile, is not just a running jacket, so the same shell also goes with you on everyday outings and in other activities.
Men's Ventile 200 jacket
Women's Ventile 200 jacket
You do not need everything at once – start here
The system works best when you wear all the layers to suit the weather and your pace, but you do not need to buy everything at once or replace your entire wardrobe. The AIR System™ also works with the clothing you already own. If you are starting from scratch, start with the next-to-skin layer: it is the most important part of the system. The most reliable foundation for a trail runner is Airbase mesh knit next to the skin with merino on top. Over these, add an insulating layer and a shell to suit the weather.
If you already have a suitable layer, buy only what is missing:
- Do you already have a merino wool base layer? Complement it with Airbase: wear the mesh layer next to your skin under the merino to stay drier than with merino alone.
- Are your next-to-skin and warming layers already in place? For cool weather and long breaks, add a lightweight Polartec Alpha™ hoodie that you can keep on while you run.
- Do you already have a running jacket or shell jacket? There is no need to replace it. Make sure it breathes and that your other layers fit comfortably underneath.
This way, you can build a system that works at your own pace. Although we put these layers together for trail running, they will not sit unused in your wardrobe: the same layers also work for other outdoor activities and change seasons with you.
Four layers, one effective system
Layer: Zero Layer - next-to-skin performance
