Whether cross-country skiing, trail running, or ski touring, the difference between a controlled outing and overheating often comes down to one detail: ventilation. Vincent Defrasne, Olympic biathlon champion, spent much of his career mastering when to open, close, and adjust layers. The “Defrasne method” is this precise management of heat generated by continuous effort, preventing the body from becoming soaked with sweat.
The foundation remains the three-layer system: a merino wool RWS base layer against the skin (for example, a BIAFO (men’s / women’s) or a MEFONNA (men’s / women’s) for a lightweight 100% merino, or a SHIRWALI (men’s / women’s) merino + Tencel warmer option), a breathable midlayer like the active fleece jacket KOKANEE (men’s / women’s) or the crewneck MEOLA, then an outer windproof or waterproof shell (jacket SHANDAR (men’s / women’s), softshell RAVEN (men’s / women’s), hardshell LONAK (men’s / women’s) or LONAK-XT (men’s / women’s)). For the lower body, a thin merino tight under softshell pants RIMO (men’s / women’s) or hardshell NUNATAK (men’s / women’s) completes the setup.
1. Avoid trapping heat: open early, before overheating
The first rule of the Defrasne method is counterintuitive: ventilate before you get too hot. Practically, this means slightly opening the front zipper of your jacket or midlayer within the first minutes of sustained effort, lowering the closure of the technical down jacket VIEDMA or hybrid jacket SKORA (men’s / women’s), and adjusting your neck gaiter before it becomes damp. The goal isn’t to cool down but to prevent the merino base layer from saturating with sweat.
2. Use garment ventilation features
AYAQ’s technical jackets, 100% made in Europe from Italian, French, German, and Portuguese fabrics, include details designed for active ventilation: two-way front zippers, breathable gussets, armholes engineered to let air circulate as soon as the closure is slightly opened. On steep climbs, opening the main zipper of a LONAK (men’s / women’s) while keeping collar protection lets excess heat escape without fully exposing the torso to wind.
On an ultra-light windbreaker SHANDAR (men’s / women’s), the combination of zipper, cuffs, and sometimes hood acts as a “regulator.” Close everything on windy descents, open widely as the slope eases and heart rate drops.
3. Adjust the midlayer to intensity
The midlayer plays a key role. An active fleece jacket like the KOKANEE (men’s / women’s) is designed to let some heat escape while remaining protective against stronger winds. The Defrasne method often starts with the merino base layer (BIAFO (men’s / women’s), MEFONNA (men’s / women’s) or SHIRWALI (men’s / women’s) depending on temperature) and the KOKANEE (men’s / women’s), with the hardshell kept in the pack. The jacket is only worn when wind or snow demands it and immediately unzipped as soon as pace picks up.
Conversely, for slower or interval activities, a technical down jacket like the VIEDMA or FORNO (men’s / women’s) can remain zipped, but its zipper should be used actively: open when approaching stops, close during breaks, avoiding sudden temperature swings.
4. Don’t forget the lower body
Ventilation isn’t just for the upper body. A merino RWS tight that’s too thick under insulated pants can quickly cause overheating, then sudden cooling when effort drops. For continuous effort, pairing a lightweight merino tight with softshell pants RIMO (men’s / women’s) offers a good balance: wool manages moisture, softshell blocks wind and breathes. In very wet conditions, the hardshell NUNATAK (men’s / women’s) protects against snow and