In trail running, weather conditions can change quickly, so adequate protection is essential. Whether protecting yourself from wind, rain or cold, you need to choose a suitable trail jacket. In this article, we explain how to choose your trail jacket.
Key takeaways:
- Choosing a jacket depends on the length of the trail and the weather.
- Waterproofness and breathability are essential criteria when choosing a trail jacket.
- A lightweight, compact jacket is ideal for short trails, while a built-to-last, protective jacket is suitable for ultra-trails.
- Details such as the jacket’s cut, hood and weight make all the difference.
Choosing a jacket by trail type and season
The length of the trail helps runners choose their trail running jackets. For a short trail of two to three hours, an ultra-light jacket is recommended. On fast routes, the focus is on lightness and breathability. For a long trail of more than three hours, protection and durability are preferable. A waterproof, windproof jacket is then ideal for tackling difficult conditions.
In cold, dry weather, we recommend following the three-layer principle. A trail jacket should provide light insulation to maintain good body warmth, without being too bulky. It should also be windproof and have an adjustable hood for better protection. If you plan to run at night or early in the morning, choosing the right trail head torch is just as important for keeping you safe on the route.
In hot, humid weather, we recommend an ultra-light jacket with ventilation zones to maximise airflow. It can be water-repellent to withstand splashes and made from technical materials that dry quickly and wick away moisture.
Waterproofness and breathability of a trail jacket
Waterproofness and the Schmerber rating
Waterproofness and breathability are essential in trail running. They directly affect comfort, especially during races in variable weather conditions. To choose the right trail jacket, look for a model offering good waterproofness while maintaining a degree of breathability. This is what membranes such as Gore-Tex and Ultrashell are designed for.
The Schmerber rating measures the waterproofness of a trail jacket. It is expressed in millimetres and measures a jacket’s ability to resist water penetration. A rating of 10,000 mm means the fabric can withstand the pressure of a 10,000 mm-high column of water.
Waterproofness of a trail jacket:
- 5,000 to 10,000 mm: light to moderate protection, ideal for light or intermittent rain.
- 10,000 to 20,000 mm: moderate to high protection, suitable for heavy rain and wet conditions.
- Over 20,000 mm: very high waterproofness, used in extreme conditions.
Breathability, MVTR and RET
Breathability is a fabric’s ability to transfer water vapour and sweat generated by the body during exercise. It helps prevent discomfort during exertion. The breathability of a trail jacket can therefore be assessed using MVTR and RET.
MVTR (Moisture Vapour Transmission Rate) measures the amount of water vapour a fabric can transfer over a 24-hour period, expressed in grams per square metre. A high value means better breathability.
MVTR breathability of a trail jacket:
- 5,000 to 10,000 g/m²/24h: moderate activity in temperate conditions.
- 10,000 to 20,000 g/m²/24h: suitable for intense effort with effective sweat management.
- Over 20,000 g/m²/24h: highly breathable, ideal for long-distance races or hot, humid conditions.
RET (Resistance Evaporative Transfer) measures the resistance a fabric offers to the transfer of water vapour. A low RET indicates better breathability.
RET breathability of a trail jacket:
- Below 6: highly breathable, perfect for intense activities.
- Between 6 and 12: suitable for breathable clothing in moderate conditions.
- Between 12 and 20: limited breathability.
- Over 20: fabric considered non-breathable.
Other criteria for choosing your trail jacket
Other factors help you choose the right trail jacket. A stretch fabric improves comfort and freedom of movement, especially during long or technical races. The jacket’s cut should suit your body shape while allowing a wide range of movement.
An adjustable hood provides good protection and adapts to changing conditions. It should be deep enough to protect you from rain, yet flexible enough to avoid obstructing your vision. A model with elastic adjustment or a drawcord system keeps it in place, even in strong winds.
During a race, every gram counts. For a short trail, choose a jacket weighing 100 to 200 g. It should be as light as possible, while still providing a minimum level of protection. For an ultra-trail, you will need a more built-to-last jacket, weighing 200 to 350 g. It provides good protection while remaining lightweight and compact. Likewise, choosing the right trail pack is essential for optimising comfort and avoiding unnecessary bulk.
Finally, some ultra-trails have specific equipment requirements. While each race has its own criteria, a trail jacket must generally have a waterproof, breathable membrane (10,000 Schmerber and a RET below 13), an integrated or attached hood, and no sections made from non-waterproof fabric outside ventilation zones.
Choosing the right trail jacket depends on the duration of the race and weather conditions. Lightweight construction, waterproofness and breathability are the main criteria. In all cases, choose a model suited to your activity to combine protection and comfort on your outings.
