How to choose the right first layer for running?

The base layer for running is one of the key pieces of gear to choose carefully. It's the layer that comes into direct contact with your skin and must ensure good breathability and prevent chafing. So, which base layer should you choose? It depends primarily on the type of run, especially the duration and the outside temperature. Here are some tips for choosing the right base layer for your running.

Short outings (up to 60 min) in warm weather (+15°C)

The first type of outing is a short run of less than an hour, or around an hour, in warm weather above 15°C. A temperature of 15°C is considered warm for running, as physical exercise raises body temperature. For this type of outing, a lightweight, breathable, and quick-drying T-shirt or tank top is an ideal solution, potentially with odor-resistant treatment and no tags for maximum comfort.

Examples: tank top , short-sleeved T-shirt

Short outings (up to 60 min) in cool (5 to 15°C) or cold (< 5°C) weather

The second type of outing is still a short run of less than an hour or around an hour, but in cooler (5 to 15°C) or colder (< 5°C) weather. For this type of run, a technical base layer is ideal. Thanks to seamless 3D stitching technology and light compression, a thin layer of air remains trapped between the skin and the base layer, retaining warmth while still allowing perspiration to wick away. A short-sleeved base layer may suffice in cool weather, while a long-sleeved version is optimal in cold weather. Another more classic option in cool weather is a lightweight long-sleeved T-shirt.

Examples: seamless short-sleeved base layer , long-sleeved T-shirt

Long outings (over 90 minutes) in warm weather (+15°C)

The third type of outing is a long run of over an hour and a half in warm weather (15°C or above). For this type of run, two options are recommended: either a lightweight T-shirt or tank top that is breathable and quick-drying, or a short-sleeved base layer that effectively wicks away perspiration. I've run several marathons wearing technical base layers, and they have a major advantage: thanks to the slight compression they provide, they stay in place and prevent chafing. On long runs, or even very long runs (like a marathon), this is an undeniable advantage and a welcome comfort, especially after several hours of running.

Long outings (over 90 minutes) in cool (5 to 15°C) or cold (< 5°C) weather

The fourth type of outing is a long run of over an hour and a half in cooler (5 to 15°C) or cold (< 5°C) weather. For this type of outing, a long-sleeved base layer is ideal. If the weather is particularly cool, a second layer, and in cold weather, potentially a third layer, will be necessary for protection, especially if there is wind or light rain, which will lower the perceived temperature.

Example: seamless long-sleeved first layer

Trail running outings (with trail running pack)

Beyond running, and for those who practice trail running, one of the major differences comes from wearing a trail running pack. This tends to rub repeatedly against the shoulders and torso, which can eventually cause abrasion on the T-shirt. To solve this problem, we designed a two-fabric trail running T-shirt specifically engineered to resist the abrasion of a trail running pack. The back, upper shoulders, and ribcage areas are made from a lightweight, breathable, and highly durable fabric, while the rest of the T-shirt is made from another lightweight, breathable, and very soft-to-the-touch fabric. It's an optimal solution for trail running while wearing a trail running pack.

Example: Two-material trail running T-shirt

In total, six possible solutions that adapt to your practice and types of outings: from the tank top, to the short-sleeved or long-sleeved running T-shirt, to the seamless technical first layer in short or long sleeves, or even to the trail running T-shirt specially adapted for wearing a trail pack.