The main function of the second layer is to regulate the body's temperature and maintain thermal insulation by transporting sweat to the outer layer(s).
It's worn directly over the base layer and is commonly made of synthetic materials or natural merino wool as these fabrics are able to maintain their insulating properties even when wet, while maintaining breathable properties.
Most insulating second layers are constructed of a variety of fleece fabrics. The principle of thermal insulation is 'loft'. Loft refers to the amount of air retained by an insulating material which works as an insulant. In extremely cold conditions, it's advisable to use multiple layers for better temperature control; layers can always be removed or added to regulate your body's temperature. Whether exercising in cold climates, warming up before a workout or for casual wear, the second layer is an essential element of the layering system. The basic function of the second layer is to provide thermal insulation together with transporting of the sweat to the outer layer(s) or outside.
To provide the highest functionality, the models combine diversely thick materials according to the particular thermoregulation requirements of various zones of human´s body (so called bodymapping). In brief, parts of the body, which are prone to chilling, are protected with a thicker material. Parts of the body prone to sweating are on the other hand protected with a thinner material.
The sporting activity you plan to go in for should be crucial in deciding what clothing to choose. It will determine the cut, shape, overall style and incorporation of sport specific features such as thumb holes in the cuffs, media pockets, waterproof zippers, draw cords, high collars and 'pit zips'. For instance, the garment for cycling or cross-country skiing should have lenghtened back part and anatomically cut sleeves. Another example: thumb holes in the cuffs are suitable for activities such as cycling, cross-country skiing or for cold-blooded persons as they provide perfect protection from cold and wind for your wrists. Most of the second layer garment features raised stand-up collar to protect your neck. Most of the second base layer clothing is also equipped with a zipper which can ease you putting it on. The zipper can also be used for ventilation.
Important features and benefits of the second layer
- high ability to contain warmth
- high breathability
- becomes dry fast
- lightweight material
The second layer is commonly a fleece pile layer made of polyester which may sometimes be combined with other synthetic fibres, equally as the base layer. The material's technology is designed to regulate core warmth for optimal comfort by providing thermal air pockets that contain heat without restricting breathability. The fleece is endowed with longer fibres which can contain more air, thus more warmth. The fleece comes in varying density; from heavy, to medium or light, which is ideal for different sports and weather conditions. Thanks to the advancing technology, fleece is not the only material used for second layer clothing, but it is still the most common one.