Back to base-ics

Britain's famously unpredictable climate can make staying comfortable in the field a challenge but the right under layers can be a game changer

- Caroline Roddis

WE'RE ALL more than capable of turning up and looking the part for a day in the field but it is what lies beneath that counts. Are your underpinnings less Bear Grylls and more threadbare and chills? Are your thermals, in fact, pants?

Done correctly, layering can keep you as cool, warm, dry or supported as the situation demands. Shopping for new base layers, however, can feel like going back to science class without having done one's homework. To make sense of it all, it's best to return to the basics. "Most of these base layers are about surface level thermal regulation," explains Simeon Gill, senior lecturer in fashion technology at the University of Manchester. "In essence, how well they can support the local environment close to the skin."

This is important because humans are heat-producing machines - at wakeful rest we produce about the same amount of heat as a 100-watt lightbulb - and the more we work the more heat we produce. As we heat up we all produce moisture that cools us when we're warm but continues to chill us once we're not. Clothing, therefore, needs to maintain our 'thermophysiological comfort'.

Ratings systems for garments on this basis can be complex and flawed, so the best way to choose a base layer is to determine how the garment's characteristics meet your unique needs. Age, sex, fitness and other factors all affect how much heat you produce and how much your skin reacts to both the cold and to different fabrics. Knowing your body shape is also important for finding base layers that can achieve a good fit - something that, no matter how technical a garment's specifications, is crucial to its effectiveness.