Avoid cotton, as it can become damp from your sweat. Instead, look for shirts that are made of : [substeps] Wool polyester wool/polyester mix polypropylene [title] Wear fleece over the base layer.
[header] How to choose cold weather fitness clothing [title] Choose a light base layer. [step] The layer closest to your skin should be a moisture-wicking material that will keep you dry as you sweat. It should also be form fitting to help insulate your body.