The layer of hiking clothingclosest to your skin is most important when you are hiking. Unfortunately, a common choice such as cotton T-shirts is not recommended as they tend to retain the moisture your body produces. This can lead to feeling chilly after your workout. Newer synthetic materials are used to make garments that wick moisture from your body but not retain it (usually less than 1%). Also, they are light but strong. Many are even treated to reduce body odor!