If you plan to be on the trail for a day or longer, a good, sturdy overnight bag is essential. As a general rule, the size of your hiking backpack will increase as your need to carry outdoor equipment and provisions increases. Larger bags suited to this purpose are called Expedition Packs. They are designed with a broad hip belt to distribute packweight to the hips instead of the shoulders. A lumbar pad will protect the base of the spine from the added stress of a heavier backpack.