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backpack (also called rucksack, knapsack, packsack, pack, Haversack, Bergen, kitbag and bookbag) is, in its simplest form, a cloth sack carried on one's back and secured with two straps that go over the shoulders, but there can be exceptions. There are many ways to carry backpacks. One way is to carry it in one hand (like a briefcase).
camera backpack
Backpacks are often preferred to handbags for carrying heavy loads, because the shoulders are better suited for bearing heavy weights for long periods of time than the hands. Large backpacks, used to carry loads over 10 kg, usually offload the largest part (up to about 90%) of their weight onto padded hip belts, leaving the shoulder straps mainly for stabilising the load. This improves the potential to carry heavy loads, as the hips are stronger than the shoulders, and also increases agility and balance, since the load rides nearer the person's own center of mass.
a backpack
Originally in ancient times, the backpack was used as a means to carry the hunter's larger game and other types of prey as a way of easier transport. In the cases of larger hunts, the hunters would dismember their prey and distribute the pieces of the animal around each one packing the meat into many wrappings and then into a bag which they place on to their back. The bag itself was made up of different animal hide and skin (depending on what sorts of animals were in the area) and sown together by the intestines of said animals, which were woven together tightly to make a sturdy thread-like material.
large internal-frame backpack
Backpack DesignsBackpacks in general fall into one of three categories: frameless, external frame, and internal frame. A pack frame, when present, serves to support the pack and distribute the weight of its contents across the body more easily (generally by transferring much of the weight to the hips and legs), so most of the weight does not rest on the shoulders, restricting range of motion and possibly causing damage from pressure on the straps. Most are capable of being closed with either a buckle mechanism or a zipper, though a few models use a drawstring for the main compartment.
In addition, outdoors packs are designed for specific purposes such as kayaking/canoeing, rock climbing, mountaineering, cross country skiing, and other such activities. Packs used in competitive strategic sports such as paintball and airsoft are often based on or actually are military gear.