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:For the personal information manager, see [[Backpack (software)]]
:''Knapsack redirects here; see also [[knapsack (disambiguation)]]''
[[Image:Rucksack1.jpg|thumb|right|A backpack]]
A '''backpack''' is, in its simplest form, a cloth sack carried on one's back and secured with two straps that go over the [[shoulder]]s (called shoulder straps) and below the [[armpit]]s.

Backpacks are often preferred to [[handbag]]s for carrying heavy loads for long periods of time, because the [[shoulder]]s 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.

== Terminology ==
The word '''backpack''' was coined in the United States in the 1910s.  ''Knapsack'' and ''packsack'' were used before; they now occur mainly as [[Regionalism (linguistics)|regionalisms]] in North America.  The British created the names ''rucksack'' (a German loanword - 'rücken' being the bodypart 'back'), ''haversack'', and ''Bergen'' (from the manufacturer's name ''Bergans'', used for a rucksack supported by an external frame, usually associated with the [[British Armed Forces]]).

== Special-purpose backpacks ==
[[Image:Canon-Deluxe Backpack-200-EG.jpg|thumb|left|Camera backpack]]
Some backpacks are specifically designed to carry certain items.  Common examples include backpacks for small, high-value items such as [[laptop computer]]s and cameras (see photo).  It is also possible to buy "picnic basket" backpacks that come with plastic dishes and utensils, a tablecloth, etc. Hydration packs carry water and have a tube connected to them from which the wearer can drink. Backpacks that carry [[skateboard]]s have also become more popular in the youth culture.
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== Backpacks for backpacking ==
[[Image:Berghaus_Vulcan.jpg|thumb|right|Large internal-frame backpack]]
One common special type of backpack (often just called a 'pack') is designed for [[backpacking]].  
Packs are more complex than most other backpacks, may have many pockets on the outside and sometimes even a subdivided main compartment. They can have ''lash points'' on the exterior, so that bulky items may be strapped on; although some backpackers will try to stuff everything into the pack. Packs typically stand about 3 feet (1 m) tall; and have a content between 60 and 100 liters

Packs come in two main types.  

The more traditional type uses a rigid, ''external frame'' which is strapped on the back and in turn carries and supports a cloth sack and potential strapped on items.  Wooden pack frames have been used for centuries around the world,{{Fact|date=February 2007}} and metal versions first appeared in the mid-20th century. Modern pack frames are usually made from lightweight aluminium tubes. The frame typically has a system of straps and pads to keep the sack and the frame from contacting the body. The open structure has the added benefit of improved ventilation and decreased sweatiness. The fabric part of the pack occupies part of the frame's length, but the frame typically protrudes above and below. These areas of the frame allow bulky items (such [[tent]]s, [[sleeping bag]]s, and [[thermal pad]]s) to be strapped on. Thus the main compartment is smaller than that of an internal-frame pack, because bulky items ([[tent]]s, [[sleeping bag]]s, [[thermal pad]]s) are strapped to the parts of the frame not occupied by the main compartment itself.

An ''internal-frame'' pack has a large cloth part in which a small frame is integrated. This frame can consist of strips of either a metal or specially designed [[polymer]] that molds to one's back to provide a good fit. Usually a complex series of straps works with the frame to distribute the weight and hold it in place. Internal-frame packs may provide a few lash points, but as the frame is fully integrated and not available on the outside, it is difficult to lash a large, heavy item so that it stays fixed and does not bounce, so most cargo must fit inside.

Internal-frame packs originally suffered from smaller load capacity and less comfortable fit during steady walking, but newer models have improved greatly in these respects. In addition, because of their snug fit, they ride better in activities that involve upper-body movement; such as scrambling over rocky surfaces. The improved internal frame models have largely replaced external frame backpacks. In Europe hardly any external-frame models are sold anymore, but in the United States, some manufacturers continue to produce them.

{| cellpadding="4" cellspacing="0"  border="1" class="wikitable"
! colspan="2" align="center" | Comparison of backpack models
|- 
! External frame
! Internal frame
|- 
| Large metal frame to which the pack is secured
| Highly reduced semirigid frame in the inside of the pack
|- 
| Good ventilation
| Tight fit and less bouncing
|- 
| Large capacity for bulky strap-on items
| Roomy internal storage
|- 
| May cost approximately US$80-130 (difficult to find in Europe)
| May cost approximately US$150-250 (or more)/€100-400
|-
|}

== See also ==
* [[Suitcase]]

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[[Category:Backpacking]]
[[Category:Camping equipment]]
[[Category:Hiking equipment]]

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[[scout-o-wiki:Rucksack]]
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