A backpack (also called rucksack, knapsack, packsack, pack, or Bergen) 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. Light weight types of backpacks are sometimes worn on only one shoulder strap, or in the hand like an ordinary bag.
Backpacks are often preferred to handbags for carrying heavy loads, because of the limited capacity to carry heavy weights for long periods of time in 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.
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 sewn together by the intestines of said animals, which were woven together tightly to make a sturdy thread-like material.
Backpacks can often simply be referred to as "packs", especially in outdoors contexts; though sometimes ambiguous compared to other bags such as saddlebags and duffel bags, context is generally sufficient for identification.
Backpacks 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.
The simplest backpack design is a bag attached to a set of shoulder straps. Such packs are used for general transportation of goods, and have variable capacity. The simplest designs consist of one main pocket. This maybe combined with webbing or cordage straps; while more sophisticated models add extra pockets, waist straps, chest straps, padded shoulder straps, padded backs, and sometimes reflective materials for added safety when the wearer is out at night. In general these packs can be produced inexpensively.
Some outdoors packs, particularly those sold for day hikes, ultralight backpacking and mountaineering are sometimes frameless as well.
An internal-frame pack has a large cloth section in which a small frame is integrated. This frame generally consists of strips of either metal or plastic that mold to one's back to provide a good fit, sometimes with additional metal stays to reinforce the frame. Usually a complex series of straps works with the frame to distribute the weight and hold it in place. The close fitting of the back section to the wearer's back allows the pack to be closely attached to the body, and gives a predictable movement of the load; on the downside, the tight fit reduces ventilation, so these type of packs tend to be more sweaty compared to external frame packs. The internal construction also allows for a large storage compartment. Internal-frame packs may provide a few lash points (including webbing loops and straps for sleeping bags and other large items), 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 and skiing. The improved internal frame models have largely replaced external frame backpacks for many activities.
Typical school backpacks generally lack the rigid frame of an outdoor-style backpack and include only a few pockets in addition to the main holding space of the pack. While traditionally very simple in design, school backpacks are often made with padded straps and backs as well as additional reinforcement to hold large numbers of heavy textbooks, as well as safety features such as reflective panels to make the wearer of the pack more visible at night. It is very common for schools (especially colleges and universities) to sell backpacks decorated with the school logo.
Specialist ergonomic back packs are available that are designed to protect young backs and distribute the weight across the strongest muscles and relieve pressure on the neck and spine.
Backpacks are sometimes worn as fashion accessories, in which they perform the same function as a purse. Some such backpacks designed specifically for women are no larger than a typical purse, and are generally associated with younger, often college-age women.
Some backpacks are specifically designed to carry certain items. Common examples include backpacks for small, high-value items such as laptops and cameras (see photo); backpacks designed to hold laptop computers in particular generally have a padded compartment to hold the computer and are especially common in college and university settings. It is also possible to buy "picnic basket" backpacks that come with plastic dishes and utensils, a tablecloth, etc. In order to supply these devices with electricity, some backpacks are equipped with solar panels.
Backpacks (often made of clear plastic) are sometimes used as a type of packaging, particularly for educational toys and games targeted at children. In retail settings, loss prevention rules sometimes require employees to use clear plastic backpacks (as well as purses) to carry materials to and from work to prevent loss by employee theft.
There are also single-strap packs that are essentially a hybrid between a backpack and a messenger bag.
Inexpensive, very simple packs that combine the drawstring and straps into a single piece of cloth or webbing are occasionally sold for use at sporting events and the like. Some high-end retailers (notably Apple Stores) use a similar design for their shopping bags as well.
Rolling backpacks are backpacks with wheels on the bottom and an extending handle to ease carrying objects inside the backpacks. Because of its design, rolling backpacks reduce the strain on one's back, which is more ergonomic than regular backpacks, though rolling backpacks can be carried on the back as well.
Many police tactical units, as well as players of military-style combat games such as paintball and airsoft, use military-style backpacks and webbing for storing gear and ammunition. There is also a small but thriving industry devoted to creating historical reproductions of military gear; such companies generally produce period-appropriate uniforms and other gear in addition to backpacks.
Some more recent military/tactical designs, especially the MOLLE and ILBE packs used by the United States armed forces, are covered with webbing loop attachment points for increased carrying capacity.
Backpacks are sometimes used as luggage, particularly as carry-on bags for airplane travel.
Backpacks form an essential part of the gear of the outdoor trekker and the urban backpacker, allowing more mobility and compactness than would be available to someone carrying most of their gear and clothing in a suitcase.
In addition to their use in outdoors pursuits, backpacks are sometimes used in other sports as well. Hydration packs, sometimes used by runners and bicyclists, carry water (in either a bladder or a rigid bottle) and have a tube connected to them from which the wearer can drink without removing the pack; this feature is also included in some more general-purpose hiking backpacks. Backpacks that carry skateboards have also become more popular in the youth culture.
One common special type of backpack (sometimes referred to as a "technical pack" or "frame pack") is designed for backpacking and other outdoors activities. These type of packs are more complex than most other backpacks. Compared to backpacks used for more day-to-day purposes such as schoolbooks, such packs are designed to carry substantially heavier loads, and as a result most such packs attach not only at the shoulders but at the hips, using a padded hip belt to distribute the majority of the weight of the pack to the legs and not the back. The often heavily padded and sometimes semi-rigid shoulder straps are mainly for balancing the weight. They usually (except for those used in ultralight backpacking) have a metal or plastic frame to support and distribute the weight of the pack. Larger packs of this type tend to have a subdivided main compartment. These trekking packs often have several pockets on the outside; they may also have lash points on the exterior (either directly attached to the frame or webbing loops), so that bulky items may be strapped on, although depending on the pack design and type of trek most backpackers will try to stuff everything into the pack. Multiday packs typically have a content between 60 and 100 liters (and are about 3ft /1 meter tall). Smaller packs with similar features are available for shorter trips.
The most common materials for such packs are canvas and nylon, either ripstop fabric for lightweight packs or heavier fabric such as cordura for more typical usage. Most such packs are purpose-designed for the outdoors market; however, it is not uncommon for military surplus packing gear to be sold to outdoorspeople as well for the same purpose. The cheaper versions of the outdoor packs are often favoured by city trekkers; as they have a large volume and still carry relatively easily.
Outdoors packs, in addition to the distinction between external-frame and internal-frame, can be further subdivided based on the duration of trip a pack might be expected to be used on; daypacks hold supplies for a single day's hiking (size about 20-30 litres), while "weekender" bags can hold two to three day's worth of gear and supplies (sizes about 40-50 litres). Larger packs generally have no specific names but are designed to distribute the weight of increased numbers of gear and supplies for longer-duration trips (60-100 litres); such packs often include complex ergonomic support features to simplify the carrying of large amounts of weight. A third type with little or no frame at all, similar to the bookbags used by students and made of light fabric (often nylon ripstop, as mentioned above), is used in ultralight backpacking to eliminate the weight of the frame and heavy fabric used in more typical outdoors packs. Despite (or perhaps because of) their lesser weight, such packs are seldom less expensive than more typical, regular-weight packs.
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.
|Frameless||External frame||Internal frame|
|Nonrigid bag strapped to shoulders||Large rigid (metal, plastic, or wood) frame to which the pack is secured||Highly reduced semirigid frame in the inside of the pack|
|Inexpensive and widely available||Good ventilation||Tight fit and less bouncing|
|Only suitable for light loads (less than about 5 kg.)||Large capacity for bulky strap-on items||Roomy internal storage, with occasional lash points for external items|
|May cost ~US$10-150||May cost ~US$80-200 (less popular and harder to find)||May cost ~US$100-600 (or more)/€100-600|