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Anatomical. The most common type of back in today's backpacks. In accordance with the name, the shape and design of such a backrest is designed taking into account the anatomy of the human body; thanks to this, the load is optimally distributed on the user's back, which allows you to carry significant weight without much inconvenience and harm to health (of course, if the backpack is properly selected and configured). The specific features of such backpacks can be different, but most often the back has protrusions and curves, which give it the necessary properties.
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Easel. This type of backrest is a one-piece structure in the form of a frame with straps (usually metal), on which the actual soft bag for things is attached. Easel backs are less comfortable than anatomical ones, so they are relatively rare, mainly in two categories of backpacks. The first is hiking models (see "In the direction") of large capacity, from 60 liters and above; in them, the soft bag is often made removable, which allows, if necessary, to hang another load on the frame that is suitable in size and weight. The second variety is backpacks for fishermen, where the frame is actually a folding chair (see "Equipment").
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Hard back. The presence of a rigid frame in the design of the backpack. Note that this feature should not be confused with the easel back: a rigid frame usually means
...one or more metal plates built into the anatomical back. The main function of such plates is to optimize the load when the backpack is unevenly filled or when carrying hard objects of an “uncomfortable” shape. Without hard inserts, the contents of the backpack could press on certain points of the back, creating discomfort, and the plates evenly distribute all the pressure on the back. At the same time, in many models it is possible to remove the frame — for example, to reduce the weight of the backpack.
— Back ventilation. This feature suggests that the back has a special design that improves air circulation between the backpack and the user's back. This, in turn, improves thermoregulation and reduces sweating. Such properties are usually achieved through the use of porous breathable materials, as well as a special relief shape of the back itself. Note that this feature will be useful not only in hot, but also in cool weather.
— Adjustment of a back on height. The ability to adjust the back of the backpack in height is found only in models equipped with a waist belt (see "Cables and belts"). The essence of this adjustment is that, thanks to a special fastening, the main straps can be moved up or down, changing the distance between these straps and the waist belt. This gives additional features for adjusting the backpack to the height and physique of a particular user.
