External frame packs were designed to carry heavy loads (>20 kg or 40 lb), giving the wearer more support and protection and better weight distribution than a simple, frameless strapped bag. Wooden pack frames were used for centuries around the world. Ötzi the Iceman may have used one in Copper Age Alpine Italy,[5][6] though some archaeologists believe the frame found with the body was part of a snowshoe. Such packs are common in military and mountaineering applications;[7] metal versions first appeared in the mid-20th century. https://i.pinimg.com/236x/98/68/18/98681863441d4f190fcf5e2b8a4e403a.jpg
The other type of external frame which recently was proposed, is made from composite plastic which is not flexible like current backpack straps and also it is a kind of material that can be shaped like human spine curvature. In this type of backpack, load directly transfers to the shoulders through the non-flexible straps. This non-flexible structure diminishes the momentum at lumbar region of the back. Strap curvature is shaped close to spine curvature and there are two flexible drawstrings to prevent backpack movement in transverse plane. The straps of this backpack are wide enough to distribute the pressure on shoulders and also a white glass wool layer is added to the internal part of them to absorb dynamic forces, which could be produced through walking. This backpack type is an experimental sample that need further options to be prepared for usage. One of the benefits of backpack with external frame is preventing the spine to incline forward during walking that would be helpful in preventing damage of long term backpack carrying.[4] https://i.pinimg.com/236x/22/70/93/227093e0e575cf60ee59fcfd4c18d7ce--my-thirty-one-thirty-one-gifts.jpg
From casual cinch sacks to smartly-designed wallets and bags, 31 Gifts (or T.O.G. as their consultants like to refer to it) has you covered wherever your day may take you. Savings-savvy office workers love the insulated totes, lunch sacks and zipper pouches that keep cold food and drinks fresh for break time, enabling them to save money by prepping their own lunches at home. Moms swear by the company’s oversized totes, stacked with plentiful pockets for diaper change necessities, coupons, favorite toys and more. Fashionistas dig the bright, colorful makeup bags and change purses, infused with both functionality and style to keep them on the cutting edge. With such a wide variety of bags, it’s very easy for a consultant to match party attendees to a product that works well for their lifestyle.    https://i.pinimg.com/originals/53/4a/b7/534ab73bc297e11c41b27a41475813cf.jpg
Typical school backpacks generally lack the rigid frame of an outdoor-style backpack and include only a few pockets in the front in addition to the main storage compartment. While traditionally very simple in design, school backpacks are often made with padded shoulder 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. https://i.pinimg.com/236x/9c/6a/6c/9c6a6c4a34ffb3d1066d68dd5ccb5247--plaque-brass.jpg
Rolling backpacks are backpacks with wheels on the bottom and an extending handle. Because of their design, rolling backpacks reduce the strain on the user, though the shoulder straps may be used to carry the pack for short distances when the terrain is not suitable for wheels. Rolling backpacks are most commonly used while traveling by airplane or train. https://i.pinimg.com/236x/1c/15/c1/1c15c163dbe92b6fcfa64e5c1f0edbd3--life-changing-container-sales.jpg
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