Large backpacks, used to carry loads over 10 kilograms (22 lb), as well as smaller sports backpacks (e.g. running, cycling, hiking and hydration), 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 wearer's own center of mass. https://i.pinimg.com/236x/81/8d/45/818d45c8d48ce1857e20a29fa8bfa10d---gifts-thirty-one-gifts.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/c0/55/ce/c055cebd7e3c24d8f3a19d5412ab7242--direct-sales-thirty-one.jpg
Many police tactical units, as well as players of military-style combat games such as paintball and airsoft, use these military-style tactical 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.
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, though some archaeologists believe the frame found with the body was part of a snowshoe. Such packs are common in military and mountaineering applications; metal versions first appeared in the mid-20th century. https://i.pinimg.com/236x/8d/6f/87/8d6f873a5f9b925fe764eecba26a075b.jpg