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New Backpack Allows Carrying of Heavier Loads

Design involves suspending backpack from frame by bungee cords

WEDNESDAY, Dec. 20 (HealthDay News) -- A new backpack design that suspends the backpack from its frame by bungee cords rather than being rigidly attached can reduce the amount of energy necessary to carry the load, possibly reducing injuries in children and allowing emergency personnel to run while carrying heavy loads, researchers report in the Dec. 21 issue of Nature.

Lawrence C. Rome, Ph.D., and colleagues from the University of Pennsylvania in Philadelphia designed a backpack that was suspended from its frame by bungee cords rather than being rigidly attached. They noted that since the hips move up and down by 5 cm to 7 cm during walking, a backpack also moves up and down, thereby increasing the vertical forces acting on the body.

The researchers found that when walking, the new backpack reduced vertical displacement from 68.5 mm to 26.5 mm, reducing accelerative forces by 82 percent. The metabolic cost of walking with the load was reduced from 640 W to 600 W, making walking with the newly designed 27-kg backpack equivalent to walking with a 21.7-kg rigid backpack. When running, the new backpack reduced accelerative forces by 86 percent.

"These findings show that a passive device can make the energetic cost of carrying loads more economical," Rome and colleagues conclude. "Being able to run with this backpack, rather than being forced to walk, would be useful for emergency personnel carrying equipment to disaster sites, for example."

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