Bungee-Powered Backpack Can Reduce Strain on Back

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Bungee-Powered Backpack Can Reduce Strain on Back

http://www.medicalnewstoday.com/medicalnews.php?newsid=59582

Old Saint Nick might very well be able to run from rooftop to

rooftop without reindeer this year, if only he carried toys in a

backpack like the one developed by biologists at the University of

Pennsylvania.

In this week's edition of the journal Nature, Penn researchers have

announced details for a suspended-load ergonomic backpack that

reduces the force of a backpack's load on the wearer by 86%,

allowing wearers to run far more comfortably with heavy loads.

While it might be useful for Santa, the backpack was created with

soldiers and emergency workers in mind and could prevent the sort of

muscle and joint injuries associated with running while carrying

heavy items. The Penn researchers also point out that the backpack

will also benefit schoolchildren, since heavy book bags have been

linked to muscle and orthopedic injury.

" For the same energetic cost, you can either carry 48 pounds in a

normal backpack or 60 pounds in a suspended-load ergonomic

backpack, " Larry Rome, a professor in Penn's Department of Biology,

said. " It is like carrying an extra 12 pounds for `free.' "

The backpack is based on a rigid frame pack, much like the type

familiar to hikers everywhere; however, rather than being rigidly

attached to the frame, the sack carrying the load is suspended from

the frame by bungee cords.

Last year, Rome, an expert in the physics of muscle movement,

introduced a power-generating backpack that converts mechanical

energy from walking into as much as 7.4 watts of electricity, more

than enough energy to power a number of portable electronic devices

at once. His findings were published in Science.

The suspended-load ergonomic backpack has a similar sliding motion

as the electricity generating-backpack, but it is tuned differently.

Rather than having stiff springs, the load is suspended by very

compliant bungee cords.

" The ergonomic backpack reduces the force of the load on the wearer

by reducing the effect of the load as it shifts up and down, " Rome

said. " What is striking is that you can feel the 86% reduction in

force with every step. "

With a normal backpack, the peak force exerted by the load on the

body during walking is twice as high as the static force, and during

running it's three times as large, exerting extreme forces on the

joints.

The backpack shifts the timing of how force is applied as the wearer

takes a step.

" Essentially, the bungee cords permit the load to stay at nearly

constant height from the ground while the wearer walks or runs

around it, " Rome said. " The pack actually reduces the metabolic cost

of walking from one point to another by about 40 watts, or the

equivalent of carrying 12 extra pounds.

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Penn researchers involved in development and testing of the

Suspended-load Backpack at the Rome laboratory at Penn are Louis

Flynn, an engineer, and postdoctoral fellow Taeseung D. Yoo. Funding

for this research comes from the National Institutes of Health and

the Office of Naval Research.