by Playfuls Staff |
21st December 2006
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.
[more]
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.
