Bungee cord backpack makes light work of heavy load

LONDON (Reuters) - Carrying heavy loads could become easier thanks to a new ergonomic backpack that uses bungee cords to take the strain off the shoulders and joints, scientists said on Wednesday.

The cords suspend the load in the pack so it stays at the same height from the ground while the wearer is running or walking and reduces the risks of muscle and joint problems.

Its designers said it will allow users to carry an extra 12 pounds (5.4 kg) while expending the same amount of energy as when carrying a normal backpack.

"For the same energetic cost, you can either carry 48 pounds in a normal backpack or 60 pounds in a suspended ergonomic backpack," said Lawrence Rome of the University of Pennsylvania.

"It is like carrying an extra 12 pounds for free," he added in a statement.

The backpack, which was designed for soldiers and emergency workers, could be useful for children and hikers.

"Being able to move at relatively high speeds is crucial for many professions as well as in some athletic competitions and recreation," said Rome, who collaborated with researchers at the Marine Biological Laboratory in Woods Hole, Massachusetts.

In most traditional backpacks the load is attached to the frame of the pack which is strapped tightly to the body. As a person walks it moves in line with the hip.

The new pack, which is described in a report in the science journal Nature, reduces the vertical displacement of the load.

"What is striking about our ergonomic backpack is that one can feel the 86 percent reduction in force with each and every step," Rome added in a statement.

The scientists have formed a company to produce the backpacks and are now working on a lighter, small version.