Paris--Millions of years of evolution have enabled human beings to develop a smooth, energy-efficient way of walking.
But, biomechanical engineers suggested on Wednesday, there's always room for improvement.
They unveiled an unpowered exoskeleton -- a small, light, spring-activated device that fits on the lower leg and reduces the energy cost of walking by around seven percent.
"The difference might seem small, but it makes a significant difference for humans," said Steve Collins of Carnegie Mellon University in Pittsburgh, Pennsylvania.
It's the rough equivalent of an infantryman being able to march seven percent more in terms of time and distance for the same energy expenditure, or a trekker freed of the energy cost of toting a four-kilo (10-pound) backpack, he said.
Exoskeletons -- externally-worn devices intended to augment physical actions or strength -- have a long history.
Back in the late 19th century, pioneering inventors toyed with coiled springs tucked into the heels of cowboy boots, or harnesses with rubber bands that were attached to the legs and sought to make walking easier.
But the weight and design of the gadgets were often an energy drain in themselves.
Partly as a result of such setbacks, exoskeleton design today favours powered devices, but in turn has to struggle with challenges such as battery range and bulk.
The new gadget, described in the science journal Nature, is a carbon-fibre mechanical device weighing about 500 grammes (1.1 pounds) for each leg.
It comprises a spring that is attached at one end to a strap around the top of the calf, and, at the other end, to the heel of the shoe.
When the heel meets the ground, the spring becomes extended, and a tiny mechanical clutch engages to ensure that the spring briefly retains this energy.
When the heel is lifted, the clutch disengages and the spring is released, thus giving up its stored energy and providing discreet help for the calf muscles as they lift the lower leg.
AFP
