Scientists develop device that improves human walk

In a world's first, researchers from Carnegie Mellon University and North Carolina State University have developed an unpowered ankle exoskeleton that reduces the metabolic cost of walking by approximately seven percent - thus helping individuals walk using less energy.The results are roughly the equivalent of taking off a 10-pound backpack and are equivalent to savings from exoskeletons that use electrically-powered devices.

The device is the result of eight years of patient and incremental work, mapped out on a whiteboard by Steve Collins and Greg Sawicki when they were graduate students together at the University of Michigan in 2007."Walking is more complicated than you might think. Everyone knows how to walk but you do not actually know how you walk," said Collins, assistant professor of mechanical engineering at Carnegie Mellon in a paper that appeared in the journal Nature.

For the innovation, the team performed careful analyses of the biomechanics of human walking and then designing a simple, ultra-light-weight device that relieved the calf muscle of its efforts when it was not doing any productive work. The calf muscle exerts energy not only when propelling the body forward, but also when it performs a clutch-like action, holding the Achilles tendon taut.

With this insight in mind, the team created an ankle exoskeleton that offloads some of the clutching muscle forces of the calf, reducing the overall metabolic rate.A mechanical clutch engages when the foot is on the ground and disengages when the foot is in the air, to avoid interfering with toe clearance. This clutch takes over the effort of the calf, producing force without using consuming any energy and thereby reducing the overall metabolic rate.

Over several years and many iterative designs, the team developed a carbon-fiber design that is ultra-light, yet rugged and functional.The entire device weighs approximately one pound per leg or less than a work boot.According to experts, the device is a triumph of elegance, simplicity and bio-specific interventions over complex, over-engineered designs.

"It is a real exciting milestone for the field of assistive devices. They have taken an assistive device and lowered the cost of human walking," reacted Thomas Roberts, expert in the biomechanics of locomotion from Brown University.One of the long-term goals of Collins and Sawicki's project is to use lightweight, energy-efficient exoskeletons to assist individuals with mobility issues.

In the future, the team intends to test the current device with individuals who have a variety of mobility issues to determine what designs might work best for different populations.They are also interested in developing exoskeleton components for the knee and the hip, where they believe they may be able to garner even larger benefits.