Devices that help people walk were once thought to be impossible to design without some kind of auxiliary power. But U.S. scientists at Carnegie Mellon University and the University of North Carolina have built a small, wearable addition to ordinary shoes that reduces the burden on the calf muscle and makes walking easier.
Burning less calories while walking seems like a bad idea, but making the walk easier may actually keep people on their feet longer, and that scientists say, has substantial health benefits.
Analyzing the human walk, biomedical engineers Steven Collins and Greg Sawicki concluded that our ankles and calves perform motions similar to a spring coupled with a clutch that intermittently stores and releases energy.
Sawicki, from the University of North Carolina, explained what’s involved.
“We found in basic science experiments that that system, your calf and Achilles tendon, works a lot like a catapult. So, the muscle holds on to the tendon and your body actually stretches your Achilles tendon quite a bit and then stores the energy in the tissue and then it’s given back to propel you forward in the world,” he said.
Sawicki said he and his colleague Steven Collins at Carnegie Mellon University designed a mechanical device, made of carbon fiber and metal, that performs the same sequence of energy give-and-take outside the body. The system takes over part of the work of walking, and reduces the amount of required energy by as much as seven percent.
Wearing the unpowered ankle exoskeleton can help people either walk farther with the same amount of energy, or restore the normal movement pattern for people who have trouble walking.
Sawicki said it takes only a few minutes to get used to the exoskeleton but the wearer quickly learns to tone down the muscle energy as the device takes over part of the load.
“You really don’t notice it until when you take it off. And when you take it off you realize that it was there and giving you the boost,” he said.
Sawicki added that the device is primarily intended for people recovering from surgery or a stroke. But all persons who spend a lot of time walking, such as police officers or hospital personnel, could benefit from it.
At the moment there are no plans to develop the ankle exoskeleton for the market, but the inventors say some manufacturers have expressed interest.