The study, “Reducing the energy cost of human walking using an unpowered exoskeleton,” was published in the journal Nature today.
The Verge describes the exoskeleton, which fits comfortably into running shoes and extends just below the knee, can reduce the energy required to walk by 7 percent. The device’s light weight (between 300 and 500 grams, or about the weight of a dress loafer) helps reduce the mass penalty that could make energy-saving more efficient.
To achieve this efficiency, the exoskeleton channels energy that would normally run through calves and tendons instead into carbon fibre, metal and a spring. The series of springs and clutches allows the Achilles tendon — which usually relies on the calf muscle to stretch and recoil — to instead rely on the exoskeleton for forward momentum.
Gregory Sawicki, a study co-author and a physiologist at North Carolina State University, says the exoskeleton is usually not noticeable after a user has it on for 20 minutes or more. However, once the user takes it off, there will be a feeling of “heaviness” that lasts around five minutes.
The scientists involved with the study believe this would be especially helpful for people with incomplete spinal injuries, weakened ankles, multiple sclerosis sufferers and the elderly, It could also help out military personnel traversing rougher areas.
While the results are promising, medical applications are still some way away. While the exoskeleton is showing promise in the act of walking, it may not save energy in other tasks like standing, turning motions, and going from sitting to standing or vice versa. It’s also not functional at high speeds, something the researchers hope to improve on.
As well, there is a risk that prolonged use of the exoskeleton could weaken the leg muscle, something Sawicki thinks might happen but cannot say is definitive.
The currently nameless exoskeleton, should it hit the market, will probably retail for a little under $1,000.
This isn’t the first exoskeleton to make walking more efficient, however it is the first to do so without the use of an external power source. A 2013 study used an air compression system that achieved a 6 percent decrease in energy used for walking.