Researchers at Carnegie Mellon University and North Carolina State University are looking to make taking long walks much easier with a new ankle exoskeleton.

The unpowered invention, which the researchers introduced on Wednesday, comes with a sleek and simple design and only uses a spring, wire and clutch mounted on a carbon fiber frame to take the stress out of going on shopping sprees and strolls through the park, according to The Guardian. With this gadget, users will spend 7 percent less energy than they would without it.

Steven Collins, one of the designers behind the exoskeleton, said that while our muscles can run on organic fuels and heel themselves, they still have limitations.

"When they produce positive work, they have a conversion efficiency of about 25%, which is about the same as an internal combustion engine in a car," he said.

Collins spent eight years working on the exoskeleton with fellow researcher Greg Sawicki, and both say the 7-percent reduction in energy is equivalent to taking off a 10-pound backpack, Gizmag reported.

The device's abilities are based on research done on the biomechanics of walking and ultrasound imaging, which showed that the calf muscle uses energy to push a person forward and perform a clutch-like action while holding the Achilles tendon tight.

The exoskeleton gives the calf muscle a break by have the spring, wire and clutch do its job, The Guardian reported. The clutch locks the wire when the user's foot touches the ground, which makes the spring stretch when the user walks forward. The clutch then disengages when the foot lifts up, and the spring relaxes in preparation for the next step.

The team conducted treadmill tests with the device and found that it was able to reduce the amount of energy used to walk by 4.6 to 9.8 percent, with an average of 7 percent.

Collins said the device feels weird when you first try it on, but it will start to feel comfortable after you walk with it for a while.

"But it's when you take it off that you really feel a big difference," he added. "You're legs feel heavy and weak."

Collins also believes the ankle exoskeleton could help make it easier to walk for people who have had a stroke, Gizmag reported. The team plans on conducting more research in order to find other ways the device can make walking easier on the body.

"As we understand human biomechanics better, we've begun to see wearable robotic devices that can restore or enhance human motor performance," Collins said. "This bodes well for a future with devices that are lightweight, energy-efficient, and relatively inexpensive, yet enhance human mobility."

The researchers published their findings in the journal Nature.