Upper-leg amputees fitted with prosthetic legs expend an extraordinary amount of energy when walking, according to researchers at the University of Utah’s Bionic Engineering Lab. The engineers cited a study from The Journal of Bone and Joint Surgery that measured amputees’ energy cost of walking. That earlier study found that the lower the level of amputation on the leg, the amputees performed the motions of walking better and used less energy doing so.

The Bionic Engineering Lab researchers developed a battery-operated exoskeleton to lower the effort required to walk with a prosthetic. The exoskeleton fits around the waist and upper leg. Electric motors move the components of the prosthetic based on directions from microprocessors using AI algorithms that “understand how the person moves and assist how the person moves,” according to Utah engineering graduate student Dante A. Archangeli.

The research team tested the powered prosthetic with six upper-leg amputees. In a study published in Nature, the researchers reported that all six subjects improved their metabolic rate when walking with the powered prosthetic compared to walking with a standard prosthesis. The average energy consumption reduced by 15.6%. According to assistant professor Tommaso Lenzi, using the experimental exoskeleton is “equivalent to taking off a 26-pound backpack.”

The engineers’ goal is to lower the metabolic consumption of upper-leg amputees walking with the exoskeleton to the level of an average nonamputee. This assistance level has exciting potential. Lenzi stated that in a couple of year the group’s design could be available for public use.