The U.S. Army plans to field test a bionic PowerWalk system next year that generates battery power from a soldier's leg movements.

The "bionic power knee harvester" attaches to both legs and is designed to extract the energy expended when the knee is flexed and negative work is undertaken, the service said Thursday. It adjusts to individual gaits so it can go unnoticed by the wearer.

"We are converting the movement of the knees when you walk into useful power," Noel Soto, a project engineer at the Army Natick Soldier Research, Development and Engineering Center, said.

The system aims to reduce the load of batteries carried by soldiers for a variety of devices, while being able to extend missions.

On a 72-hour mission, a soldier carries up to 20 pounds of battery load, and the system could recharge batteries for the soldier wearing it or for others.

Researchers aim to have the system weigh one pound and generate 3.5 watts, while a two-pound system would generate 10 watts.

The program began in 2012.

While generating power, the system could also enhance movement by acting as a brake for soldiers walking downhill.