I'm trying to design an entirely mechanical system for returning an extension spring to its extended state, without the assistance of electronics, pneumatics, hydraulics or any other form of auxiliary power. It's for a soft exosuit concept that simply enhances the speed and ease of walking or running for the user. Two cables are attached to the wearer's legs just below the knee, and as each foot hits the ground I need the extended spring to release, contract, and extend again within about a 1to 2 second timeframe. I have the springs housed in PVC tubing and mounted to a backpack frame, and what I need to know is how to return the extension springs to their extended state after being released without using any kind of auxiliary power, such as hydraulic pistons or linear actuators. (However, if there's legitimately no way to do this then I'll gladly introduce something else into the mechanism - I'm just trying to do this without those things.) I'm sure I sound like an amateur to you folks, but I'm just a guy building **** in his basement. Any and all help is appreciated.