content: Came here to say this same thing. It is an interesting idea, could a spring loaded tension energy storage system be built light enough and with ample energy storage to help accelerate a bicycle to high speed. Why not compressed air? Pedal like hell, barely moving for 5 miles compressing air into a tank which could be built lighter and store more energy than a spring system. Take a few hours to get there. Once you reach the final Km engage the pneumatic motor to boost the bike to ludicrous speed.