Powerisers or Jumping Stilts.....They are a specially designed pair of shoes that you wear that have spring-kind-of-things on them. You can jump six feet high with them and run up to 20 mph! Pretty amazing! But my question is if anybody would know how to build them, or where to get them cheap, or what are the spring parts made of? Because the springs have to be under enormous pressure to withstand the bouncing. So if you know any material that would to the same trick please let me know.