puzzle.
It sounds to me like the skates-with-springs that you have are called jumping jacks as a brand name. The original jumping jack was a kind of puppet whose legs and arms jumped up and down when you pulled the strings. http://en.wikipedia.org/wiki/Jumping_jack_(toy)
These days "jumping jacks" usually refers to a type of exercise where you jump in the air with your arms and legs spread out in a star shape.