<P> A trampoline is a device consisting of a piece of taut, strong fabric stretched between a steel frame using many coiled springs . People bounce on trampolines for recreational and competitive purposes . </P> <P> The fabric that users bounce on (commonly known as the "bounce mat" or "trampoline bed") is not elastic itself; the elasticity is provided by the springs that connect it to the frame, which store potential energy . </P> <P> A game similar to trampolining was developed by the Inuit, who would toss blanket dancers into the air on a walrus skin one at a time (see Nalukataq) during a spring celebration of whale harvest . There is also some evidence of people in Europe having been tossed into the air by a number of people holding a blanket . Mak in the Wakefield Second Shepherds' Play and Sancho Panza in Don Quixote are both subjected to blanketing--however, these are clearly non-voluntary, non-recreational instances of quasi-judicial, mob - administered punishment . The trampoline - like life nets once used by firefighters to catch people jumping out of burning buildings were invented in 1887 . </P>

What is the center of a trampoline called