Abstract: In one embodiment the invention provides an impact-absorbing unit comprising an outer wear-resistant casing (10) and one or a plurality of inner stress resistant envelopes (20) containing impact absorbing material. The outer envelope is provided with a plurality of interconnection means (65, 70) on at least one surface thereof, whereby a plurality of such units can be connected together in a closely adjacent relationship to define a substantially continuous surface. In another embodimentthe compressible elements are directly enclosed within the casing (10).In another embodiment the loose fill of compressible elements is replaced by at least one open cell foam element and valve means are provided for evacuating air from the foam, whereby to compress the foam and allow subsequent expansion thereof by exposure to ambient air pressure.