support or padding including expandable cells whose cell body in its resting state seen in transverse section is individually delimited by at least two concentric perimeters , the walls of the cell in its resting state rejoining each of the perimeters are characterized by the fact that the portion of the wall of the cell rejoining two points located ach on one of the concentric perimeters 6 and 7 can be strictly in a straight line during its centripetal path , if between two other points 28 at the entrance of the successive fissures , slits or cells 4 located on the external perimeter 7 of the path followed takes at least for a certain length an aspect strictly of a straight line or flat part 29 , one of the lat two points 28 being the same as the first one located on the external perimeter 7 at the junction or exit of a fissure : all of the consecutive points of the is flat part 29 being further away or distal in relation to the center 24 of the cell than the other points , outside of the flat part 29 , constrictive of the sheath 7 on its path between two points 28 located at the junction of the successive fissures 4 .