the sides of the trunk section of the inflatable body 1 to an outwardly directed pressure from the inside the supporting bodies 2 have a bottom section fastened on the outlet openings of the bottom part 3 and a top section fastened at the top end of the load bearing framework 5 the supporting nettings 12 are fastened on the bottom part 3 at the bottom and at the top end of the load bearing framework 5 at the top furthermore the bottom part 3 has a button strip clamp 13 which is mounted in a vertically adjustable manner substantially in the center of the front border of the bottom part 3 the button strip clamp 13 which is illustrated in cross section in fig4 serves for fixing the button strip or the buttonhole strip of a shirt 19 fitted onto the inflatable body so that the shirt 19 can be tensioned by the inflatable body 1 the button strip clamp 13 has an oval supporting tube 18 and a supporting bar 17 between which is disposed an air permeable clamping body 14 which may be produced for example from a perforated sheet if the rest of the parts in particular the supporting bar 17 and the clamping.