The invention relates to the field of ergonomic furniture. The device (1) comprises an upper support element (8) for supporting the thighs and a lower support element (9) for supporting the legs or tibias, that can be separated by an open space (11) or recess for the knees. An assembly (7) formed by the two support elements (8, 9) is mounted so that it pivots around a horizontal axis (A) on a bearing structure (2, 6), wherein rotation of the assembly (7) enables the support elements (8, 9) to accompany the lower limbs of a user during a transition from one use position to another. The device (1) is incorporated into an apparatus for maintaining a standing or sitting-standing position, having at least one footrest (4, 5). The device is applicable to the arrangement of a workstation, such as a computer workstation or an industrial workstation.
