The invention relates to a seat or seat back comprising of seat elements which are arranged to resiliently move with respect to each other and arranged to move with respect to a central axis, running centrally through the seat or seat back parallel to the spine of the occupant in a normally seated position, the first and second seat elements moving in opposite directions on either side of the central axis. The seat elements may rotate and are subject to a restoring force urging them to return them to their rest positions such that the user is able to move in a twisting position and the seat back or seat will also twist with the twisting movement of the user and provide support in the newly adopted position of the user. The seat elements could be formed from a single piece of resilient material.