A balance board has a top side and an under side. The under side is arranged to be mounted on top of a ball with a user balancing on the top side. The board is shaped to define a generally longitudinal direction and a direction generally transverse to the longitudinal direction. The board is formed from a first top portion defining the topside and having a substantially flat region on its under side and a second lower portion joined to the first top portion and defining a wall at least substantially bounding a portion of the flat region. The distance across the bounded portion in the longitudinal direction of the board is greater than in the transverse direction. With the bounded portion balanced on a ball with a diameter less than the distance across the bounded portion in the transverse direction, the board is enabled to move relative to the ball with at least a degree of spherical rotational freedom and also a degree of translational freedom in directions other than the vertical.
1. A balance board for receiving a user's feet spaced a set distance apart on the top surface and having a selected distance from heal to toe having a top side and an under side, the under side being arranged to be mounted on top of a ball with a user balancing on the top side, the board being shaped to define a generally longitudinal direction and a direction generally transverse to the longitudinal direction, the board being formed from a first top portion defining said topside and having a substantially flat region on its under side and a second lower portion joined to the first top portion and defining a wall at least substantially bounding a working portion of said flat region, the wall defining a boundary with the shape of a flattened oval comprising a generally oval shape having ends that are flattened from true oval shape, the distance across said working portion in the longitudinal direction of the board being greater than in the transverse direction, but not more than the set distance so that, with the said portion balanced on a ball with a diameter less than the distance across the said working portion in the transverse direction, the board is enabled to move relative to the ball with at least a degree of spherical rotational freedom and also a degree of translational freedom in directions other than the vertical.
2. A balance board according to claim 1 , wherein the board is symmetrical about the longitudinal direction and also symmetrical about the transverse direction.
3. A balance board according to claim 1 , wherein the wall defines a bounded portion, with the transverse distance across the bounded portion not more than the selected distance.
4. A balance board according to claim 1 , that includes a high friction layer secured to the top side to resist slipping of a user's feet.
5. A balance board according to claim 1 , in combination with a ball whose diameter is less than the distance across the said working portion in the transverse direction.