US Patent 11412857 Ergonomic chair

A convertible seat including: a support frame; and a user support having a support surface on one side defining a rounded periphery, the user support being movable from a first configuration supported by the support frame with the rounded periphery presented upwardly, to a second configuration supported by the support frame such that a seat or seat base is presented upwardly, the seat or seat base being substantially flat or at least less rounded than the rounded periphery, with the support surface being stowed substantially below the seat or seat base in the second configuration. The seat allows the attainment in a single unit both the healthy balance/core-strengthening of a fitness chair and a conventional chair.