An exercise apparatus includes a substantially flat, rigid platform for supporting a user during exercise. An inflatable tubular support having an upper portion with a first radial outside diameter, and a lower portion with a second radial outside diameter that is greater than the first radial outside diameter, is coupled to the platform by a fastener. The tubular support defines a central opening that communicates between the platform and a support surface. The platform includes a venting structure for releasing air from the central opening during use. The inflatable support includes an intermediate portion between the upper portion and the lower portion of the tubular support, the intermediate portion including a support feature to restrain the intermediate portion from radial expansion induced by an air pressure internal to the integral inflatable support.