Abstract: An exercise device can include: a platform; a handle coupled to a first side of the platform; and an inflatable member coupled to an opposite second side of the platform, the inflatable member having a rounded portion with an apex opposite of the handle, the inflatable member having an inflation port. The inflatable member can have an annular flange around an inflatable portion, the annular flange being mounted to the platform. The device can include an annular fastener ring mounted to the platform with the annular flange therebetween, the annular fastener ring being received onto a first surface of the annular flange, and a second surface of the annular flange being received onto the second side of the platform. The device can include fasteners passing through the annular flange and mounting the annular fastener ring to the platform.