Patent Document ID: 9320940
Application ID: 13872264
Patent Flag: 1

Claim One:
1. An exercise device sized for a single appendage of human support, comprising: a compressible base, the base having a horizontally-extending central flat for maintaining a balanced, upright position of the exercise device before being loaded, the base having at least one side encircling the central flat which slope outward and upward around the central flat with a slope which increases as distance from the central flat increases, the sides permitting simultaneous pitch and roll instability to the exercise device at a beginning slope immediately adjacent the central flat of less than 45°; and a relatively rigid platform joined to and horizontally covering the compressible base at a height no greater than 10 inches over a bottom surface of the flat, the platform having a shape which provides substantially equal pitch and roll instability, the platform having an exposed, flat top providing a flat surface sized for a single appendage of human support and at least 3 inches wider than the central flat, wherein the platform comprises an interchangeable grip surface on a plate, the grip surface having a different material, different amount of compressibility or different surface finish than the plate.