US Patent 8727953 Dynamic weight lifting machine

An exercise system utilizes exercise apparatus having at least two operative positions, a first operative position with a base fixedly contacting a floor, and a second operative position with the base spaced apart from the floor and horizontally moveable over the floor in any desired direction of travel. When a barbell is mounted at rest on the exercise apparatus the apparatus is in the first operative position. When the barbell is disengaged from the at rest position, the exercise apparatus moves to the second operative position.