A cushioning mat comprises a plurality of cushioning bumps arranged in a plurality of rows, the bumps of each row alternating with substantially flat bottom portions. Each bump comprises a top wall and a side wall which extends from a mat base identified by the bottom portions. The top wall and the side wall define an inner bump cavity. The bumps of adjacent rows are staggered with each other. In at least a portion of the side wall a vent opening is made which places in communication the inner cavity of the bump with the outside of the bump.