Mat

A mattress comprising a back supporting section that has a reference surface to support a back of a human in a supine position, the back supporting section comprising:

• a pair of serratus posterior superior corresponding parts that are each disposed below a region corresponding to at least a middle part between origin and insertion of each of a pair of left and right serratus posterior superior muscles of the human in the supine position;
• and
• a pair of scapula supporting sections disposed outside the pair of the serratus posterior superior corresponding parts in a width direction of a body of the human to support regions corresponding to a pair of left and right scapulae of the human in the supine position,
• wherein the serratus posterior superior corresponding parts and the scapula supporting sections are configured such that body pressure from the serratus posterior superior corresponding parts is lower than body pressure from the scapula supporting sections, and
• the scapula supporting sections each comprise a first step area disposed below a region corresponding to at least a part of a scapular spine at an end on a head side of each of the left and right scapulae, the first step area being depressed farther than the reference surface.