A stair stepping apparatus comprising: a plurality of stairs mounted on a frame and hingedly interconnected to each other in succession to form a treadmill or endless belt , the treadmill or endless belt being rotatably mounted on the frame for rotation around a path of travel, wherein each stair comprises: a step having a generally planar upper step surface (SS) having a front to rear length extending from a front edge to a rear edge , the step being comprised of a foot support; a riser having a top to bottom vertical length (URL, LRL) extending from the rear edge of the upper step surface (SS) to a bottom edge of the riser ; and the riser comprising an upper riser (UR) and a lower riser (LR) hingedly joined to each other between the rear edge of the upper step surface (SS) and bottom edge of the riser , wherein the upper riser (UR) is rigidly interconnected to the foot support at the rear edge of the upper step surface (SS) by an elbow that disposes the upper riser (UR) normally below the upper step surface (SS), the lower riser (LR) being rigidly interconnected by an elbow to a foot support of a successive step at the front edge of the upper step surface (SS). a plurality of stairs mounted on a frame and hingedly interconnected to each other in succession to form a treadmill or endless belt , the treadmill or endless belt being rotatably mounted on the frame for rotation around a path of travel, wherein each stair comprises: a step having a generally planar upper step surface (SS) having a front to rear length extending from a front edge to a rear edge , the step being comprised of a foot support; a riser having a top to bottom vertical length (URL, LRL) extending from the rear edge of the upper step surface (SS) to a bottom edge of the riser ; and the riser comprising an upper riser (UR) and a lower riser (LR) hingedly joined to each other between the rear edge of the upper step surface (SS) and bottom edge of the riser , wherein the upper riser (UR) is rigidly interconnected to the foot support at the rear edge of the upper step surface (SS) by an elbow that disposes the upper riser (UR) normally below the upper step surface (SS), the lower riser (LR) being rigidly interconnected by an elbow to a foot support of a successive step at the front edge of the upper step surface (SS). a step having a generally planar upper step surface (SS) having a front to rear length extending from a front edge to a rear edge , the step being comprised of a foot support; a riser having a top to bottom vertical length (URL, LRL) extending from the rear edge of the upper step surface (SS) to a bottom edge of the riser ; and the riser comprising an upper riser (UR) and a lower riser (LR) hingedly joined to each other between the rear edge of the upper step surface (SS) and bottom edge of the riser , wherein the upper riser (UR) is rigidly interconnected to the foot support at the rear edge of the upper step surface (SS) by an elbow that disposes the upper riser (UR) normally below the upper step surface (SS), the lower riser (LR) being rigidly interconnected by an elbow to a foot support of a successive step at the front edge of the upper step surface (SS). <EOS>