To the sides of the back without sharp boundaries is at the top of the chest wall and in the lower part on the abdominal wall. The back consists firstly of bones, joints and ligaments, for example, the spine and the thoracic ribs. On the other are great under the skin muscles, which attach to the bone and keep the body upright. There is a group superficial running and a group running in the deep muscles. The two thick muscle strands on either side of the spine as Erector spinae muscles designated. They stand out next to the groove in the middle of the back, more or less pronounced than "beads" from. Opponent of the back muscles are the abdominal and anterior neck muscles.