Restructuring skeletal alignment takes time, but can be done with consistent effort! This posture is caused by shortened biceps and shortened pecs that are strong er than the back muscles used to squeeze the shoulder blades together. Biceps: rotate the shoulder blades forward Pecs: keep them in that position. This causes damage to the neck vertebrae and muscles, causing headaches and poor range of motion. It will also prevent the arms from being fully raised above the head, k