Jessica C great question, its moved to the side so that your arms can be in alignment with your shoulder and not slightly out to the side. The goal is to find the muscles around your shoulder blade and lowest ribs and avoid over using upper should muscles (they love to over work). Normally I move the box to the other side when I switch but for filming purposes I just turned around. You would move it back to center for Pull Straps etc. Hope this helps xx~LL