If you are experiencing lower back pain, then one muscle to be paying attention to is the psoas and the surrounding muscles. This muscle is important because it is the primary muscle for moving the hips. This muscle being damaged could lead to a variety of problems and pains in the body, but mainly in the lower back. It is tightened often when sitting or slouched. This means that when you are not sitting upright or standing then it is being flexed.
Read more: Attention to psoas muscle can help back pain - Walla Walla Union-Bulletin