The quadratus lumborum muscle, often called the QL, is a paired muscle of the left and right posterior abdominal wall. Meaning, there’s one on the left and the right side of your body, and they sit on the back side of your body. Each is irregular and quadrilateral in shape (quadratus… quadrilateral… hmmm). As the deepest abdominal muscle, it is commonly referred to as a back muscle.
The quadratus lumborum muscles originate from the top of the pelvis and connect to the lowest rib. Those two connection points make it very important for stabilization of the spine and supporting good posture. Contraction of one of the QL muscles causes lateral flexion of the lumbar spine (bending to one side), elevation of the pelvis (lifting of a hip), or both. Contraction of both sides causes extension of the lumbar spine (arching the back).
The QL is one of the muscles that tends to be tight and overactive in many individuals (I can personally attest to this). In our current sedentary and seated lifestyle, the QL is constantly contracted which can cause lower back pain. There are many stretches that can help QL pain, both seated and standing. Give the ol’ Google machine a go if you are interested in those. If you are looking to work your QL muscles, try out some hip hikes (either hanging or one foot on a box) and single arm farmer carries.