Muscle guide · Back
Also called QL, side lower back muscle
The quadratus lumborum is a flat, roughly square muscle deep in the side of the lower back, running from the top of the pelvis to the lowest rib and the low-back vertebrae.
It bends the trunk to the side and helps extend it. How much it stabilises the spine is debated, but it works hard in heavy lifts and side planks.
StatPearls doubts it is a significant stabiliser, noting it produces little force in sideways tilt. A fine-wire EMG study found it working at 74% of maximum in heavy barbell lifts and 54% in a side plank, more than other muscles, and called it a better spinal stabiliser than the psoas.
The side plank and heavy lifts were where it worked hardest in the fine-wire EMG study.
A side bend stretches the side you lean away from. NHS low-back leaflets use it; no study has tested it as a QL stretch.
Trigger points in the QL can produce pain that mimics other low-back problems, and nerves running near it can be irritated. There is no agreement that a change in its tone is a primary cause of back pain.
Source 1
Each grade rates the evidence for the correction.
There is no consensus that altered QL tone is a primary cause of back pain. It is one possible contributor, not the usual culprit.
Source 1
It bends the trunk to the side and helps arch the low back. It works hard in heavy lifts and side planks.
The side plank, which loaded it to about half of its maximum in a fine-wire EMG study.
Trigger points in it can mimic other low-back pain, but there is no agreement that QL tightness is a primary cause.
Anatomy and movement education, not a diagnosis or treatment plan. If you have pain that follows an injury, is severe or getting worse, or comes with numbness, weakness or swelling, get it assessed. Health disclaimer.
