The Quadratus Lumborum (QL) muscle is a deep lower back muscle that lies on both sides of the lumbar spine. The QL muscle is critical in spinal stability and keeping the lower back strong and healthy. The Quadratus Lumborum functions in side bending, and is also active when lifting objects. QL keeps the spine strong and neutral during high impact sports like football, hockey, and also in lesser-stressful sports like tennis, volleyball, and golf.
For more information on what the QL muscle is, check out the articles below:
Quadratus Lumborum Trigger Point Release
3 Quadratus Lumborum Exercises For Bulletproofing The Low Back