Use this quick guide to understand the 3 major muscle groups in the lower back that support posture, stability, and spinal movement. Learn how the erector spinae, multifidus, and quadratus lumborum work together—and how tight or weak lower back muscles can lead to pain or injury. Whether you're dealing with chronic back pain, starting a core strengthening routine, or want to avoid future issues, this video breaks it down simply. | Spine-health