The lower spine is inherently unstable and has to rely on its surrounding muscle groups known as the core for support. The muscles that form the Core are the smaller spinal muscles and those of the trunk and pelvic girdle. In short, everything except the ribs and hips.
Core strengthening focuses on training the body to use these muscle groups while carrying out any activity. When the Core muscles are functioning correctly, movements become more precise, stable and safe.
Back pain sufferers, in particular, often find that training and strengthening the Core, even at a basic level, can greatly reduce pain and improve their overall condition.