Muscle · Lumbar spine

Multifidus

Musculus multifidus

A stack of short, deep muscles buried in the groove either side of the spine, each one bridging only two to four vertebrae before handing over to the next. Because the fascicles are so short they are poor at producing movement and excellent at controlling it: multifidus stiffens one segment at a time, keeping individual vertebrae from shearing or twisting while the long muscles do the moving. It is thickest and most powerful in the lower back. Clinically it is the muscle the Momentum system calls inhibited rather than tight — it tends to stop firing rather than clamp down, and pressure does not fix a muscle that has gone quiet.