A common model of lumbar stability shows the musculature
surrounding the spinal vertebrae forming a cylinder.
The top of the cylinder is the diaphragm, the bottom is the
pelvic floor, and the wall is formed by segmentally attaching
abdominal and posterior spinal musculature, specifically
the transversus abdominus and the segmental fibers
of lumbar multifidus.33 There is growing evidence that
demonstrates how these muscles coordinate their activity
to stabilize the spine. For example, transversus abdominis
has been shown to co-contract with: the diaphragm;34 the
pelvic floor;35 and the deep fibres of lumbar multifidus.36
According to this model, the psoas major is ideally located