Please Don't Tuck Your Tail
We are the only mammals to walk only on two feet. We are essentially upright beings, in theory, if not so much in practice these days. Our spine has evolved specific characteristics to be able to support this posture and it's integral that we understand them if we are going to maintain strong, healthy bones and tissues throughout our long lifetimes. The characteristics I would like to discuss here are the vacillating curves of the spine, forward and back that add stability and strength to this insanely mobile complex of joints. It is because of these curves that we can stand upright in gravity. When the curves break down, dysfunction ensues immediately... Even if we can't feel it right away, damage is occurring. My focus here is on the low back (Lumbar) curve. We have received a lot of, frankly, bad information over the years regarding healthy alignment of the low back. Unfortunately, much of this has been offered in our yoga classes. There is a pervasive idea that to decompress the tissues of the low back we must "lengthen" it out, usually by dropping, tucking or descending the tail. This cue in practice goes directly against all of the biomechanical principles contained in the dynamic engineering that is the lumbar curve.
The anatomical term Lordosis refers to a curve in the spine which bends in toward the body, and is opposite of the Kyphosis, a curve that bends out away from the body, like in the ribcage and sacrum. When you look closely at the lumbar lordosis, you can see that the bodies of the vertebrae are shaped to build this curve, that the disks are shaped to fit this curve and that the foramen (spaces between the vertebrae where the nerve roots emerge) are shaped to accommodate this curve. To eliminate or reduce this curve in order "decompress" the low back is acting on false logic. We are built to inhabit this curve as full-time as possible. To eliminate it causes compression in the front of the disks and expansion at the back of the disk, risking a weakening, bulging or rupture at the place most likely to affect the spinal cord and nerves. To flatten it out causes undo stress on the tiny muscles of support (Rotatores and Multifidi), as well as the Erector Spinae Group, Quadratus Lumborum and the ligaments that hold the bones in place. This stress leads to weakening and strain, and eventual loss of function.
I believe in the engineering of the body from the bones out. The shape of the bones defines the way any joint moves. What I see when I look at the bones of the spine is this wisdom: Curves are more stable than straight lines. Curves absorb and distribute force more efficiently than straight lines. Look at nearly any bridge and you'll see arches, curves over and under our roadways because a flat surface doesn't support itself. This curve is integral to our weight bearing spine standing the test of time and gravity.
Most teachers are not taught about this curve, it's engineering or function. What we're taught is that the lumbar/sacral spine must be decompressed to prevent pinching nerves. We are taught that a "neutral" pelvic alignment lifts the points at the front of the pelvis (the ASIS's), lifts the pubic bone and drops the tail. While all this sounds good in theory, it doesn't align with our anatomy or biomechanics at all. These actions diminish the lumbar curve and create a system primed for instability and weakness. In fact, a biomechanically neutral pelvis looks nothing like what is described above.
Let's discuss the whole pelvis business for a moment. This is important because it is the pelvis that most of us are taught to look at for our visual cues for good alignment, and most of us have been offered a flawed blueprint. First off, the male pelvis and female pelvis are shaped VERY differently.