Yoga Anatomy

Yoga and the Spine 31

Weight-bearing activities in general, as well as axial rotation (twisting movements),
produce symmetrical (axial) compressive forces that flatten the nucleus into the annulus,
which pushes back, resulting in a decompressive reaction (see figure 2.21). If the compres-
sive force is high enough, rather than rupture, the nucleus loses some of its moisture to the
porous bone of the vertebral body. When the weight is taken off the spine, the hydrophilic
nucleus draws the water back in, and the disc returns to its original thickness. That is why
humans are a bit taller right after getting out of bed.

E5267/Kaminoff/fig2.21/417596/alw/pulled-r1

Vertebral body

Articular process

Transverse process

Spinous process

Pedicle

Lamina

Intervertebral disc

Facet joint

E5267/Kaminoff/fig2.22/417597/alw/pulled-r1

Figure 2.20 Common elements of a vertebra’s structure.

Figure 2.21 (a) Weight-bearing forces as well as (b) twisting produce symmetrical compression
(flattening) of the nucleus, which, under pressure from the annulus, returns to its spherical shape,
thus decompressing the vertebrae.

a b