Primary and Secondary Curves
In savasana, the structures that are in full, weight-bearing contact with the floor exhibit the primary curves of the body (see curves page). These include the posterior surfaces of the calceneus, gastrocenemius, hamstrings, gluteus maximus, sacrum, thoracicd spine, scapulae, and occiput.
The structures that are off the floor mirror the secondary curves of the body—specifically, the posterior surfaces of the Achilles tendons, knee joints, lumbar region, and cervical spine.
The point of contact of the arms varies widely from person to person, depending on the unique shape and relationships of the upper-body structures—particularly the elbow joint.
Symmetry
Many people never fully relax in savasana because of an obsession with arranging the body in a perfectly symmetrical shape, which they verify visually, but which conflicts with the body’s kinesthetic (proprioceptive) feedback. In other words, what looks symmetrical is not what feels symmetrical.
Because all human bodies are inherently asymmetrical, a certain amount of surrender to this fact is necessary to achieve a deep state of emotional, as well as physical, relaxation. If you want to fully relax, you need to accept your body as it is, not as you would wish it to be.