Yoga Anatomy

Muscular joint actions

Spine

Concentric contraction Eccentric contraction

To maintain neutral curves of spine:

Spinal extensors

To maintain neutral spine against pull of

gravity and resist hyperextension of

lumbar spine:

Psoas major (upper fibers), abdominal muscles

Upper limbs

Concentric contraction

To hold scapula on rib cage:

Serratus anterior, rhomboids

To flex shoulder:

Coracobrachialis, anterior deltoid

To extend elbow:

Triceps brachii, anconeus

Lower limbs

Concentric contraction

To flex hip:

Psoas major, iliacus, rectus femoris

To maintain knee extension:

Articularis genu, vastii

To adduct and internally rotate:

Pectineus, gracilis, adductor longus and brevis

Navasana (continued)

Notes

In this pose the challenge is not the position itself so much as its relationship to gravity. If
it were rotated 45 degrees, it would be the work of sitting vertically in dandasana (which
can certainly present its own challenges; see page 130).
Ideally, the weight in this pose is distributed between the sitting bones and the tailbone.
All the weight should not be borne on the sacrum. If dandasana is a challenge because
of shortness in the backs of the legs, that same shortness makes it impossible to support
navasana correctly with the legs straight. In this case, bending the knees so that the spine
can remain neutral is a good option.