Dance Anatomy & Kinesiology

The Spine 89

FIGURE 3.19 The deep posterior spinal muscles

(posterior view).

dus (L. divided into many clefts or segments) between

transverse and spinous processes. All of these muscles

share the common action of spinal extension when

both sides contract. In addition, unilateral contraction

of the intertransversales and multifidus can produce

small amounts of lateral flexion, while the rotatores

and multifidus can produce small amounts of rotation

to the opposite side. However, many of these deep

muscles have poor mechanical advantage and are

believed to be more important for helping stabilize the

spine, and helping to control segmental movement,

rather than producing the large forces associated with

movements of the spine as a whole (Basmajian and

DeLuca, 1985; Donisch and Basmajian, 1972; McGill,

2001; Panjabi et al., 1989). These muscles also have

higher densities of receptors (muscle spindles); these

provide feedback that can be used to detect and moni-

tor precise positions of vertebrae (Moore and Dalley,

1999; Smith, Weiss, and Lehmkuhl, 1996). Due to their

deep location, the deep posterior spinal group cannot

be readily palpated.

Lateral Muscles of the Spine

There is one paired muscle, the quadratus lumborum,

that is located posterolaterally versus anteriorly or

posteriorly. This lateral location gives it the unique

capacity to produce lateral flexion of the spine without

additional movements. The other muscles that can

Attachments and Primary Actions of the Quadratus Lumborum Muscle

Muscle Inferior attachment(s) Superior attachment(s) Primary action(s)

Quadratus lumborum

(kwod-RA-tus lum-BOR-um)

Posterior iliac crest,

iliolumbar ligament

12th rib, tips of transverse

processes L1-4

Fixes or depresses lower rib

Spinal lateral flexion (same)

Stabilizes spine and pelvis

Quadratus Lumborum

The quadratus lumborum (quad, four sided + lumb, lumbar region) is a flat muscle located on either

side of the spine behind the abdominal cavity in the low back area as shown in figure 3.20. Its fibers

run upward from the iliac crest to the lowest rib, with side slips running medially to attach to the top

four lumbar vertebrae. When one side of this muscle contracts it can produce lateral flexion of the

spine to the same side. Posturally, the quadratus lumborum can help depress the last ribs, stabilize

the spine, and keep the pelvis level. This latter function of not allowing one side of the pelvis to drop

relative to the rib cage is very crucial on the swing side during walking gait and on the gesture leg

during upright dance movements.

Palpation: Sitting in a chair with the upper torso hanging forward, place your fingertips below the last

rib and toward the spine (under some of the erector spinae if possible) on the right side. Then, hike

the right hip (bring the right iliac crest toward the ribs). The tension you feel is partly due to contraction

of the quadratus lumborum.

produce lateral flexion are located either anteriorly, and so tend to also cause flexion (the abdominal

muscles), or posteriorly, and so tend to also produce extension (spinal extensors).

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