110 Dance Anatomy and Kinesiology
or a mechanism of injury, it can be helpful to use the
term “hyperextension.”
The classic concentric use of the spinal extensors
occurs when the spine extends or hyperextends
against gravity or another external resistance such
as in the prone single-arm spine arch (table 3.4I
[p. 138]). The erector spinae muscles have been
shown to be particularly active during prone exten-
sion, with greatest activity in the spinalis, followed by
the longissimus, and with the least in the iliocostalis
(Basmajian and DeLuca, 1985). The semispinalis and
deep posterior spinal group are also active to some
degree during prone extension. The latter muscle
group is believed to primarily act to help stabilize the
spine and adjust motion between individual vertebrae,
while the erector spinae provides the primary force
for full spine extension.
The spinal extensors are also commonly used
concentrically to bring the torso back up toward a
vertical position from a position of forward flexion.
In dance this use of the extensors is common, such
as when the torso is brought from a flexed positionto a vertical or a flat back position in port de bras or
center floor warm-ups in modern and jazz dance. The
spinal extensors also work very hard to prevent the
torso from tilting too far forward and to attempt to
maintain a more upright position of the torso when a
leg is lifted to the back in an arabesque, back attitude
(figure 3.33), or leap.Spinal Lateral Flexion
Spinal lateral flexion is side-bending in the frontal
plane and is termed either right lateral flexion or
left lateral flexion. Spinal lateral flexion is named in
accordance with the way the side of the upper spine
bends with reference to the lower part. So, approxi-
mation of the right sides of the vertebrae such as
when bending the torso to your right during standing
would be termed right lateral flexion. Conversely,
approximation of the lateral surfaces of the vertebrae
to the left would be termed left lateral flexion. To
be consistent with the custom of using a term that
describes the direction of the motion, the return toThe Role of Gravity in Standing Movements of the Spine
Perform the following movements from a standing position with your feet parallel and about hip-width
apart, using figure 3.11 as a reference.- Gravity and forward flexion. Place one hand with the palm on the side of the lumbar spine.
Place the other hand on your abdomen. Then, slowly roll down (as if you were going to touch the floor)
about halfway. Think about the effect gravity would have during this movement. Explain why you are
feeling the muscle contraction you are feeling, and how the abdominal and spinal extensors would
operate in this movement. - Gravity and spinal extension. Keeping your hands placed as before, slowly come back up from
this position of forward flexion to a vertical position of the spine. What muscles do you feel working?
Again, explain the role of the abdominal and spinal extensors in this movement and whether eccentric,
concentric, or both types of contractions would be involved. Now, let your torso carefully arch slightly
beyond vertical (hyperextension). Explain the influence of gravity with this movement and how it would
affect muscle use. - Gravity and spinal lateral flexion. With your hands hanging by your sides, slowly bend the torso
to the side. Again, think about the influence of gravity and try to feel and explain what muscles are
working on both the down-phase and up-phase of the movement. Include the quadratus lumborum,
as well as the abdominal muscles and spinal extensors. Now vary the position of your torso slightly
as you bend to the side (torso slightly forward of and then back of a directly side position). How does
this influence muscle use? - Gravity and spinal rotation. Lastly, with your hands hanging by your sides, rotate your torso to one
side. How is the influence of gravity different in this motion than in the previous motions? How will this
influence the contribution and contraction type of the abdominal muscles and spinal extensors?