The Rotators - CYBEX VR2 Owner's And Service Manual

The Rotators

• Reverse Action Spinal Rotation - Spinal rota-
tion is defined by the movement of the upper
torso upon a stabilized pelvis. The Torso
Rotation machine works in biomechanical
reverse action defined by the lower torso/pelvis
moving beneath the stabilized upper torso.
Although the same muscles will be working in
their respective roles as prime movers, the
orientation is different. Therefore, the internal
obliques and erector spinae which are responsi-
ble for spinal rotation to the same side respec-
tively, perform pelvic rotation to the opposite
side. The external obliques and rotators/multi-
fidus are responsible for spinal rotation to the
opposite side respectively, or pelvic rotation to
the same side. Another way to view the
muscular action is relative to the motion itself.
Pelvic rotation to the right is performed by the left internal oblique, left erector spinae,
right external oblique, and right rotator/multifidus group. Pelvic rotation to the left is per
formed by the right internal oblique, right erector spinae, left external oblique, and left
rotar/multifidus group.
• Range of Motion - Measurement of spinal motion is subject to considerable variation.
Unless a restriction occurs or is prescribed, strict thoraco-lumber rotation is generally con-
sidered to be 30 to 40 degrees to each side. However, range of motion for resistance exer-
cise should be limited to the user's ability to control the muscular contraction concentrically
and eccentrically.
• Important - It is often suggested that rotation of the spine creates one of the most traumatic
forces on the intervertebral disk, torsion. In their textbook Joint Structure and Function,
Norkin and Levangie state, "It has been suggested that the annulus fibrosis [of the interver-
tebral disk] may be the most effective structure in the lumbar region for resisting torsion.
However, the risk of rupture of the disk fibers is increased when torsion, heavy axial com-
pression, and bending are combined." Preventing unnecessary rotation in daily life is
advised, however; strong spinal muscles provide support for the spine and its components.
Increased strength and control of these muscles may be one of the best ways to prevent
spinal problems and eliminate some of the risk associated with situations that demand
spinal rotation such as sports and work related activities. To make this exercise as safe and
effective as possible always maintain proper spinal alignment as well as slow controlled
motions.
Exercise
Page 3-74
CYBEX VR2 Owner's Manual
MUSCLES TRAINED