This paper examines the anatomical and biomechanical foundations of spinal movement in dance. It analyzes how gravity shapes three primary spinal movements—forward flexion, extension, and lateral flexion—by detailing the specific muscle groups and contraction types involved in each. The paper then addresses injury risk in common dance styles, particularly during movements that require lifting from supine or contracted positions, and concludes with evidence-based safety protocols for partnered dancing, emphasizing proper alignment, positioning, and muscular co-contraction to protect the lumbar spine.
Gravity plays a crucial role in muscle and spinal movements. It holds the spine in its precarious position when one is standing upright, and will also make it fall in the desired direction whenever there is movement. Understanding how gravity influences the spine across different planes of motion is fundamental to safe and effective dancing. The role of gravity in three common movements—forward flexion, extension, and lateral flexion—reveals how dancers must recruit specific muscle groups to control and stabilize the spine throughout their range of motion.
Spinal flexion occurs when the sagittal plane is bent forward, bringing together the anterior surfaces of the trunk and the vertebrae. A perfect example of forward flexion is when someone places one hand on the abdomen and the other on the lumbar spine, then rolls down slowly toward the floor. During this movement, dancers experience tension in multiple muscle groups working in concert.
The tension felt in the muscles during forward flexion is a direct action of gravity. The pelvis tilts against the force of gravity acting on the spine, and this causes the left and right external obliques and the rectus abdominis to all work together against the action of gravity to control the spinal flexion. As the movement progresses, the transverse abdominis pulls the wall of the abdomen inward. The tension results from the opposing action of all these forces working in coordination. This synergistic muscle activation demonstrates how the core musculature must eccentrically contract to decelerate and control the forward bending motion induced by gravity.
Spinal extension is the process by which the sagittal plane returns to a position of backward bending from a position of flexion. This movement requires active muscular engagement to reverse the gravitational pull. Concentrically, the spinal movement is against gravitational action. Since the force of gravity is considerably strong, the spinal extensors as well as the deep posterior and the semispinalis muscle groups move in to facilitate extension by acting against gravity.
These muscle groups work in different ways. The spinal extensors, particularly the erector spinae, provide the force necessary to drive the full extension of the spine. In contrast, the deep posterior group acts by adjusting inter-vertebral motion, thereby stabilizing the spine. The spinal extensors work concentrically in seeking to restore the torso back to a vertical position after a spinal flexion. In cases, however, where there is a hyperextension of the spine, the spinal extensors will work eccentrically (in the same direction as gravity) to restore the torso back to a vertical position, preventing excessive backward arching that could stress the lumbar segments.
Spinal lateral flexion occurs when the frontal plane is moved to the side. It can either be left lateral flexion or right lateral flexion, depending on the direction to which the upper spine bends relative to the lower part. Left lateral flexion occurs when the surfaces on the left side of the vertebrae are approximated, and vice versa. Conversely, left lateral flexion can be said to occur when the spine is returned to anatomical position from a position of right lateral flexion.
Lateral flexion demonstrates a clear distinction between the downward and upward phases of movement, each requiring different muscular strategies. In the down phase of the spinal lateral flexion, the lateral flexors work eccentrically (in the same direction as gravity). Using the example of a right lateral flexion to illustrate this action, the right lateral flexors initiate the bending of the torso to the right. Once the spine is off-center, the left lateral flexors will work together with gravity to control the movement. The specific flexor movements will depend on the positioning of the trunk during the movement. The left internal and external obliques would be particularly important in controlling spinal movement in this case. The spinal extensors have a less pronounced role in the downward phase of the movement; however, they play a greater role in the upward phase.
On the upward phase, the lateral flexors (the erector spinae, the oblique abdominal muscles, and the quadratus lumborum) work concentrically with iliopsoas, the rectus abdominis, the deep posterior spinal extensors, and the semispinalis to restore the spine to its anatomical position. Like is the case in the downward phase, the action of specific muscles is influenced by the positioning of the trunk, as well as the strength of external resistance. In a case where the lateral flexion is accompanied by movements in the torso, the oblique muscles will work together with the rectus to control movement; however, in the case of a pure lateral flexion, the former play a more prominent role and the role of the latter is negligible.
Most dance styles pose a substantial risk of injury to the lower back. The modern and jazz dancing styles, for instance, both of which involve rising from a contraction or a supine position, could result in injury to the lumbar back. Understanding the injury mechanism helps dancers and instructors implement effective prevention strategies.
During a typical contraction-to-lift movement, the dancer first lifts the head, in which case the rectus abdominis is the only one producing spinal flexion. Then the dancer lifts the shoulders, at which point the left and right external and internal obliques join in to pull the abdominal wall inward. The spinal extensors then co-contract slightly to bring about the desired lift. However, if these do not produce sufficient force to balance the action of gravity, perhaps because the dancer does not co-contract the abdominals effectively, there is the risk of the lower back collapsing too far forward and resulting in injury. The lumbar spine becomes vulnerable when the stabilizing muscles fail to provide adequate support against gravitational load.
To avoid this, dancers are often advised to facilitate the co-contraction of abdominals by maintaining the shoulders and the head as close as possible to the lower body. This positioning reduces the moment arm of the gravitational force and makes it easier for the core musculature to maintain spinal stability throughout the movement.
"Four protective strategies for partnered dance safety"
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