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PART II THE VERTEBRAL COLUMN


of the central nervous system and is the region where the peripheral nervous system enters and exits the central nervous system.


The bony and connective tissue structures of the spine have regional differences that are related to the function and purpose of that region. Orientation of the joints, the size and location of the ligaments, and the structure and function of the muscles each play a role in these regional differences. In the cervical spine, the range of motion allows the neck to fl ex, orienting the eyes toward the ground, or to extend, moving the eyes in a direction to view the sky without the need to move more than the cervical spine. The head can turn from side to side to allow the eyes to see or the ears to hear in different directions. In the thoracolumbar spine, there is a large degree of fl exion so that a person can lean forward to pick something up off of the ground or turn the trunk to look behind the body without moving the feet. Specifi c muscles in the spinal region function as deep stabilizers to support the spine during vigorous whole- body and extremity movement. Other muscles act as superfi cial primary movers that extend, fl ex, or rotate the spine to allow spinal movement. Because of the dif- ferences in function of the various trunk muscles, exercise programs must be designed to target the correct muscle groups. For example, people with spinal instability cannot increase stability by performing only traditional sit-up


Kinesiology in Action Case Study M 1.


arie is a 72-year-old woman with spinal osteoporosis. Because of her decreased bone


density, spinal vertebrae are collapsed and wedge- shaped, most notably in the thoracic spine. These bony changes result in a marked increase in her thoracic kyphosis. Consider the following questions as they relate to this increased thoracic kyphotic curve. Place your own thoracic spine in an increased thoracic kyphotic position to help you answer the questions.


With increased thoracic kyphosis, what is the resul- tant position of the head and neck?


2. What internal thoracic cavity organs experience more constriction because of the increased thoracic kyphosis?


3. What secondary complications could arise as a result of constriction of these internal organs?


4. What spinal muscles are most likely weak because of the increased kyphosis?


5. Which muscles are most likely tight and need to be stretched?


exercises, which focus on trunk primary movers rather than trunk stabilizers.


Spinal and pelvic movements are interrelated, and movement of one infl uences the position and movement of the other. An increased anterior pelvic tilt increases lumbar extension and can increase the shear stresses at the L5-S1 level. Conversely, a posterior pelvic tilt fl exes the spine and can alter the position of discal mate- rial causing irritation and pressure to peripheral nerve roots.


DISCUSSION QUESTIONS


1. Identify the bony landmarks on typical vertebrae for each region of the spine.


2. Describe how the atlas moves on the axis during cervical rotation.


3. Discuss how the intervertebral discs influence the magnitude and direction of movement in the spine. What happens to discal material during spine flexion? Extension?


4. How might disc degeneration (loss of fluid content and elasticity) influence the facet joints, intervertebral foramen, distance between the spinous processes, and movement in the spine?


5. Describe the location and orientation of the facet joints in each region of the spine, and explain how their orientation affects movement in the region.


6. Identify the spinal ligaments associated with each region of the spine.


7. Discuss the concept of coupled motion in the spine and give an example.


8. How does excessive thoracic kyphosis influence the position of the cervical spine and head?


9. Explain the concepts of sacral nutation and counternutation and how they relate to anterior and posterior pelvic tilt.


10. What muscles contract anteriorly and posteriorly tilt the pelvis? How is the lumbar spine position changed during each movement?


11. Perform an extreme posterior and anterior tilt. At the end of each range of motion, which structures do you feel are being compressed and which may be overlengthened? What did you learn in Chapter 3 about overlength of a muscle and its strength?


12. If a muscle can be stretched by moving it in the opposite direction of its action, how would you stretch the sternocleidomastoid muscle?


13. Name the primary movers for thoracolumbar flexion, extension, and rotation.


14. What muscles act as spine stabilizers?


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