levatores costarum interspinales and intertransversarii

In other words, the same motion may not always be produced by the same muscles working together in the same way.

Bakkum, Gregory D.

Cramer Six Layers of Back Muscles First Layer Second Layer Third Layer Fourth Layer Fifth Layer Sixth Layer Other Muscles Directly Associated with the Spine Suboccipital Muscles Intertransversarii Muscles Interspinales Muscles Levator Costarum Muscles Muscles Associated with the Anterior Aspect of the Cervical Vertebrae Iliac Muscles Muscles That Indirectly Influence the Spine Muscles of Respiration Anterolateral Abdominal Muscles Rectus Abdominis Muscle Other Muscles That Have Clinical Relevance to the Back Hamstring Muscles Gluteus Maximus Muscle Piriformis Muscle Rectus Femoris Muscle Summary of Muscles Affecting the Spine Second only to the vertebral column and spinal cord, the muscles of the spine are the most important structures of the back.

A thorough understanding of the back muscles is fundamental to a comprehensive understanding of the spine and its function.

The purpose of this chapter is to discuss the muscles of the back and other muscles that have an indirect influence on the spine.

The intercostal muscles provide an example of the latter category.

These muscles do not actually attach to the spine, but their action can influence the spine by virtue of their attachment to the ribs.

The abdominal wall muscles, diaphragm, hamstrings, and others can be placed into this same category.

These muscles have a less direct yet important influence on the spine.

The musculature of the spine and trunk plays an important role in the normal functioning of the vertebral column.

Beside their obvious ability to create the variety of spinal movements, many of these muscles also help to maintain posture.

In addition, the back and trunk muscles function as shock absorbers, acting to disperse loads applied to the spine.

The shear bulk of these muscles also protects the spine and viscera from outside forces.

Although it is beyond the scope of this text to detail the kinesiology of the muscles influencing the spine, a few generalities are in order.

There is a complicated interplay of many muscles when a motion of the body, especially of the spine, is produced.

Some of the specifics of this complex interplay are only beginning to be understood, especially in asymmetric motions of the trunk (van Dieen, 1996 Danneels et al., 2001; Andersson et al., 2002 ).

Muscles known as prime movers are the most important.

For example, the psoas major and rectus abdominis muscles are prime movers of the spine during flexion of the lumbar spine from a supine position, as in the performance of a sit-up.

The erector spinae muscles are acting as synergists in this instance.

Besides producing motion, muscle contraction also stabilizes the spine by making it stiffer.

This is important not only for posture (Cholewicki et al., 1997; Quint et al., 1998 ), but also for providing a stable base for other motions of the body, such as appendicular motions ( Lorimer Moseley et al., 2002 ).

Muscle coordination seems to be under the control of the central nervous system.

The central nervous system is constantly receiving afferent information from the muscles and other surrounding tissues, such as ligaments and tendons.

On the basis of this information, the central nervous system appears to use reflex pathways to finely control muscle activity.

Some of the details of this process are beginning to be understood (Kang et al., 2002).

Interestingly, the specifics of the interplay of the muscles in producing a motion of the body are not always constant.

Levatores Costarum Interspinales And Intertransversarii