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The vertebral column, or spine, is a complex structure of bones, muscles, tendons, ligaments, and nerves that supports the body's weight and facilitates movement. The muscles of the vertebral column can be categorized into three groups: intrinsic or deep muscles, superficial muscles, and intermediate muscles. While the superficial and intermediate muscles aid in shoulder, neck, and thoracic cage movements, the intrinsic muscles are considered the true back muscles as they fuse with the vertebral column. The deep muscles, such as the quadratus lumborum and multifidus muscles, play a crucial role in rotating and extending the vertebral column. These muscles contract individually or together to produce either rotational or extensional movements in the spine.
| Characteristics | Values |
|---|---|
| Muscle Group | Erector Spinae |
| Sub-groups | Superficial, Deep |
| Superficial Sub-groups | Spinalis, Longissimus, Iliocostalis |
| Deep Sub-groups | Quadratus Lumborum, Multifidus |
| Muscle Type | Paired |
| Function | Extension and Rotation of Vertebral Column |
| Muscle Group | Transversospinalis |
| Sub-groups | Semispinalis, Rotatores, Multifidus |
| Muscle Type | Individual and Paired |
| Function | Rotation of Vertebral Column |
| Muscle | Latissimus Dorsi |
| Function | Extension, Adduction, Internal Rotation of Upper Arm |
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What You'll Learn
Multifidus muscles
The multifidus muscle is a series of long, narrow muscles located on either side of the spinal column. They are the thickest muscles in the transversospinal group and are shorter than semispinalis but longer than rotatores. They are also the deepest layer of the three layers of muscles in the back, known as the deep layer, which is tasked with the movement of the spine.
The multifidus muscle works together with the transversus abdominis muscle of the stomach and the pelvic floor muscles of the pelvis to stabilise the lumbar spine while standing or moving. The main function of the multifidus muscle is to stabilise the lumbar spine, but it also helps extend the lower spine whenever reaching or stretching. The multifidus muscle is the innermost layer of three layers of muscles of the back, known as the deep layer. The deep layer is tasked with the movement of the spine.
The multifidus muscle helps ensure spinal strength because it has more attachment points to the spine than either the intrinsic or superficial layers. This reduces spinal flexibility and rotation but increases strength and stability. At the same time, the multifidus muscle "co-contracts" with the transversus abdominis, providing stability around the entire torso, including the abdomen and lower back.
The multifidus muscle is a group of short, triangular muscles that, along with the semispinalis and rotatores, comprise the transversospinal group of deep back muscles. Each multifidus muscle bridges over three to six vertebral levels, spanning between the transverse and spinous processes of certain cervical, thoracic, and lumbar vertebrae. Although small, multifidus muscles aid several movements of the vertebral column. When contracting bilaterally, they extend the spine, while unilateral contraction aids lateral flexion of the spine to the same side and rotation of the spine to the opposite side.
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Erector spinae muscles
The erector spinae muscles are a group of muscles in the lower back that help the body maintain good posture. They are one of the core and paraspinal muscles, and are large and superficial, lying just deep to the thoracolumbar fascia. The erector spinae muscles are innervated by spinal nerves, and they cause extension of the vertebral column, resulting in erect posture.
The erector spinae muscles are divided into two layers: the superficial erector spinae and the deep erector spinae muscles. The superficial erector spinae include the spinalis, longissimus, and iliocostalis groups of muscles. These muscles extend the neck and the vertebral column, while some will even move the ribs. The spinalis group is the most medial of the three, and includes muscles that originate on vertebrae and insert on more superior vertebrae. The longissimus group of muscles helps to extend the neck and vertebral column, and are the thickest and longest muscles of the erector spinae. The iliocostalis group is the most lateral part of the erector spinae muscles and attaches to the ribs.
The deep erector spinae muscles include the quadratus lumborum and multifidus muscles. These muscles are located under the superficial muscles and are responsible for similar actions: extension and rotation of the vertebral column. The quadratus lumborum originates on the ilium and inserts on the last rib and lumbar vertebrae. The multifidus muscles originate on the sacrum and vertebrae and insert on more superior vertebrae.
The erector spinae muscles play an important role in spinal stability and can be a common cause of low back pain. In individuals with low back pain, the erector spinae flexion-relaxation phenomenon is absent. Lumbar stabilization exercises can help to restore this flexion-relaxation phenomenon and decrease low back pain.
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Transversospinalis muscles
The transversospinalis muscle group is a deep group of back muscles that lie deep to the Erector Spinae. It consists of three major subgroups: semispinalis, multifidus, and rotatores. These muscles are small and have a poor mechanical advantage for contributing to motion.
The semispinalis is the most superficial of the transversospinalis muscle group. It has the longest fascicles, spanning six segments. Its attachment sites are the thoracic vertebrae (semispinalis thoracis), cervical vertebrae (semispinalis cervicis), and occipital bone at the base of the skull (semispinalis capitis). The semispinalis capitis muscle is supplied by the descending branch of the greater occipital nerve (C2) and the C3 spinal nerve.
The multifidus muscle lies deep to the semispinalis and spans the entire length of the vertebral column. It is most developed in the lumbar region. The multifidus muscle extends from the cervical to the sacral levels, covering the laminae of the underlying vertebrae. It originates on the sacrum and vertebrae and inserts into more superior vertebrae. The multifidus and semispinalis muscle groups have been identified as rotators by some texts, but this action has been refuted by others.
The rotatores muscle lies deep to the multifidus and spans the entire length of the vertebral column. It is most developed in the thoracic region. It consists of two parts: the long (longus) and short (brevis) rotatores. The rotatores are the deepest muscles in the transversospinalis group and have the shortest fascicles, spanning one to two segments. The rotatores are identified as rotators in many texts, but this action has not been validated, and they are more likely stabilizers of the spinal column.
The transversospinalis muscle group functions in spinal stability, proprioception, and posture, stabilizing the vertebral column. Bilateral contraction of the transversospinalis muscles extends the spine, while unilateral contraction rotates the spine to the opposite side.
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Latissimus dorsi
The latissimus dorsi muscle is the widest muscle in the human body. It is a large, flat muscle that covers almost all back muscles at the posterior trunk, except the trapezius. The muscle is also referred to as "the lats muscle" or simply "the lats", especially among bodybuilders.
The latissimus dorsi muscle is found superficially in the lower two-thirds of the trunk, covering the serratus posterior muscles. It is a thin muscle that is partly covered by the trapezius on the back near the midline. The latissimus dorsi is supplied predominantly by the thoracodorsal artery, a continuation of the subscapular artery, which is a branch of the third part of the axillary artery. The thoracodorsal nerve, a branch of the posterior cord of the brachial plexus, provides innervation to the latissimus dorsi.
The latissimus dorsi has a variety of functions. It is responsible for extension, adduction, transverse extension (also known as horizontal abduction or horizontal extension), flexion from an extended position, and medial internal rotation of the shoulder joint. It also has a synergistic role in extension and lateral flexion of the lumbar spine. The muscle assists in depression of the arm with the teres major and pectoralis major. It adducts, extends, and internally rotates the shoulder. When the arms are in a fixed overhead position, the latissimus dorsi pulls the trunk upward and forward.
The latissimus dorsi muscle is also active during deep inspiration and with forceful respiratory functions such as coughing and sneezing. It assists as a muscle of both forced expiration (anterior fibres) and an accessory muscle of inspiration (posterior fibres). Most latissimus dorsi exercises concurrently recruit the teres major, posterior fibres of the deltoid, and long head of the triceps brachii, among numerous other stabilizing muscles.
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Rhomboids
The rhomboids are two bilateral, superficial muscles located in the upper back. They consist of two functionally similar muscles called the rhomboid minor and the rhomboid major. The rhomboid minor is a cylindrical muscle that originates at the ligamentum nuchae and C7 and T1 vertebra. It inserts at the medial border of the scapula near the base of the spine of the scapula. The rhomboid major is a quadrangular muscle located inferior to the rhomboid minor. It originates from the spinous processes of the T2-T5 vertebra and inserts on the medial border of the scapula, just inferior to the rhomboid minor.
The rhomboid muscles extend between the nuchal ligament, spinous processes of the thoracic vertebrae, and scapula. They are innervated by the dorsal scapular nerve, a branch of the brachial plexus. The main action of the rhomboid muscles is scapular retraction around the scapulothoracic joint. This involves the simultaneous sliding of the scapula superiorly and medially along the trunk, rotating the glenoid cavity. Therefore, the rhomboids help to stabilize the scapula into position and reinforce the shoulder.
The rhomboid minor consists of two layers: the dorsal and ventral layers. The dorsal layer attaches dorsolaterally and inferiorly to the levator scapulae, while the ventral layer inserts inferomedially to the levator scapulae. In certain individuals, a thin muscle called the rhomboid occipitalis can be found between the rhomboid minor and the occipital bone.
The rhomboid major is a broad, quadrilateral muscle. It extends obliquely in an inferolateral direction to insert into the medial border of the scapula, between the inferior angle and the root of the spine of the scapula. The attachment occurs on both the dorsal and costal aspects of the medial border of the scapula. The rhomboid muscles overlie the deep (intrinsic) muscles of the back and are covered by the trapezius muscle, except for a small triangular region over the inferior border of the rhomboid major (triangle of ausculation).
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Frequently asked questions
The multifidus muscles and the rotatores muscles are responsible for rotating the vertebral column.
The multifidus muscles originate on the sacrum and vertebrae and insert into more superior vertebrae. They extend and rotate the vertebral column. They also help to stabilise movements and take weight off the vertebral discs.
The rotatores muscles attach superiorly to the vertebrae one to two levels above the inferior attachment.
The erector spinae muscles, serratus posterior inferior, latissimus dorsi, and rhomboids muscles also help with vertebral column rotation.
Some exercises to strengthen these muscles include chin-ups, deadlifts, and yoga poses such as Cat-Cow and Downward Facing Dog.
