Anatomy of Back Muscles

Back Muscles

• The quadratus lumborum is active in lateral stability of the lumbar region and acts as a restraint to lateral shear of the vertebrae.
• It is also a weak lateral flexor of the lumbar spine.

Latissimus Dorsi

• Plays a role in core stability with overhead movement.
• Has attachments to the lumbar spinous processes through its integration with the thoracolumbar fascia.
• Active in providing core stabilization with trunk extension and quadruped exercises.

Multifidus

• Originates from sacrum, lumbar, and cervical transverse processes.
• Inserts into spinous processes of all vertebrae.
• Actions: extension of trunk and neck, lateral flexion of trunk and neck, contralateral rotation of trunk and neck.
• A deep muscle located along the back of the spine, close to the midline.
• Functions together with transverse abdominis and pelvic floor muscles to stabilize the low back and pelvis before movement of the arms and/or legs occurs.
• Important stabilizer of the back.
• Studies have shown that people with low-back pain also had wasting of the multifidus muscle on the side of the back that matched the painful side.

Integrated Function of Multifidus

• Assists in eccentric deceleration of trunk flexion.
• Assists in eccentric deceleration of trunk rotation.
• Assists in dynamic stabilization of the lumbar spine.
• Provides proprioception (awareness or sense of where the body is in space) during dynamic movements which enhance neuromuscular efficiency.

Erector Spinae

• Makes the spine erect.
• Divided into three longitudinal columns: iliocostalis, longissimus, and spinalis.
• Actions: extension of trunk, neck, and head, lateral flexion of trunk, neck, and head, rotation of trunk, neck, and head, anterior tilt of pelvis.

The Core Musculature

• Divided into two stabilization categories: local stabilization system and global stabilization system.
• Local stabilization system includes: transversus abdominis, lumbar multifidus, pelvic floor muscles, and diaphragm.
• Global stabilization system includes: quadratus lumborum, psoas major, external oblique, portions of internal oblique, rectus abdominis, and adductor complex.

Normal Movement Production

• Simultaneous contraction of the diaphragm, the pelvic floor muscles, and the abdominal muscles.
• Increase intra-abdominal pressure (IAP).
• Decrease the load on the spine muscles.
• More rigid cylinder for trunk support.

Special Mention: Thoracolumbar Fascia (TLF)

• Covers the deep muscles of the back and trunk, including the multifidi.
• Connects the lower limbs (via gluteus maximus) to the upper limbs (via latissimus dorsi).
• Attached to the internal obliques and transverse abdominus muscles, providing 3D support to the lumbar spine and aiding core stability.
• Helps to form a “hoop” around the abdomen, creating a stabilizing corset effect.

Abdominal Muscles

• Rectus abdominis attaches proximally at ribs 5-7 and xiphoid process and runs distally to attach at the pubic rami and ligaments of the pubic symphysis.
• The rectus is a paired sectioned muscle, sectioned by intramuscular tendons.
• The rectus is primarily responsible for flexion of the lumbar spine.