Anatomy of Back Muscles

Back Muscles

• Quadratus lumborum:
  • Active in lateral stability of the lumbar region, acting as a restraint to lateral shear of the vertebrae
  • Weak lateral flexor of the lumbar spine
• Latissimus dorsi:
  • Plays a role in core stability with overhead movement
  • Attaches to the lumbar spinous processes through its integration with the thoracolumbar fascia
  • Active in providing core stabilization with trunk extension and quadruped exercises

Multifidus

• Origin: Sacrum, lumbar, and cervical transverse processes
• Insertion: Spinous processes of all vertebrae
• Actions: Extension of trunk and neck, lateral flexion of trunk and neck, contralateral rotation of trunk and neck
• 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
• Important stabilizer of the back
• People with low-back pain often have wasting of the multifidus muscle on the painful side

Obliques

• External oblique:
  • Attaches proximally on the lower six ribs and runs medially and inferiorly to attach distally to the iliac crest, pubis, and linea alba
  • Fiber orientation allows for flexion, side bending, and rotation of the trunk to the opposite side
  • Works together with the internal oblique to produce rotation of the spine to both sides
• Internal oblique:
  • Attaches proximally on the lower six ribs and runs distally to attach to the iliac crest, iliopsoas fascia, thoracolumbar fascia, and inguinal ligament
  • Primary actions: flexion, side bending, and rotation of the trunk to the same side
  • Works together with the external oblique to produce rotation of the spine to both sides

Transverse Abdominis

• Attaches proximally at the costal cartilage of ribs 6-12 and attaches distally to the iliac crest
• Attaches posteriorly to the thoracolumbar fascia and anteriorly to the abdominal fascia
• Encircles the abdomen, providing stability to the spine
• Can create and increase intra-abdominal pressure, which helps stabilize the spine
• Works together with the obliques to form a loop around the abdomen, stiffening and stabilizing the spine during activity

Quadratus Lumborum

• Attaches proximally to the 12th rib, transverse processes of all lumbar vertebrae, and attaches to the iliac crest and iliolumbar ligament
• Often referred to as the "forgotten" muscle of the core

Special Mention: The Diaphragm

• Simultaneous contraction with the pelvic floor muscles and abdominal muscles increases intra-abdominal pressure, which helps stabilize the spine

Special Mention: Thoracolumbar Fascia (TLF)

• Covers the deep muscles of the back and trunk, including the multifidi
• Important structure that connects the lower limbs (via gluteus maximus) to the upper limbs (via latissimus dorsi)
• Attaches to the internal obliques and transverse abdominis 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
• Allows the core to be included in integrated kinetic chain activities such as throwing