Location and Function of Erector Spinae

Question 1

Deep-Longissimus thoracis pars lumborum (5 fascicles)

Answer 1

Location:
One from each lumbar TP to the PSIS

Function:
Ipsilateral lateral flexion
Posterior shear: greatest at lower lumbar levels
Assist with extension but close to axis of rotation; better MA at upper levels

Question 2

Deep-Iliocostalis lumborum pars lumborum (4 fascicles)

Answer 2

Location:
One from each tip of the lumbar TP to the iliac crest

Function:
Ipsilateral lateral flexion
Better rotators, due to greater MA
Posterior shear, especially at lower levels
Assist with extension but close to axis

Question 3

Superficial-Longissimus thoracis pars thoracis (12 fascicles)

Answer 3

Location:
One from each thoracic TP and ribs via the ESA to L3–S3 SP

Function:
Extension of thoracic spine
Extension of lumbar spine via increasing lordosis
Assist with ipsilateral lateral flexion

Question 4

Superficial-Iliocostalis lumborum pars thoracis (7 or 8 fascicles)

Answer 4

Location:
One from each of the lower 7–8 ribs to PSIS and sacrum with contribution to the ESA

Function:
Extension of lumbar spine via increasing lordosis
Assist with ipsilateral lateral flexion