Deep abdominals, or the iliac muscles, connect vertebrae of the lower back and pelvis to the upper femur. They are the strongest flexors of the hip.
The iliopsoas also laterally flexes the trunk. These muscles are complex, and their functions can be strongly influenced by the balance of the muscles around them. When the superficial abdominals are shortened, the deep abdominals can help in flexing of the lumbar spine, and create compression in the lumbar discs.
The psoas minor is only present about 25% of the time and is a weak flexor of the hip. It is more interesting for the problems it creates than the function it performs.
These are considered some of the most complicated muscles to understand and address.
Origin – lower vertebrae and ilium
Insertion – pubis and femur
Function – flexion of hip, and lateral flexion of the trunk, weak flexion of the lumbar spine
Tony Preston has a practice in Atlanta, Georgia where he sees clients.
He has written and taught about anatomy, trigger points and cranial therapies since the mid-90s.