The abdominals form the front & sides of the trunks of our bodies & help to support & stabilize the spine. They are comprised of three layers. Most superficially is the external oblique. The internal oblique is just beneath it. Next is the transverse abdominis, a muscle crucial to our understanding of uddiyana bandha. Together, these muscles join at the front along with the rectus abdominis, commonly referred to as the “six pack”. The abdominals attach to the bottom of the rib cage & wrap around to the transverse processes of the lumbar spine.
In concentric contraction, all three layers help to flex the spine (as the ribs draw nearer to the pubic bone). In eccentric contraction, they help to resist extension of the spine (as the ribs draw further from the pubic bone). The obliques, located on both sides, also assist in lateral flexion (as the ribs draw sideways towards the pelvis), & aid in rotational movement of the spine.
When engaged, the lower abdominals help us to create a posterior pelvic tilt, or more neutral pelvic position, as is often instructed in our yoga practice to “tuck our tailbone”. We engage the entirety of our abdominals in plank pose as we stabilize the pelvis with our core muscles to avoid our bottom from sagging towards the floor.