Pelvic Tilting and the Myth of the Transverse Abdominis

Low back pain remains a primary affliction in the United States. Barring any type of structural abnormality, the pain tends to be mechanical in nature. This can occur with changes in sitting or standing postures due to changes in pelvic tilting (Levine 1996). Deviations from neutral pelvic alignment, regardless of its direction, results in lumbar spine pain (Sung 2013). The majority of patients tend to posture into anterior pelvic tilts that increase the amount of lumbar lordosis (Chaléat-Valayer 2011). This has become a 21st century epidemic due to the amount of time spent sitting, especially at computers. With the prolonged sitting posture, there is shortening of the rectus femoris due to hip flexion. As the rectus femoris shortens, the body must create length somewhere in order for us to stand therefore the anterior pelvic tilt is designed to take tension off the rectus femoris so that we can stand somewhat straight (Kolber 2005). However, for each dysfunction in the body, there is a compensatory reaction. As the pelvis rotates anteriorly, the trunk must follow. Yet, people do not walk around bent over at the hip; the body instinctively arches back (hyperlordosis) in order to keep out eyes straight ahead (Finas 2006).

Fitness professionals such as personal trainers speak of the importance of core stability. Health care practitioners such as physical therapists and chiropractors extoll the importance of maintaining a neutral pelvis. Their solution tends to be strengthening of the transverse abominis (TrA).

The TrA originates encompasses the torso with osseous insertions around the iliac crest, pectin pubis, pubic crest, and xyphoid process (Gray 2000). It has soft tissue insertions along the inguinal ligament and linea alba anteriorly as well as the thoraco-lumbar fascia posteriorly. It derives its name from the direction of its fibers: transverse. Due to this directionality, its described mechanism of action is to compress the abdominal contents (Ota 2012).

The evidence does not support the need for TrA strengthening. The direction of pull of the fibers can pull the anterior ilia medially but not superiorly as needed to correct anterior pelvic tilting. The TrA has been blamed for poor timing that leads to lumbar instability yet many individuals demonstrate similar TrA activation regardless if they present with low back pain or not (Gorbet 2010, Himes 2012). Many patients who do have low back pain actually have a thickening of the TrA (Takashi 2011). This thickening can be associated with increases in strength or a compaction of tissues through shortening. As this occurs, the TrA increases in thickness and strength, it pulls the thoracolumbar fascia laterally (Takashi 2011). This will increase the shearing force on the lumbar spine which can create pain from osseous irritation and compression of the vascular and soft tissues.

The problem with most rehabilitation programs is the focus on strengthening the TrA. This is typically done via an abdominal draw-in maneuver which compresses the abdominal cavity and will pull the lumbar spine rigid (Ota 2012). However, this is not the change that needs to be made. The pelvis needs to be pulled from an anterior pelvic tilt to a neutral tilt. This requires strengthening of the lower fibers of a different muscle: the rectus abdominis. The rectus abdominis attaches onto the pubis and, if shortening distal to proximal, will pull the pubis superiorly and cause the pelvis to rotate posteriorly (Gray 2000).

While many clinicians will add a posterior pelvic tilt to the rehab program, this usually occurs as a progression from the abdominal hollowing. The problem with this approach is that, as the TrA becomes stronger and thicker, it holds the lumbar spine in increased lordosis. This will make it more difficult to stretch the posterior lumbar fascia which is required in order for the pelvis to rotate backwards.

A more appropriate treatment option would include soft tissue release of the thoraco-lumbar fascia, the rectus femoris and TrA. As these tissues relax and lengthen, the rectus femoris will be able to function better in order to create and maintain a neutral pelvis which has been shown to decrease complaints of low back pain (Levine 1996). Progression to a strengthen program should include the rectus femoris (via posterior pelvic tilts, not crunches/sit-ups) and the hip extensors (hamstrings/gluteus maximus).

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