Before I get started with the purpose of this post, which I’ve tried to state succinctly in the title, I’d like to provide a few points about what this post is not.
- It’s not about low back pain
- It’s not about the purpose of the transverse abdominis
- It’s not about how the abdominal drawing in (abdominal hollowing) maneuver affects the transverse abdominis directly
- It’s definitely not about the pelvic floor
With all that being said, I don’t think isolating the transverse abdominis is particularly useful for general orthopedic health or any form of sport/functional preparation. Additionally, I do not think core strengthening is that important in the treatment of low back pain.
I’m sure I’ll still get comments discussing claims that I’m not trying to make but those above few lines serve as my due diligence to prevent that.
In the physical therapy and strength and conditioning worlds, we discuss intra-abdominal pressure a lot. And I believe that’s a good thing. Increasing intra-abdominal pressure can be useful in transmitting forces through the extremities, minimizing excessive lumbar movement during compound exercises, and creating an overall state of proximal stability.
Because the transversus abdominis is the deepest abdominal muscle, has a closer connection with the innermost fascia and the spine itself, and was emphasized by a lot by research in the 90’s, it is often thought of as a prime stabilizer of the lumbar spine.
Without looking at any specific research, and simply reflecting back on basic anatomy, it seems strange to think than a very thin muscle could have such a large role. The the lumbar spine is surrounded by multiple layers of muscle, ligaments, fascia and is stabilized by bony congruency and the intervertebral disks. The lumbar spine is not a loose, unstable structure that inherently needs discrete muscle activation to be stable.
When lifting heavy weights or participating in sports that require rapid direction changes and high velocity (not picking up a penny or doing a bridge), improving lumbar stability may be useful.
One way we can reinforce the stability, and relative stiffness (a term I originally learned from Eric Cressey), that the lumbar spine already possesses is by seeking to improve intra-abdominal pressure. Intra-abdominal pressure has been shown to increase stiffness of the lumbar spine (Hodges, 2005)
An exercise often utilized to increase intra-abdominal pressure, and therefore stability of the lumbar spine, is the abdominal drawing-in (or abdominal hollowing) maneuver. This exercise has gotten a lot of attention due to being associated with deeper muscle activation of the transverse abdominis.
But isolating one abdominal muscle is not advantageous when seeking to achieve higher levels of stability (or ever; but that’s a topic for another post). In fact, in a study of 7 healthy male subjects, intra-abdominal pressure was over 11 times higher when performing abdominal bracing opposed to abdominal hollowing (116.4 mmHg and 9.9 mmHg respectively). The standard deviation of pressure, for the abdominal bracing exercise, was even greater than the entire pressure from abdominal hollowing (Tayashiki, 2015).
Additionally, in a study of 11 healthy males, abdominal bracing was better able to facilitate lumbar muscle co-contraction and minimize lumbar spine displacement, compared to abdominal hollowing, against rapidly applied perturbations (Vera-Garcia, 2007).
To summarize, based on anatomical plausibility, current research on evaluating changes in intra-abdominal pressure, and lumbar spine muscle co-contraction/lumbar spine displacement against perturbations, abdominal bracing is superior to abdominal hollowing.
- The lumbar spine is not a floppy structure in need our conscious efforts to remain stable; especially during daily activities
- When lifting very heavy objects, or participating in rapid movements, increasing general lumbar stiffness through increasing intra-abdominal pressure may be useful
- Abdominal hollowing (drawing-in) is not good at increasing intra-abdominal pressure. Please don’t tell someone to draw their belly button in before performing a heavy squat (I saw this recently)
- Please don’t make people afraid to move due to making them believe a small thin muscle and/or specific maneuver is going to stabilize their spine
Hodges, P. W., Eriksson, A. M., Shirley, D., & Gandevia, S. C. (2005). Intra-abdominal pressure increases stiffness of the lumbar spine. Journal of biomechanics, 38(9), 1873-1880.
Tayashiki, K., Takai, Y., Maeo, S., & Kanehisa, H. (2016). Intra-abdominal pressure and trunk muscular activities during abdominal bracing and hollowing. International journal of sports medicine, 95(02), 134-143.
Vera-Garcia, F. J., Elvira, J. L., Brown, S. H., & McGill, S. M. (2007). Effects of abdominal stabilization maneuvers on the control of spine motion and stability against sudden trunk perturbations. Journal of Electromyography and Kinesiology, 17(5), 556-567.