I recently mentioned that I am a new mother. Becoming a mother has been the best thing that has ever happened to me. So much joy, anticipation, and learning to be had. Of the many things that women anticipate through their journey of pregnancy and motherhood are the physical changes that lay ahead. I have personally always thought that pregnant women are the most beautiful, perhaps it’s the delight of life blossoming within us that shines through somehow. With this said, I actually really enjoyed being pregnant, both emotionally and physically. After my sons birth and the day after our discharge from the hospital I immediately started taking daily walks and doing very gentle rehab oriented Pilates. I took it slowly initially as I could feel that my pelvis had sustained some serious changes; it literally felt like my coxal bones were less attached to my sacrum. I felt physically ready to return to my pre-pregnancy physical activities at about 5 weeks postpartum, but wasn’t emotionally ready to leave my babe, so I waited until 8 weeks to return to my pre-pregnancy exercise routine. Enter more anticipation. What I wondered most was how my pelvic floor would hold up during plyometric exercises such as jumping jacks and burpees. It did not. I totally peed myself in kickboxing. As I continued to get back in shape and focus on pelvic floor rehabilitation I gradually leaked less and less during plyometrics and by around 3 months postpartum was able to perform jumping jacks with zero leakage.
This brings me to my main point, the importance of pelvic floor rehabilitation for postpartum mothers, not only so they can perform jumping jacks without peeing themselves, but also because the pelvic floor muscles play an important role in back stability and strength. For the remainder of this post I will introduce:
- Skeletal Structures of the Sacroiliac Joint
- Skeletal Structures of the Lumbar Vertebral Column
- Muscles of the Pelvic Diaphragm (with images, so you have something to visualize when your Pilates or yoga instructor cues this evasive and mysterious muscle group)
- The Purpose of the Sacroiliac Joint
- How the Muscles of the Pelvic Diaphragm Support Sacroiliac Joint Stability
Next week, I will post Motherhood, Leaky Bladders, and Low Back Pain Part Two. In this post I will cover:
- Correlation Between Chronic Back Pain and Stress Urinary Incontinence
- Pelvic Diaphragm Facilitation and Multifidus Facilitation
- Exercises to identify the Muscles of the Pelvic Diaphragm
- Exercises to Strengthen Muscles of the Pelvic Diaphragm
Now please bear with me as I take on a much more formal tone… 🙂
Skeletal Structures of the Sacroiliac Joint
The sacroiliac joint is a large diarthrodial joint comprised of the lateral surfaces of the sacrum and the medial surfaces of the iliums of the coxal bones. The areas of articulation are known as the auricular surfaces. The auricular surfaces are textured with symmetrical ridges and depressions which facilitate stability and guard against vertical shear forces. According to Nestor, the motions of the sacroiliac joint involve two to four millimeters of nutation and counternutation. During nutation the superior surface of the sacrum moves anteriorly and inferiorly while the coccyx moves posteriorly. During counternutation, the superior surface of the sacrum moves posteriorly as the coccyx moves anteriorly.
Skeletal Structures of the Lumbar Vertebral Column
The lumbar vertebral column consists of 5 articulating vertebrae which sit just superior to the sacrum. According to Floyd (2012), the lumbar spine is responsible for the majority of trunk movement as it flexes eighty degrees, extends twenty to thirty degrees, laterally flexes thirty-five degrees, and rotates forty-five degrees (p .333).
Muscles of the Pelvic Diaphragm
The primary muscles of the pelvic diaphragm are coccygeus, iliococcygeus, pubococcygeus, and the external anal sphincter (Martini, Nath, Bartholomew, 2012, p. 347). For the purposes of this article, it is only necessary to examine coccygeus, iliococcygeus, and pubococcygeus
Coccygeus originates at the ischial spine and the sacrospinous ligament and it inserts at the lateral and inferior borders of the sacrum and coccyx. It’s action is to flex the coccygeal joints, tense the pelvic floor, and support the pelvic viscera (Martini, Nath, Bartholomew, 2012, p. 347).
Iliococcygeus originates at the ischial spine and the tendinous arch that runs along the obturator internus fascia. It then inserts at the coccyx and anococcygeal raphe. It’s action is to flex the coccygeal joint, tense the pelvic floor, and elevate and retract the anus (Martini, Nath, Bartholomew, 2012, p. 347).
Pubococcygeus originates at the inner margins of the pubis and from the anterior part of the obturator fascia. It then inserts onto the side of the anal canal towards the coccyx and sacrum. It’s action, like iliococcygeus, is to flex the coccygeal joint, tense the pelvic floor, and elevate and retract the anus (Martini, Nath, Bartholomew, 2012, p. 347).
The Purpose of the Sacroiliac Joint
The vertebral column and trunk are supported by the sacrum, and in turn, the sacrum is supported by the two coxal bones. Given this, the primary role of the sacroiliac joint is to support the weight of the body, transmit forces from the upper body to lower body, and to provide shock absorption against vertical shear forces that may occur during spinal loading or movements such as walking or jumping.
How Muscles of the Pelvic Diaphragm Support Sacroiliac Joint Stability
According to Pel, Spoor, Pool-Goudzwaard, Hoek Van Duke, and Snijders (2008), vertical sacroiliac joint shear is reduced by transversely oriented pelvic muscles that increase the interlocking and compressive forces between the coxal bones and the sacrum (p. 415). Research conducted by Pel, Spoor, Pool-Goudzwaard, Hoek Van Duke, and Snijders (2008), suggests that contraction of transversus abdominis along with muscles of the pelvic diaphragm can increase compressive forces of the sacroiliac joint by 400%, producing a reduction in sacroiliac joint shear force by 20% (p. 415).
The pelvic floor muscles, M. coccygeus, and M pubococcygeus, and iliococcygeus, contribute to the stabilization with respect to the sacrum. It has been suggested that this stabilization by force closure has an analogy with a classical stone arc. When sideways displacement of both ends of the arc is opposed, mechanical equilibrium of the stones is achieved by compression forces and not by shear forces. In the pelvis, the pelvic floor muscles may help coxal bones to support the sacrum by compression forces, while shear forces between the sacrum and coxal bones are minimized (Pel, Spoor, Pool-Goudzwaard, Hoek Van Duke, and Snijders, 2008, p. 419-420).
Bush, H. M., Pagorek, S., Guo, J., Ballert, K. N., & Crofford, L. J. (2013). The Association of Chronic Back Pain and Stress Urinary Incontinence: A Cross-Sectional Study. Journal of women’s health physical therapy, 37(1), p.11-18. doi: 10.1097/JWH.0b013e31828c1ab3
Calais-Germain, B. (2003). The Female Pelvis: Anatomy & Exercises. Seattle, Wa.: Eastland Press Inc.
Floyd, R.T. (2012). Manual of Structural Kinesiology. New York, NY: McGraw Hill.
Huang , Q., Li, D., Yokotsuka, N., Zhang, Y., Ubukata, H., Huo, M., & Maruyama, H. (March 1 2013). The Intervention Effects of Different Treatment for Chronic Low Back Pain as Assessed by the Cross-sectional Area of the Multifidus Muscle. Journal of Physical Therapy Science, 25(7), p.811-813. doi: 10.1589/jpts.25.811
Jellad, A., Bouzaouache, H., Ben Salah, Z., & Sana, S. (July 2009). Osteoarthritis of the sacroiliac joint complicating resection of the pubic symphysis. Interest of a rehabilitation programme. Annals of Physical and Rehabilitation Medicine, 52(6), p.510-517. doi: 10.1016/j.rehab.2009.03.002
Martini, F. H., Nath J. L., & Bartholomew, E. F. (2012). Introduction to Anatomy and Physiology. San Francisco, CA: Pearson Education Inc.
Nestor, K. (n.d.). Sacroiliac Joint. Physiopedia. Retrieved from: http://www.physio-pedia.com/Sacroiliac_joint.
Pel, J. J. M., Spoor, C. W., Pool-Goudzwaard, A. L., Hoek Van Dijike, G. A., & Snijders, C. J. (18 January 2008). Biomechanical Analysis of Reducing Sacroiliac Joint Shear Load by Optimization of Pelvic Muscle and Ligament Forces. Annals of Biomedical Engineering, 36(3), p. 415-424. doi: 10.1007/s10439-007-9385-8
Visible Body Software. (2014). [All images].