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Lumbopelvic mechanics
  1. B Mitchell1,
  2. E Colson1,
  3. T Chandramohan2
  1. 1Reservoir Sports Medicine Centre, Olympic Park Sports Centre and Centre for Sports Medicine Research, University of Melbourne, Melbourne, Victoria, Australia
  2. 2Reservoir Sports Medicine Centre

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    It has annoyed us for a long time when patients present stating that they have been having “core conditioning/core stabilisation/core strengthening/pelvic stabilisation”, etc. It is also annoying to find the same terms used in peer reviewed scientific articles with the assumption that they mean something to the readers. Maybe they do to others, and we are missing something! We would like to get some discussion going on this and are happy to open the batting.

    We think of lumbopelvic mechanics as three distinct groups:

    1. Intrapelvic stability

    2. Peripelvic stability

    3. Functional stability.

    Intrapelvic Stability

    This is dependent on the transversus abdominis contracting with intact posterior sacroiliac joint ligaments. The anatomy of the transversus abdominis is such that it has a major origin off the iliac crest and inguinal ligament/conjoint tendon to insert into the linea alba. Therefore it and the pelvic floor are the only muscles that give direct closure across the sacroiliac joint. The long lever arm involved gives it great mechanical advantage, as long as the sacroiliac joint ligaments are intact.1

    Problems arise from two mechanisms.

    1. Loss of the active structures that provide intrinsic pelvic closure (the transversus abdominis and the pelvic floor muscles) because of

      • inhibition of the transversus abdominis caused by first onset low back pain2;

      • pain inhibition through joint inflammation: “osteitis pubis”, hip joint pathology, and sacroiliac/lumbar spine joint dysfunction;

      • a tear of the conjoint tendon/inguinal ligament disrupting the origin of the transversus abdominis;

      • past abdominal surgery inhibiting contraction or affecting the nerve supply to the transversus;

      • tearing of the pelvic floor muscles during child birth;

      • weakness of the pelvic floor muscles secondary to poor toilet habits.

    2. Loss of passive structures

      • pelvic ligamentous laxity due to either body type (hypermobility) or external trauma (either single incident or prolonged postural loading), or hormone induced ligamentous laxity (pregnancy);

      • laxity of the sacroiliac joint ligaments will cause loss of the closure moment at the sacroiliac joint. A very small loss of ligament strength here can have a profound effect on the closure moment. Is this how Vleming’s posterior sling exercises work on post partum women? Further is this the mode of action of sclerotherapy of the sacroiliac joint ligaments?

    Peripelvic Stability

    Once the pelvis is stable and we have a firm foundation, we can look at the pelvis reacting with the rest of the body.

    Pelvis on hip joint (pelvifemoral control)

    • Does the knee roll inwards as the subject single leg squats?

    • Does the pelvis dip as the patient reaches single leg stance?

    • Is the lack of pelvifemoral control a strength or timing problem around the hip joint (gluteus medius and gluteus maximus) or is it an inability to appropriately weight transfer on to that side because of hip, knee, or ankle problems, burnt out nerve root pathology, or just disuse of one side because of chronic injury.

    Pelvis on lumbar (and thoracic) spine (lumbopelvic control)

    • This is concerned with ability of the deep multifidus to contract to control the lumbar segments and the superficial multifidus to orientate the spine on the pelvis.3

    Functional Stability

    Once the muscle strength and activation patterns are in place to allow force transfer through the pelvis, then linking these activities into normal activities and actions and conditioning the lumbopelvic complex can take place. This is really just an “on-field” extension of peripelvic stability. Once the athlete has all the necessary components to hold the pelvis stable on the femur and lumbar spine, can they coordinate that into their particular sporting or every day activity?

    This type of stability is more concerned with technique, coaching, and video analysis. Also, as conditioning will no doubt affect the fatigue status of the athlete, high level physical conditioning allows the athlete to maintain a stable pelvis without physical fatigue, hence appropriate strength/endurance and power training is applicable to the type of athletic activity and the stage of the athletic season.

    Most gym based strength, conditioning coaching, and fitness programmes fall into this category. However, it is our belief that, if the intrapelvic and peripelvic problems are not addressed initially, that is where these patients break down. Conversely, if inadequate conditioning is performed before return to sport/competition, then the athlete will break down, as there is no transmission of their rehabilitation on to the field of play.

    People present at various points along the continuum of disease. Some lack functional stability, and some lack peripelvic strength and coordination, but have a stable pelvis. Others have a pelvis that swings in the breeze.

    A recreational athlete with a sedentary occupation does not need the same level of intrapelvic strength and endurance as an Australian Football League onballer or elite soccer player. Yet someone doing a lot of vacuuming and weight bearing with poor ergonomics needs quite good intrapelvic and peripelvic strength without the need for the endurance of an elite athlete in these muscles.

    We look forward to hearing the thoughts of others on this topic.


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