Motor control of the core: a trunk muscle investigation

Susan Morris

    Research output: ThesisDoctoral Thesis

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    Abstract

    [Truncated abstract] Seminal work in the late 1990's by Hodges and Richardson (Hodges and Richardson 1996, Hodges and Richardson 1997b, Hodges and Richardson 1999b) altered the direction of physiotherapy intervention and prophylactic advice for chronic low back pain. This series of studies by Hodges and Richardson reported transversus abdominis – a deep abdominal muscle ‐ behaved differently from the other trunk muscles and specifically stabilised the lumbar spine in an anticipatory postural adjustment (APA). The transversus abdominis was reported to stabilise in a non‐ directional manner in healthy people but was either inactive or delayed in those with CLBP. Dissemination of this information to the clinical world of physiotherapy rapidly resulted in the training of both healthy people and those with CLBP to bilaterally co‐contract the transversus abdominis before movement to stabilise the lumbar spine. "Abdominal hollowing" exercises were taught in supine and transferred to functional tasks when patients were skilled enough to “isolate” the transversus. As a physiotherapy student in Australia in the 1990's I was a beneficiary of this training. The mechanisms and roles of the core muscles and involvement in CLBP, however, have been argued consistently in the literature and consensus has not been reached. A number of assumptions were made in the interpretation of the early work on transversus abdominis, including; that both sides of transversus abdominis (left and right) contract together; that onsets in APAs reflect motor control not initial conditions; that the APA does not cause movement and; that the deficit in transversus abdominis APAs in CLBP reflects a deficit in core stiffness. This thesis attempts to explore issues of the control and behaviour of the core muscles and the trunk in an independent and profound manner in order to test these assumptions. Since the initiation of this thesis and partially as the result of work from this thesis, the pendulum has begun to swing away from training muscles to stiffen the spine (Allison and Morris 2008). Trunk motor control research is difficult primarily because of the atypical anatomy and biomechanics of the trunk. Tools of investigation of motor behaviour have been predominantly designed to study the limbs and, as such, can behave differently in the trunk. Mechanistic investigation requires localisation of effects which is not easy to attain in the core of the body.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2010

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