Someone wrote on another list:
<Over the last two decades there has been much research and development
towards an improved awareness and understanding of spinal biomechanics,
relative to its stability and the inter-relationship of associated
musculature. Much of this has been attributed to the works of Panjabi
(1992a, 1992b) who proposed a conceptualised model of 'The Stabilizing
System of the Spine'.........
The generation of required muscular forces can be seen in the classical works
of Bergmark (1989). Using a spine model with joint stiffness and forty
muscles he identified a local system and a global system. Bergmark
describes the local system as the deep muscles of the spine and the deep
portions of some of the muscles that have their insertion and origin at the
vertebrae in order to control the curvature of the spine and provide
stiffness to maintain mechanical stability.
The global system includes the more superficial muscles of the spine that
are linked to the thorax and pelvis and produce large torque and force
moments. Thus controlling the external forces that result in movement.
However, Panjabi (1992a) suggests that deterioration of the musculotendinous
subsystem to receive and/or carry out the neural commands or to produce
adequate and coordinated muscle tensions may result in decreased stability.
This introduction leads quite naturally into another P&P for further
discussion:
INTRODUCTORY NOTE
For newcomers to this forum, these P&Ps are Propositions, not facts or
dogmatic proclamations. They are intended to stimulate interaction among
users working in different fields, to re-examine traditional concepts, foster
distance education, question our beliefs and suggest new lines of research or
approaches to training. We look forward to responses from anyone who has
views or relevant information on the topics.
PUZZLE & PARADOX 132
Is the current model of spinal stabilisation based upon a local and global
systems of muscular control as valid as may appear from some of the
literature?
For a start, has anyone determined how independent or interdependent are the
local and global systems in different static and dynamic situations,
especially in active sports? The local system presumably is intimately
concerned with "core stability" (i.e. in the clinical sense where this refers
to stability of adjacent or nearby vertebrae), while the global system refers
mainly to overall stability of the trunk in gross physical activity. Can
some apparent deficiencies or mistiming of muscle action at the local level
be compensated for by actions at the global level without automatically
leading to pain or dysfunction?
Is the current emphasis on local system deficiencies really justified as a
cause and not a symptom of spinal pain and disability-- or are global
compensatory mechanisms (especially if associated with breath holding)
capable of ensuring continued movement and overall stabilisation efficiency
and preventing possible back pain and dysfunction? Is there a dynamic
interplay of control mediated by different proportions of local and global
system involvement at any given time in any given stabilising or mobilising
task, so that it is inappropriate to refer to either one or other system
being the main player in spinal stabilisation?
Please supply any references that relate directly to this issue.
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Here are references for statements made in the text:
SM McGill & J Cholewicki (2001)"Biomechanical Basis for Stability: An
Explanation to Enhance Clinical Utility". J of Orthopaedic and Sports Phys
Therapy 31(3): 96-100.
Bergmark A (1989) Stability of the Lumbar spine. A study in mechanical
engineering. Acta Orthopaedica Scandinavia. Vol.60: 230
Panjabi M M (1992a) The Stabilising System of the Spine. Part I. Function,
Dysfunction, Adaptation, and Enhancement. J of Spinal Disorders. (5), 4:
383-389.
Panjabi M M (1992b) The Stabilising System of the Spine. Part II. Neutral
Zone and Instability Hypothesis. J of Spinal Disorders. (5), 4: 390-397.
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Dr Mel C Siff
Denver, USA
http://groups.yahoo.com/group/Supertraining/
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