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M.Siff: >TRANSVERSUS ABDOMINIS ACTION > >Here is a quick puzzle and paradox - is the role of transversus abdominis (TVA) as supremely important as some individuals have been suggesting? After all, the body is extremely efficient at recruiting different systems and processes if one of the important systems involved in a given action is injured, ill-adapted, fatigued or otherwise compromised in its ability to offer its optimal contribution. Not only does this happen in the muscular system, but MRIs show that this plasticity of function even happens in the brain. > >Those who work clinically often will notice how many patients with physical differences or dysfunctions "compensate" by using different muscles or patterns to carry out a given task without any apparent ill- effects. One example close to home -- my paraplegic wife who is paralysed from thoracic level T3 is able to carry out tasks that nobody should be able to do with that level of injury, but she often does and does so without injury. > >So much has been written recently about how essential transversus abdominis is to trunk stabilisation and mobility, but has anyone ever undertaken studies to show that people who may not be able to activate it very effectively may compensate very effectively by using other patterns of muscle activation and use? Is there really any convincing proof that "less than optimal" TVA activation definitely results in significantly less efficient and more dangerous trunk action in all daily activities? > John writes: Certainly clinically we see that people with apparently poor TVA activation compensate using other less appropriate muscles to try and stabilise the lumbar spine. It is often these muscles (eg hams, hip flexors) that become initially symptomatic as they eventually fail to compensate for a role they are not well adapted to carry out. In fact the 'model' that the TVA research is based on is that of a tripartite system (originally created by Panjabi) whereby stability of the lumbar spine relies upon 'passive' structures (eg discs and bony structures), 'active' structures and overall central nervous system control. So, for instance, if one structure fails (eg a disc becomes unstable) it may be that the body compensates by developing bony osteophytes to try and re-assert some 'passive' control. Of course all this compensation is subconscious. So yes, as you say, the body does compensate. However, clearly the ability to compensate is limited and at the point that the body fails to compensate adequately we see symptoms. There are clearly many people out in the real world who have 'bulging' discs or considerable OA on x-ray who have no symptoms and others who, with the same pathologies are riddled with symptoms. So compensation certainly occurs but when it fails it may be that 'conscious' intervention to activate the TVA helps to bring the body back to a less symptomatic state. M.Siff: >Studies of actions other than trunk stability have shown that the same >muscles do not necessarily become involved or become involved to the same extent or in the same pattern in different people or in the same person at different times (e.g., there was an article in the Scientific American within the last 2 years which used fMRI - functional MRI to demonstrate this). If this happens with other movements, why should actions involving TVA be any different? John writes: Interestingly, Dr Paul Hodges recently commented on research using a PET scanner and studying TVA activation showed that the normal areas of the motor cortex that were active with skeletal muscle activity were not associated with TVA activity which was an early indication that the TVA may be under distinct motor control from other muscle groups. The research also indicates that whilst muscles such as hamstrings, glutes and rectus abdominus were activated in terms of both TIMING and DEGREE of contraction DEPENDENT UPON DIRECTION OF MOVEMENT, TVA's timing and degree of contraction was the same INDEPENDENT OF DIRECTION OF MOVEMENT. SO, yes, there is evidence that might suggest actions involving the TVA could be different to other muscles. That individuals display muscle recruitment patterns unique to each individual is undoubted... it does not contradict TVA theory. Mel writes: Is there any genuine proof, other than the current conjecture, that TVA contributions to trunk action is not as predictable and deterministic as is being claimed by some therapists? Does it really matter all that much if it sometimes does not contribute as it "should" during human movement and its decrease in function is compensated for by other muscle actions? Are there any references which help to resolve this paradox? John writes: I think clearly that 'some therapists' out there are making insupportable claims in respect of TVA but that doesn't negate the convincing research that indicates this is a very exciting and promising area of study. No-one conversant with the evidence would deny your assertion that the body will compensate for dysfunctional systems but equally it is clear that the body fails to compensate adequately in all cases hence the need for therapeutic intervention, (including TVA activation) > >Dr Mel C Siff >Denver, USA >http://groups.yahoo.com/group/Supertraining/ -- John Spencer