Tuesday, 19 March 2013

The Role of the Transverse Abdominis in Low Back Pain

by Jason Ford 

What does Transverse Abdominis do?
The function of the TrA is to stabilize the pelvis and low back prior to movement of the body. It acts within a feedforward bilateral muscle activation rationale from spinal perturbations with everyday activities. Rehabilitation is typically aimed at restoring motor control of this key stabilizing muscle. Literature points to effective means of treating low back pain with trunk stabilization and strengthening of deep abdominal musculature to improve motor control1. 
Diane Lee gives a great description of how to activate the TrA through abdominal drawing-in maneuver (ADIM). However, how long does it take for someone to learn this and do you think they will really do this correctly and efficiently if they are pain?  It has been shown that teaching a patient to perform the ADIM maneuver can be time consuming and difficult.3

How effective is activating the Transversus Abdominis?
It has been shown that the TrA is activated after the deltoid (~50ms) with arm movement task studies with LBP patients.4 A recent study showed that during a volitional recruitment task for the TrA , induced pain was shown to attenuate the activity of the TrA.5  It has also been discovered that pain will alter a muscle’s role as an agonist or antagonist to control movement for protection through the pain adaptation model.6 This has also been demonstrated with many prior studies of reduced TrA muscle thickness with chronic LBP. In turn, the delay of TrA timing and optimal muscle activation is altered, potentially making exercises that activate it ineffective when pain is present.
If we abolish the pain, would motor control and activation of TrA resolve itself? There has not been any conclusive data to show that the spine is controlled less when the activation of TrA is changed and altered timing of the TrA leads to poor core stability. The feed-forward activation of TrA can be interpreted differently from a small study that showed 3 of 8 pain-free individuals did not have the feedforward responses in 70% of trials with bilateral arm tasks.7 Even prophylactically, the isolated muscle pattern in pain-free subjects is controversial.8 This goes to show further that low back pain is complex, multimodal and overall challenging to treat. 

Is a lack of strength or stability really the reason for the low back pain? 
Do we claim to 'stabilize' every patient?  A recent study stated that some patients are not unstable at all and showed that LBP patients actually have increased stability rather than decreased stability.9 Even if we feel a patient is unstable, how do we diagnose it as unstable?  Special tests to clarify this are inconclusive.  P/A force over specific segments of lumbar spine have been found to be useful to identify the segmental impairment.  However, will activating the TrA fix this? PPIVMs for extension & flexion have poor sensitivity values. A common test practiced is the prone instability test also giving poor diagnostic values.10  You might as well flip a coin to determine instability by the values. 

Some thoughts…
As musculoskeletal specialists, we have significant knowledge and a pertinent role in management of low back pain. We need to concentrate on teaching the patients how to control their symptoms independently.  To me, this means giving the patient tools to provide self-pain relief through therapeutic means.  Activating transverse abdominis stating it will give stability when everyday aches and pains arise just doesn’t seem feasible. The use of foam rolls, towel rolls or any other affordable methods can be very effective in not only giving relief, but obtaining joint motion and allowing an exercise program to be more advantageous.  If a treatment doesn't give someone relief or change, he or she will not be adherent to it, consecutively, returning to health care providers and starting the sequence again.
Since low back pain re-occurs in 70% of cases depending on source, we may not be challenging this problem appropriately. I think having the transversus abdominus as an active component in the treatment is somewhat useful but not conclusive.  Pain relieving exercises and education need to be the forefront of each program so muscle activation can be optimal.

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