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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