Corrective exercise: what are we correcting?
For some reason I keep receiving emails extoling the virtues of ‘corrective exercise’.
Whenever I hear the term
‘corrective exercise’ the question that always pops into my head is “what the hell are we
correcting?” especially
as ‘corrective’ exercise is often touted as alleviating or eliminating pain and preventing
injury.
Over the past few years delving into the research on movement, posture, pain, muscle firing
etc. one thing that
is consistent is that there are not too many well defined ‘corrects’ that we can use to
‘correct’ to.
Surely to confidently embark on what you feel is a ‘corrective’ strategy you would have to
have objective
evidence of a ‘correct’ and evidence that deviation from this ‘correct’ is the cause of
whatever you are trying
to cure or prevent? Perhaps I am being over analytical here!?
One of the underpinning concepts it would seem in the field of ‘corrective exercise’ is that
we need to have
‘good’ posture and ‘balanced’ muscles. One thing I rarely see adequately explained is how
these postures or
imbalances actually lead to acute or chronic pain and the mechanisms involved. This fear
mongering is heavy on
the melodrama and light on evidence.
Where does this magical blueprint come from? I am unaware of an agreed upon definition of
‘good posture’ that we
can objectively use to then define ‘bad’ and then ‘correct’ to. We seem easily seduced by
complex anatomical
theories about ‘correcting’ and ‘neutral’ that often are not really supported by the
available evidence. perhaps
we should apply this scrutiny to many of the ideas that propose deviation from a ‘correct’
as the cause of
pain?
Even before we look at any of the evidence we should really have a look at the basic
scientific plausibility of
the idea.
Basic science
Part of the process of pain originating from a specific tissue, such as a muscle, occurs by
the stimulation of
nociceptors contained within the tissue. Nociceptors are receptors that sense noxious
stimulus or more plainly
put danger! They encode this stimulus and then relay this message to the brain via the
spinal cord. The brain
then decides if this information it is receiving is sufficient to then become the experience
or output of pain.
We have to appreciate that this information from the tissue may not be enough on its own to
be translated into
the perception of pain.
Some nociceptors can be polymodal meaning they sense mechanical, chemical and thermal
stimulus that could cause a
threat to the tissue, others just sense a single stimulus and some are quick at sending
information and others
slow.
Now nociceptors are set to have a high threshold meaning that the stimulus required to make
them send a signal
back to the brain needs to be pretty high. This makes perfect sense because if the
nociceptors had a low
threshold to a stimulus then they would be popping off all the time and life would become a
pretty painful
experience.
These sensitivity levels can alter and we may see this with people in persistent pain and
also when the state of
the tissue changes such as during periods of inflammation and the resultant chemical cascade
that occurs.
If we think about people with a normal tissue state then ‘poor’ postural ‘deviations’ will
provide a mechanical
stimulus to the tissue that is actually very low, much more of a position rather than a
motion. The likelihood is
that the mechanical stimulus would not reach the level required to activate the receptors
designed to sense a
high stimulus and then transduce this back to the brain.
Now it could be hypothesised that a prolonged low-level mechanical stimulus could create
pain, the question is do
we have the required research to suggest that a persistent low-level mechanical stimulus
will activate a high
threshold receptor?
Another theory is that poor posture over the long term leads to tissue damage that then
causes nociception.
Unfortunately this does not seem to hold water either. If wear and tear to our tissues was
simply to blame for
pain then we would not see many asymptomatic people with tissue damage……but we do!
This study of spine imaging *Click Here* estimated the prevalence of disc
degeneration was 52% for ASYMPTOMATIC 30 year olds
rising to 80% for the 50 year olds. Wear and tear to our tissues is the same as getting grey
hair, going bald or
getting wrinkles it’s just less apparent as it’s not external. Your brain may not recognize
this as a threat as
it may not your grey hair.
How many people have what could be considered as ‘poor’ postures and never develop any pain?
I bet you can think
of quite a few people you know. Going back to the beginning of the piece you will remember
that nociception from
the tissue on its own is not enough for the perception of pain.
WE ARE ADAPTABLE
Tissues are amazing at adapting to increased loads. In fact if you go to the gym that is
exactly what you are
asking your tissues to do, adapt to an increased load. These loads will be much higher and
in more extreme joint
ranges than your average bad posture.
The same maybe true of a muscle being ‘overworked’ and fatigued via a faulty posture as a
source of pain. Surely
over time a muscle would adapt to the level of endurance required to meet the demands of a
task? A bit like
training for a marathon! It has also been discussed that we have alternating recruitment of
muscle fibres within
muscles to avoid becoming so fatigued.
The human biological system has the ability to adapt and to self-repair. We have large
tolerances and variations
in both anatomy and function. The ‘corrective’ paradigm seems to assume an inherent
fragility with the most minor
deviations causing major problems.
We certainly seem to have a body of evidence that suggests people in persistent pain do not
have very different
postures from those that are not in pain.
Here we see cervical spine postures no different between people with and without neck pain
*Click Here*
There was no difference here in this study of lumbar lordosis of those that had back pain and
those that
didn’t *Click
Here*
I pulled together some of the evidence on posture and pain in this blog *Click Here*
Surely if posture, pain and tissue damage were closely correlated we would see this clearly
and consistently
reflected in the evidence base? We could then make a good case for a ‘corrective exercise’
program but
unfortunately we don’t.
Another proposed cause of pain from poor posture is ongoing tissue stress and subsequent
inflammation. Have we
solid evidence that ‘poor’ posture leads to an inflammatory state of the tissue that could
lead to pain? If you
are reading this and have some then please send it to me.
Again surely if postural deviations created inflammation and a change in the chemical state
of the tissue then we
would see a more consistent correlation between people with ‘poor’ posture and pain?
Is the proposed prolonged low-level mechanical stimulus enough to trigger an inflammatory
response? If we look at
Dye’s excellent model of ‘tissue homeostasis’ *Click Here* then the stimulus would have to be large enough to
exceed the zone
of normal tolerable loading and enter the zone of supra-physiological loading disrupting the
bodies normal
physiological processes, I am unconvinced it would.
Postural positions adopted for extended periods certainly could negatively influence nerves
through tension and
compression of both the nerve itself and via forces applied to the nerve from prolonged
muscular contraction.
This may affect the intra neural blood flow and nerves are especially sensitive to decreases
in oxygen and
resultant ischemia with associated low tissue PH (acidosis) that can occur from the reduced
flow of blood. The
sensitised nerve may then be triggered into sending danger signals by much more normal
forces applied to the
nerve rather than the usually higher forces required to trigger danger signals.
This could actually happen to ANY posture that we adopt for an extended period of time. That
could be a hunched
posture or what we maybe described as a ‘good’ posture. The major factor would be that the
posture is unchanging
not the actual position that we adopt. Rather than the postural position it would be a lack
of MOVEMENT that is
problematic.
This is why after we sit for a long time we often need to get up and move around. We feel
stiff and irritable and
in need of some basic pump and flow to our tissues to drive more of the good stuff and flush
out the bad! Often
we will get up move about for a bit and feel much better, it is just a basic warning system
to move!
In this situation ANY movement might help without the need for it to be ‘correct’ or
‘correcting’
Muscle imbalances
One of the reasons I often hear blamed for poor posture is a ‘muscle imbalance’, one muscle
being stronger than
another around a joint pulling it out of the ‘correct’ position.
I imagine this like a bit of a tug of war!
A question that pops into my mind, which I warn you can be a strange place, is that in a
situation that requires
a small percentage of contractile force would this difference in strength become
apparent?
During the low-level isometric contractions employed in maintaining a posture it is
estimated we use between 4-7%
of MVC (maximal voluntary contraction). (The Ergonomics of working postures P142, Corlett E
et al 1985)
Perhaps only above the threshold of the difference in strength would one muscle actually
“win” the battle. At a
lower level demand perhaps they simply balance each other out if it were in fact a tug of
war. So would we be
likely to see strength imbalance lead to postural changes when such low levels of MVC are
required to maintain a
posture?
Our posture is also influenced by a number of different systems such as the visual and
vestibular systems not
solely the strength or length of two opposing muscles (amongst many) around a joint. Perhaps
just looking at two
muscles is an overly simplistic view of posture.
We often look to ‘correct’ muscle firing patterns, especially with back pain, with no real
evidence of how they
should fire in the first place. Here we see two pieces of research that show abdominal
muscle firing and function
have little to do with getting better from back pain *Click Here* & *Click Here*. Perhaps altered muscle firing is a result of rather
than a
cause of back pain and therefore is not implicated in resolving the pain.
This paper challenges the idea that we have a ‘correct firing’ of the core muscles
independent of functional
activity *Click
Here*
Here is a bit more on the core stability debate and a look at some of the evidence *Click Here*
Psychological impact
We must also think about the psychological impact here as well. How does telling someone
they are ‘imbalanced’
and in need ‘correcting’ affect their sense of fragility? Could this translate into an
interpretation of being
‘broken’?
Could we see the term as a nocebo? The nocebo is the opposite of a placebo, essentially it
has the potential to
make things worse not better especially if there is no problem to begin with and one is
created.
The awareness of the importance of this side of our interaction with people is growing *Click Here* and even if we
had credible evidence that people are in need of ‘correction’ it would probably be better to
not dress it up as
such.
It may also reinforce the role of the therapist or trainer as the person required to ‘fix’
their ‘posture’ or
‘muscle firing’. Both of which are quite possibly based more in the imagination rather than
reality.