Monday 28 January 2019

Under Pressure

This blog is all about the abdomen and the pressure it's under most of the time.   

Structure of the trunk
The abdomen starts below the diaphragm and ends with the pelvis.  In effect, we have three cavities sitting one on top of the other; thoracic, abdomen and pelvic.


The abdomen is different to the thorax and pelvis because it doesn't have a bony casing.  The thorax, for example, has the rib-cage to protect organs and add stability to the thoracic spine.  

Instead, the abdomen's stability relies largely on muscle and thick sheets of connective tissue that the muscle attaches into.   The abdomen also has the lumbar spine for stability and controlled movement.   

Because of the abdomen's soft tissue structure, it's important to keep the muscles in balance with each other.  This way the abdomen can cope better with the pressures and stresses it faces.

Below is an image we could have for our abdomen from Katy Bowman, an American BioMechanics specialist.

“If you go into my garage, you'll find a deflated air mattress - totally floppy and, more importantly foldable.  But all I have to do is fill it with air and voila!, that same piece of equipment is now rigid and supportive.  I don't need my air mattress to be rigid and supportive all of the time; only when I have guests.  Most of the time, I just need it to fold up and be out of the way.  It's helpful to think of your abdomen in this way.  Your muscles become firm and supportive when you need them to, and soft and relaxed when you don't.” *
The Core
The muscles that Katy talks about are part of our 'core' muscles.    How these 'core' muscles function is covered in previous blogs Getting down to the core   Let's hear it for the diaphragm and Take a breather.  

Core muscles - the abdominal canister
The abdominal cannister
The core muscles extend beyond the abdomen.   The diaphragm starts in the mid-thorax.  The deep abdominals, pelvic floor and related connective tissue attach all the way down at the base of the spine, sitting bones and pubic joint of the pelvis.   Together, they create a deep abdominal cannister that spans across all three cavities - thorax, abdomen and pelvis.

With diaphragmatic breathing, on inhale, the downward movement of the diaphragm produces downward intra-abdominal pressure.  On exhale, the diaphragm rebounds back up together with deep abdominal (transverse abdominal) and pelvic floor contraction.  

In theory then, the abdomen is stable on both inhale and exhale.  This optimal core stability relies on optimal breathing, posture and motor control of these deep core muscles.     

Under pressure
At the same time, these deep muscles are also responsible for our postural control -  this control will vary depending on whether we're standing still, running or carrying an enormous back pack.   

The deep muscles also have to regulate internal pressure changes in the three cavities.    The diaphragm is key here, aiding pressure change due to talking, singing, laughing, coughing and defecating amongst other things.

Deep versus external muscle
Clearly these deep muscles have many functions and face numerous pressures.  They're also not working completely alone.   There are different ideas and models of exactly which other muscles work together with them.   One model includes the deep hip flexors (psoas and illiacus) the deep spinal extensors, part of quadratus lumborum, the internal oblique and the deep hip rotators.  These together form an inner sleeve around this abdominal cannister surrounding the thoraco-abdominal-pelvic cavity.**    

On top of this we have an external set of muscles, closer to our skin.   These include glute max, latissimus dorsi, superficial spinal extensors and superficial abdominals.   We can call the two sets of muscles 'deep' and 'external'.

For optimal core function we need the deepest muscles to coordinate well together, as Julie Wiebe shows in the video below.  We also need the deep and the external muscles to work in balance with each other.

Why we lose optimal core function
Some of the many factors that challenge optimal core function are listed below.

1.  Tension in the abdomen - from gripping muscles consciously or unconsciously
If we grip our abs or hold our breath this will have a significant effect on the other muscles of the core.   This might be holding in the deep muscles abdominals to flatten our belly or it could be a less conscious holding of the upper abdominals and diaphragm as part of our stress response.  

Julie Wiebe's video about breathing below explains more.  Julie is an American Physiotherapist.   She describes a diaphragm and pelvic floor piston mechanism of breathing.  She names abs, diaphragm and pelvic floor as 'team mates' who need to be free and available to work together in a dynamic system of core stability.   Julie stresses the importance of this coordination of our team mates rather than strength of muscles. When she's talking about 'leaking' she's referring to the Stress Urinary Incontinence we'll cover in Part 2 of this blog.

2.  Tension in the abdomen - due to posture and breathing
Posture and breathing pattern are very closely related to each other.    If our breathing pattern is chest breathing say, then our posture will be one of an upward tilted thorax (front lower ribs flare up).  The neck and shoulder muscles over work to draw air in for each breath.   Upper, external abs then force out the exhale.    Its likely that our deep core muscles will have altered motor control, neither diaphragm, pelvic floor nor deepest abdominals able to work as a team.

Other aspects of posture will also create pressures for the abdomen.   One example is a posture of carrying the pelvis out in front of the thorax and the legs.  The pelvis sits above the front of the feet rather than further back above the heels.  This transmits additional forces through the front of the abdomen.   Here, impact forces from running will affect abdominal muscle and connective tissue even more. 

Other common postural pressures come from a tilted or twisted position of the pelvis and/ or the thorax.  This creates pressure through the abdomen as it is pulled in one or more directions by the structures above and below.   
3.  Tension beyond the abdomen
We may notice when we exercise how tight our shoulder and neck muscles feel.  Or maybe we're more aware of tense hamstrings.   Either way, tight shoulders, hips and glutes will all create tension through the abdomen via connective tissue (facial) lines throughout our bodies.   This tension is likely to be related to posture, breathing pattern and any torsion through the ribs or pelvis.

4. Excessive loading through the abdomen
On top of all this (gripping patterns, breathing and posture) we then add in movement and loading.    
So this could be walking with a heavy bag on one shoulder, on uneven ground with restricted movement in one hip.    We can imagine the one sided load from the bag.  We can picture what the lower back and other leg may need to do to compensate for the lack of movement in the restricted hip side.

Or, another example of load could be lying on the back of the body with head lifted, legs straight and hovering just above the mat.   The abdomen (and the lumbar spine) are having to bear a huge load and so need to be functioning optimally to cope.   We only need to add in some breath holding here to immediately take away potential optimal core function.

Core dysfunction
And so when things do go wrong, we move from core function to dysfunction.   The deep muscles no longer coordinate with each other.   The deep and the external muscles get out of step too.

Core dysfunction means that the deep system isn't able to stabilise and the external system also can't sufficiently compensate for this.

A common pattern is deep muscles work too little, too late while the external muscles work too soon and at an intensity that is too high.  

In the next blog, we'll look at other associated problems including hernias, urinary stress incontinence, diastasis recti and pelvic organ prolapse. 

For now though, coming back to Katy Bowman's inflatable mattress metaphor - soft and relaxed abdominal muscles are definitely a good thing.

Relaxed muscles function best and are able to work and coordinate as part of a team.  They are better able to cope with the demands we put on them.  Being aware of our posture and how we breathe is also key.   And that goes hand in hand with keeping good, free, even movement throughout our body.   Sounds just like a great Pilates lesson to me...

*  (Katy Bowman, Diastasis Recti.  The whole body solution to abdominal weakness and separation. 2016 Short Run Press Ltd
** Key, J    The core’: Understanding it, and retraining its dysfunction.   Journal of Bodywork and movement therapies (2013) 17, 541-559.