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Muscle Stiffness – Part II: Expectation Violation

28 Nov 2018


In part I of this post I talked about how a recent research paper suggested that persistent muscle stiffness – like persistent pain – could be due to a perceptual error:  the nervous system has become oversensitive – the threat of damage has passed but it is still on high alert, and therefore we perceive pain or stiffness.

To be clear, we are not talking about stiffness that is there for a reason – disc prolapse, muscle sprain or tendon overload – but persistent stiffness or pain that has exceeded its need in terms of any potential or real damage.  I’m going to use pain and stiffness interchangeably, because the same applies to both of them.

There are various ways to come at persistent pain: distraction techniques, relaxation techniques, looking at sleep health, making modifications to the way we go about daily activities, and so on.  But there is another powerful approach we can take to correct perceptual error, and to understand how that works we need to understand a little about how the brain works.  Don’t worry, I’ll keep this simple with an analogy.

Early ideas of brain function were squarely based on a computer analogy: the brain was an input-output device that moved sensory information through different processing stages until reaching an end point.  In this model visual perception would start with data received by the eyes that is then interpreted in the visual centre at the back of the brain resulting in an image.  But we know that the wiring does not run from A to B to C:  there are feedback loops from C to B, C to A, and B to A.  Throughout the brain there is as much feedback as feedforward – a feature of the brain colloquially called loopiness.

What is the advantage of a loopy brain?  It permits us to do better than a stimulus-response behaviour system would allow, and instead confers the ability to make predictions ahead of actual sensory input.

Consider the act of catching a ball.  If our nervous system worked in an ABC fashion, there would be a delay of hundreds of milliseconds between the light reaching your retina and the motor command being sent to catch the ball, and we would constantly reach for where the ball used to be.  We are able to catch balls only because we have deeply hardwired internal models of physics.

This is a specific example of internal models of the outside world.  The brain predicts what will happen if you were to perform some action under specific conditions.

But we know that internal models also underlie conscious perception.  The brain matches expectations to incoming sensory data to give rise to perception.   When we suffer pain for a long period of time, pain itself becomes hardwired.  When we bend forward to pick something up, consciously and unconsciously we have an expectation of pain and so that is what we experience.

So how can we change the internal model that feeds into our perception of pain or stiffness?

Let’s take the example of driving a car.  We generally drive without giving any conscious thought to how we do it.  We have an internal model of motor commands that combines with incoming sensory information so that although you are conscious of driving, you’re conscious neither of the movements nor of the sensations of driving unless something changes – like a strong wind or a flat tyre.  When these new situations cause your normal expectations to be violated, consciousness comes online and your internal model adjusts.

Only when our expectations are violated and our predictions prove wrong can we access our internal model and have it adjust.  Expectation violation is used in treating mental health issues – phobias in particular – and is key in changing our internal predictive models.

How can we make use of expectation violation in relation to persistent pain or stiffness?  In a nutshell, it involves doing the thing that is painful, or something close to it, usually against resistance (which we know affords a degree of inhibition of pain), pushing through some initial sensations of pain or stiffness – the patient acknowledging (perhaps with some surprise) that their pain or stiffness is no worse, or is diminishing with repetition – then gradually increasing the intensity with which the action or movement is performed.

So if forward bending is a painful movement (that will generally therefore be avoided), I might have someone bend at the hips and knees (straight back) with a weight in each hand and gradually tweak the movement towards a forward bend.   I do this a fair bit with any patient with low back pain for the related by slightly different purpose of building a sense of confidence in their ability to move.

That may sound straightforward, but when pain is persistent it is far from a simple.  I should add that using resistance work in this way is just one of many interventions that might be in play.  There is also much to consider, the most important being that pushing into pain can have the opposite effect of sensitising (flaring-up) the area further.  That sounds like a contradiction, and there is a fine line that one walks between the two possibilities, and one has to be ready to back off or change tack if any increase in pain doesn’t settle quickly (in a day or so).   It would be unusual if the road to recovery were a smooth one; expect it to be gradual, with setbacks along the way.

Eric Meira (aka the Science PT) writes about Load and Expectation Violation – in somewhat more colourful style – here, and again here in Hunting Pain


Why do Muscles Feel Stiff – Part I

19 Sep 2018

Moseley Indentor

Muscle stiffness is a common complaint of patients presenting to my clinic.  Common questions are “why do I feel so stiff?”; “why do my muscles feel so tight?”; “why do I have knots?”

In the most straightforward of cases, patients will report that their stiffness relates to a certain posture, position, or movement, and when I assess them I will find a palpable tightness and an associated limitation of movement in a related part that is suggestive of the muscles in question being overloaded.

It would be reasonable to assume that the brain registers threat in terms of a lack of blood flow to the overworked muscle, which in turn could cause metabolic stress and activate chemical sensors (nociceptors).

But sometimes the muscle stiffness complained of correlates neither with palpable stiffness, nor with a reduction in movement.  So why then do we still feel stiff?

While there is only limited research on stiffness, a paper published by Moseley and Stanton in 2017, showed that in subjects with chronic low back pain, subjective stiffness correlates poorly with objective stiffness i.e., participants’ ratings of how stiff their back muscles felt related poorly to the objective stiffness measured by the researchers using a piece of kit called an indentor.  The authors posit that the reason for this is a “perceptual error”:

“feelings of back stiffness are a protective perceptual construct, rather than reflecting biomechanical properties of the back”

Just as we can feel pain in the absence of damage – because pain results from a perception of threat – see blog about this here – so, it would seem, we can feel stiffness in the absence of any objective tightness. The reason for this, just as with pain, may be a perception (wrongly or rightly) of threat to the muscles and joints where stiffness is felt.

In this case, we might think of stiffness as we do chronic pain as having become a learned response; the nervous system is over-sensitive to information it receives (in this case oversensitive to the need for blood flow to the area).  The brain in not registering stiffness just due to inputs from the muscle itself, but also due to associations with environments (computers), lack of sleep, stress, fear or avoidance of movement.

So what can we do to address muscle stiffness when we suspect that it is not just mechanical but due also to the area being sensitised?  This will be the subject of Part II of this blog post.


Image: The indentor used to measure muscle stiffness in paper ” Feeling Stiffness in the Back: a protective perceptual inference in chronic back pain” by Stanton, Moseley, Wong and Kawchuk, in Scientific Reports, Aug 17.

With permission:


Sun’s Out Guns Out

14 May 2018

Mr Burgundy

Flexing in front of the mirror actually makes your biceps bigger!!!  Well maybe.  A study just out showed that focusing on the targeted muscle/movement during weight-training (watching oneself in the mirror might fall into that category) increased arm circumference by 12.6%  (internal focus) compared to a group who focused on the outcome/weight itself/ or action (external focus) – 6% increase.

Using an external focus of attention (the outcome rather than the movement) has been shown to improve sporting performance and endurance and is used extensively in sports coaching, where there is a good amount of research to support it.  Studies on weight training are more limited and so far show conflicting results.  See Effects of Attentional Focusing Strategies on Muscular Power in Older Women, Jul 15) which comes up with the opposite finding.  I’m afraid the jury is still out on this one!

There are compelling reasons to incorporate resistance training into your exercise routine.  Benefits of resistance training include improved physical performance, movement control, walking speed, functional independence, cognitive abilities, and self-esteem.

Using load in your training may assist prevention and management of type 2 diabetes by decreasing visceral fat and improving insulin sensitivity; enhance cardiovascular health by reducing resting blood pressure, decreasing bad cholesterol, and increasing good cholesterol; promote bone development, with studies showing 1% to 3% increase in bone mineral density.

Resistance training may also be effective for reducing low back pain and easing discomfort associated with arthritis and fibromyalgia and has been shown to reverse specific aging factors in skeletal muscle

If it’s a time issue that’s stopping you from adding weights to your routine then there’s good news in this piece of research just out: Do We Need a Cool-Down After Exercise? Sports Med, April 2018

The conclusion is no.   Existing evidence would suggest that a cool down does not significantly ameliorate either delayed onset muscle soreness or muscle stiffness after exercise, prevent injury, or improve exercise performance later the same day (though it might to a bit the next!).  I’m not sure I’ll be giving up my warm down just yet, but I won’t beat myself up too much if I don’t have time either.

Enjoy the sun, and do work on those abs, guns, and buns if you get the chance!

See also:
Resistance Training is Medicine: Effects of Strength Training on Health – Current Sports Medicine Reports, August 2012

Image: Still from The Legend of Ron Burgundy


Are you sitting comfortably: the myth of good posture

22 Mar 2018

low ceiling

That’s the Guardian’s (5/3/18) headline – not mine – for an article in which two well regarded physical therapists and researchers explain why it doesn’t matter how we sit, or what posture we assume because there is no evidence to support an association between sitting and back or neck pain.

Slouch on: bad posture not bad for your back (

This was the heading of a radio interview posted on Twitter featuring another two physiotherapists and researchers from Western Australia, in December 2016.

Confused by this message?  You should be!  It was not so long ago that we were being told that sitting was the new smoking (and maybe it still is, because sitting may well have health implications well beyond back and neck pain).   I agree with a lot of what these researchers say but I worry that sometimes these, dare I say it headline grabbing statements, are sending out a message that is too simplistic.

This is a bit of a long post, so go to the last three paragraphs if you want to cut to the chase.  Read on if you want a better understanding of why we are getting mixed messages about sitting.

I took a look at the paper behind the Twitter headline.  To cut a long research paper short, the researchers looked at participants’ normal sitting posture and took lots of measurements relating to it – that bit is fine – then had them respond to a questionnaire that asked them a whole range of psycho -social questions – how stressed are you? how much sleep do you get? as well as how many hours are you on the computer per week? playing games on the computer per week? exercise? They also got a raft of questions about neck pain: do they/have they suffered neck pain?  what duration? is it worse when you sit? etc.

I often feel like I need to go back to college and do a research module in order to be confident about critiquing a research paper, but not in this case.  I reckon my seven-year-old daughter would see one problem with this research in no time.  The radio presenter is straight onto it: the study was done on 17 year olds!

The researcher’s response to this is that in another study he has done, one in five seventeen year olds suffered neck or back pain.  I haven’t looked at the latter paper yet, but again, it doesn’t ring true in my experience – though I accept there may be many reasons why I don’t see these patients. I will be take a look at the paper and report back.  Don’t get me wrong – interviewee Peter O’Sullivan is a good guy and says a lot of good things in the radio interview above.

I looked at a 2010 systematic review of the association between sitting and low back pain.  It forms part of the limited body of evidence that fails to show an association between LBP and sitting.  Of the five papers with data of good enough quality to include in the study, only three were prospective studies.

A prospective study is the ideal for answering this kind of question (note the paper discussed above was not prospective).  You start with a group of healthy participants and you follow them for a number of years – the more the better –  during which time they report on a variety of variables, including some very specific to sitting.  You’d want to know about the nature of the sitting – desktop computer, laptop, duration of time over the week, number of hours without a break and so on and so on, as well as all the psycho- social factors and other bio factors – exercise, other tasks.  And of course you’d want them to report on pain.

But one of the prospective studies was of construction workers – I’m sure I don’t need to explain further (they didn’t do much sitting). One was on newly employed workers (same problem as the 17 year olds, and it was only a two year study).  The third was on nurses, which would seem to have more validity but it was only for a 12 month study and was from 2004 (not in itself a problem except for the point that I’m coming to re laptops).

My point here is that when experts say there is no evidence to support a hypothesis – in this case “slouched sitting causes low back (or neck) pain” –  we need to be sure that the research to which they are referring is rigorous enough. In my opinion the results thrown up by the current body of research are questionable.  We just don’t have sufficient evidence yet to say conclusively that how we sit and for how long is unimportant to back and neck pain.

A great litmus test in these situations is to apply common sense.  Imagine you were made to crouch in a room with a low ceiling for a few hours.  Do you think your neck or back might start aching?  Similarly, if you sit at a laptop – which often combines a degree of slouch with looking down – for eight hours a day (doesn’t count if you separate the screen and keyboard) I’d predict that the odds of your suffering back or neck pain would go up.  Whether you do or not would depend on a whole lot of other factors.

Once again, biomechanics – the study of forces (like gravity) on living organisms (us) matters.  Don’t worry too much about how you sit, but be sure to fidget and take breaks from sitting.  The body has an amazing ability to compensate, but there is a threshold at which the body’s natural reserve will be used up.  Sitting staring into a laptop for eight hours a day, five days a week, perhaps combined with some other biomechanical or psycho-social factors could easily push you past that threshold.

I’ve not moved from my computer for two hours and my back hurts – seriously!

(Image: still from Being John Malkovich)


Make Coordination and Variability a Priority

18 Jan 2018


Key message 1: Coordination plays a key role in our having ease of movement and staying injury free

Key message 2:  We can improve our coordination

Key message 3: We also need variability in the tasks or exercises we undertake.

Coordination is what makes some people move with ease, grace and fluidity while others’ movement appears laboured, difficult, and sometimes painful.

Good coordination really amounts to the activation of the right muscles, in the right sequence, at the right time for the performance of a particular task and helps to keep us pain free and avoid injury.  It also contributes to other motor abilities such as mobility, stability, balance, and strength (sport-specific strength training can be described as coordination against resistance*).

Coordination, therefore, should be a prime training objective.

Coordination can be improved with any task, movement, or exercise using tweaks in the way in which the task/movement is done, and then progressively tweaking back towards the intended task. It requires practice and repetition.

A practical application might be improving coordination during an forward lunge. Initial tweaks might involve holding the back of a chair or wall while lunging; starting with stepping and progressing to a lunge; stepping out wide; adding a hand reach across the body.

But coordination alone is not enough.  It will not prepare you for the unpredictable or unaccustomed –  having your children jump on and hang off you  (a particular favourite of my girls), tripping up or stumbling, changes in terrain or training surface.  For these things we need adaptability, and to acquire adaptability we need to vary the exercises or tasks we do, and the way we do them.

What might that mean in practice?

If you like to squat at the gym, then you might vary the way you squat: play with foot position – staggered, wide, narrow, toes in/out; vary the weights you use: hand weights, bar, medicine ball; vary the rate and rhythm of the squat; take small steps within the squat position – lateral, forward, backward etc.

If you go to a Pilates class and the exercises are the same every week then maybe try a different class.

If you are digging, weeding, or raking the garden, try to vary the way you work, even if it is only a slight change to the way your body would prefer to perform the task.

For a more significant challenge to your coordination try a dance or Zumba class.

Or just play – with the kids or grandchildren, frisbee, hula!

The upshot is that just as we need to keep challenging our brains in new and interesting ways in order to keep our memories and other cognitive functions sharp, so we need to stimulate our motor system in new and interesting ways in order to stay physically sharp.

Use it or lose it!

* Frans Bosch – Strength Training and Coordination: An integrative Approach


Why Biomechanics Matter

01 Dec 2017


Key message 1: Psychology is always important.  Pain is an output of the brain; it is one of the ways the brain lets us know that it perceives a threat.

Key message 2: Biomechanics is the study of forces (mechanics) and their effect on living systems (bio).

Key message 3: We are a living system interacting with a physical world of forces.

Key message 4: Biomechanics is always important.

There has been a huge shift to the biopsychosocial model in manual therapy in the last decade and understanding how psychological factors influence our experience of pain has and continues to change the way physical therapists communicate with, educate, and treat patients.

I think it would be fair to say that while psychological considerations have been in the ascendency, the idea that biomechanics doesn’t matter has been gaining some traction.

Why biomechanics matter

So just in case you are thinking – in the light of my pain series – that pain is all in the brain, then let me explain in broad terms why biomechanics matters hugely.  This might seem blindingly obvious; to say that biomechanics doesn’t matter is like saying gravity doesn’t matter. The more important question might be: when is biomechanics important and when are psychological factors important?

Eric Meira (aka the science PT) uses a great analogy of asking a bunch of paratroopers how they’d feel about being asked to jump out of a plane at 11000 feet without a parachute?  “Scared of getting injured you idiot” comes the reply.  Is a psychological intervention appropriate in this case to help them overcome their fear of injury? Of course not!

What are they scared of? Not being able to handle the huge amount of force with which their mass suddenly decelerates as it hits the ground.  F=ma.  Biomechanics! (Eric Meira)

In a similar way, it’s not enough to tell someone that it is safe to jump, bend, or run when they are in pain.  The role of the physical therapist is to enable successful movement, train, and educate in such a way that it is safe to do those things; provide the necessary safety equipment (motion, coordination and control) and training to use it (at different speeds, positions, and with different loads).   Otherwise fear is a rational response.

When psychology is key

Sometimes we just become fearful of movement, or of re-injuring ourselves.  This may be because we have had an MRI scan that showed a bulging disc in our low back, or because our back has “gone” during lifting in the past, or a therapist or surgeon has told us not to make a certain movement with our back, knee, or shoulder.

The analogy now is that you are simply asking someone to step out of a plane that is sitting on the ground.   The individual needs to be shown that they have the motion, and control of that motion, to pursue meaningful activities with confidence.  And that means gradually progressing the level of difficulty of the activity and ideally moving beyond it, so that it can be performed at greater speed, with more load than necessary, and in more extreme joint positions.  You’ll hear me refer to this as building in a “buffer zone” of function.

In summary:

  • Psychology always needs to be considered
  • Biomechanics is the study of forces in living systems
  • We are a living system interacting with gravity and ground reaction force
  • Biomechanics matter

Understanding pain part 4: persistent pain

08 Nov 2017

Pirate attack (640x396)

Key message 1: pain is an output of the brain in response to multiple inputs.  Inputs come not just from pain sensors, but also from memories, beliefs and attitudes, fear, stress, fatigue and so on.

Key message 2: sometimes the output of pain exceeds the need for pain.  The danger has passed, but the brain is still receiving information that vigilance is needed and pain persists.

Key message 3: understanding the pain mechanism can help us to “self-audit” i.e., ask ourselves what other inputs may be fueling or sustaining our pain experience?

Key message 4:  we are inherently adaptable and can habituate to pain.  With the right help and a staged return to meaningful activities our response to danger signals from our tissues can diminish.

In part one of this series I used Greg Lehman‘s analogy between the way an alarm sounded by a ship’s lookout gets passed up the chain of command to the Captain and how nociceptors ( the body’s pain sensors) pass information up to the brain.  At various levels in the chain of command a decision is made as to whether the alarm warrants action – and so gets passed further up the chain – or can be ignored.

Sighting a light off on the starboard side would be a normal occurrence on a ship and on hearing the lookout’s alarm the first mate/spinal cord may decide there is no reason to notify the Captain.  If, on the other hand the ship was navigating pirate infested waters then the first mate would be sure to notify the Captain and she may well decide to change course.

Persistent pain/Sensitisation

The ship may have left the pirate infested waters where vigilance was necessary to protect it, but if the fear of pirates remains it can stay on high alert and be over-sensitive to information it receives.  In the same way the body can continue to experience pain long after the potential threat has passed.  We become “sensitised”:  pain becomes a learned response.  Sensitisation, as it is called, has to be considered whenever someone has been experiencing pain for a prolonged period of time.


The opposite of sensitisation is habituation.  Habituation means that for the same input over time the output is smaller.  If you get into a hot bath with cold feet the water can at first seem intolerably hot, but very soon we habituate to the temperature and it feels fine.  It’s the same with pain.  We can start to build our tolerance to performing meaningful activities, which can lead to habituation and less pain.  We know that pain doesn’t always mean damage and that we can gradually “turn down” our response to danger signals from our tissues.

When you have been experiencing pain for a long time it is important to return to physical activity just as it is after a shorter episode of pain.  The progression back to exercise will be slower and there may well be setbacks along the way.  Understanding that this is the case can help to overcome any setbacks.

The Captain (brain) can also send information back down the chain.  She can say it’s okay, we know what those lights are; you don’t need to worry about them anymore – the danger has passed.


Abdominal exercises sitting and using lunge sequences

07 Nov 2017

Abdominal exercises performed upright and in our normal relationship to gravity have better carryover to daily activities like lifting children into car seats (one of my own personal training objectives!).  I show a couple of examples here from which you can extrapolate.  The possibilities are, of course, endless.


Understanding Pain – part 3: why load is good

18 Oct 2017


The majority of patients I see in clinic have non-specific pain, that is, it cannot be attributed to a specific pathology like a fracture, tear, or sprain.  Nevertheless, the pain alarm has been triggered indicating that action needs to be taken.

It can feel like a joint is out of place, but we know that most joints don’t go out of place unless there is significant trauma.  It’s more accurate to think of the body in its current state as being unable to find a solution to performing a particular movement.

The purpose of what I do as an osteopath/movement therapist is to enable the body to find a solution by giving it more movement options; to allow it to take another path; a path that doesn’t keep using the same fatigued, sensitised, and sometimes degenerate tissue.

A way of making that process more effective is to work with the body upright and moving, and, provided the area in question isn’t too painful, to start applying load (resistance) to the painful area at an early stage.

Load could mean use of a weight or resistance band, but could equally be a step, lunge, jump, squat (lower body) or a push-up (upper body), which make use of gravity and ground reaction force acting on the mass of the body.

What does load do?  In a nutshell it accelerates an adaptive process within the body.  What do I mean by adaptive process?

In simple terms, I mean tissues like muscles and tendon become stronger; new healthy tissue gets laid down around the damaged or degenerate tissue.

Our nervous system adapts and learns to coordinate movements differently, and with greater speed and efficiency.

But there is a further benefit.  You are able to lift weight or bend with weights.  You might still experience a little pain, perhaps no pain.  You don’t just feel stronger physically, you feel stronger mentally.  You have less of a sense of vulnerability, less fear, less need for your protective mechanism.

You have less pain!