Are you perturbed…?

To be perturbed is described as being anxious, unsettled, or upset and there is no doubt that some of my blogs have perturbed a few of you over the years, however, for once that is not my intention with this one. Perturbed also has another definition, that is to influence a subject or object so that it alters its normal or regular state and changes path or direction, it is this type of perturbed that I want to talk about.

You may, or may not be aware that I love working with the shoulder, I think it is a remarkable, exciting, yet challenging area. One such challenge is when a shoulder has suffered a loss of stability either through trauma or other issues. Restoring an individuals shoulder back to full function once it has dislocated, subluxed or just generally lost its sense of stability can be a challenge, both physically and psychologically.
However returning a patients shoulder mobility, strength and even control can often be the ‘easy’ part in rehab, but restoring an individuals faith, trust, and confidence into an area that has, or still is, causing them fear, apprehension, pain, and disability is far harder to achieve.
When ever there is a lack of confidence or trust in anything, a graded and progressive exposure to novel, challenging, and even threatening tasks and stimuli is required over a period of time for adaptation and desensitisation to occur, again both physically and psychologically.
In fact thanks to the recent Pain Science and Sensibility Podcast with Sandy Hilton and Cory Blickenstaff I have learnt that this may need to be done a little differently than I have been doing. Sandy and Cory discuss this paper here, where it seems the greater the exposure to an expected risk or threat the better the positive outcome is if it successfully challenges or violates the individuals perceived expectations, go listen to Sandy and Cory talk more on this here.
Anyway back on track, a great way to achieve some graded exposure to perceived threat and risk for an unstable shoulder I find is with perturbations.
Perturbations are simply a therapist, or anyone else for that matter, applying external forces to a patients arm or shoulder that they are not in control of, that try to offset, change direction, and alter the patients shoulders equilibrium. Fancy stuff hey, but they are dead simple to do and apply, and there are a million and one ways they can be done. I discuss and demo a lot of these on my shoulder courses (shameless plug here).
pertubation 1

me performing a version of open chain shoulder perturbations on a recent course in Norway

Shoulder perturbations usually involve the therapist pushing, pulling, tapping or slapping a patients arm or body in various different directions, speeds, and forces, with the patient in various different positions and in different levels of support and stability
I usually start with perturbations that are the least threatening and perceived as less risky for the patient and progress them as they became more confident, however, as I said earlier after listening to Sandy an Cory’s recent podcast I may change this for some of my patients and violate their expectations a little more robustly. Of course we still need to respect healing times, and forces applied to any post traumatic or surgical stabilised shoulder.
I usually start shoulder perturbations in a closed kinetic chain positions such as four point kneeling, I then apply the perturbations close to the shoulder joint or even to the torso, at a low intensity, rhythmically and regularly for about 10-20 seconds and repeat 3-4 times. I progress this by increasing the intensity, changing the direction and regularity of the perturbations. I then progress by reducing the base of support as well as going from closed to open kinetic chain positions. I also like to progress by asking patients to close their eyes as this adds another level of unexpectedness and again can challenge their sensations of control and stability.
I also like to bias the direction of the perturbations depending of the direction of shoulder instability, targeting the portion of the rotator cuff that needs to work more to control humeral head displacement. However, I still often hear and see therapists getting this direction specificity of the rotator cuff completely ‘arse about face’ that means wrong!
The rotator cuff does NOT act like a physical barrier to the humeral head, it does NOT contract against the humeral head to prevent its displacement. The rotator cuff actually contracts in the opposite direction of humeral head movement, think of a tug of war with the humeral head in the middle and the cuff pulling back on it. This direction specificity has been shown here and also here during perturbations.
So for anterior shoulder instability it is the posterior cuff of the infraspinatus (and supraspinatus as they are conjoined) that contracts to prevent anterior displacement, therefore internal rotation perturbations are better, and for posterior shoulder instability its subscapularis that contracts to prevent posterior humeral head displacement and so external rotation perturbations are best.
So there you go, a quick little blog on the use of perturbations in the management of unstable shoulders. Of course there will be physical effects from doing them, in fact they can be quite bloody demanding and fatiguing when done at higher intensities and speeds, but the main benefits from this method I feel are psychological. Perturbations can challenge perceptions and expectations of shoulder instability when factors are out of an individuals control and when the expectations are challenged, the threat is reduced.
Get me… am I a physiotherapist or a pseudo psychologist?
As always thanks for reading



  1. Thanks for the mention, Adam! Glad you liked the podcast. One of the several interesting points that was made in the paper was variability in the exposure level, jumping around the heirarchy of feared tasks vs. progressively climbing the heirarchy, seems to add some resilience in the populations that they’ve studied. So, where in the past I might have progressed a patient in a very sequential manner, this suggests that jumping around a bit may help with the sustainability of the effect. Another interesting finding was that they would do what was called “compound exposures” where they would add multiple stimuli over time. An example to the shoulder might be varying the amount of load in a surprising way in addition to varying the timing and direction of load in mutliple ways. They found that the compounding would also add to the maintenance of the effect in the populations that they’ve studied. Cheers!

  2. Jumping around quite a lot is probably best, specifically by the time we get to perturbation. There is quite a lot in motor learning literature about the advantages of variability in practice and contextual interference. Pretty much all of the literature points to little stracure in practice, for both retention and transfer. As for addition of complexity to the task I think Gentile taxonomy of task is a nice conceptual frame work to advance in practice, together with the other things we use, such as load.

  3. I listened to the podcast and found it very interesting. I hate to be tethered to previous ideas but please rock my preconceptions…
    With altering the hierarchy of graded exposure do you also risk failing and as a result affecting confidence to persist with the approach?

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