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Athletic development specialists dedicated to the art and science of excellence in movement

"Stiffness is a Strategy"

The term “mobility” gets thrown around with impunity, yet often without context.  Come on, who doesn’t like “mobility”, just as how can you argue with “functional training”?  However, without proper context, problems arise with attacking mobility in isolation and chasing mobility for mobility’s sake.

Recognize that stiffness, or immobility, is a strategy chosen by the central nervous system.  One hypothesis behind stiffness is the brain is guarding the body, almost a sense of hypervigilance.  Gray Cook has a pithy way to describe the neurology of immobile versus the unstable…the immobile system is PARANOID.  It won’t let go.  Joints and muscles get stiff because the brain’s afraid to move them, and often for good reason when people don’t move well.  The unstable system is CONFUSED.  It has plenty of mobility but doesn’t know how to use it.  Of course, these systems can be hybrid as well.

Absent structural limitations (such as a spinal fusion), stiffness results from output from the brain.  Sometimes stiffness occurs at rest.  Maybe we even feel “tight.”   But it’s all there for a reason.

Implication: if you add mobility, you need to provide the body with a new form of stability, lest it reset to its acquired pattern.  Mobility with the addition of stability may actually lead to improvements in mobility. 

“Global muscle retraining is required to correct multisegmental or myofascial dysfunction in terms of controlling the site and direction of load that relates to provocation. The strategy here is to train low-load recruitment to control and limit motion at the site of pathology and then actively move the adjacent restriction, regain through range control of motion with the global stability muscles and regain sufficient extensibility in the global mobility muscles to allow normal function.” (Comerford 2001)(See also, addition of weights enhanced the effectiveness of stretching exercise for increasing joint ROM with 4 of the 6 selected measurements, Swank 2003)

In short: train mobility and stability together.  Only give the system as much mobility as its ready to tolerate!

Ideally we are relaxed at rest and stiff/stable when needed.  This ying and yang of mobility and stability occurs in simple movements like walking (certain parts of the body stiffening to brace impact with the ground) and also in dynamic movements like collision sports.

Adding mobility requires unlearning previous strategies and retraining new ones.  Within each intervention it’s important to understand the evidence of how and why each works.  In coaching, rehab, and general fitness there’s a tendency to reflexively apply the WD-40/Duct Tape Model, but a more nuanced approach is often needed.

“Low joint stiffness may compromise robustness to external perturbations; however, a limited stretch reflex combined with more powerful longer latency reactions are available to maintain the limb on track. Although increasing stiffness is a strategy which is sometimes used during movement, via co-contraction, increasing both robustness and movement accuracy the CNS seems to prefer maintaining the limb at a very low stiffness level, a strategy which is potentially energy efficient and relies on multiple reflex pathways and visual correction for stability in the face of perturbations.”  (Popescu 2003)

We don’t want joint tight at rest, but sometimes that’s the best strategy available to that individual based on present physical limitations.   People without these impairments might be stiff for other reasons, but it’s the same nervous system producing these outputs.  

If we create mobility without stability one of three things typically happens:

1)      Get a fleeting improvement, but because the nervous system hasn’t been given a reason to adopt a new strategy, it defaults back to old habits.  Remember, stiffness is a strategy…sometimes as a defensive mechanism, but if pain is/was present, stiffness can appear in unpredictable fashion.

2)      Mobility without stability leaves individual vulnerable. (Dancers with decreased hip and ankle/foot joints ROM are less prone to develop patellofemoral pain syndrome. When making an association between joint ROM and injuries, not only the ROM at the targeted joint should be considered, but also the ROM at neighboring joints.  Steinberg 2012)

3)      Get lucky and stability automatically resets.

Stability need not be high tension via planks or heavy lifting.  It may develop through improved skill acquisition, whether in basic movements or sport specific corrections.  The appropriate level of intervention will vary based on individual need.

Interestingly, several studies in the literature use this exact terminology.  Surely there are others that refer to the strategic nature of stiffness with other language, but here are several where the exact terminology “stiffness is/as a strategy” is used. 

  • Brown (2006) - "adjustment in ankle stiffness is a strategy adopted by the CNS to passively control movement of the COM (center of motion)"
  • Jaskowski (2000) "limb stiffness is a strategy developed to cope with task demands"
  • Robinson (2009) "postural stiffness is a strategy used by some individuals with vestibular loss to compensate for impaired balance"
  • Nagai (2001) "greater co-contraction of antagonists with resultant ankle joint stiffness as a strategy to maintain postural stability"

Watch someone perform a task with which they are not familiar.  Movements are stiff because they haven’t learned to rid themselves of stiffness.  Stiffness is a strategy to keep them from hurting themselves.  If you take away stiffness too fast, they may fall.  Long term goal of training is to remove the brain’s sense of paranoia.

Although these references relate to dynamic stiffness, the same logic applies to passive stiffness.  Stiffness reflects the brain’s strategy for heightened vigilance at rest.  Maybe the brain has a good reason for this strategy.  Mobility training alone may reset the system and stability may be a default output, but that leaves too much to chance. 

In sum: mobility must be met with stability.  Earn the right to use mobility, and don’t just mobilize what feels tight.  TIMING and SEQUENCE of the interventions matters.  Sometimes the brain has your best interests in mind.  As Shirley Sahrmann is fond of saying for those in pain (paraphrased), “I don’t care where you don’t move, I care where you do move.”

References

Popescu F, Hidler JM, Rymer WZ.  Elbow impedance during goal-directed movements.  Exp Brain Res. 2003 Sep;152(1):17-28. Epub 2003 Jul 23.

Brown LA, Polych MA, Doan JB.  The effect of anxiety on the regulation of upright standing among younger and older adults.  Gait Posture. 2006 Dec;24(4):397-405. Epub 2006 Oct 20.

Jaƛkowski P, van der Lubbe RH, Wauschkuhn B, Wascher E, Verleger R.  The influence of time pressure and cue validity on response force in an S1-S2 paradigm.  Acta Psychol (Amst). 2000 Sep;105(1):89-105.

Robinson BS, Cook JL, Richburg CM, Price SE.  Use of an electrotactile vestibular substitution system to facilitate balance and gait ofan individualwith gentamicin-induced bilateral vestibular hypofunction and bilateral transtibial amputation. J Neurol Phys Ther. 2009 Sep;33(3):150-9.

Nagai K, Yamada M, Uemura K, Yamada Y, Ichihashi N, Tsuboyama T. Differences in muscle coactivation during postural control between healthy older and youngadults.  Arch Gerontol Geriatr. 2011 Nov-Dec;53(3):338-43. Epub 2011 Feb 9.

Swank AM, Funk DC, Durham MP, Roberts S.  Adding weights to stretching exercise increases passive range of motion for healthy elderly.  J Strength Cond Res. 2003 May;17(2):374-8.

Steinberg N, Siev-Ner I, Peleg S, Dar G, Masharawi Y, Zeev A, Hershkovitz I.  Joint Range of Motion and Patellofemoral Pain in Dancers.  Int J Sports Med. 2012 May 4. [Epub ahead of print]

Comerford MJ, Mottram SL.  Functional stability re-training: principles and strategies for managing mechanical dysfunction.  Man Ther. 2001 Feb;6(1):3-14.

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