Darbe Schlosser
THOUGHT PAPER / MOTORVATION
BEFORE THE FREEZE
Why Parkinson’s rehabilitation may be asking the wrong question about freezing of gait
A dynamic systems perspective on movement, learning, and stability, drawn from more than 14,000 hours of one-on-one work with people who have Parkinson’s. This is not a finding. It is a hypothesis, and an invitation to ask better questions.
I The wrong question
When someone with Parkinson’sfreezes, the instinct is to ask why. We look for the trigger: the doorway, theturn, the crowded room, the divided attention. These triggers explain less thanthey appear to.
The same personhas walked through that same doorway a thousand times. Until one day, theycannot.
If the doorwaywere the cause, the freeze would have happened the first time. It did not.Which means the doorway is not the cause. It is the final straw on a systemthat had already changed.
So perhaps themore useful question is not why did this person freeze, but whatchanged inside the nervous system that made freezing possible in the firstplace.
A trigger only works on a system that is already vulnerable.If that is true, the freeze is not the start of the problem. It may be thefirst moment the problem becomes visible.
II The story almost everyonetells
I have heard aversion of the same story more times than I can count. I was doing well. Iexercised every day. I stayed active. Then suddenly, everything changed.
That moment ofchange is almost always when freezing began. And almost everyone describes itas sudden.
But “sudden” isa statement about perception, not about mechanism. A hurricane is not sudden.Long before anyone names a storm, thousands of small atmospheric interactionsare already unfolding. By the time we see it, the storm is not beginning. It issimply the first thing large enough to notice.
What iffreezing works the same way? What if the freeze is not the start of a decline,but the first visible sign of a movement system that has been slowly losingstability for months, or years?
I am not claiming Parkinson’s is a chaotic system in theformal mathematical sense. That has not been demonstrated. Thehurricane is a metaphor, borrowed from nonlinear dynamics, and I am using itonly to raise testable questions, not to assert a mechanism. It points at onereal and testable question: if freezing is the storm, what was the weatherdoing for the year before?
III Movement as a dynamic system
To take thatquestion seriously, it helps to stop thinking about movement as a set ofmuscles firing independently, and start thinking about it as a set ofrelationships that have to be continuously balanced. This is not a new way ofseeing movement: motor coordination research already treats action as coupledvariables shaped by feedforward and feedback control, rather than as isolatedmuscles working on their own.
In healthymovement, space and time are coupled. If you want to move bigger, you naturallyslow down enough to cover the distance. If you want to move faster, the size ofthe movement usually has to change. Running and marching are not two separateactivities so much as two solutions to the same underlying trade-off: fast withsmaller excursions, or slower with larger ones.
A healthynervous system organizes this automatically, thousands of times a day,adjusting joint angles, stride length, cadence, weight transfer, force, andtiming together so the whole pattern stays efficient. This constantre-optimization may be one of the quiet foundations of movement stability.
Here is thehypothesis at the center of this paper: what if Parkinson’s graduallyimpairs this ability to re-optimize? Not the ability to move, but theability to keep adjusting the relationships between the parts of a movement ascontext changes.
If that istrue, the consequences would be subtle at first. The movement would stillhappen. The person would not fall. It might even look fine. But underneath, theparameters would no longer be adapting together the way they should.
IV What is the nervous systemactually learning?
For decades,the dominant message in Parkinson’s rehabilitation has been clear and largelycorrect: move more, walk more, exercise harder, raise the heart rate, stayactive. I believe in this. The evidence for exercise is strong, and nothinghere should be read as an argument against it.
But underneaththat message is a question we rarely ask. When a person is moving hard, what istheir nervous system actually learning?
Consider aboxing-style session, the kind common in our field. I offer it as anillustration, not as a criticism of any specific program. The instruction is topunch bigger, punch faster, work harder. Heart rate climbs. Sweat pours. Byevery visible measure, it is a successful session. But did the person learn amore stable way to move? Or did they repeat, hundreds of times, a pattern inwhich timing, trunk rotation, joint angles, and effort no longer matched eachother?
Healthy scaling
Wants a bigger punch. Slows the movement slightly, rotates the trunk more, shifts weight, and lets hips, shoulder, elbow, and hand scale together. The whole pattern stays coordinated.
Compensated effort
Is told to go bigger and faster. Drives from the arm alone, never adjusts the timing, effort rises while coordination falls. The punch still lands, but a less stable pattern is being rehearsed.
If the secondpattern is repeated often enough, the nervous system is not practicingstrength. It is practicing a less stable movement strategy, possibly withoutanyone noticing, including the person performing it.
I will admitsomething that is difficult to put in a paper. I see a version of this almostevery day. Someone posts a video of a person with Parkinson’s exercising, andthe comments fill with encouragement. That encouragement is understandable, andoften deserved: the person is showing up, working hard, which for many is thebiggest hurdle. Everyone is moving, everyone is celebrating, everyone isencouraging one another. But while others see progress, my eye keeps catchingsomething else: timing that no longer matches amplitude, effort rising whilecoordination quietly falls away, a system that looks busy rather than stable. Icannot prove what I am seeing, and I hold it as a hypothesis rather than averdict. But after enough hours, the pattern becomes hard to unsee.
I watch the early conditions of a hurricane forming, whileeveryone celebrates the sunny weather.
So I have toask the uncomfortable version of the question. Am I the only one seeing this?Or has the field grown so enthralled with exercise, which is comparatively easyto study, easy to fund, and easy to promote, that we have stopped asking theharder questions beneath it? Movement quantity is simple to measure and simpleto cheer for. Movement quality is neither. My worry is that we have optimizedfor the part that is easy to see.
V The error you never felt
There is asecond hypothesis underneath all of this: that people with Parkinson’s may havea reduced ability to detect their own subtle movement errors. This is not awild guess: people with Parkinson’s are known to show altered proprioceptionand reduced awareness of certain non-motor changes, so the idea that somesubtle movement errors might go unregistered is at least consistent with whatis already observed.
In healthymovement, you make small errors constantly and correct them just as constantly.The nervous system compares what you intended with what actually happened,registers the mismatch, and adjusts. This loop runs silently, beneathawareness.
Now imaginethat loop is blunted, just slightly. Not enough to cause a fall. Just enoughthat small mismatches stop being noticed. Each uncorrected repetition is not acatastrophe. It is a tiny compensation, a micro-adaptation, barely anything onits own. But practiced thousands of times without correction, thosecompensations may slowly become the system’s new default.
Practice does not only reinforce good patterns. It reinforceswhatever pattern is actually being repeated, monitored or not.
This reframesthe central concern. The risk may not be exercise. The risk may be unmonitoredrepetition under impaired self-correction.
VII The nonlinear part
This is wherenonlinear dynamics enters.
A system thataccumulates small inefficiencies does not necessarily decline in a smooth,proportional way. It can tolerate a great deal for a long time while lookingstable from the outside. The person keeps walking, keeps functioning, keepsdoing well. And then, past some threshold, the same system can transitionabruptly into a qualitatively different state.
In dynamicalterms, freezing looks less like a symptom that switches on and more like astate transition: the movement system slipping from one mode of organizationinto another. Some existing models already frame freezing of gait as anetwork-level disturbance or a change of state rather than a purely local,peripheral event; what this lens adds is to carry that same logic out of thebrain-network picture and into the practice environment, where training anddaily movement may be nudging the system toward or away from those transitions.
Seen this way,a trigger like a doorway or a turn does not cause the freeze. It is a smallperturbation that happens to arrive when the system is already close to atipping point. The disproportion is what you would expect from a systemoperating near a threshold.
I will sayagain what I said before: this is an analogy anda lens, not a proof. The lens earns its place not by being true, butby changing the questions we ask.
VII What this would change
If even part ofthis is correct, it shifts the goal of rehabilitation. The question moves fromonly asking how hard is this person working to also asking is thenervous system learning a more stable way to move. These are not the samequestion, and they do not always have the same answer.
It would meantreating movement quality, not just movement quantity, as a primary target. Andquality can be operationalized with observable parameters, such as how wellspace and time stay coupled, how consistent timing is from one repetition tothe next, and whether a person shows signs of detecting and correcting theirown errors. It would mean designing practice so that error-detection issupported rather than bypassed. It would mean thinking of cueing not only as away to externalize control in the moment, but as a way to temporarily restorethe coupling between space and time that the system is struggling to hold onits own. And it would mean paying attention to stability long before freezingappears, on the premise that the most treatable moment may be the one beforethe system reaches its threshold.
Quality oflife, in the end, is determined by what a person can still access when they arenot moving well. The aim is not only to help people recover from freezing onceit arrives. It is to understand what happens in the months and years before,and to intervene while the system is still flexible enough to change.
THE BETTER QUESTIONS
1. What changed in the nervous system before the freeze, rather than what triggered it, and could we learn to detect those changes within practice sessions?
2. Is the system learning stability, or just accumulating effort?
3. Can the person still detect their own subtle movement errors, and what does practice reinforce if they cannot?
4. Can we measure the coupling of space and time, in both gait and upper-limb tasks, and does improving it change what happens next?
If these questions are even partly the right ones, thenfreezing is not simply an event to be managed. It is the visible edge of aslower story we have not yet learned to read. That story is where I intend tokeep looking.
[Yourname]
Founder, MOTORVATION · THINK and Move Well
This paper presents ahypothesis and a point of view, not a clinical guideline or a claim of provenmechanism. Shared to invite discussion among clinicians, researchers, andpeople living with Parkinson’s.
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