Movement analysis: why your assessments miss the essential

1/4h LabO #242, Watch the episode on YouTube

In the warm-up everything lines up, in competition the symmetry collapses. Most assessments then go looking for a weak muscle, and go around in circles. Movement analysis through the sensorimotor loop answers differently: before correcting the movement, look at how the brain reads the information that comes before it.

What a classic movement assessment leaves in the blind spot

A runner shows up on the field. In the warm-up, easy high knees, low intensity, and everything lines up: clean alignment, tidy cadence, identical right-left ground contact times. Nice work. Then you raise the intensity, more ground contact, more strike. Within a few strides, the symmetry is gone. No way to regulate anymore. In training it passes, in competition it breaks.

The reflex we've all had is to go looking for a weak muscle or a missing range of motion. You test, you strengthen, you stretch. And you go around in circles. The real lead is elsewhere: proprioceptive information from the ankle, inherited from several sprains, sending a false alarm up to the nervous system. The brain receives signals that don't agree, it no longer knows whom to believe, and it pulls the handbrake before the athlete has even been able to put their force into the ground.

Hence the question that opens everything that follows: what if the problem was not in the movement itself, but in the way the brain reads information before moving? That is the blind spot of the assessments we all practice. We'll see how to reread an assessment through the sensorimotor loop, and why it changes the way you correct.

Look at what is really practiced among sports coaches, physical preparation coaches, physiotherapists, osteopaths. The assessment almost always comes down to one thing: the motor output. We measure the movement produced. We note ranges of motion, muscle shortening, strength ratios. It's useful, and yet it describes the end result without ever questioning what comes before it.

You know the tools. The FMS (Functional Movement Screening) gives a final score that extrapolates toward a kind of injury risk: a good indicator of movement quality, to keep on the side. Muscle shortening tests, scored from 0 to 4 (0 or 1 for very stiff, 4 for hypermobility and hyperlaxity), build a spider-web map, muscle group by muscle group, right side, left side. Strength ratios spot the lagging groups to target specialization cycles. All these tools stand up and deserve to stay in the assessment.

What they lack is something essential: they are done on one or two repetitions. No fatigue, no dual task. Yet on a team sport field, fatigue and dual task are the norm, not the exception. An athlete can be perfect on one cold repetition and drop off as soon as the system is truly challenged.

And then the motor output represents a third of the system, and it is the last step in the chain. The better calibrated you are on the perception side, the better interpretation and decision-making will go, and the better the motor output will be executed. Working only the end of the chain amounts to ignoring the two thirds that determine it.

The sensorimotor loop, the real object of movement analysis

One sentence sums it up: I move to perceive, I perceive to move. What you perceive will directly mediate the movement capacity you observe in the person in front of you. This is the perception-action loop, at the base of the theories of motor learning and motor coordination.

Type "how we move" into a search engine and you land on a short answer: voluntary movement is commanded by the brain via the motor cortex. That's true, and far too thin for a movement professional. The sensorimotor loop is a vivid way of understanding the nervous system and how it really works. It allows the body to move in a precise and coordinated way. Throw it off balance, and movement suffers.

If you have to retain just one thing: the nervous system does four things, in order. It takes in information from the environment. It interprets it. It makes a decision based on those interpretations. It sends a motor command to the muscle. The motor output comes last, after three steps the classic assessment never sees.

Afference and efference

Information intake goes through the sensory receptors: vision, somatosensation, vestibular. These inputs create an afference, an upward flow toward the interpretation and decision-making centers. Once the decision is made, an efference comes back down and produces the motor output. This output moves the body, which immediately generates new perceptions, which restart the loop. Hence the term perception-action loop: input through the receptors, output through the muscle, and the output feeding the next input in return.

How the brain organizes movement

For a movement professional, ignoring the nervous system in movement borders on heresy. Here is the map, non-exhaustive, of the structures that build a movement.

The cortical and subcortical levels

The frontal lobe creates voluntary movement. The parietal lobe manages the placement of the limbs and body in space. The occipital lobe processes vision. The supplementary motor areas ensure axis stabilization and bilateral movements. The brainstem regulates autonomic functions, reflex stabilization and baseline tone: keep this point in mind, because it means that when you talk about posturology, you are actually talking largely about the brainstem. The basal ganglia initiate movement. The thalamus regulates force, among other things. The cerebellum ensures stabilization and coordination in movement. The peripheral nerves conduct the impulse. Each of these levels should be testable and interpretable by a movement professional.

The three major sensory inputs

Upstream of all this, three entry doors feed the system. Somatosensation, in the broad sense, which includes proprioception, itself linked to the mechanoreceptors. Proprioception is the awareness of your body in space and time: the ascending information that draws a map of your body, and the goal is to have the most precise map possible. The visual system and oculomotor function, that is, the ability to move the eyes as fast as possible, in depth, right, left, in saccades and pursuits: six muscle groups per eye, which are trained like a biceps or a quadriceps. The vestibular system, the sense of balance. These three inputs are the fuel of the entire loop.

Calibrating each input to 100%: the onion image

The nervous system is built like an onion. During a child's development, from 0 to 7 years, following the logic of Piaget's stages, motor function adds layers as it goes, until a mature onion is obtained. Keep this image in mind to understand what an optimization assessment is really looking for.

The goal of an assessment is not to treat a pathology. Vestibular physiotherapists take care of the pathological. Optimization aims at something else: a 100% mature onion, where all the sensory inputs are calibrated to the maximum. Balance becomes a physical quality in its own right, pushed to 100% of its capacity the way you push strength or speed. Proprioception must provide the finest body map. Oculomotor function must be as efficient as possible, which weighs enormously in information-intake sports like soccer, handball, basketball.

To these three calibrated inputs is added a fourth requirement: the proper integration of all the information, whatever happens, in the act of moving in the real world, on a field, at a desk, or for a child learning at school. A robust sensorimotor loop means as many layers as possible, the most complete calibration possible, for the cleanest possible motor, cognitive and emotional outputs.

Safety or survival: the filter that decides before the movement

Another way of seeing the loop: a threat balance. Imagine sand falling at the point of the inputs. Each grain is a piece of information: the sensory inputs, but also stress, emotions, beliefs, activity, sleep, nutrition. All this sand falls into an interpretation filter fitted with a sieve.

The higher the quality of an information, the finer the grain. A fine grain passes through the sieve and falls on the safety side: there, the system can produce force, speed, resilience, endurance, coordination. A grain that is too coarse (average sensory inputs, high stress, shaky sleep, poor nutrition) doesn't pass the sieve and falls on the survival side: fatigue, dizziness, tension, pain. And if survival accumulates too much, you hit the survival buzzer, even more advanced states.

What the filter looks for: surplus, errors, mismatches

The interpretation filter sits between the old brain and the new brain. The new brain is the cortical parts. The old brain is the subcortical structures, like the brainstem or the thalamus. At this point, the system looks at three things: is there a surplus of information, an error in information, or a mismatch? These are what tip the balance from the coarse grain toward survival.

The most telling mismatch is motion sickness. In a car, passenger side, you look at your phone. Your vestibular system tells you that you are moving, your visual system tells you that you are not moving. The two signals don't match. The filter doesn't know which one is right, and it still has to warn the conscious mind that something is off. How? Rising nausea, a spinning head: the onset of motion sickness, on the survival side. A mismatch between two inputs is enough to tip the whole system.

When the mismatch pulls the handbrake

Back to the runner from the start. He has sprained his right ankle several times. While running, his visual system tells him he is going straight, that he is not falling. His vestibular system confirms it, via the otolith organs: good vertical rebound, good horizontal advance thanks to the utricles, little head movement. But on the proprioceptive side, because of the sprains, the information coming up from the ankle says it is going sideways, as at the time of the injuries.

The nervous system finds itself facing a mismatch: vision says it's fine, the vestibular system says it's fine, the ankle's proprioception says he is falling. At the level of the filter, impossible to decide. So it pulls the handbrake, because it wants neither another sprain nor a fall. That is why at low intensity everything stays symmetrical, and why as soon as you add ground contact, you stimulate certain mechanoreceptors, wake up the ankle's proprioception, and the symmetry collapses. As long as you haven't identified the proprioceptive problem, you are looking in the wrong place. In training it passes, in competition it breaks.

All this draws a continuum. On one side, a poorly calibrated loop brings out pain, chronic fatigue, lack of mobility, tension, stress, poor posture, poor motor control, lack of balance, dizziness, hyperactivity, poor coordination. On the other, a loop that calibrates, that adds layers, that masters the body better sensorially, leads to more freedom of movement, coordination, strength, speed, endurance, good balance, and even better endocrine, immune and digestive health, because the brainstem also manages the autonomic functions. And bridges form toward other populations: the child who sits better to write, the executive who stays focused longer. It is the same loop, read the same way.

The three phases of movement and the role of the brainstem

The finest layer of the analysis breaks every movement down into three steps ordered in time. First, a proactive, or anticipatory, reflex stability. Second, the voluntary movement. Third, a retroactive, or compensatory, reflex stability. The visible movement is only the second phase, framed by two unconscious reflex phases.

The cannonball analogy and the EMG evidence

To grab a door handle, you use the biceps. Yet if you look at the EMG, the gastrocnemius activates before the biceps. This prior activation is the proactive reflex stability. The image that fixes the mechanism: to fire a cannonball, you must first anchor the cannon to the ground. Fire from a canoe, and the ball doesn't go far. Anticipatory reflex stability stabilizes the body before the voluntary movement, completely unconsciously, through reflex pathways that go through the brainstem.

A decisive detail: this stability occurs ipsilaterally, on the same side as the hemisphere that initiates the movement. To move your right arm, it is your left frontal lobe that sends the command, and before that command, a stabilization comes down from the brainstem on the left side, the same side as the arm. The anchoring always precedes the movement.

The brainstem as a crossroads

The brainstem has three major structures: the midbrain, the pons and the medulla oblongata. The midbrain carries two cranial nerves, the pons four, the medulla oblongata four. Add the two outgrowths above the midbrain, nerve 1 and nerve 2, and you get the 12 pairs of cranial nerves. Knowing how to test each pair precisely should be part of a movement professional's toolbox, precisely because anticipatory reflex stability goes through this area.

That is also why the brainstem is the central crossroads. It mediates baseline tone, hence posturology. It carries reflex stability, hence the link with archaic reflexes. It is an interpretation center of the loop, hence the link with functional neurology. And it commands the autonomic functions, hence overall health. It is through this structure that training, posturology, archaic reflexes and functional neurology link up into a single coherent system. Locating the imbalance on the loop, then recalibrating the input concerned, is what a good assessment aims for, instead of stacking heavy programs that only work the motor output.

FAQ

What is biomechanical movement analysis?

It is the evaluation of the motor output: joint ranges of motion, muscle shortening, strength ratios, movement quality through tools like the FMS. Useful and worth keeping, but partial. These measurements describe the movement produced without questioning the perceptions, interpretation and decision that precede it, whereas the motor output represents only a third of the system and comes last in the chain. They are also done on one or two repetitions, without fatigue or dual task, which leaves out the real conditions of competition.

Posture and movement analysis: what contributions in sports medicine?

Field experience shows that posturology is not an isolated domain. Postural observables (knees in flessum or recurvatum, iliac spines, centering of the navel, foot roll-through, dorsiflexion, height of the malleoli) inform on baseline tone, and baseline tone is mediated by the brainstem. Linking posture, brainstem and sensorimotor loop opens a side of optimizing existing potential, beyond the development of physical qualities alone, even in national and international level athletes.

And then, once the assessment is done?

Once the imbalance is located on the sensorimotor loop, the work consists of recalibrating the inputs concerned, in a logic of neuro-postural reprogramming. If the ankle's proprioception is the cause, that is what gets recalibrated, rather than adding heavy motor-output programs that don't treat the cause. We add layers to the onion to tip the system toward the safety side rather than the survival side.

How can you be sure this approach is reliable?

Several markers: trainings attended around the world (United States, Australia, England, France), covering existing curricula in functional neurology and archaic reflexes; a collaboration with a neuroscience laboratory to link movement and neuroscience; a scientific study launched in schools in 2025, whose first results, arriving at the end of the year, indicate that working on motor function and the brain changes the way of learning; a book; and field feedback accumulated over fifteen years of practice with high-level athletes.

Related articles

• The sensorimotor loop: how the body senses, decides and moves

• Sensorimotor loop: what if performance was decided before the muscle?

• Improving your practice through the sensorimotor loop: why the same exercise works for one person and fails for another

• The sensorimotor loop: understanding how you move

Discover the Neuro-Postural Reprogramming training