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Mechanism
Intermediate
8 min read

Balance

Three independent sources of information the brain has to reconcile. Standing still is not a stable state: it is a permanent correction, and closing your eyes is enough to make that visible.

Standing is not a state

The picture of a body "in balance" suggests a stable state, reached and then held. The measurements say otherwise: standing without moving, the body sways continuously, and those sways are constantly corrected.
What we call balance is therefore a process, not a position. It never stops, including when nothing seems to be happening.

Three sources, one conclusion

The nervous system has three channels of information about the position of the body, and they are independent.

Where the information comes from

Source
What it reports
What defeats it
Vision
The position of the body relative to the surroundings
Darkness, surroundings that are themselves moving
Proprioception
The position of the segments relative to one another
An unstable surface, fatigue
Vestibular apparatus
The movements and orientation of the head
Damage to the inner ear
Proprioception has its own page. Vision is the most obvious channel. The third is the least known, and it is housed inside bone.

The vestibular apparatus

Vestibular apparatus
A set of fluid-filled cavities in the inner ear that detect the movements and orientation of the head. It plays no part in hearing, although it shares the same bony region.
organ of balance
It is built in two parts, which do not measure the same thing.
The semicircular canals are three tubes set in three different planes. When the head turns, the fluid inside them lags behind the wall, and that lag is detected. They therefore signal rotations.
The otolith organs contain minute crystals resting on a sensitive membrane. Their weight tips them when the head tilts, and their inertia shifts them when it accelerates in a straight line. They therefore signal orientation relative to vertical and linear accelerations.
Certainty level · Established
Balance control rests on integrating visual, proprioceptive and vestibular information, whose relative contribution varies with conditions.
This is agreed across the reference works in neuroscience, established notably by removing or perturbing one source at a time. The exact proportions depend on the task, the supporting surface, the lighting and the person: no single split holds everywhere.
Kandel ER, Koester JD, Mack SH, Siegelbaum SA (2021) · Purves D, Augustine GJ, Fitzpatrick D, Hall WC, LaMantia AS, Mooney RD, Platt ML, White LE (2018)

The experiment everybody has already done

Stand on one leg, then close your eyes. The difficulty rises immediately and markedly.
Nothing has changed in the leg: not the strength, not the position, not the surface. What changed is the number of channels available. The system was working with three sources, two remain, and it has to lean harder on them.
That is the simplest demonstration of the principle: balance is not a quality of the body, it is the result of sufficient information and fast correction.

When the sources disagree

The three channels do not always say the same thing, and the system then has no way of knowing which is right.
This is what happens in a ship's cabin: the vestibular apparatus signals movement, vision sees only a still room. The conflict between the two is the mechanism most often invoked to account for motion sickness.

What this illuminates elsewhere in the corpus

The walking page describes a single-leg stance occupying more than a third of the cycle, during which the pelvis must be held. The lunge page describes a narrow base that makes sideways control a constraint in its own right.
In both cases the muscular command presupposes reliable position information. Gluteus medius can only correct a pelvis if something has signalled that it was tipping.
And the sense of effort itself is not a reliable gauge.
Certainty level · Probable
The perception of the force produced depends partly on signals tied to the command sent, and not only on peripheral receptors.
The review gathers work on perceived position, movement and force. The respective share of central and peripheral origins remains debated across tasks, but the existence of a central contribution is widely accepted.
Proske U, Gandevia SC (2012)

Why no scene accompanies this page

Limit
An organ inside bone
The vestibular apparatus sits within the thickness of the temporal bone, and its cavities measure a few millimetres. The skull does appear in Body Lab's scenes; what it contains does not.
Showing a skull on a page devoted to balance would mean showing a container for its contents — the same rule as for the brain page.

What this page does not do

Caution
No exercise, no assessment
This page describes a sensory system. It proposes no balance exercise, no protocol, and assesses no individual situation — the practices presented under that name cover very heterogeneous content.
Vertigo, a spinning sensation, instability that settles in, repeated falls or an associated hearing loss belongs to a health professional.

Sources

Main sources

  • Kandel ER, Koester JD, Mack SH, Siegelbaum SA (2021). Principles of Neural Science, 6th edition. McGraw Hill.
  • Purves D, Augustine GJ, Fitzpatrick D, Hall WC, LaMantia AS, Mooney RD, Platt ML, White LE (2018). Neuroscience, 6th edition. Oxford University Press.
  • Proske U, Gandevia SC (2012). The proprioceptive senses: their roles in signaling body shape, body position and movement, and muscle force. Physiological Reviews.
Put it into practice in Shapier

Explore mobility exercises

Working on body control in movement happens in Shapier; Body Lab only explains where the information that makes this control possible comes from.
Explore mobility exercises
Body Lab explains; Shapier lets you act and track.

Check my understanding

Standing without moving, what is the body actually doing?
Why does closing your eyes make standing on one leg immediately harder?
In a ship's cabin, what happens to the balance system?
Choose an answer

Read next

  • Proprioception
    The sense that continuously reports the position and tension of the body without your having to look at it. It is what makes walking in the dark possible — and it is not equally reliable for everything it measures.
    Described without a scene
  • Walking
    The most frequent movement of the human body, and the least described. One step involves some twenty muscles whose main work is braking, and a balance problem nothing signals.
    With a 3D scene
  • Motor control
    How an intention becomes a movement. Feedback arrives too late to correct a fast movement, so the nervous system is forced to predict — and a quick movement is launched rather than steered.
    Described without a scene

Available offline

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Trust and method

Author
equipe-editoriale-shapier
Editorial review
Thanh Chau
Scientific review
Pending
Published on
August 2, 2026
Reviewed on August 2, 2026
Next review due August 2, 2027
Limits of this page
  • No scene accompanies this page: the vestibular apparatus is buried in the temporal bone and appears in none of the anatomical sources Body Lab uses.
  • The respective share of the three information sources varies with the task, the surface, the lighting and the person: no single split holds everywhere.
  • This page proposes no balance exercise and assesses no individual situation. Practices called balance training cover heterogeneous content.
  • Vertigo, instability that settles in, repeated falls or an associated hearing loss belongs to a health professional.
Sources
  • Kandel ER, Koester JD, Mack SH, Siegelbaum SA (2021). Principles of Neural Science, 6th edition. McGraw Hill.
  • Purves D, Augustine GJ, Fitzpatrick D, Hall WC, LaMantia AS, Mooney RD, Platt ML, White LE (2018). Neuroscience, 6th edition. Oxford University Press.
  • Proske U, Gandevia SC (2012). The proprioceptive senses: their roles in signaling body shape, body position and movement, and muscle force. Physiological Reviews.
Educational content. Body Lab does not diagnose and does not replace professional advice.
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