23/09/2026
FEEDBACK VS FEED- FORWARD
1. Feedback mechanism — “Control after the movement starts”
The CNS uses sensory information from the movement to detect errors and modify the ongoing or subsequent movement.
Flow:
Motor command → Movement → Sensory feedback → CNS compares with desired movement → Correction
Examples:
You reach for a cup and your hand is slightly off → visual/proprioceptive feedback helps you correct the trajectory.
During walking, proprioceptive input from the ankle helps adjust the next phase of gait.
In rehabilitation, a patient watches their knee position during a squat and corrects it.
Key point: It is generally slower, because correction depends on sensory information arriving after movement has begun.
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2. Feed-forward mechanism — “Predict and control before the movement”
The CNS uses previous experience and an internal model to predict the required movement and generates an anticipatory motor command before or during the initial phase of movement, without waiting for sensory error information.
Flow:
Previous experience/internal model → Prediction → Motor command → Movement
Examples:
Before lifting a heavy object, trunk muscles activate in advance to stabilize the spine.
Before stepping onto an unstable surface, postural muscles may activate anticipatorily.
An experienced football player begins a kick with an appropriate force based on the expected ball resistance.
Key point: It is fast, but prediction can be wrong. Sensory feedback is then used to correct the error.
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The important relationship
They are not competing mechanisms. Normal skilled movement uses both:
Feed-forward → initiates/predicts movement → Feedback → detects/corrects error
Feature Feedback Feed-forward
Physiotherapy relevance
In motor rehabilitation, feed-forward control is particularly important for anticipatory postural adjustments (APAs). For example, before a person raises an arm, trunk and lower-limb muscles may activate to maintain postural stability. After stroke or neurological injury, impaired anticipatory control can contribute to balance and movement dysfunction.
Easy memory:
Feed-forward = “Think → Act”
Feedback = “Act → Sense → Correct.”
