Reactive postural control is defined as responses to perturbations that are

• A. Predictable perturbations
• B. Unexpected external perturbations
• C. Under conscious planning
• D. Habituated responses

Answer: (B)

Reactive postural control involves automatic, rapid corrections to balance when the body is perturbed by something that comes from the outside in an unexpected way. This means the perturbation isn’t predicted or planned for, so the nervous system must quickly detect the loss of stability and generate corrective actions to bring the center of mass back over the base of support. These quick, involuntary adjustments rely on sensory input from the feet, legs, and vestibular system and can use strategies such as ankle, hip, or stepping responses depending on the disturbance.

If the perturbation were predictable, you’d be able to prepare in advance and use proactive, planned adjustments rather than reactive corrections. If the perturbation were merely under conscious planning, the response would be volitional rather than automatic. Habituated responses describe learned reactions to repeated stimuli, which isn’t the defining feature of reactive postural control in the face of a truly unexpected disturbance.