Which statement correctly differentiates static sway measures from reactive balance measures?

• A. Static sway measures quantify quiet stance postural control; reactive measures assess responses to external perturbations
• B. Static sway measures assess responses to perturbations; reactive measures quantify quiet stance
• C. Static sway measures measure cognitive load
• D. Static sway measures assess gaze stabilization

Answer: (A)

The essential distinction is between balance during stillness and balance in response to a disturbance. Static sway tests examine quiet stance postural control, measuring how much and how the body sways when there’s no intentional perturbation (using metrics like sway area, path length, and velocity of the center of pressure). Reactive balance tests, on the other hand, assess how the system responds to an external perturbation, looking at recovery performance such as time to stabilization, corrective steps, or ankle/hip strategies after a push or platform move.

So the statement that static sway measures quantify quiet stance while reactive measures assess responses to external perturbations captures this key difference. The other options aren’t the defining contrast: cognitive load isn’t the primary feature of static sway, and gaze stabilization isn’t the central distinction between quiet stance control and reactive responses.