How do sway velocity and sway amplitude provide different insights into postural control?

• A. Sway amplitude reflects the speed of corrections; sway velocity reflects the magnitude
• B. Sway amplitude reflects the magnitude of corrective movements; sway velocity reflects the speed of corrections
• C. Both measure the same aspect of postural control
• D. Sway velocity reflects the magnitude; sway amplitude the speed

Answer: (B)

Sway amplitude measures how large the corrective movements are—the magnitude of the sway excursions you see as the body makes adjustments to stay upright. It tells you how far the system has to correct from its baseline position.

Sway velocity, on the other hand, measures how fast those corrections happen—the speed at which the center of pressure or body sway changes. It reflects the rapidity of the neuromuscular responses and sensory processing that drive those adjustments.

So, the best answer is that sway amplitude reflects the magnitude of corrective movements, while sway velocity reflects the speed of corrections. If someone sways a lot but corrects slowly, that points to large corrective demands with delayed responses; if corrections are very fast but small in magnitude, the system is making quick, precise adjustments. The other statements mix up magnitude and speed or treat the two measures as the same.