What is the effect of fatigue on postural control and sway metrics?

• A. Fatigue only affects cognitive function.
• B. Fatigue has no effect on postural control.
• C. Fatigue decreases sway magnitude.
• D. Fatigue increases sway magnitude and velocity, slows corrective responses, and may shift strategy toward more conservative or compensatory patterns, raising fall risk.

Answer: (D)

Fatigue disrupts postural control by weakening the neuromuscular commands and sensory processing that keep you stable. As you become fatigued, it’s harder to generate rapid, precise corrective actions, so sway magnitude and sway velocity tend to increase. The system also slows in its ability to initiate and execute corrective responses, leading to longer response times after a destabilizing movement. Because the ankle strategy becomes less reliable with fatigue, people often rely more on proximal or compensatory strategies (like hip motions or stepping) to regain balance, which changes the overall pattern of sway and can raise the risk of a fall. In short, fatigue makes balance more variable and mistakes in correction slower, while pushing the system toward more guarded or compensatory strategies.