In impedance control, which statement best describes its role in rehabilitation devices?

• A. It directly measures external forces without influencing movement.
• B. It replaces the need for safety monitoring.
• C. It modulates resistive dynamics in the user–device interaction to shape assistive force.
• D. It determines user interface layout.

Answer: (C)

Impedance control defines how the device responds to the user’s movement by setting a dynamic relationship between motion and force. By tuning virtual stiffness, damping, and sometimes inertia, the system can provide controlled assistive or resistive forces in real time, shaping how the user experiences the movement and ensuring a safe, compliant interaction during therapy. This focus on modulating interaction dynamics to produce the desired assistive force is what makes it the best description. It isn’t simply about measuring external forces, replacing safety monitoring, or arranging the user interface—those are separate concerns.