*2.2. Experimental Protocol*

The testing protocol included four standing and four walking conditions (Table 1). Each of the conditions required either left and right (L/R) or up and down (U/D) continuous head movement. Two of the standing conditions were visual motion sensitivity (VMS) tasks and involved movement of the head and trunk en bloc. The walkway for the walking trials was 3.9 m long to stay within the optical field of the camera-based motion system. Participants completed two 30-second trials of each condition. All testing was completed at the Balance Disorders Laboratory at Oregon Health & Science University.

**Table 1.** Description of standing and walking conditions.

Note: VMS = visual motion sensitivity; L/R = Left and right; U/D = Up and down.
