Fig. 3
Experimental setup. We employed a support surface and task combination involving a wobble board, introducing mechanical instability along the ML axis, and a body-sized, modified Trail Making Task (TMT) Part A, which mainly imposed visual demands along the AP axis. Participants stood either on a force plate or a wobble board and, in both conditions, either maintained an upright stance or traced a path through randomly projected numbers on a screen. (a) No wobble board, no TMT—standing upright (baseline condition). Participants stood upright on a stable surface, with full-body kinematics, eye gaze and pupil diameter, and ground reaction forces and moments recorded. This condition serves as the baseline for assessing postural adaptation to mechanical and cognitive postural perturbations. (b) No wobble board, TMT—TMT Part A while standing upright. Participants performed the TMT Part A using a laser pointer while standing upright on a stable surface. This condition tests cognitive-motor coordination under stable postural conditions. (c) Wobble board, no TMT—standing on a mediolaterally oriented wobble board. Participants stood on a mediolaterally oriented wobble board, inducing instability primarily along the mediolateral axis. Full-body kinematics, eye gaze and pupil diameter, and ground reaction forces and moments were recorded to assess postural control under unstable conditions. (d) Wobble board, TMT—TMT Part A while standing on a mediolaterally oriented wobble board. Participants performed the TMT Part A using a laser pointer while standing on a mediolaterally oriented wobble board. This condition tests cognitive-motor coordination under unstable postural conditions.
