Fig. 1

Apparatus and experimental conditions. a Virtual visual scenery of a simulated room used for both physical and visual perturbations while standing. Objects and walls in the virtual room provided depth cues that were manipulated in relation to the physical actions of the platform and participant. There were four perturbation directions (forward, backward, upward, and downward; FP, BP, UP, DP, respectively) and three sensory conditions: static-camera, dynamic-camera, and eyes closed. b Virtual visual scenery used during walking conditions projected a moving road on a large 360° dome-shaped screen. There were four perturbation directions, and perturbations occurred either during left or right foot contact. c Depiction of the 16 muscles assessed. Ipsilateral muscles (sub-index “i”) refer to those recorded from the perturbed stance foot during walking conditions (contralateral denoted by sub-index “c”); i.e., the layout in panel C depicts indexing relevant to perturbation induced during left foot stance. The electrodes’ positions were determined according to SENIAM guidelines. TA tibialis anterior, GC gastrocnemius lateralis, RF rectus femoris, BF biceps femoris, RA rectus abdominis, PS paraspinal, EO external oblique, D deltoid medial, L left, R right