Foot-to-forearm tactile feedback for lower-limb exoskeleton control: a pilot benchmarking study in healthy adults

Real-time tactile feedback has been applied in exoskeleton-based neurorehabilitation, particularly in spinal cord injury, through Foot-to-Forearm Feedback (FFF) at ground contact. Its effects on healthy individuals across varied terrains remain less understood. This pilot study investigated seven healthy participants controlling a lower-limb exoskeleton under two conditions (with and without FFF) across five scenarios: Flat, M-Shape, A-Shape, V-Shape, and Random. Objective measures included step count, sacroiliac joint (SIJ) segment length, and SIJ angle. Subjective experience was assessed by overall preference and a Global Experience Index (GEI) derived from questionnaire ratings. Analyses showed no consistent differences in step count, SIJ length, or SIJ angle between Control and FFF. In three runs, technical issues occurred (e.g., a loose cable). Subjective data showed that five of seven participants (71.4%) preferred FFF, one reported no difference, and one preferred the Control condition. Scenario-specific analyses indicated a preference for FFF in Flat (5/7 = 71.4%), but a lower preference in Random (2/6 = 33.3%). GEI scores decreased under A-Shape and Random conditions, though FFF partially mitigated the reduction in A-Shape. These preliminary findings suggest that FFF may influence subjective experience in healthy users, but confirmation will require larger samples and further investigation across scenarios.