Comparison of Toe Clearance Characteristics Between Simulated Obstacle Crossing Using Visual Height Cues and Actual Obstacle Crossing

Abstract

Highlights: What are the main findings? Simulated obstacle crossing using visual cues successfully evoked height-dependent limb scaling but resulted in significantly reduced safety margins compared to actual crossing. The absence of physical risk led to a systematic underestimation of TCmin and increased motor variability, as noted in the quartile coefficient of variation, with the most pronounced deficits observed in the trail limb. What are the implications of the main findings? Simple repetition in risk-free simulated environments may be insufficient for acquiring the precise motor control strategies required for safe real-world navigation. Effective fall prevention training should incorporate task-relevant feedback mechanisms to bridge the dissociation between motor intention and execution precision. Background/Objectives: Tripping is a major cause of falls and necessitates accessible training. This study aimed to fundamentally evaluate the biomechanical fidelity of a simplified simulated obstacle-crossing paradigm using visual height cues. Methods: Two experiments that included healthy young adults evaluated toe clearance (TC) responsiveness during simulated crossing to four visual cue heights (Experiment 1: n = 16) and compared it with actual crossing (4–16% leg length) to assess biomechanical fidelity (Experiment 2: n = 18). Linear mixed models were used to analyze the effects of obstacle height, task condition, and walking course on vertical TC metrics, including minimum and maximum clearance and quartile coefficient of variation (QCV) for both the lead and trail limbs. Results: In Experiment 1, TC parameters scaled systematically with cue height (p < 0.001), confirming that visual cues elicited adaptive gait adjustments. In Experiment 2, although the maximum TC scaled similarly across conditions, the minimum TC was systematically reduced in the simulated condition compared to actual obstacle crossing (p < 0.001). Furthermore, the simulated condition exhibited increased QCV (p < 0.001), particularly for the trail limb at the highest obstacle height. Conclusions: Motor intention and execution precision were dissociated in the simulated obstacle crossing. Without physical risk, the central nervous system appeared to prioritize effort economy over the precise fine-tuning of safety margins. These results suggest that task repetition in risk-free simulations alone may be insufficient for acquiring safe obstacle-crossing strategies and highlight the importance of task-relevant feedback for ensuring biomechanical fidelity in fall-prevention research.