The cost of dual-task walking: cognitive demands restrict visual search and gait planning

Abstract

Adaptive walking relies on proactive visual search to plan foot placement and maintain stability. This study examined how cognitive load and task complexity affect gaze behaviour and gait biomechanics during a precision target-stepping task in healthy young adults. We also quantified the frequency of cross-stepping during the experimental task. Twenty-three participants (18-23 years) walked along an L-shaped pathway containing raised stepping targets under single-task (ST) and dual-task (DT) conditions. Targets had four different layouts to create high and low difficulty conditions. Eye movements were recorded using mobile eye-tracking, and gait kinematics were captured via motion capture. Compared with ST, DT walking produced slower walking speeds, longer stance times, and reduced velocity between stepping targets, indicating a more inefficient gait strategy. Eye-tracking analyses revealed fewer and shorter fixations on task-relevant targets and a greater number of fixations directed toward task-irrelevant areas under DT conditions. In DT, saccadic amplitudes were reduced despite increased outside fixations, suggesting a breakdown in visual exploration between proximal and distal regions of the walkway. Cross-stepping was more frequent in ST conditions than in DT. These findings indicate that increased cognitive load compromises proactive visual search, likely through working-memory and attentional limitations that disrupt feedforward gait planning. Contrary to expectation, cross-stepping occurred more often during ST than DT walking, suggesting that in this population cross-stepping may not be a maladaptive strategy. Overall, these results highlight the cognitive demands of adaptive walking even in young, low-risk individuals and underscore the importance of preserving visual-motor coordination under cognitive stress. HighlightsO_LICognitive load during walking restricts proactive visual search and alters gait dynamics in healthy young adults. C_LIO_LIDual-tasking led to slower walking speeds, longer stance times, and reduced step-to-step velocity. C_LIO_LIEye-tracking showed fewer and shorter fixations on stepping targets, and more gaze directed toward task-irrelevant areas under dual tasking. C_LIO_LIReduced proactive gaze under dual-task conditions likely reflects limitations of available cognitive resources rather than task-specific prioritisation. C_LIO_LIFindings highlight how cognitive demands compromise visual-motor coordination, supporting interventions that promote gait automaticity and reduce cognitive load. C_LIO_LICross-stepping was more frequent in ST than in DT conditions, suggesting that cross-stepping may not be maladaptive in healthy young people. C_LI