Balance control during obstacle-crossing in older adults after a fatiguing protocol

BACKGROUND: Obstacle-crossing (OC) requires dynamic balance and cognitive attention, which may decline with age and fatigue. While age-related gait changes are known, the combined effects of fatigue and cognitive demand on OC remain unclear. RESEARCH QUESTION: How does performance fatigability affect balance and crossing performance during single- and dual-task OC in older versus younger adults? METHODS: Seventeen older and 17 young adults (9 females in each group) with post-fatigue Rating of Perceived Exertion (RPE) > 15/20 were included. In Visit 1, participants were familiarized with OC and a working memory task. In Visit 2, they performed single- and dual-task OC trials before and after a fatiguing sit-to-stand protocol. Motion capture and force plates recorded toe-obstacle clearance, foot placement, crossing velocity, and balance (measured as center of mass-center of pressure inclination angle, IA). Fatigue was assessed via RPE and knee extension torque. Cognitive performance was evaluated by accuracy and reaction time. Data were analyzed using repeated measures ANOVAs and mixed-effects models (α =.05). RESULTS: Both age groups experienced similar exertion and strength loss post-fatigue. Increased mediolateral IA indicated reduced balance control, though crossing velocity and foot placement remained stable. Post-fatigue, the typical increase in toe-obstacle clearance during dual-tasking was reduced. Surprisingly, cognitive performance improved post-fatigue, with higher accuracy and faster reaction times. SIGNIFICANCE: Fatigue impaired gait balance control in both age groups, shown by increased IA. The reduced toe-clearance during dual-tasking post-fatigue suggests decreased emphasis on safe obstacle navigation. Improved cognitive performance without slowing suggests a shift in attentional priorities.