Virtual Reality Illusions Systematically Perturb Balance in Young and Older Adults

Virtual reality (VR) illusions—manipulated visual cues that alter perceived motion—have shown potential to perturb balance and elicit postural adaptations. While younger adults demonstrate clear responses to illusions, less is known about how older adults respond to similar perturbations during dynamic tasks. Understanding age-related differences in these responses is critical for developing inclusive, VR-based balance rehabilitation interventions. This study aimed to (1) determine whether older adults respond to VR illusions differently than younger adults, (2) evaluate the influence of illusion magnitude and direction on balance performance across age groups, and (3) explore the relationship between postural responses and functional performance across both age groups during a VR exergame. Both older and young adults exhibited increases in centre of pressure (CoP) displacement when exposed to VR illusions, indicating response to the illusions. Although older adults consistently showed higher CoP displacements than young adults, they exhibited smaller increases in absolute CoP displacement from the illusion-free phase to the illusion phase compared to younger adults, possibly because they were operating closer to their limits of stability. The directional tendency of CoP displacement showed a significant association with the illusion direction in both age groups. Game performance declined with higher illusion magnitudes and anterior directional illusions, with higher CoP displacements observed during unsuccessful ball returns in both young and older adults. These findings suggest that VR illusions can systematically and reliably perturb balance in young and older adults. The consistent responses across age groups support the use of scalable, game-based VR interventions for assessing and training balance, with potential applications in personalised rehabilitation strategies targeting age-related balance impairments. • Older adults showed consistently higher CoP displacements than young adults • Illusion-induced CoP displacement increases were greater in young than older adults • CoP displacement and game performance were driven by illusion magnitude and direction • Directional tendency of CoP aligned systematically with illusion directions • Unsuccessful VR gameplay attempts elicited larger CoP displacements