Task-prioritization and balance recovery strategies used by young healthy adults during dual-task walking

Background: Maintaining dynamic balance is an essential task during walking, with foot-placement playing a critical role. Dual-task studies analyzing steady-state walking with cognitive loads have found healthy adults prioritize cognitive task performance at the expense of maintaining control of their balance. However, few studies have focused on the influence of cognitive loads on more difficult motor tasks, such as walking with unexpected foot-placement perturbations. Individuals often recover from a loss of balance using an ankle or hip strategy; however, how cognitive loads affect these balance recovery strategies remains unknown. Research question: How do individuals prioritize cognitive resources and does the balance recovery strategy used change following mediolateral foot-placement perturbations during steady-state walking when performing cognitive tasks of increasing difficulty? Methods: Fifteen young healthy adults walked during unperturbed and perturbed conditions with increasing cognitive loads (no cognitive load, attentive listening, spelling short words backwards and spelling long words backwards). No specific task-prioritization instructions were given. Medial and lateral foot-placement perturbations were applied prior to heel-strike during random steps. Results: Cognitive performance decreased between the unperturbed and perturbed conditions. While balance control decreased during perturbed relative to unperturbed walking, the additional cognitive load had little effect on balance control during the perturbations. Lastly, the balance recovery strategy used, as measured by peak joint moments at the ankle and hip, was unaffected by the additional cognitive loads. Significance: Individuals appear to prioritize their balance control over cognitive performance when experiencing foot-placement perturbations and do not change their balance recovery strategy with the addition of a cognitive load. These results highlight the flexibility of task-prioritization in young adults and provide a foundation for future studies analyzing neurologically impaired populations.