How Does Explicit Prioritization Alter Walking During Dual-Task Performance? Effects of Age and Sex on Gait Speed and Variability

Background. Previous studies have demonstrated that the performance of a secondary task during walking alters gait. Objective. This study investigated the effects of task prioritization on walking in young and older adults to evaluate the "default" prioritization scheme used, the flexibility to alter prioritization and cortical resources allocated to gait and a secondary cognitive task, and an age-associated changes in these abilities. Design. A cross-sectional study that explicitly altered the focus of attention was used to investigate the effects of prioritization in young and older adults who were healthy. Methods. Gait speed and gait variability were evaluated in young adults (n=40) and older adults (n=17) who were healthy, both during usual walking and under 3 dual-task conditions: (1) no specific prioritization instructions, (2) prioritization of gait, and (3) prioritization of the cognitive task. Results. Young adults significantly increased gait speed in the gait prioritization condition compared with gait speed in the no-instruction condition; a similar tendency was seen in the older adults. Gait speed was reduced when priority was given to the cognitive task in both age groups; however, this effect was less dramatic in the older adults. In the young adults, prioritization of gait tended to have different effects on gait speed among both men and women. In the older adults, but not in the young adults, all dual-task conditions produced increased gait variability, whereas prioritization did not titer this gait feature. Limitations. The sample size and the relative homogeneity of the older adults could be considered as possible limitations of the study. Conclusions. Even among young adults, the effects of secondary, cognitive tasks on gait speed are strongly influenced by prioritization. This finding was less significant in the older adults, suggesting that there is an age-associated decline in the ability to flexibly allocate attention to gait. Somewhat surprisingly, when prioritization was not explicitly instructed, gait speed in both young and older adults most closely resembled that of the condition when they were instructed to focus attention on the cognitive task.