How young and older healthy adults negotiate competing task goals during treadmill walking

We investigated how younger and older healthy adults modify their stepping when new step goals are introduced that drive them away from their preferred walking patterns. Across both studies, physically high-functioning older adults exhibited executive function decrements that were significantly associated to overall poorer stepping performance in these contexts. In Study 1, the observed EF declines were significantly associated to decreased overall stepping performance (% Green strides). However, analyses of how participants modified their stepping to accommodate the competing step goals revealed stepping variability was the primary contributor to better overall stepping performance. Across the different experimental conditions, group differences in variability suggested that the young adult group was more successful at manipulating the magnitude of their stepping variability compared to the older adult. In Study 2, our results again demonstrated performance decrements in the Stroop Interference task (response inhibition) compared to the YH group. Better Stroop Color-Word performance was significantly associated with the better stepping GNG performance. However, no group differences were observed in response inhibition measures assessed in the computer GNG task. That said, we contend the stepping GNG task allowed us to create stepping conditions that incorporated (varying) cognitive and physical demands that are relevant in walking contexts. In fact, the stepping Go-NoGo (GNG) task conditions revealed older adults made more stepping errors compared to the young adults when navigating obstacles but not targets. Furthermore, older adults made more stepping errors when navigating an obstacle that was preceded by a target (as opposed to a preceding obstacle). These results demonstrated that healthy adults are not simply challenged by a single target or obstacle in their path, but specific sequences of target and/or obstacles.