Stability control during the performance of a simultaneous obstacle avoidance and auditory Stroop task.

Navigation through complex environments requires a greater degree of control and attentional resources from the central nervous system to ensure postural stability and efficient goal completion as compared to quiet standing or unobstructed walking. Furthermore, when a cognitive task is also performed in a dual-task scenario, additional resources may be required. The purpose of the current study was to examine the effects of performing a concurrent cognitive (auditory Stroop task) and complex locomotor task (with a stationary or dynamic obstacle) on frontal plane stability control quantified using a margin of stability (MOS) measure. Fourteen healthy young adults performed 40 dual-task trials (randomized in a balanced design for auditory Stroop congruency and obstacle movement). Results indicated that frontal plane MOS was greatest for the obstacle crossing step and was greater for the dynamic obstacle as compared to the stationary obstacle. Conversely, frontal plane MOS was the smallest for the pre-crossing step, indicating that this point in the obstacle stepping strategy may be the least stable. No effect of cognitive task difficulty was observed for any of the experimental conditions, providing support for a 'posture-first' strategy. These findings suggest that an increase in stability is prioritized for the obstacle crossing step, potentially at the expense of reduced stability in the step immediately preceding the obstacle. These results have implications for better understanding how the CNS controls stability at different events during the obstacle crossing strategy in a complex environment.