Allocation of attention and dual-task effects on upper and lower limb task performance in healthy young adults.

Many daily activities require separate tasks of the arms and legs to be performed together, as in driving where one foot controls the accelerator, one arm steers, and the other arm and foot shift gears and clutch. Strategies and underlying mechanisms for attention allocation and task prioritization have been explored in standing and walking while performing a manual or cognitive task. These studies reveal a task-related strategy that often, but not always, prioritizes the lower limb task of walking. However, in the absence of locomotion and gait-related postural control, as in sitting, multi-limb dual-task strategies are largely unexplored. Therefore, to characterize dual-task interference of arm and leg tasks during a driving-like activity, seated participants were assessed for the interference effect on hand velocity and movement time of a three-phase reach task and on the error in tracking of a foot-pedal ramp-tracking task. We found that the dual-task cost to reaching shown as decreases in reach performance differed among the three phases, that the cost to foot-pedal tracking also differed by phase, and that the between-task trade-off and prioritization strategy varied between the steep and gradual tracking ramps. Therefore, we propose that attention to concurrent reaching and foot-pedal tracking was flexibly allocated based on phase of the tasks.