Dual task performance in a healthy young adult population: results from a symmetric manipulation of task complexity and articulation.

The ability to execute and maintain gait while performing simultaneous cognitive, verbal, or motor tasks ('dual-tasking') is beneficial in many ways. It is well-documented, however, that dual-tasking can result in cognitive or motoric interference that results in diminished gait performance, and impaired secondary task performance. When manipulating cognitive load, it is common to have participants respond verbally to stimuli. While this is an ecologically valid way to measure the effects of cognitive load on gait, it ignores the additional demands inherent in the verbal aspect of the task. In the present study, we manipulated complexity and articulation within a single working memory task, in order to examine their relative impact on continuous spatiotemporal gait parameters. Fourteen healthy young adults (11 women) aged 18-30 (M=22.14, S.D.=2.28) were asked to memorize a random, non-repeating, sequence of three, five, or seven digits. Articulation was manipulated by either having participants rehearse the digits aloud, or rehearse the digits silently during the performance of the gait task. Gait parameters were quantified with a GAITRite instrumented carpet. Velocity, step time, swing time, and stance time demonstrated a significant (p<0.05) interaction between complexity and articulation, with articulation having a greater effect at higher levels of complexity. These results suggest that verbal secondary tasks may actually create a 'triple-task' in which the cognitive complexity of the task interacts with both the articulatory demands of the response modality, and the motoric demands of the gait task.