Changes of postural sway in narrow-base stance by concurrently performing cognitive task

Posture-cognition studies show that postural control is affected by cognitive task. Therefore, the effect of factors such as task difficulty is evaluated in dual-task paradigm but the impact of difficulty of cognitive and postural task on postural control remains inconclusive. The purpose of the present study was to examine the interaction effect of cognitive and postural tasks difficulty on postural control. Twenty healthy young volunteers (Mean age 22 ± 2.3 years) performed six random conditions while standing on a force platform. Conditions involved combinations of two level of postural task difficulty (standing on the floor and narrow base) and three level of cognitive task difficulty (without, easy and difficult cognitive tasks). Two way ANOVA (significant level p < 0.05) results demonstrated marked decrease in the standard deviation of the center of pressure in the anterior-posterior and medial-lateral directions for the difficult cognitive task condition in both postural task. (p < 0.05). Also, the easy cognitive task reduced the standard deviation of the center of pressure in the anterior-posterior direction in the narrow base standing condition (p < 0.05). According to the results of the present research, it seems that the difficult cognitive task requires a greater part of attention capacity; subsequently, attention is withdrawn from the postural task and automatic control regulates posture more efficiently through unconscious, fast, and reflexive processes. Also, postural control is simultaneously affected by the difficulty of postural and cognitive tasks. Therefore, in designing appropriate interventions, it seems necessary to pay attention to the interactive effects of posture and cognitive tasks.