Objectives: The role of cognitive process for postural control was shown in dual task studies. However, there was no definite evidence how verbal instructions influence the allocation of attention to postural control. This study determined whether young and elderly adult are able to deliberately control the resource allocation when performing a sensorimotor and cognitive task simultaneously and are there any differences between young and older adults in this regard.

Methods: Cross-sectional study was performed in 16 young adults aged (23.95±3.31) and 20 older adults (61±2.21). Participants selected by non-probable sampling method. Parallel standing and tandem standing on hard surface were used as postural tasks. Force plate was used for postural performance. Postural sway was measured and the choice reaction time task was conducted as cognitive task. Dual- task performance was measured under three different instructions including pay attention to cognitive task, postural task, and equal attention to both tasks.

Results: for postural performance the main effect of instructions and interactions by difficulty and groups were not significant (P≥0.05) for cognitive performance, the main effect of group was significant (F=5.672, P=0.023), showing that elderly adult have longer reaction time. The interaction of instruction by group effect and also interaction of instruction by postural difficulty on mean reaction time was also significant, (F=3.710, P=0.030), (F=5.242, P=0.008) respectively.

Discussion: Because of age related changes in brain, flexibility in older adults are less than young adults.