Background and Purpose of Study: Patients with Parkinson’s disease often need physiotherapy for the management of their gait and balance problems. Dual task performance compromises postural stability in Parkinson’s disease which can lead to falls and also deterioration in the performance of the simultaneous tasks, when the attention capacity resources are shared amongst different tasks. The purpose of this study was to observe the effects of performance of secondary motor task and secondary cognitive task on postural stability in persons with Parkinson’s disease using clinical steady standing tests, and to further clarify whether the type of task was a major determinant of the severity of dual task interference. Materials & Methods: It is a randomized experimental study with same subject design. 42 subjects were included in the study selected on the basis of inclusion & exclusion criteria. All the subjects were required to maintain 5 steady stance positions (feet apart, feet together, stride stance, tandem stance, single leg stance) without any secondary task and while doing a secondary motor task (thumb and finger opposition) and a secondary cognitive task (reciting the days of the week backwards) separately. Time spent in each of the positions was recorded using a stopwatch, the maximum time being 30 seconds.The general Linear Model Repeated Measures Analysis of Variance (ANOVA) was used to examine the changes in the outcome variables under 3 different conditions. Results: The difference between the mean time duration during the performance of secondary motor task and secondary cognitive task was significant (at p < 0.05) in the feet together; stride stance, tandem stance and single leg stance position. This indicated that the performance of cognitive task was more detrimental to postural stability than the performance of motor task in the more difficult stance positions.Conclusion: The performance of even simple motor and cognitive task resulted in deterioration of postural stability in this study. The cognitive task was more demanding task for the subjects and hence resulted in greater dual task interference and postural instability.

Keywords: Dual task performance, Postural stability, Parkinson’s disease