Effect of a visual dual task on postural stability—A comparative study using linear and nonlinear methods

BACKGROUND AND AIMS: The dual‐task experimental paradigm is used to study the attentional demands of postural control. Postural control is impaired in poststroke patients, and dual‐task balance studies address the visual needs of postural control in stroke patients. A nonlinear approach can help us understand the overall behavior of the dynamic system. METHODS: A total of 20 chronic stroke patients and 20 healthy subjects with similar age, height, and weight participated in this study. The stability and complexity of postural control were assessed using linear and nonlinear methods. All data and parameters (center of pressure [COP] velocity, anteroposterior and mediolateral directions displacement, length of COP path, and phase plane) were analyzed using the Kolmogorov–Smirnov test. RESULTS: When postural control was examined based on linear analysis, the results showed that the main effect of the group was not significant, but the main impact of position was significant for all parameters of the COP variation (p < 0.05). Examination of postural control based on nonlinear analysis also showed that the main effect of the group was not significant, and the main effect of status was significant only for the parameters of approximate entropy in both directions and short‐term Lyapunov view in the anterior‐posterior direction (p < 0.05). CONCLUSION: According to the results of this study, the assessment of postural control and gait performance in poststroke patients, as well as the dual tasks they have to perform in daily life, is crucial for their independence in activities of daily living.