Multitasking while walking – be it mentally drafting a grocery list or replying to a text message on a phone—is simply second nature to many. For stroke survivors with weakened mobility and cognitive capabilities, however, this common practice of "dual-task walking", can present a formidable challenge. A research team at The Hong Kong Polytechnic University (PolyU) that pioneered early studies on dual-task walking and fall risk in post-stroke individuals has conducted a follow-up study, which reveals that the interaction of cognitive task type and complexity can influence the degree and pattern of "dual-task interference" (DTI), resulting in a slip in physical and mental performance. The findings offer valuable clinical implications for the design of dual-task assessment and training for stroke rehabilitation.
Led by Prof. Marco PANG, Shun Hing Education and Charity Fund Professor in Rehabilitation Sciences, Chair Professor of Neurorehabilitation and Head of the Department of Rehabilitation Sciences at PolyU, together with Prof. Charlotte TSANG, Assistant Professor from the Department, the research assessed the dual-tasking ability of individuals with chronic stroke. During the study, participants were assessed on two mobility conditions, namely walking on flat ground and navigating obstacles, while they simultaneously performed various cognitive tasks, ranging from auditory discrimination to shopping list recall and serial subtraction.
The research team adopted a standardised metric known as the "dual-task effect" (DTE) to measure the patients' performance in mobility (walking distance) and cognitive function (accuracy in performing tasks). The findings revealed that the patients were often affected by DTI when walking and simultaneously carrying out cognitive exercises. The interference led to a decline in performance in the cognitive task, the walking task or both, ultimately increasing fall risks and hindering a return to a normal life.
The study also demonstrated that dual-task walking performance is highly task-dependent. Cognitive tasks that involve internally driven responses, such as performing serial subtractions, made greater demands on working memory, mental tracking and internal processing, thereby inducing greater DTI. The greatest mobility interference was observed during these internally driven tasks, resulting in clinically significant reductions in walking distance. Furthermore, the combined, interactive effects of task type and complexity affected dual-task performance more significantly than either factor alone.
Prof. Pang elaborated, "The results of our study underscore the importance of individualised assessments to better understand the dual-task challenges faced by post-stroke patients. Dual-task exercise training has been shown to reduce DTI and decrease fall risk during walking. Clinically, it is essential to develop a comprehensive DTE profile to evaluate post-stroke patient mobility. Standardised assessments involving cognitive tasks across various domains and complexities are key to guiding effective functional training for individuals with chronic stroke."
Prof. Tsang added, "As strokes affect different brain regions responsible for various cognitive and physical functions, a one-size-fits-all approach that targets only a single cognitive domain and difficulty level is inadequate for identifying crucial functional deficits in stroke survivors. The precise identification of the specific functional deficits, followed by personalised training, is vital for achieving effective rehabilitation outcomes."
The study sheds light on the need to move beyond traditional, standalone functional training and to incorporate realistic, dual-task scenarios of the type that patients would encounter in daily life to improve rehabilitation efficacy. The paper, titled "Effects of Cognitive Task Type and Complexity on Dual-Task Interference During Level-Ground Walking and Obstacle Negotiation in Individuals with Stroke", has been published in Neurorehabilitation and Neural Repair.
