Functional mobility, which encompasses movements required for everyday activities, involves the ability to perform two tasks simultaneously, a concept known as dual-tasking (DT). The impact of interference between these tasks is observed by comparing the performance of a single task with that of the same task when associated with a second task, known as the dual-task effect (DTE). The decline in these functions due to aging and the associated increase in DTE might impair basic functions involving mobility, consequently increasing the risk of falls. Thus, this study aims to evaluate the DTE in functional mobility tasks across young, middle-aged, and older adults and to examine how different types of secondary tasks affect DT performance.

This laboratory-based cross-sectional observational study involved forty-four young adults (32.5 ± 6.9 years), thirty-five middle-aged adults (54.6 ± 6.3 years), and twenty-eight older adults (73.9 ± 7.0 years). DT conditions included performing three functional mobility tasks (the 3-meter Walking Test, Figure-8 Walk, and Four Square Step Test) alone and simultaneously with four different secondary tasks [Coin Transference (CTT), Stroop Color Word (SCWT), Digit Span (DST), and Semantic Verbal Fluency (SVFT) tasks]. The time taken to complete the mobility tasks was measured, while performance on secondary tasks was assessed based on the CTT rate, number of errors (SCWT and DST), and rate of recalled words (SVFT). The DTE was calculated, and patterns of dual-task cost were analyzed across all task conditions.

Decreases in functional mobility performance during dual-task performance were observed across all experimental groups. Older adults took longer to perform complex tasks involving turning and anterior/lateral/posterior displacements during dual-task conditions compared to young and middle-aged adults. The CTT and SCWT caused a high level of interference under dual-task conditions, while the SVFT and DST induced reduced impairments in functional mobility tasks. Most dual-task conditions led to “mutual interference”, where participants performed worse on both the primary and secondary tasks in the dual-task conditions.

All primary functional mobility tasks experienced interference under dual-task conditions. The relationship between dual motor and cognitive tasks may depend on the difficulty level presented to a given population. This study highlights the importance of understanding dual-task interference to develop targeted interventions for reducing fall risk, especially in older adults.