Impact of Chemotherapy on Motor–Cognitive Dual-Task Performance in Strength and Mobility Tests

<b>Background/Objectives</b>: Chemotherapy often leads to persistent physical and cognitive impairments, and while the dual-task paradigm is a sensitive tool for detecting such deficits, its application to functional strength in oncology remains largely unexplored. <b>Methods</b>: This cross-sectional study, while not designed to establish causality, included 44 participants including cancer patients (11 undergoing chemotherapy and 15 post-treatment survivors) and healthy controls. Functional fitness was assessed with the Senior Fitness Test battery under single- and dual-task conditions. The dual-task condition incorporated a cognitive subtraction task, and the dual-task cost was calculated. Group comparisons were analyzed using <i>t</i>-tests and ANOVA with effect sizes reported (<i>p</i> < 0.05). <b>Results</b>: Within-group comparisons showed that the cancer group exhibited reduced performance from the single- to the dual-task condition, with significant declines in strength and mobility (Chair Stand Test, <i>p</i> = 0.011; Timed Up and Go, <i>p</i> < 0.001). Greater dual-task costs were observed in the Arm Curl Test for cognitive (<i>p</i> = 0.005) and success (<i>p</i> = 0.004) outcomes. <b>Conclusions</b>: Dual-task testing revealed greater impairments in cancer patients and survivors, supporting the impact of chemotherapy-related cognitive impairment and highlighting the need for integrated motor-cognitive rehabilitation strategies. Further research is warranted in this field, employing larger sample sizes and stratified analyses by specific cancer types, and including a spectrum of complexity in the cognitive task to characterize the effects of cancer and its treatment on motor-cognitive integration.