High-Intensity Interval Training on Cardiorespiratory Fitness, Cognitive Function, and Functional Capacity in Adults with Stroke: A Systematic Review and Meta-Analysis

Background/Objectives: Stroke is a leading cause of long-term disability worldwide and is frequently associated with reduced cardiorespiratory fitness, impaired functional capacity, and cognitive decline. High-intensity interval training (HIIT) has emerged as a promising rehabilitation strategy; however, its effects across multiple domains remain unclear. This systematic review and meta-analysis aimed to evaluate the effects of HIIT on cardiorespiratory fitness, cognitive function, and functional capacity in adults with stroke. Methods: A systematic search was conducted in PubMed, Scopus, CINAHL, and Web of Science up to April 2026. Randomized controlled trials involving HIIT interventions in adults with stroke were included. Outcomes of interest were cardiorespiratory fitness (VO2peak), functional capacity (gait speed, walking distance, mobility, and balance), and cognitive function. Pooled effect sizes were calculated using a random-effects model. Methodological quality was assessed using the PEDro scale, and risk of bias was evaluated with the Cochrane RoB-2 tool. Results: In total, 17 studies (n = 809 participants) were included, with 12 contributing to the meta-analysis. HIIT significantly improved cardiorespiratory fitness (SMD = −0.849; p = 0.005), gait speed (SMD = 0.693; p = 0.014), walking distance (SMD = 0.604; p < 0.001), functional mobility (SMD = −0.711; p = 0.027), balance (SMD = 2.447; p = 0.002), and cognitive function (SMD = 1.741; p < 0.001). However, substantial heterogeneity was observed across most outcomes. Conclusions: HIIT appears to be an effective intervention for improving cardiorespiratory fitness, functional capacity, and cognitive performance in individuals with stroke. Nevertheless, the variability across studies suggests that its effectiveness is context-dependent. Further research is needed to standardize protocols and determine optimal implementation strategies.