Immediate task-specific and delayed generalized adaptations to variable dual-task training in community-dwelling older adults: a randomized waitlist-controlled trial

Background Aging is accompanied by progressive declines in cognitive and physical function. Dual-task training, which combines cognitive and motor demands, is a promising nonpharmacological approach, yet evidence that its benefits generalize beyond trained tasks and persist over time remains limited. This study examined the immediate and longer-term effects of a variable dual-task intervention on motor and cognitive function in community-dwelling older adults. Methods Fifty adults aged ≥ 65 years, including participants meeting criteria for mild cognitive impairment, were randomly allocated to an intervention group (IG; n = 30) or waitlist control (WLC; n = 20). The IG completed a 12-week, twice-weekly program (24 sessions × 60 min) designed to be highly variable across cognitive and motor demands to minimize task-specific learning. Outcomes were assessed at baseline, post-intervention, and three-month follow-up, including the Timed Up and Go Test, Five Times Sit-to-Stand Test (5xSTS), Eriksen Flanker Test, Trail Making Test, and Digit Span Test. Between-group effects and long-term trajectories within the IG were analyzed using linear and generalized linear mixed models under an intention-to-treat approach. Results The intervention produced a significant improvement in functional lower-limb strength relative to the WLC at post-intervention (5xSTS: Group × Time interaction p = 0.005, standardized mean difference [SMD] = 0.54), maintained within the IG at three-month follow-up. No significant between-group effects were observed for the remaining motor or cognitive outcomes at post-intervention. Within the IG, improvements in functional mobility (Timed Up and Go, SMD = 0.28), inhibitory control (Flanker reaction time, SMD = 0.40–0.42), and short-term memory (forward Digit Span, SMD = 0.62) were absent immediately post-intervention and emerged only at follow-up. Conclusions Variable dual-task training produced immediate gains in functional lower-limb strength that persisted at follow-up, alongside delayed improvements in functional mobility, inhibitory control, and short-term memory consistent with a post-training consolidation process. These findings suggest two complementary pathways: task-specific overlap between training and assessment may explain the immediate motor gains, whereas variable practice may foster broader cognitive and mobility benefits that emerge over time. Trial registration German Clinical Trials Register, DRKS00038787 ( https://www.drks.de/DRKS00038787 ), retrospectively registered on 19/12/2025.