Dual‐Task Single‐Leg Hop Performance Exposes Persistent Asymmetry and Movement Deficits After Anterior Cruciate Ligament Reconstruction: A Randomised Crossover Experimental Study

Background Dual‐task paradigms are increasingly used to investigate cognitive–motor interactions after anterior cruciate ligament reconstruction (ACLR), yet their effects on hop performance, movement quality and limb symmetry remain insufficiently quantified. The objective of this study was to compare these outcomes under single‐ and dual‐task conditions between individuals after ACLR and healthy controls. Methods Thirty‐one participants (15 ACLR and 16 healthy controls) were included in this multicentre randomised repeated‐measures experimental study. Participants performed the single‐leg hop for distance (SLHD) under single‐task and dual‐task conditions using counterbalanced sequences. Movement quality was assessed using the Qualitative Assessment of Single‐Leg Landing Scale (QASLS). In the dual‐task condition, participants performed the hop while simultaneously completing a standardised visuo‐attentional working‐memory task. Dual‐task cost (DTC) was calculated for SLHD, QASLS and limb symmetry index (LSI). The primary outcome was SLHD DTC. Analyses were based on linear mixed‐effect models, with sequence‐specific findings reported descriptively to support transparency regarding the counterbalanced design. Results Under dual‐task conditions, SLHD DTC was numerically higher in the ACLR group than in controls in sequences A1 (6.5 ± 6.5% vs 2.7 ± 6.9%; p = 0.227) and A2 (1.1 ± 1.1% vs −0.7 ± 6.8%; p = 0.316), although these between‐group differences were not statistically significant. QASLS DTC was not significantly greater in the ACLR group in sequence A1 (0.19 ± 0.23 vs 0.12 ± 0.36 points; p = 0.385) or A2 (0.43 ± 0.28 vs 0.56 ± 0.87 points; p = 0.613). The largest between‐group differences were observed for LSI DTC, which was significantly higher in the ACLR group in sequences A1 (3.8 ± 1.9% vs 0.7 ± 1.3%; p < 0.001) and A2 (6.5 ± 2.4% vs 0.6 ± 1.2%; p < 0.001). Repeated‐condition sequences B1 and B2 were retained to explore potential order, learning and fatigue effects and were not interpreted as DTC sequences. Sequence‐specific descriptive findings in the ACLR group showed dual‐task‐related effects for limb symmetry in A1 and A2, whereas controls showed minimal changes. Conclusion Dual‐task conditions were associated with measurable changes in SLHD performance, movement quality and limb symmetry after ACLR. Trail Registration: Clinical trial.gov.identifier: NCT06768957