Errors matter: the biomechanics of unsuccessful landing trials.

Landing tasks coupled with cognitive-motor demands are used to assess biomechanical risk markers for ACL injury. However, unsuccessful trials are typically discarded despite reflecting real-game scenarios, as they arise from decision-making or motor-control errors. This exploratory study investigated the biomechanics of unsuccessful trials in cognitively-challenging landing tasks using cluster analysis. Unsuccessful landings were classified as failed (decision-making error) or bad (motor error) trials. Multivariate average of successful trials defined the optimal pattern, and abnormal failed and bad trials were identified based on their distance from it. Peak sagittal and frontal plane hip and knee biomechanics were extracted and analysed using principal component and hierarchical cluster analysis. Failed trials revealed four distinct motor strategies (p < 0.001), including risk markers like greater frontal-plane misalignments. Two clusters emerged among bad trials (p < 0.001), with low separation and relatively small principal component scores, suggesting that the type of landing error (decision-making vs. motor-planning) may influence kinematics and joint-loading. This study highlights a possible dimension of injury risk that may be overlooked when considering only successful task execution. The biomechanical analysis of unsuccessful trials may help identify cognitive-motor factors affecting neuromuscular control and motor planning, potentially complementing current ACL injury risk screening approaches.