Anticipation and sequential demands influence on-field change-of-direction kinematics related to ACL injury risk

Anterior Cruciate Ligament (ACL) injuries are a significant concern in multidirectional sports, often occurring during change-of-direction (COD) maneuvers under high biomechanical loads. While laboratory-based studies have provided valuable insights into ACL injury mechanisms, they often fail to replicate the complexity of real-world scenarios. This cross-sectional study aimed to investigate the kinematic patterns and performance of COD maneuvers in ecologically valid settings, incorporating on-field testing with reduced constraints, multiple angles, and both preplanned and unplanned conditions. Additionally, the study examined how kinematics evolve during a sequence of CODs, simulating game-like scenarios.

Twenty male soccer players performed COD sequences on artificial turf, with joint and segment kinematics captured using wearable inertial measurement units (IMUs).

Results revealed that limiting movement planning did alter COD movement executions and elicited a mix of protective and risk-associated movement adaptations. Unplanned CODs exhibited less favorable trunk and pelvis alignment in regard to ACL injury risk, but they also showed safer sagittal knee and frontal hip kinematics, however, at the cost of performance. Notably, kinematic patterns deteriorated in the last COD of an unplanned sequence, with participants displaying characteristics associated with elevated injury risk: more extended knees, higher hip abduction at sharper angles, and misaligned trunk rotation.

These findings suggest that the combined cognitive and physical demands of sequential CODs constrain motor planning, leading to riskier biomechanical patterns. This study underscores the importance of incorporating realistic, game-like conditions in ACL injury research to better understand the interplay between performance and injury risk. The results highlight the need for injury prevention programs to address the cognitive and physical demands of unplanned, sequential CODs, offering a more comprehensive approach to mitigating ACL injury risk in multidirectional sports.