Kinematic and Muscle Activity Differences in Anterior Cruciate Ligament Injury Risk in Semi-Professional Female Football Players: Influence of Limb Condition and Change of Direction Task

ABSTRACT: Introduction. Anterior cruciate ligament (ACL) injuries remain a critical issue in female football, with a prevalence of 0.7 injuries per squad and season. Most injuries occur through non-contact mechanisms, frequently linked to valgus collapse, which emphasizes the importance of quality of movement and motor control strategies. Hamstrings protect against anterior tibial translation during side-cutting, while quadriceps activity increases anterior shear forces, and gastrocnemius contributes to ACL loading by amplifying quadriceps recruitment. Despite this, few prevention studies have incorporated electromyographic (EMG) analysis to identify risk factors. Limb dominance has also been highlighted as an important determinant of injury susceptibility. Therefore, the first objective of this study was to evaluate angular velocity and knee angle kinematics, as well as muscle activity in hamstrings, quadriceps, and gastrocnemius, in players with previous knee injury caused by valgus collapse in the dominant limb (DL), players with previous injury in the non-dominant limb (NDL), and healthy players during three side-cutting tests. Methods. A cross-sectional study was conducted with 16 female football players, categorized into Injured Dominant Limb (InjDom), Injured Non-Dominant Limb (InjNDom), and Healthy. Participants performed three change-of-direction tasks (CODAT, GOB, and Turn). Kinematics were assessed using a motion capture system (Qualisys AB, Sweden), while surface EMG (Delsys Europe, UK) measured activity of biceps femoris, semitendinosus, vastus medialis, and gastrocnemius lateralis. Analyses included pre-load and stance phases, considering minimum, peak, and range of motion values, as well as average rectified and peak EMG amplitudes. A two-factor mixed model with pairwise comparisons was applied (p < 0.05). Results. Injured players displayed altered kinematics and muscle activity compared to Healthy, influenced by limb dominance. InjDom showed greater internal tibial rotation and peak angular velocity in the transverse plane, alongside higher semitendinosus activity during pre-load and increased gastrocnemius activity during stance. Conclusions. Differences in kinematic and muscle recruitment outcomes were associated with limb dominance, whereas change of direction amplitude only affected muscle activity during stance. These findings support the inclusion of limb dominance and EMG-based outcomes in ACL injury prevention strategies.