INFLUENCE OF DUAL COGNITIVE-MOTOR DEMANDS ON KNEE MECHANICS RELATED TO ACL INJURY IN RUN-AND-CUT TASKS

Among females, non-contact anterior cruciate ligament (ACL) injuries remain a critical concern in dynamic sports involving rapid decelerations and accelerations, and directional changes. Although injury mechanisms and risk factors are well-documented, the role of cognitive demands during movement execution remain underexplored. Real-world sport performance requires athletes to manage environmental cues, maintain and manipulate information in working memory, and make rapid decisions while simultaneously executing movement. Concurrent cognitive and motor demands are likely to compete for attentional resources, which may influence movement coordination during unanticipated conditions relevant to ACL injury-risk mechanics. Therefore, the purpose of this dissertation was to examine the effects of cognitive load and movement anticipation on knee joint biomechanics during a 45° sidestep run-and-cut task.

Chapter 4 examined the influence of cognitive load and anticipation on knee joint biomechanics and EMG activity using linear mixed-effects models. A significant interaction between anticipation and cognitive load was observed for anteroposterior ground reaction forces. Anticipation also increased peak knee extensor moments, whereas unanticipated cuts involved reduced braking forces and greater knee flexion at initial contact and peak, indicating increased joint excursion. Chapter 5 quantified cognitive-motor dual-task costs to characterize patterns of cognitive-motor interference. No significant differences in cognitive performance were observed across conditions. However, in the anticipated condition, higher dual-task effect (DTC) scores were positively associated with peak knee external rotation and adduction moments, as well as anteroposterior ground reaction forces, whereas in the unanticipated condition, DTC was associated with both knee joint moments and flexion angle. Participants demonstrated heterogeneity in attention trade-off strategies, with some prioritizing motor stability at the expense of cognitive accuracy.

Overall, the findings reveal that cognitive load and anticipation shape movement through distinct but interacting attentional mechanisms, linking cognitive–motor processes to variability in knee joint control relevant to ACL injury risk. This integrative approach advances understanding of how attention and biomechanics interact during complex movements. Future work should apply these methods to more demanding cognitive tasks and clinical populations to enhance ecological and practical applications.