The Effect of Different Cognitive Demands on ACL Risk Biomechanics and Prefrontal Activation During a Single-Leg Drop Jump

Background: Cognitive load is an important factor influencing anterior cruciate ligament (ACL) injuries. However, few studies have systematically manipulated and quantified cognitive load to examine its biomechanical and neurophysiological consequences. Purpose: This study aimed to investigate the impact of varying cognitive load levels on biomechanical variables associated with ACL injury risk. The study further explored whether individual cognitive performance was related to alterations in ACL injury risk indicators and examined prefrontal cortical activity as an objective marker of mental workload. Study Design: Controlled laboratory study. Methods: A total of 30 athletes engaged in team sports performed a single-leg drop vertical jump (SL-DVJ) under 5 cognitive conditions of varying complexity using a modified Go/No-Go task. Biomechanics, behavioral, and prefrontal hemodynamic data variables were recorded. Cognitive performance was assessed through a computerized Go/No-Go task. Results: Higher cognitive load significantly increased peak ground-reaction forces and altered joint kinematics, specifically reducing knee flexion and increasing knee abduction during landing, especially in conditions that required high cognitive demand ( P < .001). These changes were accompanied by increased prefrontal hemoglobin (OxyHb) concentrations, suggesting elevated cortical activation. Furthermore, lower cognitive performance, notably lower accuracy and higher precision-adjusted response time, was associated with more pronounced biomechanical patterns (such as greater ground-reaction forces) and an increase in the risk of ACL injury ( r = −0.471, P < .01; r = 0.650, P < .001, respectively). Conclusion: An increased cognitive load altered the biomechanics of movement during an SL-DVJ, leading to a potential for increased risk of ACL injury. Moreover, athletes with poorer cognitive control may have been more susceptible to these effects. Prefrontal cortex (PFC) activity increased under conditions of higher cognitive demand. The pattern of regional activation varied according to the type of stimulus (eg, higher OxyHb concentrations for the ventrolateral PFC were observed during the change goal-stimulus condition), suggesting a specific functional organization of the PFC according to the particular demands of executive control. Clinical Relevance: These findings highlight the importance of integrating cognitive challenges into injury prevention and rehabilitation strategies. The findings emphasize the need to consider cognitive load as a central variable in injury risk mitigation and to evaluate cognitive performance as a potential prognostic indicator.