Mechanism of Anterior Cruciate Ligament Loading during Dynamic Motor Tasks.

INTRODUCTION This study determined anterior cruciate ligament (ACL) force and its contributors during a standardized drop-land-lateral jump task using a validated computational model. METHODS Three-dimensional whole-body kinematics, ground reaction forces, and muscle activation patterns from eight knee-spanning muscles were collected during dynamic tasks performed by healthy recreationally active females (n=24). These data were employed in a combined neuromusculoskeletal and ACL force model to determine lower limb muscle and ACL forces. RESULTS Peak ACL force (2.3±0.5 BW) was observed at ~14% of stance during the drop-land-lateral jump. The ACL force was primarily generated through the sagittal plane and muscle was the dominant source of ACL loading. The main ACL antagonists (i.e., loaders) were the gastrocnemii and quadriceps, while the hamstrings were the main ACL agonists (i.e., supporters). CONCLUSION Combining neuromusculoskeletal and ACL force models, the roles of muscle in ACL loading and support were determined during a challenging motor task. Results highlighted the importance of the gastrocnemius in ACL loading, which could be considered more prominently in ACL injury prevention and rehabilitation programmes.