The Effects of an Overhead Goal and Movement Anticipation on Lower Extremity Biomechanics and Muscle Activation Patterns

Noncontact anterior cruciate ligament (ACL) injury is becoming more common among sport-related injuries. Several "high-risk" movements such as landings and cutting have been associated with ACL injury along with several biomechanical risk factors. These risk factors, specifically at the hip, knee, and neuromuscular abnormalities (unbalanced quadriceps-hamstrings activation ratios) have also been identified as possible causes that lead to ACL injury. Females are nearly 2.5 times more likely to experience an ACL injury while playing volleyball when compared to their male counterparts. While research continues to investigate the reasoning for this injury, the results may not be accurate to what athlete's experience while playing in a real competition. The purpose of this study was to determine the effects of a physical overhead goal and a subsequent unanticipated lateral cut on the kinematics, kinetics, and muscle activation of the hip and knee of the dominant leg during the landing of a stop vertical jump task (volleyball block). Participants completed four testing conditions - with a target and an anticipated cut following the landing (WTA), with a target and an unanticipated secondary cut (WTUA), and then both anticipated and unanticipated secondary movements with no overhead target (NTA, NTUA). Results indicated that when a target was added to the testing environment, there was a significant decrease in the initial contact (IC) knee flexion angle and an increase in the peak knee extension moment. When comparing anticipated and unanticipated tasks, there were decreases in the IC knee abduction angles and peak knee extension moments in the unanticipated trials compared to the anticipated trials. Significant interactions were also seen in the peak knee abduction moments and the IC hip flexion angles specifically when the target is present. These findings suggest that the more realistic testing environment altered hip and knee landing mechanics, which in turn can be used to help better evaluate the risk factors for ACL injury.