NEUROMUSCULAR ACTIVATION DURING HIGH INJURY-RISK MOVEMENTS PERFORMED IN A SIMULATED SPORT ENVIRONMENT BY ATHLETES CLEARED TO RETURN TO PLAY FOLLOWING ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION 
Creators: name: Sublett, Kat
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2022

description: Secondary anterior cruciate ligament (ACL) injury rate for athletes under 25 years who return to play (RTP) after ACL reconstruction (ACLR) is 23%. Noncontact mechanisms are most common with sport-related ACL injury usually manifested during sudden deceleration, landing, and change of direction (cutting) maneuvers: these are collectively termed as high injury-risk kinematics. Unbalanced neuromuscular (NM) activation of prime movers of the lower limb during high injury-risk kinematics has been long hypothesized to impact reinjury rate. This study originally planned to investigate possible NM influence on joint kinematics during high injury-risk cutting maneuvers via two specific aims: (1) examination of the hamstrings to quadriceps muscle coactivation ratio (H/Q ratio) and knee joint stability, via sagittal knee flexion angle, and (2) examination of the hamstrings, quadriceps, and gastrocnemius muscles activation and dynamic valgus via frontal plane knee abduction angles. However, due to technical and COVID-related delays, the original plan was altered to meet the project’s due date requirement. Thus, a revised approach was taken and included the fundamental step of the proposed data analysis—extraction and preliminary analysis of the positional data. Fifteen club-level athletes (mean age =  19.8 ± 1.15; 6 female) were recruited for the study and were divided into two groups: returning to play following a lower limb musculoskeletal injury (n=8) or a non-injured participant pilot group (n=7).  The task required participants to intercept a virtual moving target while avoiding non-player virtual characters in a sport-like virtual reality-based simulation environment. Participant’s behavior across trial difficulty was examined relative to the number of non-player characters (none, two, three, four or five) present in a given condition. Raw cartesian positional data (x,z) were extracted from the head-mounted display and processed to index speed and acceleration time series, with summary values of the mean maximum and mean standard deviation of speed and acceleration, as well as the mean minimum acceleration computed for each of the six experimental difficulty conditions. These measures are the first step toward identifying cutting maneuvers for eventual movement-context analyses as originally proposed. In addition, the preliminary results provide the first insight into the effects of changing difficulty of the athletic avoidance tasks on participants’ maneuvers. Specifically, a trend toward an increase in acceleration, deceleration, and speed variability was observed during conditions with more non-player characters compared to those with no, or less obstacles. This provides the first evidence that a sport-like virtual reality task can induce changes in athletic behaviors known to associate with high injury-risk kinematics.