Effects of a Raised Surface on Lower Extremity Kinematics, Kinetics, and Muscle Activation During a Sidecut in Recreational Female Softball Players

Noncontact anterior cruciate ligament (ACL) injury is a common sports-related injury. “High-risk” dynamic movements, such as a sidecut, have been associated with increasing the risk of noncontact ACL injury. Certain biomechanical abnormalities, specifically at the hip and knee, and neuromuscular abnormalities, such as unbalanced quadriceps-to-hamstrings activation ratios and certain activation patterns prior to initial contact and after initial contact, have also been associated with an increased likelihood of noncontact ACL injuries occurring. Approximately 78% of all NCAA Division I softball game-day injuries are classified as noncontact where there is no direct contact to a player. Internal derangement of the knee accounted for 221 game day injuries, and 31% of these injuries were noncontact ACL injuries. The base runner was at the greatest risk of injury, with 28.8% of athletes base running at the time of injury. Additionally, 9% of base runners, or 187 athletes, were injured while contacting the base. The purpose of this study was to determine the effects of a raised surface on lower extremity kinematics, kinetics, and muscle activation patterns during a sidecut, simulating rounding first base. Participants completed two base conditions – with a base present (WB) and no base (NB) present with a controlled entrance and exit speed. Results indicated the only biomechanical difference between base conditions was greater peak knee adduction moments in the NB condition compared to the WB condition. These findings suggest that the body may be in a better position when a raised surface is present during a sidecut and decrease the risk of noncontact ACL injury. Therefore, examining movement patterns at the ankle may provide a better explanation for noncontact ACL injuries that occur during this time. Regarding muscle activation, there was significantly greater quadriceps activation post-contact compared to pre-contact. Significantly greater quadriceps activation creates a large anterior shear force on the ACL, increasing risk of injury.