The National Institutes of Health has awarded a 3-year research grant to Principal Investigator Christopher M. Powers, PhD, PT, to examine mechanics of non-contact anterior cruciate ligament (ACL) injuries in female athletes. This project represents a collaborative effort between several institutions including the University of Southern California (Divisions of Biokinesiology & Physical Therapy and Preventive Medicine); University of North Carolina at Chapel Hill (Division of Epidemiology); Santa Monica Orthopaedic Group (Santa Monica , CA); and the Competitive Athletic Training Zone (Pasadena, CA ).

As female participation rates at all levels of sporting activity have dramatically increased, so have certain sports injuries. In particular, the incidence of ACL injury in female athletes has been reported to be 4 to 6 times greater than male athletes participating in the same sports . Seventy percent of these injuries occur during an incident that involves no direct contact with another player or object, and often take place during a dynamic task such as a landing or cutting as the athlete is decelerating and/or changing direction. Female soccer athletes may face an exceptionally high risk: An analysis of collegiate soccer players during the early 1990s found that 31 percent of females had an ACL injury, compared to only 13 percent of males. According to Powers, “surprisingly, little is known about women's sport-specific movement patterns and how they may contribute to knee injury. In order to prevent these injuries, we need to better understand how they occur and potential risk factors”

The objective of Project 1 is to quantify gender differences in biomechanical and neuromuscular aspects of sport specific movements, and to determine how gender specific movement patterns vary across different stages of maturation. Eighty female and 80 male athletes between the ages of 9-24 will undergo biomechanical testing while performing cutting, landing, and kicking activities. This biomechanical testing will be conducted in the Musculoskeletal Biomechanics Research Laboratory within the Division of Biokinesiology & Physical Therapy at USC. An eight-camera motion analysis system, three force plates, and surface electromyography will be used to measure lower extremity kinematics (joint angles), kinetics (joint torques) and muscle activation patterns while athletes perform these tasks. It is hypothesized that after the onset of puberty, significant gender differences will be found at the hip and knee and that these differences will be suggestive of “at risk behavior” with respect to ACL injury.

The objective of Project 2 is to assess the influence of a training program in altering biomechanical and neuromuscular aspects of movement in female athletes, and determine whether a given response to a training program varies across different stages of maturation. One-hundred and eighty female athletes (90 intervention and 90 controls) between the ages of 12-24 will participate in the Prevent Injury and Enhance Performance (PEP) program developed by the Santa Monica Orthopaedic and Sport Medicine Research Foundation. Previous work has demonstrated a 74% reduction in ACL injuries among female high school soccer players who participated in the PEP program. While these findings support the use of a training program to reduce ACL injuries, the underlying mechanism behind the success of such a training program remains unclear. For example, it is not known if training alters lower extremity mechanics in a way that would be suggest ive of decreased risk for ACL injury. Therefore, subjects for Project 2 will undergo biomechanical testing before and after participation in the PEP program. It is hypothesized that following the training program, females will demonstrate movement patterns that are less suggestive of “at risk behavior.”

The objective of Project 3 is to assess the mechanical and neuromuscular demands of specific exercises that are included in an injury prevention program that has been shown to reduce the incidence of ACL injuries. Biomechanical assessment of fifteen female athletes performing eight specific exercises will be carried out. It is hypothesized that the specific demands imposed by certain exercises within the intervention program will correspond to changes in hip and knee mechanics following participation in the program.

“Taken together, the data from this study will address important questions related to the influence of gender, age and training on ACL injury potential, and will provide a foundation on which further investigation of injury prevention and rehabilitation can be based,” says Powers.