COMMENTARY: Time for a Paradigm Shift in Conceptualizing Risk Factors in Sports Injury Research

Certified athletic trainers are positioned to play an integral role in sport-related, recreation-related, and exercise-related injury research and prevention efforts. The Centers for Disease Control and Prevention1 have specifically identified certified athletic trainers and their potential to contribute to this important area of research in their recently published Injury Research Agenda for 2009–2018. From a public health perspective, identifying factors associated with injury is one of the initial steps in the injury prevention process. The ultimate goal of this line of research is to identify populations that are at greatest risk for subsequent injury and to develop effective screening and intervention strategies to reduce the incidence and burden of injury. Therefore, the manner in which risk factors are conceptualized in initial research has significant bearing on the development of subsequent screening and intervention strategies. In the current issue of the Journal of Athletic Training, Reinking et al2 examined the factors associated with exerciserelated leg pain in high school cross-country athletes. After a discussion of modifiable and nonmodifiable risk factors, the authors conceptualized risk factors for exertional leg pain as intrinsic (within the body) or extrinsic (outside the body) factors; sports injury researchers have traditionally conceptualized risk factors associated with injury in this manner.3–5 This study provides an opportunity to discuss how risk factors are conceptualized in the context of sports injury research. The seminal work by sports injury researchers such as van Mechelen et al3 and Meeuwisse5 provided a theoretic framework for sports injury research, and although these models have evolved since they were first described,6–9 they have consistently characterized risk factors for injury as intrinsic factors and extrinsic factors. It is important to consider that injuries often result from the complex interaction of multiple factors3,7,10 in a dynamically changing environment,6 but the characterization of risk factors as intrinsic or extrinsic limits the clinical importance and usefulness of results in relation to future injury screening and prevention efforts. More importantly, characterizing risk factors in this manner provides limited insight into whether something can be done to intervene and mitigate the contributing influence of any given factor or combination of factors with regard to subsequent injury.11 Injury epidemiologists and public health professionals, on the other hand, use a different approach to conceptualizing risk factors for disease or injury by focusing on those risk factors that are modifiable and those that are nonmodifiable. Conceptualizing risk factors as modifiable and nonmodifiable is important from a clinical and injury prevention perspective, because modifiable risk factors are amenable to intervention.11 Researchers12,13 of chronic diseases, such as cardiovascular disease, hypertension, and type 2 diabetes, have conceptualized risk factors as modifiable and nonmodifiable. Some of these risk factors include physical activity, diet, smoking, and obesity, to name a few. Subsequent intervention efforts have been developed and evaluated to address these factors, with various degrees of success. Conceptualizing risk factors as modifiable and nonmodifiable aligns with the ‘‘Translating Research into Injury Prevention Practice (TRIPP)’’ framework described by Finch,9 which applies a public health approach to sports injury prevention. Clinicians and injury researchers are most interested in modifiable risk factors associated with injury because they provide the vector for developing injury prevention interventions. Although nonmodifiable risk factors may not be useful as targets for intervention, they are particularly important in identifying populations that are at greatest risk for injury, so that injury prevention strategies can be directed to those with the most pressing need. This information can be used to develop risk profiles for specific injuries, to screen athletes to identify those at greatest risk for injury, and to guide injury prevention interventions that target modifiable risk factors. This information can also be used to develop interventions and social marketing campaigns that are culturally and ecologically appropriate for the populations at greatest risk for injury.14 When only nonmodifiable risk factors associated with injury are known, this information can be used to counsel athletes and parents about potential risks during the preparticipation screening process, so they can make informed decisions about participation. Recently, researchers have conceptualized risk factors as modifiable and nonmodifiable in the sports medicine literature. Emerging research10,15–17 into the risk factors associated with anterior cruciate ligament (ACL) injuries is one of the best examples in the sports medicine literature of how the conceptualization of risk factors has evolved. Early work15 in this area conceptualized risk factors as intrinsic and extrinsic, while recognizing the importance of focusing on factors that are modifiable. Subsequent consensus statements10,16 on the risk factors for ACL