Toward a comprehensive model of physical activity

Background and purpose. Despite the widely acknowledged public health burden and years of individually based intervention approaches, physical inactivity remains a growing concern among industrialized nations. Interventions aimed at changing individual dispositions that increase physical activity generally result in small changes in behavior that dissipate within weeks. Correlational research testing theories and models focusing on these same individual dispositions explain, at best, 20-40% of the variance in physical activity. As a result, recent calls have been made for consideration of broader, multilevel, ecological approaches to physical activity promotion. The purpose of this article is to define a comprehensive model for understanding physical activity and consider future directions for research. Methods. Relevant literature is reviewed within each of the areas being discussed. Results and conclusions. Ecological models incorporate both intra- and extra-individual influences that may impact on individual physical activity. However, the role of extra-individual factors has not been clearly defined in current ecological models of physical activity. We present the theoretical background of ecological models of health behavior, and define an ecological model for physical activity promotion. This model portrays physical activity behavior as being influenced by interplay between environmental settings and biological and psychological factors. Further testing of this and existing ecological models of physical activity is recommended. (C) 2002 Elsevier Science Ltd. All rights reserved.