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Seeking a contemporary understanding of factors that influence physical activity
Commentary
Seeking a Contemporary Understanding of Factors that Influence Physical Activity David Buchner, MD, MPH, Rebecca Miles, PhD
T
he Mozart opera, Abduction from the Seraglio, went far beyond the usual limits of tradition with its long, elaborate arias. Asked about the opera, Emperor Joseph II responded with the terse and famous comment, “Too many notes.” This supplement to the American Journal of Preventive Medicine contains articles from the Cooper Clinic Conference Innovative Approaches to Understanding and Influencing Physical Activity. The articles paint a picture of “a very complex causal web” of factors affecting physical activity behavior. As one ponders the boxes and arrows in logic models of how determinants, correlates, mediators, confounders, and moderators operate at intrapersonal, interpersonal, physical environment, and social/cultural environmental levels, should our comment be the analogous “too many boxes and arrows?” Curiously, physical activity behavior is not inherently complex. Up until a few hundred years ago, the study of physical activity determinants was not as complicated, because the means to accomplish daily tasks in a sedentary manner had not been invented yet. We can now study the choice to be active or inactive because of technology that created many sedentary options for accomplishing daily tasks. But technology also opened the door to a large number of new types of activities that were either unusual or impossible prior to good equipment, including bicycling, skiing, basketball, and roller-skating. We have not met anyone proposing to promote physical activity by going backwards in time, for example, by returning to manual labor on farms. The tack we are on is to put back into our lives a healthful and enjoyable subset of physical activities. In pursuing this tack, we are undergoing a paradigm shift in our approaches to promoting physical activity. On the public health practice side of this shift, public health is rebuilding its emphasis on healthy environments by including a new focus on active community environments. Unheard of ten years ago, partnerships
From the Physical Activity and Health Branch, CDC/NCCDPHP (Buchner), Atlanta, Georgia; and the Department of Urban and Regional Planning and the Center for the Study of Population, Florida State University (Miles), Tallahassee, Florida Address correspondence and reprint requests to: David M. Buchner, MD, MPH, Chief, Physical Activity and Health Branch, CDC/ NCCDPHP, 4770 Buford Highway NE, MS K-46, Atlanta, GA 303413717. E-mail: [email protected] OR [email protected].
Am J Prev Med 2002;23(2S) Published by Elsevier Science Inc.
between public health and urban planners, transportation planners, and park planners are growing steadily. On the research side of the paradigm shift, researchers are shifting to transdisciplinary models and multilevel research designs. The conference essentially proposed and sought to encourage, as part of this shift, a more structured approach to research. The approach involves: (1) more standardization in terminology; (2) a shift away from disciplinary-based conceptual models focusing on a subset of variables, and a shift toward trans-disciplinary, multilevel models better suited to the breadth of variables affecting activity; and (3) more attention to the mechanisms and details of how interventions influence physical activity behavior. A more structured and coherent approach is important. To an ever greater extent, a research study influences practice because it is included in evidence syntheses. A case in point are the evidence syntheses of the Task Force on Community Preventive Services, that have recently identified six recommended or strongly recommended interventions to increase physical activity behaviors. Of 253 reports retained for full review, 159 were excluded from the syntheses, often because of limitations in execution or design. More structure also benefits an important group of “customers” of this research: practitioners who seek to do competent and useful evaluations of community physical activity initiatives. These practitioners need coherence to the logic models guiding the evaluation, e.g., which variables are the important mediators to track? They need measurement tools that correspond to boxes in the logic models. As research in physical activity evolves, it needs to pay increasing attention to such “customers.” In this way, the impact of research results is leveraged. As this supplement takes stock of where we are and where we need to go, several points are worth considering. First, the articles point us in the strategic direction of a comprehensive approach to promoting physical activity. Given the breadth of possible determinants, we do not sense that a few key determinants of physical activity behavior have emerged, and that just a few community interventions could produce large effects on activity. Rather, it appears that large effects on activity are
0749-3797/02/$–see front matter PII S0749-3797(02)00480-4
3
produced by adding many small and medium-sized intervention effects. Second, the articles imply that we need to track indicators of the extent and quality of interventions to promote activity, as well as of determinants and mediators. For example, passing a sidewalk ordinance is a policy change intended to promote walking through improving the physical environment. But if the policy is not enforced, or if pieces of sidewalks do not form useful and attractive networks, the impact of the policy will be disappointing. We do not yet know which mediators are efficient and important to track. Possibly, it could be important to monitor an indicator of whether or not a city has an electronic map displaying existing sidewalk segments, as most cities do not currently have such a resource. Or one might want to track whether a sidewalk map was distributed and explained to policymakers and citizen groups. Third, the papers suggest that we are developing some key themes and identifying subgroups of interest. This is useful for both research and practice. Separate analyses of subgroups may be important to theory development. Studies of walking, the most common physical activity, may emerge as a discrete area of study. Studies of how the environment affects people with fewer activity options seems to be an emerging theme. People with fewer options include older adults who have experienced decline in physical abilities. Options may also be limited for children who are required to ride to school and not offered physical education classes at school. Fourth, we are entering a period of creative theory building. The traditional theories that derive only from disciplines historically most involved research in physical activity (exercise physiology, behavioral science, and public health/medicine) are no longer state-of-the-art. As transdisciplinary models are created, the assumptions of the existing theories will need to be re-examined. For example, one of the papers questions the assumption (from economic theories of transportation demand) that all travel demand is derived from the desire to reach particular destinations. In such models,
4
walking for the sake of enjoyment or exercise is excluded, despite its obvious importance to an active lifestyle. Fifth, the papers suggest that more attention needs to be paid to the statistical methods used in studies of the factors influencing physical activity. This includes methods that permit analyses across levels, that test for effects of selection bias, and that do not assume linearity between determinants and behavioral outcomes. Finally, we are revisiting the issue of personal choice and physical activity. While personal commitment is key to adopting a regularly active lifestyle, we are understanding how choice is bounded and influenced by other factors. McGinnis et al. identify five domains that affect health: genetic and gestational endowments, social circumstances, environmental conditions, behavioral choices, and medical care.2 All these domains affect physical activity and are addressed in this issue. For example, a paper estimating the genetic influence on activity levels suggests genetic endowment makes it easier for some people to adopt an active lifestyle. But note that physical activity levels have declined over a relatively short period of time, so that genetic factors are unlikely to explain the decrease. Indeed, humans are genetically designed to be active each day. We seek a contemporary understanding of the factors that influence physical activity behavior, of the mechanisms by which they operate, and of how to modify the behavioral determinants. We need researchers and practitioners willing to expand their approaches and consider unfamiliar variables and models. We may need a fair number of boxes and arrows, but the greater challenge lies in getting the research data collected and applying it wisely to public health practice.
References 1. Kahn EB, Heath GW, Powell KE, Stone EJ, Brownson RC. Increasing physical activity. A report on recommendations of the Task Force on Community Preventive Services. MMWR Morb Mort Wkly Rep 2001;50:1–14. 2. McGinnis JM, Williams-Russo P, Knickman JR. The case for a more active policy attention to health promotion. Health Aff 2002;21:78 –93.
American Journal of Preventive Medicine, Volume 23, Number 2S
Seeking a Contemporary Understanding of Factors that Influence Physical Activity David Buchner, MD, MPH, Rebecca Miles, PhD
T
he Mozart opera, Abduction from the Seraglio, went far beyond the usual limits of tradition with its long, elaborate arias. Asked about the opera, Emperor Joseph II responded with the terse and famous comment, “Too many notes.” This supplement to the American Journal of Preventive Medicine contains articles from the Cooper Clinic Conference Innovative Approaches to Understanding and Influencing Physical Activity. The articles paint a picture of “a very complex causal web” of factors affecting physical activity behavior. As one ponders the boxes and arrows in logic models of how determinants, correlates, mediators, confounders, and moderators operate at intrapersonal, interpersonal, physical environment, and social/cultural environmental levels, should our comment be the analogous “too many boxes and arrows?” Curiously, physical activity behavior is not inherently complex. Up until a few hundred years ago, the study of physical activity determinants was not as complicated, because the means to accomplish daily tasks in a sedentary manner had not been invented yet. We can now study the choice to be active or inactive because of technology that created many sedentary options for accomplishing daily tasks. But technology also opened the door to a large number of new types of activities that were either unusual or impossible prior to good equipment, including bicycling, skiing, basketball, and roller-skating. We have not met anyone proposing to promote physical activity by going backwards in time, for example, by returning to manual labor on farms. The tack we are on is to put back into our lives a healthful and enjoyable subset of physical activities. In pursuing this tack, we are undergoing a paradigm shift in our approaches to promoting physical activity. On the public health practice side of this shift, public health is rebuilding its emphasis on healthy environments by including a new focus on active community environments. Unheard of ten years ago, partnerships
From the Physical Activity and Health Branch, CDC/NCCDPHP (Buchner), Atlanta, Georgia; and the Department of Urban and Regional Planning and the Center for the Study of Population, Florida State University (Miles), Tallahassee, Florida Address correspondence and reprint requests to: David M. Buchner, MD, MPH, Chief, Physical Activity and Health Branch, CDC/ NCCDPHP, 4770 Buford Highway NE, MS K-46, Atlanta, GA 303413717. E-mail: [email protected] OR [email protected].
Am J Prev Med 2002;23(2S) Published by Elsevier Science Inc.
between public health and urban planners, transportation planners, and park planners are growing steadily. On the research side of the paradigm shift, researchers are shifting to transdisciplinary models and multilevel research designs. The conference essentially proposed and sought to encourage, as part of this shift, a more structured approach to research. The approach involves: (1) more standardization in terminology; (2) a shift away from disciplinary-based conceptual models focusing on a subset of variables, and a shift toward trans-disciplinary, multilevel models better suited to the breadth of variables affecting activity; and (3) more attention to the mechanisms and details of how interventions influence physical activity behavior. A more structured and coherent approach is important. To an ever greater extent, a research study influences practice because it is included in evidence syntheses. A case in point are the evidence syntheses of the Task Force on Community Preventive Services, that have recently identified six recommended or strongly recommended interventions to increase physical activity behaviors. Of 253 reports retained for full review, 159 were excluded from the syntheses, often because of limitations in execution or design. More structure also benefits an important group of “customers” of this research: practitioners who seek to do competent and useful evaluations of community physical activity initiatives. These practitioners need coherence to the logic models guiding the evaluation, e.g., which variables are the important mediators to track? They need measurement tools that correspond to boxes in the logic models. As research in physical activity evolves, it needs to pay increasing attention to such “customers.” In this way, the impact of research results is leveraged. As this supplement takes stock of where we are and where we need to go, several points are worth considering. First, the articles point us in the strategic direction of a comprehensive approach to promoting physical activity. Given the breadth of possible determinants, we do not sense that a few key determinants of physical activity behavior have emerged, and that just a few community interventions could produce large effects on activity. Rather, it appears that large effects on activity are
0749-3797/02/$–see front matter PII S0749-3797(02)00480-4
3
produced by adding many small and medium-sized intervention effects. Second, the articles imply that we need to track indicators of the extent and quality of interventions to promote activity, as well as of determinants and mediators. For example, passing a sidewalk ordinance is a policy change intended to promote walking through improving the physical environment. But if the policy is not enforced, or if pieces of sidewalks do not form useful and attractive networks, the impact of the policy will be disappointing. We do not yet know which mediators are efficient and important to track. Possibly, it could be important to monitor an indicator of whether or not a city has an electronic map displaying existing sidewalk segments, as most cities do not currently have such a resource. Or one might want to track whether a sidewalk map was distributed and explained to policymakers and citizen groups. Third, the papers suggest that we are developing some key themes and identifying subgroups of interest. This is useful for both research and practice. Separate analyses of subgroups may be important to theory development. Studies of walking, the most common physical activity, may emerge as a discrete area of study. Studies of how the environment affects people with fewer activity options seems to be an emerging theme. People with fewer options include older adults who have experienced decline in physical abilities. Options may also be limited for children who are required to ride to school and not offered physical education classes at school. Fourth, we are entering a period of creative theory building. The traditional theories that derive only from disciplines historically most involved research in physical activity (exercise physiology, behavioral science, and public health/medicine) are no longer state-of-the-art. As transdisciplinary models are created, the assumptions of the existing theories will need to be re-examined. For example, one of the papers questions the assumption (from economic theories of transportation demand) that all travel demand is derived from the desire to reach particular destinations. In such models,
4
walking for the sake of enjoyment or exercise is excluded, despite its obvious importance to an active lifestyle. Fifth, the papers suggest that more attention needs to be paid to the statistical methods used in studies of the factors influencing physical activity. This includes methods that permit analyses across levels, that test for effects of selection bias, and that do not assume linearity between determinants and behavioral outcomes. Finally, we are revisiting the issue of personal choice and physical activity. While personal commitment is key to adopting a regularly active lifestyle, we are understanding how choice is bounded and influenced by other factors. McGinnis et al. identify five domains that affect health: genetic and gestational endowments, social circumstances, environmental conditions, behavioral choices, and medical care.2 All these domains affect physical activity and are addressed in this issue. For example, a paper estimating the genetic influence on activity levels suggests genetic endowment makes it easier for some people to adopt an active lifestyle. But note that physical activity levels have declined over a relatively short period of time, so that genetic factors are unlikely to explain the decrease. Indeed, humans are genetically designed to be active each day. We seek a contemporary understanding of the factors that influence physical activity behavior, of the mechanisms by which they operate, and of how to modify the behavioral determinants. We need researchers and practitioners willing to expand their approaches and consider unfamiliar variables and models. We may need a fair number of boxes and arrows, but the greater challenge lies in getting the research data collected and applying it wisely to public health practice.
References 1. Kahn EB, Heath GW, Powell KE, Stone EJ, Brownson RC. Increasing physical activity. A report on recommendations of the Task Force on Community Preventive Services. MMWR Morb Mort Wkly Rep 2001;50:1–14. 2. McGinnis JM, Williams-Russo P, Knickman JR. The case for a more active policy attention to health promotion. Health Aff 2002;21:78 –93.
American Journal of Preventive Medicine, Volume 23, Number 2S