The Transportation Research Board and the Institute of Medicine formed a 14-member committee to examine the connection between the built environment and the physical activity levels of the U.S. population.

Key Findings

• Physical activity levels have declined sharply over the past half-century because of reduced physical demands of work, household management and travel together with increased sedentary uses of free time.
• The built environment can facilitate or constrain physical activity. For example, ready access to parks and trails may facilitate walking for exercise; sidewalks and mixed-use development are likely to be more important to encourage walking to local shopping and for other utilitarian purposes.
• The relationship between the built environment and physical activity is complex and operates through many mediating factors, such as sociodemographic characteristics, personal and cultural variables, safety and security and time allocation.
• The available empirical evidence shows an association between the built environment and physical activity. However, investigators have conducted few studies capable of demonstrating a causal relationship, and evidence supporting such a relationship is currently sparse. In addition, the characteristics of the built environment most closely associated with physical activity remain to be determined.
• Weaknesses of the current literature include the lack of a sound theoretical framework, inadequate research designs and incomplete data. Most of the studies conducted to date have been cross-sectional (research that looks at a single point in time). Longitudinal study designs using time-series data are also needed to investigate causal relationships between the built environment and physical activity.
• The built environment in place today has been shaped by long-standing polices and the practices of many decision-makers. Many existing development patterns have resulted from zoning and land use ordinances, design guidelines and funding criteria for transportation infrastructure focused primarily on motorized transportation, values and preferences of homeowners and home buyers, and racial and economic concentration of the poor and disinvestments in their neighborhoods.

See Conclusions and Recommendations.

Funding

The Robert Wood Johnson Foundation (RWJF) provided $720,000 from September 2002 through April 2005 to support this solicited project.