Urban trails and physical activity: a natural experiment.

BACKGROUND: The built environment in which a person lives and works is thought to have a strong influence on his or her level of physical activity. However, this belief is largely based on cross-sectional studies underlining the need for prospective studies using natural experiments.
DESIGN: This study adopted a quasi-experimental research design with multiple control neighborhoods and was conducted between 2005 and 2007. Data were analyzed in 2008. SETTING/PARTICIPANTS: The subjects were children, adolescents, and adults in free-living conditions within one experimental and two control neighborhoods. INTERVENTION: An urban greenway/trail was retrofitted in a neighborhood that lacked connectivity of the residential pedestrian infrastructure to nonresidential destinations. MAIN OUTCOME MEASURES: The main outcomes were 2-hour counts of directly observed physical activity in the general neighborhood and, at the school level, active transport to school.
RESULTS: At the neighborhood level, the 2-hour counts of physical activity significantly increased between 2005 and 2007 (p=0.000) in the intervention neighborhood, with a median increase of 8.0 counts. The control neighborhoods had a significant decrease in counts (p=0.000). The pre- and post-intervention changes between experimental and control neighborhoods were significantly different for total physical activity (p=0.001); walking (p=0.001); and cycling (p=0.038). There was no noted change over time for active transport to school in either the intervention or control neighborhoods.
CONCLUSIONS: Changes to the pedestrian connectivity of the built environment infrastructure may lead to greater levels of physical activity. However, this positive effect was limited to physical activity at the neighborhood level and not to active transport to school. 2010 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.