title: Context-Specific Outdoor Time and Physical Activity among School-Children Across Gender and Age: Using Accelerometers and GPS to Advance Methods.
abstract: BACKGROUND
  Being outdoors has a positive influence on health among children. Evidence in this area is limited and many studies have used self-reported measures. Objective context-specific assessment of physical activity patterns and correlates, such as outdoor time, may progress this field.
  
  
  OBJECTIVE
  To employ novel objective measures to assess age and gender differences in context-specific outdoor weekday behavior patterns among school-children [outdoor time and outdoor moderate to vigorous physical activity (MVPA)] and to investigate associations between context-specific outdoor time and MVPA.
  
  
  METHODS
  A total of 170 children had at least one weekday of 9 h combined accelerometer and global positioning system data and were included in the analyses. The data were processed using the personal activity and location measurement system (PALMS) and a purpose-built PostgreSQL database resulting in context-specific measures for outdoor time, outdoor MVPA, and overall daily MVPA. In addition, 4 domains (leisure, school, transport, and home) and 11 subdomains (e.g., urban green space and sports facilities) were created and assessed. Multilevel analyses provided results on age and gender differences and the association between outdoor time and MVPA.
  
  
  RESULTS
  Girls compared to boys had fewer outdoor minutes (p < 0.05), spent a smaller proportion of their overall daily time outdoors (p < 0.05), had fewer outdoor MVPA minutes during the day (p < 0.001) and in 11 contexts. Children compared to adolescents had more outdoor minutes (p < 0.05). During school and within recess, children compared to adolescents had more outdoor MVPA (p < 0.001) and outdoor time (p < 0.001). A 1-h increase in outdoor time was associated with 9.9 more minutes of MVPA (p < 0.001).
  
  
  CONCLUSIONS
  A new methodology to assess the context-specific outdoor time and physical activity patterns has been developed and can be expanded to other populations. Different context-specific patterns were found for gender and age, suggesting different strategies may be needed to promote physical activity.
authors.affiliation: Department of Sports Science and Clinical Biomechanics, University of Southern Denmark , Odense , Denmark.
authors.forename: Charlotte Demant
authors.initials: CD
authors.lastname: Klinker
authors.affiliation: Department of Sports Science and Clinical Biomechanics, University of Southern Denmark , Odense , Denmark.
authors.forename: Jasper
authors.initials: J
authors.lastname: Schipperijn
authors.affiliation: Department of Family and Preventive Medicine, University of California San Diego , San Diego, CA , USA.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Kerr
authors.affiliation: The National Institute of Public Health, University of Southern Denmark , Copenhagen , Denmark.
authors.forename: Annette Kjær
authors.initials: AK
authors.lastname: Ersbøll
authors.affiliation: Department of Sports Science and Clinical Biomechanics, University of Southern Denmark , Odense , Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: Troelsen
keywords: GPS; accelerometer; children; context-specific; outdoor behavior; physical activity; spatial behavior