title: Mapping the walk to school using accelerometry combined with a global positioning system.
abstract: BACKGROUND
  Walking to school is associated with higher levels of physical activity, but the contribution of the journey itself to physical activity before school is unknown.
  
  
  OBJECTIVE
  This study combined accelerometer and GPS data to investigate the level and location of physical activity in children walking to school.
  
  
  METHODS
  Participants were 137 children (aged 11.3 + or - 0.3 years) from London, England, measured in June-July 2006. Physical activity was measured by accelerometry, and location was determined with a GPS receiver. Travel mode was self-reported. Accelerometer and GPS data were time-matched to provide activity level and location for each 10-second epoch where both were available. Journeys were mapped in a GIS.
  
  
  RESULTS
  Mean accelerometer counts per minute before school (8:00 am to 9:00 am) were 43% higher in those who walked to school than those traveling by car (878.8 + or - 387.6 vs 608.7 + or - 264.1 counts per minute [cpm], p<0.001). Eleven percent (4.5 minutes) of daily moderate to vigorous physical activity (MVPA) occurred in this hour, with walkers recording 2.1 minutes more than car travelers (p = 0.004). Children followed direct routes between home and the school playground. Total activity during the walk to school was twice that in the playground (2131.3 + or - 1170.7 vs 1089.7 + or - 938.6 cpm, p<0.001), with the journey contributing three times as much MVPA as time in the playground.
  
  
  CONCLUSIONS
  Our results provide evidence that the journey to school is purposeful and contributes to higher total physical activity and MVPA in children. Combining accelerometer and GPS data may aid our understanding of the environmental context of physical activity.
authors.affiliation: Department of Exercise, Nutrition, and Health Sciences, University of Bristol, Bristol, United Kingdom. ashley.cooper@bris.ac.uk
authors.forename: Ashley R
authors.initials: AR
authors.lastname: Cooper
authors.forename: Angie S
authors.initials: AS
authors.lastname: Page
authors.forename: Benedict W
authors.initials: BW
authors.lastname: Wheeler
authors.forename: Pippa
authors.initials: P
authors.lastname: Griew
authors.forename: Laura
authors.initials: L
authors.lastname: Davis
authors.forename: Melvyn
authors.initials: M
authors.lastname: Hillsdon
authors.forename: Russell
authors.initials: R
authors.lastname: Jago
mesh_terms: D000054:Acceleration; D002648:Child; D005260:Female; D040362:Geographic Information Systems; D006801:Humans; D008131:London; D008297:Male; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D012574:Schools; D016138:Walking