title: Quantifying the physical activity energy expenditure of commuters using a combination of global positioning system and combined heart rate and movement sensors.
abstract: BACKGROUND
  Active commuting may help to increase adults' physical activity levels. However, estimates of its energy cost are derived from a small number of studies which are laboratory-based or use self-reported measures.
  
  
  METHODS
  Adults working in Cambridge (UK) recruited through a predominantly workplace-based strategy wore combined heart rate and movement sensors and global positioning system (GPS) devices for one week, and completed synchronous day-by-day travel diaries in 2010 and 2011. Commuting journeys were delineated using GPS data, and metabolic intensity (standard metabolic equivalents; MET) was derived and compared between journey types using mixed-effects linear regression.
  
  
  RESULTS
  182 commuting journeys were included in the analysis. Median intensity was 1.28 MET for car journeys; 1.67 MET for bus journeys; 4.61 MET for walking journeys; 6.44 MET for cycling journeys; 1.78 MET for journeys made by car in combination with walking; and 2.21 MET for journeys made by car in combination with cycling. The value for journeys made solely by car was significantly lower than those for all other journey types (p<0.04). On average, 20% of the duration of journeys incorporating any active travel (equating to 8 min) was spent in moderate-to-vigorous physical activity (MVPA).
  
  
  CONCLUSIONS
  We have demonstrated how GPS and activity data from a free-living sample can be used simultaneously to provide objective estimates of commuting energy expenditure. On average, incorporating walking or cycling into longer journeys provided over half the weekly recommended activity levels from the commute alone. This may be an efficient way of achieving physical activity guidelines and improving population health.
authors.affiliation: MRC Epidemiology Unit and UKCRC Centre for Diet and Activity Research (CEDAR), School of Clinical Medicine, University of Cambridge, Cambridge, UK.
authors.forename: Silvia
authors.initials: S
authors.lastname: Costa
authors.affiliation: MRC Epidemiology Unit and UKCRC Centre for Diet and Activity Research (CEDAR), School of Clinical Medicine, University of Cambridge, Cambridge, UK.
authors.forename: David
authors.initials: D
authors.lastname: Ogilvie
authors.affiliation: Norwich Medical School and UKCRC Centre for Diet and Activity Research (CEDAR), University of East Anglia, Norwich, UK.
authors.forename: Alice
authors.initials: A
authors.lastname: Dalton
authors.affiliation: MRC Epidemiology Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK.
authors.forename: Kate
authors.initials: K
authors.lastname: Westgate
authors.affiliation: MRC Epidemiology Unit, School of Clinical Medicine, University of Cambridge, Cambridge, UK.
authors.forename: Søren
authors.initials: S
authors.lastname: Brage
authors.affiliation: MRC Epidemiology Unit and UKCRC Centre for Diet and Activity Research (CEDAR), School of Clinical Medicine, University of Cambridge, Cambridge, UK. Electronic address: jrp63@medschl.cam.ac.uk.
authors.forename: Jenna
authors.initials: J
authors.lastname: Panter
mesh_terms: D061725:Accelerometry / Q000379:methods*; D000328:Adult; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D040362:Geographic Information Systems / Q000295:instrumentation*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D057566:Self Report; D011795:Surveys and Questionnaires; D014186:Transportation; D017132:Workplace
keywords: Active commuting; Cycling; Exercise; GPS; Geographical Information Systems; Transportation; Walking