title: Measuring physical activity in public open space--an electronic device versus direct observation.
abstract: OBJECTIVE
  To evaluate the practicality and validity of using infra-red beam counters (IRBCs) to measure walking path use and overall park use.
  
  
  METHODS
  Direct observation was carried out simultaneously with IRBC data collection in five parks on seven non-consecutive days during February-March in 1998 and on matched days in 1999. A second validation study was undertaken in one park in October 1999.
  
  
  RESULTS
  The IRBC over-estimated the observed number of people using walking paths by 14% to 78%. When assessed by path volume, the difference between the IRBC and observer ranged from 10% under-estimation to 16% over-estimation. In a more rigorous evaluation of path volume the IRBC under-estimated the observed count by 20%. The extent to which the IRBC equated with the number of observed park users varied from 69% under-estimation to no difference.
  
  
  CONCLUSIONS
  IRBCs are not appropriate for measuring the number of people engaging in physical activity in parks.
  
  
  CONCLUSIONS
  IRBCs cannot replace direct observation for the collection of valid data on physical activity participation in parks. Further research is needed to determine settings in which electronic devices such as IRBCs may provide valid data on physical activity participation.
authors.affiliation: Western Sydney Area Health Service, New South Wales, Parramatta. Andrew_Milat@wsahs.nsw.gov.au
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Milat
authors.forename: Joanne
authors.initials: J
authors.lastname: Stubbs
authors.forename: Susanne
authors.initials: S
authors.lastname: Engelhard
authors.forename: Peter
authors.initials: P
authors.lastname: Weston
authors.forename: Billie
authors.initials: B
authors.lastname: Giles-Corti
authors.forename: Susan
authors.initials: S
authors.lastname: Fitzgerald
mesh_terms: D003625:Data Collection / Q000295:instrumentation / Q000379:methods*; D004581:Electronics / Q000295:instrumentation*; D006801:Humans; D007259:Infrared Rays; D009517:New South Wales; D019370:Observation; D011634:Public Health; D016138:Walking / Q000502:physiology / Q000706:statistics & numerical data*