title: Testing for inter-group contamination in a controlled longitudinal study of added physical education.
abstract: OBJECTIVE
  This case report examines whether there was any cross-contamination between students enrolled in classes that received additional physical education, and their siblings who were enrolled in preceding and succeeding class-cohorts.
  
  
  METHODS
  A controlled longitudinal study extending over 6 years of primary school.
  
  
  METHODS
  An urban and a rural primary school in Québec.
  
  
  METHODS
  546 primary students, comprising approximately equal numbers of boys and girls from the urban and the rural school.
  
  
  METHODS
  Entire class-cohorts were given and hour of additional physical education ach day throughout their primary schooling, with immediately preceding and succeeding class-cohorts serving as controls.
  
  
  METHODS
  The measured data included standing height, body mass, maximal oxygen intake (direct treadmill test) and PWC170.
  
  
  RESULTS
  We found no evidence of cross-contamination between siblings in experimental and control class-cohorts.
  
  
  CONCLUSIONS
  Although a theoretical possibility, cross-contamination between students in preceding and succeeding class-cohorts does not seem an important source of error in primary school students, presumably because such children prefer to play with friends from their immediate age cohort.
authors.affiliation: Faculty of Health Sciences, Université de Québec à Trois Rivières, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Labarre
authors.forename: J C
authors.initials: JC
authors.lastname: Jéquier
authors.forename: R J
authors.initials: RJ
authors.lastname: Shephard
authors.forename: H
authors.initials: H
authors.lastname: Lavallée
authors.forename: M
authors.initials: M
authors.lastname: Rajic
mesh_terms: D015982:Bias; D001824:Body Constitution; D001827:Body Height; D002648:Child; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D010101:Oxygen Consumption; D010806:Physical Education and Training; D011792:Quebec; D012107:Research Design; D012423:Rural Health; D012801:Sibling Relations; D014504:Urban Health; D014938:Work Capacity Evaluation