title: Short-term changes in sedentary behaviour during adolescence: Project STIL (Sedentary Teenagers and Inactive Lifestyles).
abstract: OBJECTIVE
  Changes in body composition and body image during puberty will impact on sedentary behavioural choices.
  
  
  OBJECTIVE
  The study aimed to investigate the effects of changes in pubertal status, body composition and body image on changes in time spent being sedentary.
  
  
  METHODS
  Eighty-three school students aged 10-15 years were studied at 6-month intervals. BMI and percentage body fat (%BF) were calculated from anthropometric measures. Sedentary behaviour and sleep time were computed for weekday and weekend days using momentary-time-sampling diaries. Body image was measured using the Physical Self-Perception Profile for Children. Pubertal status was assessed from self-reported secondary sexual characteristics.
  
  
  RESULTS
  During weekdays, boys' sedentary behaviour increased by a significantly greater amount for those who increased pubertal level compared with those who did not. No significant correlations were found between changing pubertal status, body composition, and body image for either gender. For girls, but not boys, a significant amount of the variance of the change in weekend day sedentary behaviour was explained by changing %BF, independent of changing pubertal status.
  
  
  CONCLUSIONS
  Only a part of the hypothesis was supported by these data. Changes in sedentary behaviour were not associated with behavioural choices triggered by body compositional changes.
authors.affiliation: Department of Human Sciences, Loughborough University, UK. I.D.Murdey@lboro.ac.uk
authors.forename: Ian D
authors.initials: ID
authors.lastname: Murdey
authors.forename: Noël
authors.initials: N
authors.lastname: Cameron
authors.forename: Stuart J H
authors.initials: SJ
authors.lastname: Biddle
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Marshall
authors.forename: Trish
authors.initials: T
authors.lastname: Gorely
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D041923:Adolescent Development; D001823:Body Composition; D001828:Body Image; D015992:Body Mass Index; D002648:Child; D005260:Female; D015438:Health Behavior; D006801:Humans; D008019:Life Style; D008297:Male; D009043:Motor Activity; D012737:Sex Factors; D012890:Sleep