title: Motivation and body-related factors as discriminators of change in adolescents' exercise behavior profiles.
abstract: OBJECTIVE
  A prospective study was conducted to explore the relative contributions of weight-related self-perceptions and exercise-related motivation variables in predicting change in leisure-time exercise within a sample of adolescents in the United Kingdom.
  
  
  METHODS
  A cohort of 310 adolescents (51% male, Mean age = 14.08 ± .32 years at baseline) was classified into four groups on the basis of reported change in leisure-time exercise over 10-months: those who maintain, drop out from exercise, take up exercise, and those who were continually inactive. Discriminant function analyses were conducted to predict group membership from adolescents' profiles of motivational and weight-related perceptions at baseline.
  
  
  RESULTS
  For boys, the first discriminant function (DF1) revealed that exercise maintainers reported higher identified regulation, introjected regulation, competence, relatedness, and body satisfaction than all other groups (between-group R(2) = .45). DF2 was more indicative of current exercise levels than change, indicating higher intrinsic motivation and lower amotivation for both active groups at baseline (between-group R(2) = .40). In girls, DF1 showed that exercise maintainers reported higher intrinsic motivation, identified regulation, autonomy, competence, relatedness, and lower external regulation than all other groups (between-group R(2) = .58). DF2 indicated that higher body mass index, and perceiving greater pressure to lose weight positively predicted drop out, and negatively predicted exercise uptake (between-group R(2) = .26).
  
  
  CONCLUSIONS
  Fostering autonomous (self-determined) motivation seems a key determinant to maintaining leisure-time exercise for both boys and girls. Additionally, reducing perceptions of pressure to lose weight and promoting positive interactions with others during exercise may be particularly useful to prevent dropout in girls.
authors.affiliation: School for Health, University of Bath, Bath, United Kingdom. f.b.gillison@bath.ac.uk
authors.forename: Fiona B
authors.initials: FB
authors.lastname: Gillison
authors.forename: Martyn
authors.initials: M
authors.lastname: Standage
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Skevington
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D001294:Attitude to Health; D001828:Body Image; D003430:Cross-Sectional Studies; D015444:Exercise / Q000523:psychology*; D005260:Female; D015438:Health Behavior; D006801:Humans; D007899:Leisure Activities / Q000523:psychology; D008297:Male; D009042:Motivation; D011446:Prospective Studies; D012649:Self Concept; D017678:Sex Distribution; D013334:Students / Q000523:psychology; D006113:United Kingdom / Q000453:epidemiology