title: Television viewing: moderator or mediator of an adolescent physical activity intervention?
abstract: OBJECTIVE
  To determine whether the amount of television (TV) watched by participants enrolled in a physical activity intervention mediates or moderates program effectiveness.
  
  
  METHODS
  Nine-month, controlled, school-based physical activity intervention.
  
  
  METHODS
  Public high school.
  
  
  METHODS
  One hundred twenty-two sedentary adolescent females (mean +/- standard deviation age = 15.04 +/- 0.79 years).
  
  
  METHODS
  Supervised in-class exercise, health education, and internet-based self-monitoring.
  
  
  METHODS
  Physical activity by 3-day physical activity recall; TV viewing by self-reports; cardiovascular fitness by cycle ergometer.
  
  
  METHODS
  T-tests were conducted to examine between-group differences. Linear regression equations tested the mediating or moderating role of TV watching relative to the intervention.
  
  
  RESULTS
  TV viewing moderated the intervention's effect on vigorous activity; the intervention significantly predicted change in physical activity among high (beta = -.45; p < .001), but not among low (p > .05), TV watchers. TV viewing did not mediate the intervention effect.
  
  
  CONCLUSIONS
  Consistent with displacement theory, adolescents who watched more TV prior to the intervention showed postintervention increases in vigorous physical activity and concomitant decreases in TV viewing, whereas those who watched less TV showed no change in physical activity or TV viewing.
authors.affiliation: Department of Psychology and Social Behavior, University of California-Irvine, Irvine, California 92617, USA. dgraham@uci.edu
authors.forename: Dan J
authors.initials: DJ
authors.lastname: Graham
authors.forename: Margaret
authors.initials: M
authors.lastname: Schneider
authors.forename: Dan M
authors.initials: DM
authors.lastname: Cooper
mesh_terms: D000293:Adolescent; D015992:Body Mass Index; D002320:Cardiovascular Physiological Phenomena; D005260:Female; D006266:Health Education; D006801:Humans; D016014:Linear Models; D009043:Motor Activity; D010101:Oxygen Consumption; D010809:Physical Fitness; D012574:Schools; D013690:Television