title: Examination of mid-intervention mediating effects on objectively assessed sedentary time among children in the Transform-Us! cluster-randomized controlled trial.
abstract: BACKGROUND
  The optimal targets and strategies for effectively reducing sedentary behavior among young people are unknown. Intervention research that explores changes in mediated effects as well as in outcome behaviors is needed to help inform more effective interventions. Therefore, the purpose of this study was to examine the mid-intervention mediating effects on children's objectively assessed classroom and total weekday sedentary time in the Transform-Us! intervention.
  
  
  METHODS
  The results are based on 293 children, aged 7- to 9-years-old at baseline, from 20 schools in Melbourne, Australia. Each school was randomly allocated to one of four groups, which targeted reducing sedentary time in the school and family settings (SB; n = 74), increasing or maintaining moderate- to vigorous-intensity physical activity in the school and family settings (PA; n = 75), combined SB and PA (SB + PA; n = 80), or the current practice control (C; n = 64). Baseline and mid-intervention data (5-9 months) were collected in 2010 and analyzed in 2012. Classroom and total weekday sedentary time was objectively assessed using ActiGraph accelerometers. The hypothesized mediators including, child enjoyment, parent and teacher outcome expectancies, and child perceived access to standing opportunities in the classroom environment, were assessed by questionnaire.
  
  
  RESULTS
  The SB + PA group spent 13.3 min/day less in weekday sedentary time at mid-intervention compared to the control group. At mid-intervention, children in the SB group had higher enjoyment of standing in class (0.9 units; 5-unit scale) and all intervention groups had more positive perceptions of access to standing opportunities in the classroom environment (0.3-0.4 units; 3-unit scale), compared to the control group. However, none of the hypothesized mediator variables had an effect on sedentary time; thus, no mediating effects were observed.
  
  
  CONCLUSIONS
  While beneficial intervention effects were observed on some hypothesized mediating variables and total weekday sedentary time at mid-intervention, no significant mediating effects were found. Given the dearth of existing information, future intervention research is needed that explores mediated effects. More work is also needed on the development of reliable mediator measures that are sensitive to change overtime.
  
  
  BACKGROUND
  ACTRN12609000715279. ISRCTN83725066.
authors.forename: Valerie
authors.initials: V
authors.lastname: Carson
authors.forename: Jo
authors.initials: J
authors.lastname: Salmon
authors.forename: Lauren
authors.initials: L
authors.lastname: Arundell
authors.forename: Nicola D
authors.initials: ND
authors.lastname: Ridgers
authors.forename: Ester
authors.initials: E
authors.lastname: Cerin
authors.forename: Helen
authors.initials: H
authors.lastname: Brown
authors.forename: Kylie D
authors.initials: KD
authors.lastname: Hesketh
authors.forename: Kylie
authors.initials: K
authors.lastname: Ball
authors.forename: Mai
authors.initials: M
authors.lastname: Chinapaw
authors.forename: Mine
authors.initials: M
authors.lastname: Yildirim
authors.forename: Robin M
authors.initials: RM
authors.lastname: Daly
authors.forename: David W
authors.initials: DW
authors.lastname: Dunstan
authors.forename: David
authors.initials: D
authors.lastname: Crawford
mesh_terms: D001315:Australia; D002648:Child; D016000:Cluster Analysis; D005178:Faculty; D005260:Female; D015438:Health Behavior; D006801:Humans; D016014:Linear Models; D008297:Male; D009043:Motor Activity; D055361:Multilevel Analysis; D010290:Parents; D012574:Schools; D057185:Sedentary Behavior; D012959:Socioeconomic Factors; D016896:Treatment Outcome