title: A cluster analysis of physical activity and sedentary behavior patterns in middle school girls.
abstract: OBJECTIVE
  To identify similar patterns of physical activity (PA) and sedentary behavior in sixth-grade girls using cluster analysis; to determine which clusters of girls were associated with greater daily minutes of objectively measured PA; and to examine whether girls in these clusters experienced change in PA from sixth to eighth grade.
  
  
  METHODS
  An adventitious cohort of girls (n = 957) from the Trial of Activity for Adolescent Girls were measured at sixth and eighth grade. Activities were identified using the 3-day physical activity recall and a self-report survey and used to create clusters of sixth-grade girls who had similar PA/sedentary behaviors. Accelerometry was used to assess PA in sixth and eighth grade. Data analysis consisted of FASTCLUS procedure and mixed model repeated measures analyses in SAS statistical software.
  
  
  RESULTS
  Cluster analysis yielded six clusters (C1: educational sedentary; C2: sports and play; C3: organized sports teams/classes/lessons in past year; C4: active transport and chores; C5: electronic media; C6: sleep). Sixth-grade girls in C2 and C3 had greater average daily minutes of moderate-to-vigorous physical activity (MVPA), metabolic equivalent of a physical activity-weighted MVPA, and vigorous physical activity compared with other clusters (p < .05). In eighth grade, sedentary time increased and PA declined among girls in all clusters (p < .05). Girls in C2 had the greatest decline in PA, whereas girls' PA in C3 declined less.
  
  
  CONCLUSIONS
  Encouraging participation in organized sports teams/class/lessons in middle school girls may promote greater MVPA and vigorous physical activity than other activities and may help to better sustain PA levels over time.
authors.affiliation: Department of Exercise Science, Arnold School of Public Health, University of South Carolina, Columbia, 29208, USA. trilk@mailbox.sc.edu
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Trilk
authors.forename: Russell R
authors.initials: RR
authors.lastname: Pate
authors.forename: Karin A
authors.initials: KA
authors.lastname: Pfeiffer
authors.forename: Marsha
authors.initials: M
authors.lastname: Dowda
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Addy
authors.forename: Kurt M
authors.initials: KM
authors.lastname: Ribisl
authors.forename: Dianne
authors.initials: D
authors.lastname: Neumark-Sztainer
authors.forename: Leslie A
authors.initials: LA
authors.lastname: Lytle
mesh_terms: D061725:Accelerometry; D000293:Adolescent; D002648:Child; D016000:Cluster Analysis; D005260:Female; D006801:Humans; D009043:Motor Activity; D012574:Schools / Q000706:statistics & numerical data; D057185:Sedentary Behavior; D057566:Self Report