title: Physical Activity Trajectories During Daily Middle School Physical Education.
abstract: BACKGROUND
  Optimal levels of moderate-to-vigorous physical activity (MVPA) have been shown to improve health and academic outcomes in youth. Limited research has examined MVPA trajectories throughout a daily middle school physical education (PE) curriculum. The purpose of this study was to examine MVPA trajectories over a daily PE curriculum and the modifying effects of sex, body composition, and cardiorespiratory endurance.
  
  
  METHODS
  One hundred 7th- and 8th-grade students participated in daily PE lessons. There were 66 lessons throughout the semester. MVPA was monitored during each lesson using NL-1000 piezoelectric pedometers. Students were classified into FITNESSGRAM Healthy Fitness Zones using estimated VO2 Max and Body Mass Index (BMI). A population averaged generalized estimating equation was employed to examine MVPA trajectories.
  
  
  RESULTS
  On average, students' MVPA decreased over time (β = -0.35, P < .001). Poor student VO2max classification significantly modified the trajectories (β = -0.14, P < .001), however poor BMI classification did not have a modifying effect (β = 0.03, P = .158).
  
  
  CONCLUSIONS
  MVPA decreased in daily PE over time and cardiorespiratory endurance significantly modified the trajectories. The results support that extra efforts have to be made by teachers and students to sustain MVPA behaviors over a semester.
authors.affiliation: Dept of Exercise and Sport Science, University of Utah, Salt Lake City, UT.
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Burns
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Brusseau
authors.forename: James C
authors.initials: JC
authors.lastname: Hannon
mesh_terms: D056044:Actigraphy; D000293:Adolescent; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D015438:Health Behavior; D006801:Humans; D008297:Male; D010806:Physical Education and Training / Q000379:methods*; D012574:Schools; D013334:Students