title: Minimum Wear Duration for the activPAL Professional Activity Monitor in Adolescent Females.
abstract: This study aims to determine the minimum number of days of monitoring required to reliably predict sitting/lying time, standing time, light intensity physical activity (LIPA), moderate-to-vigorous intensity physical activity (MVPA) and steps in adolescent females.
  
  
  
  195 adolescent females (mean age = 15.7 years; SD = 0.9) participated in the study. Participants wore the activPAL activity monitor for a seven day protocol. The amount of time spent sitting/lying, standing, in LIPA and in MVPA and the number of steps per day were quantified. Spearman-Brown Prophecy formulae were used to predict the number of days of data required to achieve an intraclass correlation coefficient of both 0.7 and 0.8.
  
  
  
  For the percentage of the waking day spent sitting/lying, standing, in LIPA and in MVPA, a minimum of 9 days of accelerometer recording is required to achieve a reliability of ≥ 0.7, while a minimum of 15 days is required to achieve a reliability of ≥ 0.8. For steps, a minimum of 12 days of recording is required to achieve a reliability of ≥ 0.7, with 21 days to achieve a reliability of ≥ 0.8.
  
  
  
  Future research in adolescent females should collect a minimum of 9 days of accelerometer data to reliably estimate sitting/lying time, standing time, LIPA and MVPA, while 12 days is required to reliably estimate steps.
authors.affiliation: 1 Athlone Institute of Technology.
authors.forename: Kieran P
authors.initials: KP
authors.lastname: Dowd
authors.affiliation: 2 University of Limerick.
authors.forename: Helen
authors.initials: H
authors.lastname: Purtill
authors.affiliation: 3 University of Leicester.
authors.forename: Deirdre M
authors.initials: DM
authors.lastname: Harrington
authors.affiliation: 4 Queen Margaret University.
authors.forename: Jane F
authors.initials: JF
authors.lastname: Hislop
authors.affiliation: 5 University of Strathclyde.
authors.forename: John J
authors.initials: JJ
authors.lastname: Reilly
authors.affiliation: 2 University of Limerick.
authors.forename: Alan E
authors.initials: AE
authors.lastname: Donnelly
mesh_terms: D061725:Accelerometry / Q000295:instrumentation*; D000293:Adolescent; D015444:Exercise; D005260:Female; D006801:Humans; D018670:Monitoring, Ambulatory / Q000295:instrumentation*; D011187:Posture; D012016:Reference Values; D013997:Time Factors
keywords: activPAL; adolescent; minimum; physical activity; sedentary behavior; wear time