title: Re-evaluation of accelerometer thresholds for MVPA at age 16 in subjects previously studied at age 12.
abstract: BACKGROUND
  A study deriving a threshold for moderate- to vigorous-intensity physical activity (MVPA) in terms of accelerometer counts in 12-year-old children was repeated with a subset of the same children at 16 years.
  
  
  METHODS
  Fifteen girls and thirty boys took part in 6 activities (lying, sitting, slow walking, walking, hopscotch and jogging) while wearing an Actigraph 7164 accelerometer and a Cosmed K4b2 portable metabolic unit. Random intercepts modeling was used to estimate cut points for MVPA (defined as 4 METs).
  
  
  RESULTS
  Using a single model, the sex-specific thresholds derived for MVPA at 16 years were some way below the 3600 counts/minute used for both sexes at age 12, particularly for girls. However graphical examination suggested that a single model might be inadequate to describe both higher- and lower-intensity activities. Models using only lower-intensity activities close to the 4 METs threshold supported retention of the 3600 counts/minute cut point for both sexes.
  
  
  CONCLUSIONS
  When restricting to lower-intensity activities only, these data do not provide sufficient evidence to change the previously established cut point of 3600 counts/minute to represent MVPA. However, further data and more sophisticated modeling techniques are required to confirm this decision.
authors.affiliation: School of Oral and Dental Science, University of Bristol, Bristol, United Kingdom.
authors.forename: Alex
authors.initials: A
authors.lastname: Griffiths
authors.forename: Calum
authors.initials: C
authors.lastname: Mattocks
authors.forename: Andy Robert
authors.initials: AR
authors.lastname: Ness
authors.forename: Kate
authors.initials: K
authors.lastname: Tilling
authors.forename: Chris
authors.initials: C
authors.lastname: Riddoch
authors.forename: Sam
authors.initials: S
authors.lastname: Leary
mesh_terms: D056044:Actigraphy / Q000295:instrumentation / Q000379:methods*; D000293:Adolescent; D000886:Anthropometry; D015331:Cohort Studies; D004734:Energy Metabolism / Q000502:physiology; D004739:England; D015444:Exercise / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D012107:Research Design