title: Validity of ActiGraph child-specific equations during various physical activities.
abstract: OBJECTIVE
  The purpose of this study was to examine the validity of seven child-specific ActiGraph prediction equations/cut points (Crouter vector magnitude two-regression model [Cvm2RM], Crouter vertical axis two-regression model [Cva2RM], Freedson child equation, Treuth equation, Trost equation, Puyau equation, and Evenson equation) for estimating energy expenditure and time spent in sedentary behaviors, light physical activity (LPA), moderate physical activity (MPA), and vigorous physical activity (VPA).
  
  
  METHODS
  Forty boys and 32 girls (mean ± SD; age = 12 ± 0.8 yr) participated in the study. Participants performed eight structured activities and approximately 2 h of free-living activity. Activity data were collected using an ActiGraph GT3X+, positioned on the right hip, and energy expenditure (MET(RMR); activity VO(2) divided by resting VO(2)) was measured using a Cosmed K4b(2). ActiGraph prediction equations were compared against the Cosmed for MET(RMR) and time spent in sedentary behaviors, LPA, MPA, VPA, and moderate and vigorous physical activity.
  
  
  RESULTS
  For the structured activities, all prediction methods were significantly different from measured MET(RMR) for three activities or more (P < 0.05); however, all provided close estimates of MET(RMR) during walking. On average, participants were monitored for 95.0 ± 36.5 min during the free-living measurement. The Cvm2RM and the Puyau methods were within 0.9 MET(RMR) of measured free-living MET(RMR) (P > 0.05); all other methods significantly underestimated measured MET(RMR) (P < 0.05). The Cva2RM was within 9.7 min of measured time spent in sedentary behaviors, LPA, MPA, and moderate and vigorous physical activity, which was the best of the methods examined. All prediction equations underestimated VPA by 6.0-13.6 min.
  
  
  CONCLUSIONS
  Compared with the Cosmed, the Cvm2RM and the Puyau methods provided the best estimate of MET(RMR) and the Cva2RM provided the closest estimate of time spent in each intensity category during the free-living measurement. Lastly, all prediction methods had large individual prediction errors.
authors: Department of Exercise and Health Sciences, University of Massachusetts Boston, Boston, MA 02125, USA. scott.crouter@umb.edu
authors: Scott E
authors: SE
authors: Crouter
authors: Magdalene
authors: M
authors: Horton
authors: David R
authors: DR
authors: Bassett
mesh_terms: D056044:Actigraphy / Q000295:instrumentation / Q000379:methods; D000293:Adolescent; D000704:Analysis of Variance; D002153:Calorimetry, Indirect; D002648:Child; D003661:Decision Support Techniques; D004734:Energy Metabolism; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D015233:Models, Statistical; D009043:Motor Activity / Q000502:physiology*; D010101:Oxygen Consumption; D012044:Regression Analysis